cda journal, vol 28, nº 10

CDA Journal Volume 28, Number 10 Journal october 2000

departments

727 The Editor/Achieving Consensus 733 Impressions/Building the Multi-Generation Dental Team 812 Dr. Bob/A Breath of Fresh Air

features

745 Current Issues in An introduction to the issue. By Donald A. Curtis, DMD, and Richard T. Kao, DDS, PhD

748 Occlusion: What It Is and What It Is Not Management of the occlusion is directly correlated to the successful treatment and maintenance of the teeth, but it has not been scientifically proven that it is directly correlated to the musculoskeletal disorders that affect the jaw. By Charles McNeill, DDS

760 Occlusal Considerations in Determining Treatment Prognosis Occlusion influences the prognosis of individual teeth and the overall treatment prognosis. By Richard T. Kao, DDS, PhD; Raymond Chu, DDS; and Donald A. Curtis, DMD

771 Occlusal Considerations for Implant Restorations in the Partially Edentulous Patient Appropriate occlusal considerations can decrease restorative complications. By Donald A. Curtis, DMD, Arun Sharma, BDS, MS; Fredrick C. Finzen, DDS; and Richard T. Kao, DDS, PhD

780 Occlusion: An Orthodontic Perspective Excellent static occlusal and functional goals are critical elements in the long-term stability of orthodontic treatment. By Paul M. Kasrovi, DDS, MS; Michael Meyer, DDS; Gerald D. Nelson, DDS

792 A Practical Guide to Occlusal Management for the General Practitioner An classification system outlined in this article can assist the general dentist in the diagnosis, treatment planning, and management of problems associated with the stomatognathic system. By Gordon D. Douglass, DDS, MS; Larry Jenson, DDS; and Daniel Mendoza, DDS head

Editor cda journal, vol 28, n 10 º

Achieving Consensus

Jack F. Conley, DDS

he CDA Applied Strategic have been adopted by the CDA House. Planning Committee completed the majority of Phase I of the In the spirit of the education and 2004 Strategic Plan for the membership goals of the Strategic Plan, association with its draft report we believe that dissemination and review Tto the Board of Trustees in mid-August. by interested members is important at The Board accepted that report, which this time. Therefore, we are providing includes a vision statement, a mission a brief summary along with comment statement, core values, and goals for the in this space. Your comments should association. be directed to the members of your Yet to be completed in Phase I at component society delegation well in the time of this writing, is a review of advance of the Nov. 19-21 session of the feedback received from shadow teams CDA House of Delegates. and the Board that was the subject of In our opinion, the new vision, discussion at a final meeting of the mission, and core values statements committee on Sept. 9. Shadow teams of (see box) for CDA have been carefully association stakeholders (people with developed by the Applied Strategic an interest and stake in the outcome Planning Committee and should be of the Strategic Plan), representing a embraced by all membership. Taken wide range of association membership together, they provide an excellent interests, were identified by each of the foundation for the future of organized 25 members of the committee. The role in California. of these groups was to provide feedback Goals and objectives that address to the committee during its development the first section of the plan, corporate of the Strategic Plan. At the September operations, may not immediately meeting, the committee completed minor hold the attention of the membership modifications and editorial revisions at large. However, they speak to the based upon the feedback it received, importance of achieving shared visions completing Phase I of the Applied and guiding practices of all subsidiaries Strategic Planning process and departments of the association, the The process has now entered Phase adjustment of internal staff structure, and II, with the effort to inform component the commitment of all employees to serve society leaders and delegates and other the best interests of the members of the interested members of organized California Dental Association. dentistry about the plan in advance Governance goals and objectives of the 2000 CDA House of Delegates include a restructuring of the volunteer next month in San Diego. The proposed leadership, a recruitment and training 2004 CDA vision, mission, core values, program to develop a corps of qualified and goals will be placed before the and effective leaders, and a fully House of Delegates for adoption, which operational charitable and educational is Phase III of the process. Phase IV foundation. In this space, we have -- implementation -- is the ultimate commented annually about the lack objective once the elements of the plan of a more robust pool of volunteer

october 2000 727 editor

cda journal, vol 28, nº 10

Proposed Strategic Plan

CDA Vision CDA, celebrating the diversity and unity of the dental family, is the source of inspiration, motivation, empowerment and pride for all oral health care professionals. The organiza- Several other membership goals tion embodies a spirit of respect, synergistic cooperation and commitment. Through include activities often requested by public policy and advocacy, education and other means, CDA promotes the health of the the association members, including an public, the profession and the individuals it serves. aggressive marketing program, addressing the allied dental health personnel CDA Mission The mission of the California Dental Association is to be the recognized symbol of needs of members, and an ombudsman excellence in education, advocacy and innovation, serving its members and assisting the program to assist them in dealing with dental community in their responsibility to the public. third-party payer issues. The committee also recognized a severe professional CDA Core Values problem area when they vowed to form Service collaboration with entities such as health Respect Education care foundations, dental schools, and Inclusive the legislature to consider student debt Integrity issues and formulate a plan to address Oral health and its impact on overall health this significant problem for younger practitioners. Public policy goals are also an important part of the Strategic Plan. They include aggressive representation leaders. Implementation of this part of effectively convey to the public the benefit of the profession by the association and the strategic plan is vital to an effective of choosing a CDA member dentist. This the promotion of the health of the public organization in the future. A good goal also speaks to an effective public before legislative and regulatory bodies training program in leadership skills relations program by CDA regarding these in order to become recognized as the is also fundamental to a successful, initiatives. respected voice on oral health issues. CDA volunteer-driven organization. The membership goals include a would become established as a leader Central to the education section of the comprehensive membership resource in improving access to oral health care Strategic Plan is development of a learning center that provides exceptional service services, be recognized as a major player center concept, which uses existing CDA and programs that are desired by the in influencing the outcome of legislative educational vehicles such as publications, membership. It will seek to survey what elections, and ultimately seek to create Online, and Sessions. It expresses a members need and want on an ongoing a new win-win-win model of dental commitment to lifelong learning and year- basis. Also included is a contact center to reimbursement. round virtual distance learning, including provide response to membership inquiries The rationale for strategic planning interactive continuing education programs. and a plan to maintain interactive provided by the committee provided Included in the plan are implementations cooperative meetings for the membership, some principal reasons why this process of system protocols for exchange of including virtual, Web, town hall, and face- is important to organized dentistry in pertinent information, which will allow to-face. Another membership goal directly California. Three of these impress us a continuum of information that ranges seeks to increase CDA membership to with their importance based upon our from responses to basic member inquiries, represent a greater percentage of dentists observations of the workings of the to comprehensive educational information. and reflect the diversity of licensed association in recent years. First on the It also speaks to an association dentists in California. This goal focuses on list is “to better represent and serve commitment to support efforts of the recruitment of students at all educational the members,” followed by “to raise the dental schools to obtain necessary funding levels to careers in dentistry, development perceived value for membership in CDA to fill faculty openings with quality people. of an innovative dues structure that raises among all California dentists.” We believe Another goal seeks support for continuous the perceived value of membership, and a that the first will lead to the second. quality improvement (and the QUIL3 membership recruitment plan for dental Various sources of input have clearly program) by the membership if CDA is to faculty. shown a need for improvement of the

728 0ctober 2000 editor

cda journal, vol 28, nº 10

services received by the membership. The Additional details describing the membership today expects an increased Applied Strategic Plan were included in level of representation and advocacy from the September CDA Update. Take the the association that has not been part of time to review them and advise your local the traditional mix. The plan, in our view, leadership and delegates to the House effectively addresses the needs that have of your opinions regarding the plan. The been frequently expressed. accomplishments of the profession in the The other reason that jumps out in years ahead depend upon participation support of this plan is “to create continuity and support at every level of the of purpose and action across all levels of membership. CDA.” In our experience, purpose and efficiency are essential if we are to make the best uses of our resources. The CDA family of companies has experienced difficulty in recent years making the best use of our efforts and resources. In the development of this plan, we have seen the evolution of a new commitment by staff and volunteers to develop a focus that will help to address these previous shortcomings. Dentistry, and the world that influences it, has been radically changing, requiring that dentistry change its modus operandi. The membership has been aging, and the expectations of younger members regarding association service and value are different. If organized dentistry is to have any success in meeting the challenges of today and tomorrow, it must transition to a new approach of doing business. The last two decades of the 20th century were periods of remarkable growth for CDA that are unlikely to be repeated. Just like the individual dental office, the association needs to focus its efforts and resources if it is to successfully face the new challenges of the 21st century. In the past, organized dentistry maintained a strong voice, as it was able to represent about 80 percent of the dental profession. This segment of the dental population has been eroding in the past decade. Failure to increase our ranks and resources will result in an organization that fails to address the needs of members.

october 2000 729 head

Impressions cda journal, vol 28, n 10 º

Building the Multi-Generation 10. However, it can cause dissonance if I she may have a positive attitude or other Dental Team place the same expectations on someone attribute I would never want to restrict.” By Debra Belt else who is prepared to give nine yards Linssen says he has found pros and How would you describe your out- when asked for nine yards, eight hours of cons to working with both younger and look? How about your work ethic or view work when asked for eight hours. That’s older team members. “Older colleagues of authority? There’s a good chance that why it’s important to clarify expectations offer wisdom and experience. They have when you were born affects your perspec- of employees and employers; to give both seen everything. On the down side, there tive on such things. parties a chance to address their needs may be resistance to new ideas. With You may be a “traditionalist,” born and feel like they’ve been heard.” younger team members, there is enthu- before 1946, with a tendency toward a Pieter Linssen, DDS, a 1997 dental siasm; they want to learn and see every- practical outlook, dedicated work ethic, school graduate says he has found respect thing. On the other hand, there is the lack and respectful view of authority. Perhaps and positive relationships as an associ- of experience.” you’re a “boomer,” born between 1946 and ate working with two private practices in Shanel-Hogan points out other vari- 1960, with an optimistic outlook, driven Placerville and Granite Bay, Calif. “Both ances in perspective that can result from work ethic and love/hate view of author- offices foster a family atmosphere and coming of age in different decades. “‘Gen ity. Or maybe you’re part of “Generation respect is given to all members of the X’ had different role models as they were X,” born between 1960 and 1980, and tend teams. They are both smaller practices, growing up; they have witnessed authority toward a realistic outlook, balanced work with fewer than 10 people, and you get a figures who have slipped and fallen, and ethic, and unimpressed view of authority. chance to know people and find out about they have seen their parents be ‘downsized’ No matter where you fall on this their thought processes.” by companies they were loyal to for many generational scale, one thing is certain. He admits that in some cases he has years. They tend to have a more realistic All three groups come together in the had to relax his expectations a little bit. view of things. A ‘boomer’ may view this as workplace. For dentists, integration of the “If you constrict someone in a business cynical.” Or a young team member may ask generations on a team is essential as Cali- sense, you constrict them in an artistic why things are being done a certain way fornia and the nation face a shortage of sense as well. Someone may not have the and a more traditional person could see dentists, hygienists, and dental assistants. exact technical expertise I want, but he or this as a challenge. Also, ‘Gen Xers’ have In light of this, leaders in dentistry are focusing on today’s employees and what motivates them to enter and stay in the profession. Low Vitamin C Can Increase Risk for Generational attributes and expecta- People who consume less than the recommended dietary allowance for vitamin C have tions were the focus of the sixth annual slightly higher rates of periodontal disease, according to a study in the August issue of the Allied Dental Health Symposium “Genera- Journal of . tion X and The Dental Team” presented Researchers analyzed vitamin C intakes and periodontal disease indicators in 12,419 in July by CDA’s Council on Education U.S. adults. They found that patients who consumed less than the recommended 60 and Professional Relations. Attendees mg per day (about one orange) were at nearly 1 1/2 times the risk of developing severe included leaders in dental hygiene, dental as those who consumed three times the RDA. assisting and dental laboratory technol- ogy as well as CDA President Kent Farn- Researcher Robert Genco, DDS, PhD, chair of the Oral Biology Department at the sworth, DDS, and President-Elect Jack S. State University of New York at Buffalo, says the relationship between severe vitamin C Broussard, DDS. deficiency and gum health has long been known. “In the late 18th century, sailors away at The symposium facilitator and key- sea would eat limes to prevent their from bleeding,” Genco said. “The relationship note speaker, Kathleen Shanel-Hogan, between vitamin C and periodontal disease is likely due to vitamin C’s role in maintaining DDS, MA, is concentrating her current and repairing health connective tissue along with its antioxidant properties.” PhD studies on transformative learn- “Periodontal disease is an inflammatory disorder that increases tissue damage and ing and change. “When working with loss. Since vitamin C is known as a powerful scavenger of reactive oxygen species, which different groups, you encounter different form part of the body’s antioxidant defense system, low levels of dietary vitamin C may expectations,” she explains. For instance, compromise the body’s ability to neutralize these tissue-destructive oxidants,” Genco said. “I identify with the ‘boomer’ work ethic where I get out there and work hard; if someone asks for nine yards, I give them

october 2000 733 head impressions cda journal, vol 28, nº 10

been criticized for being materialistic when about differences between individuals.” States suffer from the condition. often they are concerned about money due In her presentation at the symposium, Possible explanations for the to large educational loans hanging over Shanel-Hogan included information from symptoms of burning mouth include ill- their heads. the book Beyond Generation X, a guide fitting dentures, nutritional deficiencies, “When I went through school, tuition for managers by Claire Raines. “Claire disturbances in salivary flow, and hyper- and fees were $3,200 a year,” Shanel- talks about the most frequent requests sensitivity to dental materials. Usually Hogan says. “It’s hard for me to image stu- ‘Gen Xers’ make of their managers (see no single factor is entirely responsible. dents coming out of school with $100,000 sidebar). This is a good place for dentists Dentists must rule out as many of or more debt, but I would want them to to start for ideas; take a look at this list, the potential contributors as possible, know I understand their situation.” brainstorm ideas about how it might the authors said. When no clear etio- “My generation’s greatest fears are work and then talk to staff members.” logical factor is found or only minimal failure and lack of security,” says Linssen, Building these trans-generation skills relief is obtained by treatment of the who contributes these fears to coming of will also be helpful for communicating identified contributors, then the default age in the late 1980s when the economy with the up-and-coming “Generation Y.” diagnosis of wasn’t as strong, and families were The seven most frequent requests is customarily made. However, after experiencing an unprecedented boom of “Generation Xers” make of their managers: diagnostic testing to rule out causes of divorce. “In dentistry, the opportunities nnShow your appreciation. oral burning symptoms and/or treating to start a new practice are not nearly as nnBe flexible and try to understand that those symptoms with some success, bountiful as they once were. The cost of “Xer’s” don’t consider jobs to be their a definitive diagnosis of true burning education and technology places a lot of lives. mouth syndrome may emerge. limits on start up.” nnCreate a team environment. According to the authors, it Still, Linssen says he has a positive nnHelp develop skills. appears that true burning mouth outlook on his career, even though his nnInvolve your team in decision making. syndrome is a neuropathic disorder, or generation has a tendency to define suc- nnKeep a perspective and lighten-up! hyperalgesia. The study also indicated cess in a different way than previous gen- nnSet an example. that hormonal activity may play a role erations. “It’s becoming harder and harder because all the patients studied had for us to define ourselves. I hear a lot of Recognizing Burning Mouth Syndrome significantly lower than normal estro- people my age saying: ‘I will never work Burning mouth syndrome has been gen and progesterone levels. 8 to 5 or have a desk job.’ It seems that described as a complex of many symptoms the opportunity to travel and do more with very few signs and multiple etio- ‘soul-searching’ is important now. I feel logical contributing factors. Although it is fortunate that dentistry offers not just a often not definitively diagnosed, dentists chance to make a living but a lifestyle.” should take the condition seriously and Despite the departure from a more perform diagnostic testing to rule out traditional view of success, Linssen says causes, treat the symptoms, and attempt that qualities like work ethic are very to arrive at a true diagnosis, according to individual. “Work ethic comes from what an article in the May-June 2000 issue of you were taught growing up.” Northwest Dentistry. Shanel-Hogan also notes that the Burning mouth syndrome is charac- qualities and characteristics of different terized by chronic (at least six months), generations are just “starting points for continuous, progressive, unexplained discussion.” When we talk about differ- pain, the authors state. Estimates are that ences, it’s just as important to find out more than 1 million people in the United

734 0ctober 2000 impressionshead cda journal, vol 28, nº 10

Physicians Reclaim Practices at Bargain Rate As physician practice management companies continue to struggle financially, many physicians are buying back their practices, sometimes at bargain prices. According to a story in the Aug. 21, 2000, issue of American Medical News, the newsletter of the American Medical Association, many physicians are now buying back their practices from both practice management companies and hospital systems at prices far below the original price paid to acquire the practices in the first place. For example, MedPartners, a now-defunct practice management company, paid the 120 members of the Talbert Medical Group in California $95.2 million to buy their practice. Just a few years later, in 1999, the medical group bought the practice back for $3.7 million, only $31,000 per physician. Poor performance explains the bid of practice management firms to jettison their assets, according to Robert Bohlman, a consultant with the Medical Group Management Association. However, the practices most often being sold back are those owned by hospital systems. Eighty percent of hospitals that bought practices -- to ensure a flow of referrals -- lost money in the millions per year. Many hospital systems have decided to get out of the business of owning physician practices.

Smoking Bans Send Kids the Message becoming smokers,” Wakefield said. “If hand and fingers. In addition, the patient Parents may be able to reduce the you are a parent, banning smoking inside was able to perform many activities he chances that their teenagers will take up your home can decrease the chances of was unable to do with his prosthesis, cigarettes by banning smoking within your child taking up smoking. This applies including throwing a baseball, turning the their homes, even if they smoke them- even if you are a parent who smokes.” pages of a newspaper, writing and tying selves, according to a study in the British his shoelaces. Medical Journal. Transplant Recipient Using New Hand A survey of more than 17,000 U.S. A 38-year-old man who received a Honors high school students found that restrict- hand transplant was able to write and tie Paul A. Reggiardo, DDS, has been ing smoking at home, at school, and his shoes one year after the surgery, ac- awarded the American Academy of Pedi- in public places appears to reduce teen cording to an article in the Aug. 17 issue of atric Dentistry’s 2000 Merle C. Hunter smoking. the New England Journal of Medicine. Leadership Award. He is in private prac- “Smoke-free environments lead to Four months after the first human tice in Huntington Beach, Calif. smoke-free kids,” said Dr. Melanie A. hand transplantation surgery in France, Wakefield, the lead author of one of three a similar operation was performed at the studies on secondhand smoke and chil- Jewish Hospital of Louisville, Ky. The left dren published in the Aug. 5 issue of the hand of a 58-year-old male, matched for British Medical Journal. size and skin tone, was transplanted to a The link between smoking restrictions 37-year-old man who had lost his domi- and reduced teen smoking was strongest nant hand 13 years earlier. for smoking bans set by families in their Although moderate acute cellular re- homes, the report said. jection of the skin of the graft developed “Communities that pass strong laws six, 20, and 27 weeks after transplanta- to restrict smoking in public places will tion, all three episodes resolved complete- not only be protecting their residents ly after treatment. from the effects of environmental tobacco By one year, temperature, pain, and smoke, but can protect their children from pressure sensations had developed in the

october 2000 735 introduction

cda journal, vol 28, nº 10

Current Issues in Occlusion

Donald A. Curtis, DMD, and Richard T. Kao, DDS, PhD

cclusion plays a central role The second article outlines how in the practice of dentistry. occlusion can affect treatment prognosis. However, the scientific basis As the tooth- apparatus for many occlusal procedures weakens through disease and over time, has remained controversial. For adaptive changes occur in response to Oexample, in the 1980s, occlusion was popular occlusal force. Strategies for improved as testimonials supported its importance adaptive response are discussed. This in oral rehabilitation, periodontal disease article takes an original approach in progression, and craniomandibular pain. looking at occlusal force as a prognostic Empirical theories and clinical strategies determinant of treatment outcome. were developed that perhaps overstated the The third article reviews the use of importance of occlusion. dental implants in the partially edentulous In the late 1980s, epidemiological patient. The article emphasizes the studies questioned the scientific importance of treatment planning and how Contributing basis for many relationships between attention to occlusal relations can decrease Editor occlusion and dysfunction. This resulted restorative complications. Both the type and Donald A. Curtis, in confusion, a loss of interest, and frequency of restorative complications are DMD, is a professor even a backlash in the sentiment reviewed, as are considerations for splinting in the Department of the profession. Within a short and cantilevers with implant restorations. of Preventative and period, the topic of occlusion was not The fourth article outlines why most Restorative Dental only unpopular, but also considered referrals for orthodontic treatment are Sciences at the University of California at San unscientific and superficial hyperbole. occlusion-related and why the importance Francisco School of The goal of this issue is to emphasize of occlusion continues to be controversial Dentistry. that occlusal considerations are in orthodontics. The six warning signs of important and that science has shown a child with a developing malocclusion Author a well-established association between are reviewed, and how unfavorable occlusion and dental health. growth patterns can be altered with early Richard T. Kao, DDS, PhD, is an associate This issue of the Journal of the treatment is emphasized. Included is a adjunct professor in California Dental Association includes five discussion of current thinking on the the Periodontology papers intended to update practitioners relationship between temporomandibular Department at the with new information about the relevance joint dysfunction and orthodontics. University of the Pacific of dental occlusion to their practice. The last article offers the clinician a and currently has a private practice limited to The first article describes the evolution simple and practical classification system periodontics and dental of numerous theories, techniques, and that can assist in the diagnosis, treatment implants in Cupertino, treatment philosophies as related to planning, and management of occlusion. This Calif. He is a diplomate occlusion. Though some of these ideas classification system has been successfully of the American Board of have been disproved, others remain used in our teaching program at UCSF. Periodontology. empirically true, while others have been We hope you enjoy and benefit from validated by scientific evidence. this issue on occlusion.

october 2000 745 occlusion

cda journal, vol 28, nº 10

Occlusion: What It Is and What It Is Not

Charles McNeill, DDS

abstract Dental occlusion is much more than the physical contact of the biting surfaces of opposing teeth or their replacements. Occlusion is more comprehensively defined biologically as the coordinated functional interaction between the various cell populations forming the masticatory system as they differentiate, model, remodel, fail, and repair. Morphologic variations are very common and represent the norm. Even though the occlusal or musculoskeletal relationship may not meet the definition of the clinician’s concept of an optimum or ideal occlusion, it must be appreciated that for that particular patient, the tissues of the masticatory system may have developed a stable, functional, healthy, and comfortable equilibrium. However, when the functional equilibrium is perturbed or when the occlusion is being re- established, specific treatment criteria are as important today, if not more important with the rapid growth of implant placements, as ever before. Treatment of the occlusion should be considered on an individual basis based on the specific physiologic needs of the various tissue systems within the masticatory system rather than on a preconceived, stereotyped or universal basis. It has long been established and recently proven that proper management of the occlusion is directly correlated to the successful treatment and maintenance of the teeth and, at times, the supporting tissues. On the other hand, it has not, to date, been scientifically proven that occlusion is directly correlated to the musculoskeletal disorders that affect the jaw (temporomandibular joint or masticatory muscle disorders).

author cclusion is most appropriately the cell populations in these tissue defined as the functional systems is determined by the biological Charles McNeill, DDS, is a professor of clinical relationship between the environment. When there is a perturbance dentistry and director of components of the masticatory to this dynamic functional equilibrium the Center for Orofacial system including the teeth, due to injury, disease, adverse functional Pain at the University of Osupporting tissues, neuromuscular system, demands, or a loss in the adaptive capacity California at San Francisco temporomandibular joints, and craniofacial of the tissues, tissue failure can occur. School of Dentistry. skeleton.1 The masticatory tissue systems However, the cell populations of the function in an integrated and dynamic various masticatory tissue systems have manner in which stimuli created by great potential for physiologic repair, function signal tissues to differentiate, reducing the demand for treatment. Thus, model, and remodel. The behavior of occlusion should be defined physiologically 748 october 2000 occlusion

cda journal, vol 28, nº 10

not morphologically. Occlusion should not tests is required to appropriately allows for changes in muscle tone, in the be defined simply, as in most dictionaries, categorize and manage the three different number of sarcomeres, in connective as any contact or relationship between types of occlusion. tissue apposition at the muscle- the incising or masticating surfaces of the tendon interface, in the muscle fiber maxillary and mandibular teeth and/or Physiologic Occlusion direction, and in the migration of muscle dental arches.2 Occlusion is not a static, A physiologic occlusion is defined insertions.9 At the occlusoradicular unchanging structural relationship, but as an occlusion in which a functional level, slight to moderate (age rather a dynamic, viable physiologic equilibrium or state of homeostasis exists dependent), limited physiologic mobility, relationship among the various tissue within the tissues of the masticatory and even minor tooth repositioning are systems. When this viable equilibrium is system. The biologic processes and local forms of adaptation (Figure 2). disrupted or injured, the resulting occlusal environmental factors are in balance. The Inappropriately, the term discrepancies can adversely affect the teeth stresses acting on the teeth are dissipated “malocclusion” is used sometimes to and, at times, the supporting periodontal normally with a balance existing between imply a nonphysiologic occlusion and/or a tissues. However, occlusal discrepancies, the stresses and the adaptive capacity need for occlusal treatment. Malocclusion especially ones that have developed over of the supporting tissues, masticatory implies that the occurrence of occlusal time, have not been proven to be the cause muscles, and TM joints. This type of variation is in itself disease. But many of musculoskeletal disorders affecting the occlusion is typically found in the healthy, so-called malocclusions are essentially jaw. Conversely, occlusal discrepancies can comfortable patient who does not require morphologic variations that are judged be the effect of a jaw disorder, for example, dental treatment even if the occlusion against normative population means.10 osteoarthritis of the tempormandibular itself does not present morphologically as It has been estimated that approximately joint causing a collapse of the posterior a theoretical ideal occlusion. A physiologic 95 percent of the population has occlusion on the affected side. occlusion can present as a number of some form of a malocclusion, i.e., disparate structural variations but, in a crowding, malalignment, or structural Occlusal Classification given individual, represents an acceptable abnormality.11 In fact, a developmental Occlusion can be classified into three functional occlusal relationship. morphologic variation without evidence general types of physiologic stages as To maintain a physiologic equilibrium, of tissue pathology is actually a follows:1,3-5 the masticatory tissues continually physiologic adaptation to a combination nnA physiologic occlusion commonly adapt throughout life to various of intrinsic and extrinsic factors. The termed a “normal” occlusion suggesting internal biologic factors and external resulting functional equilibrium that that disease and/or dysfunction are not environmental factors as well as time- ensues becomes the most physiologic present and treatment is not required; dependent changes. Physiologic variations relationship for that particular individual. nnA nonphysiologic occlusion, commonly in dental and skeletal relationships Occlusion is not and should not be referred to as a “traumatic” or typically occur slowly, over time, during defined by rigid, stereotyped structural “pathologic” occlusion suggesting that growth or as acquired variations that have ideal relationships that are theoretically limited disease and/or dysfunction is had sufficient time to allow for tissue required for optimum health, function, present and treatment may be required; adaptation. The fibrous connective tissues and comfort. It is quite evident that the and and underlying mesenchymal layers of the tissues of the masticatory system are nnA treatment occlusion often referred to TMJ are particularly capable of adaptation extremely capable of adapting to their as an “ideal” or “therapeutic” occlusion by continual progressive and regressive environment, and extreme caution and suggesting that specific treatment remodeling.6 Studies have shown strong care must be taken before this functional criteria are required to treat the effects evidence that the potential for tissue equilibrium is clinically altered. On the of trauma or disease. repair following insults is much greater other hand, if the equilibrium shifts An integrated diagnostic rationale for the TMJ than other synovial joints toward a nonphysiologic state due to based on an adequate collection of whose articular surfaces are composed loss of function from adverse loading information from the patient’s history, of hyaline cartilage (Figure 1).7,8 Also, the including parafunction, by a loss of the clinical examination, and other indicated natural capacity for muscle adaptation capacity to adapt, or from disease, then

october 2000 749 occlusion

cda journal, vol 28, nº 10

Figure 1. The different zones of cell populations covering Figure 2. A list of possible mechanisms that allow for Figure 3. From left to right, sagittal and anterior-posterior the surface of the mandibular condyle as opposed to other muscle adaptation. tomograms and sagittal magnetic resonance image of active synovial joints, which are covered by hyaline cartilage. osteoarthritis in the TMJ resulting in possible sudden changes (supracontact) in the posterior occlusion on the same side.

Figure 4. Panoramic view of a fractured right condyle Figure 5. Working casts mounted in centric relation on Figure 6. Restorations placed in the mouth aided by the resulting in a sudden, abrupt change in the occlusion. an articulator during the laboratory sequence to facilitate centric relation reference position of the mandible (condyle) to returning the restorations to the patient’s mouth in the the cranium. treatment room using a reliable reference position. the occlusal category could change to a and, at times, from iatrogenic causes12 proven to be directly correlated to nonphysiologic occlusion. (Figure 3 and Figure 4). Tissue systems musculoskeletal conditions affecting the begin to fail and unless the direction of jaw (TMD) except for a weak association Nonphysiologic Occlusion the functional equilibrium repairs itself, with a unilateral lingual cross-bite in A nonphysiologic occlusion is defined treatment is usually required. Based on children and those with five or more as an occlusion in which the tissues of tissue damage, pathology or dysfunction, missing posterior teeth.13 But, the studies the masticatory system have lost their the occlusion would be categorized as a associating loss of posterior support functional equilibrium or hemostasis nonphysiologic occlusion. and TMJ degenerative changes reported in response to the functional demand, A nonphysiologic occlusion is directly that is a necessary additional injury, or disease. The masticatory tissues related to dental health, or lack thereof, contributing factor.14,15 Also, the studies are biologically distressed and unable to but not to musculoskeletal jaw disorders relating missing posterior teeth and adapt to the environmental factors acting (TMD). Dental signs and symptoms articular degeneration did not address the on the system and/or the functional related to a nonphysiologic occlusion confounding factor of age, making the demand exceeds the adaptive capacity of include an uncomfortable, uneven, or association suspect. the system. Pathologic changes can result “lost” bite; sensitive, painful, or sore teeth; To date, clinical studies have from sudden or abrupt insults or from worn, cracked, or broken restorations, shown a negative association between loading of sufficient magnitude or duration teeth, roots, or implants; and abnormal dental or parafunction and that there is insufficient opportunity for , widened periodontal jaw disorders. Nor does the type of tissue adaptation. These sudden, disruptive ligament, fremitus, tooth migration, guidance contact (working, anterior, or changes can be caused by trauma including and occlusion-related periodontal canine guidance contacts) or working or parafunction, inflammation, or disease pain. However, occlusion has not been nonworking contacts in laterotrusive jaw

750 0ctober 2000 occlusion

cda journal, vol 28, nº 10

movements have any association with mobility and/or lack of stability (i.e., lack determined by clinical judgment and are jaw disorders.16 There is an association of proximal contacts, tooth extrusion or based on the individual structural and between occlusal variations of sufficient migration); poor alignment, crowding, functional demands of the patient. Also magnitude and musculoskeletal jaw or rotations of the teeth; structural consideration should be given to the disorders, but it is not typically a causal damage to the teeth (i.e., tooth fracture, clinician’s training, skill, and experience as one. The associated significant occlusal chipping, abnormal wear, root resorption, well as the patient’s health, interests, and variations are a severe skeletal anterior and possibly ); pericementitis, abilities when establishing the specific open bite (overjet greater than 6 to 7 mm). widened periodontal ligament, or treatment category. and a discrepancy of greater than 2 mm related periodontal destruction; missing The decision to maintain the existing between the centric relation or retruded teeth; impaired masticatory function occlusion is based on the clinical findings contact position and the intercuspal (i.e., mastication, swallowing, speech); that a functional equilibrium between the position.17 However, it is important and esthetic considerations.19 Occlusal tissue systems has been established; and, to point out that association does not treatment is not indicated when there thus, the resulting acceptable occlusion prove cause and effect; and, in fact, open are concurrent problematic general or should be maintained. The intra- and bite and asymmetrical retruded contact dental health conditions. If there is a interarch tooth relations, the intercuspal position-intercuspal position (RCP-ICP) lack of physical or emotional stability, position (maximum intercuspation discrepancies are usually the effect of jaw lack of maxillomandibular or dental or centric occlusion), and the vertical disorders rather than the cause.18 stability, or lack of interest, concern dimension of the occlusion are acceptable. or compliance by the patient, occlusal Great care should be exercised to maintain Treatment Occlusion treatment should not be instituted. an acceptable functional equilibrium Treatment of the occlusion should Lastly, when there are complaints of pain before changing it to meet some idealized be considered on an individual basis including chronic pain syndromes, e.g., theoretical concept. If a clinical decision based on the specific physiologic needs fibromyalgia, systemic pain, orofacial is made to modify or re-establish the of the various tissue systems within pain or dental pain, occlusal treatment occlusion, there should be definite the masticatory system rather than is not indicated. Unfortunately, many and substantial reasons to support a preconceived, stereotyped concept. theoretical, ideal occlusal treatment plans the decision. Indeed, a modification Treatment of the occlusion includes are stereotyped and are the same for classification is predicated on the fact that occlusal adjustment of a single tooth to every patient regardless of the diagnosis. there needs to be some modification of a full-mouth adjustment or equilibrium, The predetermined occlusal scheme is the intra- and/or interarch relations, but restorative therapy with a single fabricated to treat all patients regardless not of the existing intercuspal position restoration to a full-mouth rehabilitation, of their functional needs or dental or vertical dimension of occlusion. They prosthodontic therapy including implant diagnoses. To superimpose the clinician’s are deemed acceptable and, therefore, dentistry, and/or orthodontic therapy concept of an ideal structural and/or should be maintained. Whereas a re- including orthognathic surgery. In general, functional relationship on a particular establishment category is determined by the goals are the same for all treatment patient is inappropriate. the fact that there is not only a clinical approaches: Restore anatomical form by need to re-establish or reorganize the restoring or replacing missing structure; Treatment Category intra-interarch relations but that the establish structural stability by optimizing To plan the proper occlusal treatment intercuspal position and/or the vertical the force distribution; and provide required for a specific set of conditions, dimension of the occlusion needs to be functional harmony for mastication, diagnostic decisions must be made first. re-established as well. deglutition, and speech. The rationale for The diagnostic decisions are based on Once the treatment classification has treatment is to improve dental health, the type and extent of treatment that been determined, treatment planning function, comfort, and esthetics. needs to be performed; namely, whether and sequencing must be considered. Occlusal treatment is indicated for the to maintain, modify or re-establish the Maintenance dentistry requires very following dental conditions: pulpal and existing occlusal schema.20 The three little planning in that a limited number periodontal sensitivity; progressive tooth different treatment categories are of restorations is simply introduced

october 2000 751 occlusion

cda journal, vol 28, nº 10

to an established, acceptable occlusal dimension needs to be re-established, stimulation from surface electrodes scheme. Whereas, the modification a new, reproducible reference position placed over the sigmoid or mandibular classification requires slight to is required because, by definition, the notch stimulates the motor root of the moderate change or improvement, original intercuspal position is no longer trigeminal nerve and the facial nerve with such as minor occlusal adjustment, available or acceptable, e.g., orthodontic, an “all or none” motor response and is, tooth movement, or opposing tooth orthognathic, complex restorative, or therefore, reproducible. Studies suggest restoration or replacement, prior to prosthetic/implant treatment (Figures 5 that the stimulation acts only in the accepting the original acceptable occlusal and 6). periphery without the participation of the scheme. However, the re-establishment central nervous system as reported by the classification usually requires major Reference Positions manufacturer.23 Nonetheless, clinicians changes to a clinically unacceptable There are, in general, three jaw have developed techniques with the use of occlusal scheme primarily associated with relations that are used clinically as electrical stimulation of the facial and some the need to establish a new intercuspal reference positions: the intercuspal masticatory muscles that by their report position and/or vertical dimension of the position (ICP), myocentric (MC) and provide a reproducible and acceptable occlusion. centric relation (CR), or the retruded mandibular position. This approach There are specific and rather precise contact position (RCP).1 The intercuspal must account for variations in muscle technical requirements and clinical position is clinically the most reproducible tone throughout the day with changes in considerations involved when an reference position. It is determined activities of daily living, various emotional occlusion scheme has to be re-established morphologically by the shape and location states, posture, and fatigue. or reorganized. The newly re-established of the teeth, by the periodontal sense occlusal scheme does not benefit from organs through proprioception, and by Centric Relation time-related adaptation but, rather, must muscle memory, which is reinforced by The definition of centric relation keeps be integrated with and conform to the tooth contact. The sensory input allows changing in the literature. Conceptual remaining tissues of the masticatory the mandible to open and close rapidly approaches to the definition of centric system. The jaw relationship must be and repeatably in the same position. relation can be anatomic, orthopedic, or stabilized and painful or pathological When ICP is unacceptable, there are two operational. The anatomical definition conditions treated prior to definitive alternative clinical approaches to establish is the traditional dental concept of the occlusal therapy.21 This requires a reproducible reference position. Either optimum structural relationship of the careful attention to detail and proper a joint-ligamentous dictated position, CR mandible to the cranium. One of the treatment sequencing including possible or RCP, or a muscle-dictated position, MC, seven anatomical definitions published pretreatment with an interocclusal can be used reliably to relate the mandible in the seventh edition of the “Glossary of appliance; prior ancillary treatment, to the cranium on a relative reproducible Prosthodontic Terms” is as follows: “The i.e., endodontic, periodontic, or surgical basis. Variations of a muscle-dictated maxillomandibular relationship in which treatment and, at times, prolonged jaw relationship determination using the condyles articulate with the thinnest provisional treatment. Lastly, and very either tongue, speech, or rest position, or articular portion of their respective importantly, when re-establishing the voluntary repeated mandibular closures discs in the anterior-superior position occlusal scheme, a treatment reference are reported in the clinical literature but against the posterior slope of the articular position must be established. During are not easily standardized and, therefore, eminentia.”24 The orthopedic definition is maintenance and modification treatment, will not be presented. based on the physical medicine concept the reference position has, by definition, of a closed-pack relationship of articular already been established by virtue of Myocentric structures as determined by function. the fact that the intercuspal position The MC reference position is obtained The condyle would be “seated” in the and vertical dimension of the occlusion through the use of transcutaneous fossa with an interposed articular disk, have been deemed acceptable and only electrical neural stimulation creating if not compromised, as determined by need to be maintained. But when the a neuromuscularly oriented occlusal the mandibular muscles during function, intercuspal position and/or vertical position.22 The theory is that the i.e., the compression or functional

752 0ctober 2000 occlusion

cda journal, vol 28, nº 10

Figure 7. Treatment objectives. Figure 8. Stable intercuspal position of the condyles within Figure 9. Centric stops allowing occlusal loading forces to the fossae and cusp fossae contacts of the opposing teeth. be directed axially.

Figure 10. Placement of a shim in the anterior tooth Figure 11. Left mandibular laterotrusion resulting Figure 12. Excursive pathways during working, region results in the condyle becoming more seated superiorly in rotation of the left condyle and translation of the right nonworking, and protrusive mandibular movements allowing for or in the most posterior tooth region results in a possible condyle and working guidance contacts on the left teeth and smooth gliding movements of the mandible. distraction of the condyle. nonworking contacts on the right side. Note: If tooth contacts are not deflective, the contacts by themselves are not detrimental to smooth gliding movements of the mandible. loading of the articular structures during CR is that it allows the clinician to in a more upright position with gentle chewing and swallowing. The closed- evaluate the progress and outcome of the manipulation directed more superiorly pack relationship of articular structures treatment based on a definite starting than posteriorly and with the patient in any joint is considered to be both and ending point. One clinical advantage aiding the closure. Thus, technique and physiological and biomechanically of the hinge axis is that technically the experience become critical, but it has been stable. Because tomographic surveys of patient’s horizontal axis of closure can shown that this approach can become nonsymptomatic subjects have shown be transferred to an articulator allowing clinically replicated.27 great variation in condylar position, for the possibility of alterations, within this functional definition may be more limits, of the vertical dimension of Specific Treatment Objectives accurate than the first one, which is occlusion. The mandible is manipulated Once the treatment category has been based on anatomical relationships that in a retruded direction while being determined, specific clinical objectives cannot be validated. The third and supported in a superior direction at the need to be established to develop more operational definition is based on gonial angles to allow the condyles to optimum dental health (Figure 7). The the concept that in order to perform be braced in the most anterio-superior specific objectives that are suggested from precise, complex occlusal treatment, direction against the posterior slopes a optimum functional standpoint include: it is technically advantageous to use a of the eminentia.26 Techniques must nnMaximum symmetrical distribution of reproducible border position of the jaw.1 be altered after condylar fracture, bony the centric contacts in the intercuspal CR or RCP is independent of degeneration, and soft tissue alterations position (which may be in CR, tooth contact and is determined by because the structural components that depending on the treatment category); manipulation of the mandible in a rotary originally provided for a physiologic nnAxial or near axial loading of the teeth; movement about a transverse horizontal position of the condyle are no longer nnAn acceptable occlusal plane; axis.25 The operational significance of available. The patient may have to be nnGuidance contacts allowing for

october 2000 753 occlusion

cda journal, vol 28, nº 10

freedom without deflection in closing angulation of the occlusal plane is on the Conclusion and excursive gliding mandibular average approximately 10 degrees higher In the past, the dental literature movements; and or steeper than the Frankfort plane. in the field of occlusion was primarily nnAn acceptable vertical dimension of The importance of these occlusal planes based on clinical observations, case occlusion and interocclusal resting is their influence on cusp height and reports, and testimonials. Technical bias range.1 position and their relationship to tissues drove treatment rather than scientific Even distribution of tooth contacts in the masticatory system. knowledge in many cases. However, today in the intercuspal position is desirable Functional harmony is improved by there is a definite momentum within to establish maximum stability and providing unrestricted smooth gliding the dental profession to move from a optimum distribution of the closing movements of the mandible. Excursive clinically based position to an evidenced- forces (Figure 8). The natural number guidance contacts can be provided by based position in the field of occlusion. of ICP contacts averages approximately one or more teeth, e.g., canine guidance, The scientific literature’s questioning of seven bilateral contacts, with the molars anterior guidance, or group-working the association between occlusion and loaded more than the premolars, which guidance. There appears to be no scientific musculoskeletal jaw disorders does not are loaded more than the cuspids.28 If evidence to support one occlusal scheme invalidate the well-established association the location of the occlusal load occurs over the other,13 and a wide variety of between occlusion and dental health.34 only in the most distal molar region, contacts are found naturally. Functional However, it is difficult to prove cause specifically the third molar and possibly harmony requires that tooth contact and effect between the relationship in the second molar region, it may act as during mandibular movements be guiding of occlusion and the health of the a deflective contact causing the ipsilateral ones as opposed to deflective contacts masticatory system due to the lack of condyle to become unloaded (distracted) (Figure 11). Deflective contacts, also called scientifically established criteria for an with the contralateral condyle undergoing premature or interceptive contacts, are optimum treatment occlusion. Also, there increased compression (Figure 9x).29 defined as occlusal contacts that divert still is a lack of knowledge regarding the Axial loading of the teeth (Figure the mandible from a normal path of natural history of the various occlusal 10x) in a slight mesial direction allows closure or interfere with normal, smooth, relationships; and the large number of the reaction forces on closure or during gliding mandibular movement and/or possible contributing factors make the clenching to be transmitted vertically deflect the position of the condyle, teeth confounding factors extremely difficult to rather than laterally along or near to (analogues), or prostheses (Figure 12). control in clinical trials. the long axes of the teeth. Vertical The vertical dimension of the The same requirements for proper loading forces are better accepted by the occlusion is defined as the distance occlusal therapy are as valid today as viscoelastic periodontal ligament than between two anatomical points, e.g., in the past. Because implants do not horizontal forces.30 Nonaxial loading on the face or jaws, when the occluding have a forgiving periodontal ligament generates mechanical moments or members (teeth, bite blocks) are in with special protective senses, the need torquing forces at or near the alveolar contact.2 The postural resting range for more precise occlusal treatment crest of supporting bone. Axial loading usually is a 1 to 3 mm open position of the becomes even more critical. Until more of dental implants is even more critical mandible relative to ICP. General body, evidence is established, treatment of because of decreased proprioceptive input head and neck posture, speech, sleep, age, the occlusion should be individualized as a consequence of investing bone rather stress, and pain all influence the postural to meet the patient’s needs based on than the periodontal ligament.31 resting range. Clinical rest position today’s evidence and not on a clinician’s The plane of occlusion is defined as is not a position of minimal muscle belief system of an optimum structural the average imaginary plane established activity but rather an upright postural relationship for its own sake. Treatment by the incisal and occlusal surfaces of position.32 Patient accommodation to of the occlusion should only be considered the teeth.2 Because of the compensating significant changes in vertical dimension when there are clinical signs and/or anteroposterior and mediolateral of the occlusion suggests that it is not symptoms within the masticatory system curvatures of the teeth, the plane of immutable but can be modified within that can be definitively related to the occlusion is actually curvilinear. The reason without clinical consequence.33 dysfunctional and pathological conditions

754 0ctober 2000 occlusion

cda journal, vol 28, nº 10

study. J Craniomandib Disord Facial Oral Pain 5:121-8, 1991. experimental occlusal interference studies: What have we of the various tissue systems. Treatment 13. McNamara JA, Seligman DA, Okeson JP, Occlusion, learned? J Prosthet Dent 82:704-13, 1999. orthodontic treatment, and temporomandibular disorders: A To request a printed copy of this article, please contact: plans need to be modified based on the review. J Orofacial Pain 9:73-90, 1995. Charles McNeill, DDS, Box 0758 patient’s abilities, desires, compliance, 14. MacDonald JWC, Hannam AG, Relationship between UCSF School of Dentistry, 707 Parnassus Ave., San Francisco, health, and emotional status in addition occlusal contacts and jaw-closing muscle activity during tooth CA 94143-0758 or at [email protected]. clenching: Part I. J Prosthet Dent 52:718-29, 1984. to the clinician’s abilities, training, and 15. MacDonald JWC, Hannam AG, Relationship between experience. The cardinal rule should be occlusal contacts and jaw-closing muscle activity during tooth to proceed carefully with treatment of clenching: Part II. J Prosthet Dent 52:862-7, 1984. 16. Kahn J, Tallents RH, et al, Prevalence of dental occlusal the occlusion using the least invasive variables and intra-articular temporomandibular disorders: procedure as much as possible with all the Molar relationship, lateral guidance and nonworking side skill and expertise possible. Treatment contacts. J Prosthet Dent 82:410-5, 1999. 17. Pullinger AG, Seligman DA, Quantification and validation of of the occlusion is essential to, and a predictive values of occlusal variables in temporomandibular requirement for, appropriate professional disorders using a multifactorial analysis. J Prosthet Dent dental care; it is rarely essential to, or 83:66-75, 2000. 18. Seligman, Pullinger AG, Analysis of occlusal variables, a requirement for, the management of dental attrition and age for distinguishing healthy controls musculoskeletal disorders affecting the from female patients with intracapsular temporomandibular jaw (TMD). disorders. J Prosthet Dent 83:76-82, 2000. 19. Wise MD, Failure in the Restored Dentition: Management and Treatment. Quintessence Publishing, London, 1995, References pp13-147. 1. McNeill, C, Fundamental treatment goals. In, McNeill, C, ed, 20. Braly BV, Occlusal analysis and treatment planning for Science and Practice of Occlusion. Quintessence Publishing, restorative dentistry. J Prosthet Dent 27:168-71, 1972. Chicago, 1997, pp 306-22. 21. Dyer EH, Importance of a stable maxillomandibular 2. Zwemer TJ, ed, Boucher’s Clinical Dental Terminology, 3rd ed. relationship. J Prosthet Dent 30:241-51, 1973. CV Mosby, St Louis, 1982, p 203. 22. Jankelson B, Neuromuscular aspects of occlusion. In, 3. Okeson JP, Management of Temporomandibular Disorders Boucher LJ, ed, Occlusal articulation. Dent Clin N Am 23:157-68, and Occlusion, 3rd ed. Mosby-Year Book, St Louis, 1993, pp 1979. 109-26. 23. Dao TTT, Feine JS, Lund JP, Can electrical stimulation be 4. Mohl ND, Diagnostic rationale. In, Mohl ND, Zarb GA, et used to establish a physiologic occlusal position? J Prosthet al, eds, A Textbook of Occlusion. Quintessence Publishing, Dent 60:509-14, 1988. Chicago, 1988, pp 179-84. 24. Academy of , Glossary of prosthodontic 5. Ramfjord SP, Ash MM, Occlusion, 3rd ed. WB Saunders, terms, 7th ed. J Prosthet Dent 81:39-110, 1999. Philadelphia, 1983, pp 164-6 and 188-218. 25. McNeill C, The optimum temporomandibular joint condylar 6. Moffett B, Classification and diagnosis of position in clinical practice. Int J Perio Rest Dent 5:53-76, 1985. temporomandibular joint disturbances. In, Solberg WK, 26. Becker CM, Kaiser DA, Schwalm C, Mandibular Clark GT, eds, Temporomandibular Joint Problems: Biologic concentricity: Centric relation. J Am Dent Assoc 83:158-60, Diagnosis and Treatment. 2000. Quintessence, Chicago, 1980, pp 21-31. 27. Wood DP, Elliott RW, Reproducibility of the centric relation 7. Rasmussen C, Temporomandibular arthropathy, clinical, bite registration technique. Angle Orthod 64:211-221, 1994. radiologic, and therapeutic aspects with emphasis on 28. Korioth TWP, Number and location of occlusal contacts in diagnosis. Int J Oral Surg 12:365-97, 1983. intercuspal position. J Prosthet Dent 64:206-10, 1990. 8. deLeeuw R, Boering G, et al, Clinical signs of TMJ 29. Hylander WL, An experimental analysis of osteoarthrosis and internal derangement 30 years after temporomandibualr joint reaction force in Macaques. Am J nonsurgical treatment. J Orofac Pain 8:18-24, 1994. Phys Anthrophol 51:433-56, 1979. 9. Palla S, Occlusal consideration in complete dentures In, 30. Caffesse RG, Fleszar TJ, Occlusal trauma. In, Wilson TG, McNeill, C, ed, Science and Kornman KS, Newman MG, eds, Advances in Periodontics. Practice of Occlusion. Quintessence Publishing, Chicago, 1997, Quintessence Publishing, Chicago, 1992, pp 205-25. pp 457-67. 31. Wismeijer D, van Waas MAJ, Kalk W, Factors to consider in 10. Bjork A, Krebs A, Solow B, A method for epidemiologic selecting an occlusal concept for patients with implants in the registration of malocclusion. Acta edentulous mandible. J Prosthet Dent 74:380-4, 1995. Odontol Scand 22:27-41, 1964. 32. Rugh JD, Drago CJ, Vertical dimension. A study of clinical 11. Profitt WR, Epker BN, Ackerman JL, Systematic description rest position and jaw muscle activity. J Prosthet Dent 45:670, of dentofacial deformities: the database. In, Bell WH, Profitt 1981. WR, White RP, eds, Surgical Correction of Dentofacial 33. Rivera-Morales WC, Mohl ND, Relationship of occlusal Deformities. WB Saunders, Philadelphia, 1980, Vol 1, pp 105-54. vertical dimension to the health of the masticatory system. J 12. Kampe T, Hannerz H, Strom P, Five-year follow-up of Prosthet Dent 65:547-53, 1991. mandibular dysfunction in adolescents with intact and 34. Clark GT, Tsukiyama Y, et al, Sixty-eight years of restored dentitions: a comparative anamnestic and clinical

october 2000 755 prognosis

cda journal, vol 28, nº 10

Occlusal Considerations in Determining Treatment Prognosis

Richard T. Kao, DDS, PhD; Raymond Chu, DDS; and Donald A. Curtis, DMD

abstract To function in occlusal harmony, the masticatory apparatus -- composed of the teeth and its supporting structures, temporomandibular joints, and associated neuromusculoskeletal structures -- must operate in an integrated and dynamic manner. Loss of integrated function, or of homeostasis in response to functional demand, may generate problems in occlusion. In health, adaptive changes occur with the teeth and periodontium in response to functional occlusal forces. With periodontal and endodontic disease, this adaptive capacity diminishes. The ability to foresee how these changes may influence dental treatment is important in the art of determining treatment prognosis.

authors rognosis is the prediction or can influence either or both the prognosis Richard T. Kao, DDS, Raymond Chu, DMD, is an forecasting of the probable of individual teeth and overall treatment PhD, is an associate assistant clinical professor course and outcome of a prognosis. Whereas the prognosis of the adjunct professor in the in the Restorative disease. In clinical dentistry, the individual teeth will define which teeth are Periodontology Department Department at the at the University of the University of California definition of prognosis has been available for incorporating into the various Pacific and has a private in San Francisco and has Pextended to include the probable outcome treatment plan, the overall treatment practice limited to a private practice limited that can be achieved with treatment. prognosis will define whether a treatment periodontics and dental to prosthodontics in With clinical experience, the mechanics of should be undertaken, which of the implants in Cupertino, Cupertino, Calif. dental procedure become less challenging. available teeth conforms to the treatment, Calif. He is a diplomate of the American Board of Donald Curtis, DMD, Rather, the ability to appropriately and whether it is likely to be successful. Periodontology. is professor in the diagnose the condition and determine This review paper will describe how Restorative Department which procedure will provide the optimal occlusion influences the prognosis of at UCSF and has a private outcome is the more difficult task. Unlike the individual teeth and, subsequently, practice limited to clinical procedures, which are technique- the overall treatment prognosis. prosthodontics in Berkeley, Calif. oriented, the art of determining prognosis Occlusal harmony exists when the is based on each individual’s collective various components of the masticatory learned and clinical experiences. Due to system are healthy and can withstand the variety of past experiences, views of the functional stress (Figure 1). When treatment prognosis may vary. the tooth is affected by periodontal Numerous factors influence dental and endodontic diseases, the tooth prognosis (Table 1). These determinants becomes weakened. Despite therapy, 760 october 2000 prognosis

cda journal, vol 28, nº 10

the adaptive capacity of the tooth has occlusal contact and wear are minimal, been compromised, which changes the occurring briefly during chewing and prognosis of the tooth. This paper will swallowing. With the presence of review how these occlusal variables parafunctional habits such as clenching influence prognosis. and bruxism, occlusal forces can 3 Figure 1. Occlusal harmony is dependent on each become extensive. Trenouth showed components of the masticatory system to withstand Factors that Influence Functional that in subjects with bruxism, total functional occlusal demand. Demand occlusal contact time (38.7 minutes) was approximately seven times longer type of study can never be undertaken. Intensity of Occlusal Forces than in control subjects (5.4 minutes). For practicing clinicians, the solution Classically, occlusal forces are With longer periods of occlusal contact, is one of eliminating as many etiologic evaluated based on local factors such there is an increase in frequency and variables as possible to achieve the best as periodontal health, surface area of the total amount of occlusal force. Some possible prognosis. Thus, if parafunctional periodontal support, clinical have postulated that this increases habits exist, they should be managed. height, and the contact angle to the stress on the periodontium. This idea, opposing dentition. Also important is however, is not supported by clinical Age the number of posterior tooth-to-tooth studies. Shefter and McFall,4 in a clinical In determining the overall treatment stops, which distribute the occlusal survey of 66 adults, studied the occlusal prognosis, age is perhaps the most force. New insights have come from relation as it relates to periodontal important determinant. A treatment is a computer modeling and orthodontic status. Collected data included dental success if it is functional and survives the studies that indicate that other variables histories, periodontal analysis, analysis life span of the patient. A prognosis for a can also be significant. Musculoskeletal of malocclusion, centric discrepancies, treatment plan may be fair for a patient factors can influence the forces placed patterns of excursive movements, and 70 years of age (if the anticipated life span on the dentition. Profit1 has shown patterns of occlusal contact and wear. is 95 years old), but have a more dismal that an individual with a high Frankfort Periodontal analysis indicates that outlook for a patient 30 years of age. This mandibular plane angle will generate occlusal factors play a minimal role in is often seen in cases where a 30-year-old about half of the first molar occlusal the progression of periodontal disease patient with 5 to 6 mm of attachment loss forces as an individual with a low angle. in healthy dentitions. An issue not may require more aggressive treatment Additionally, Hannam and Wood2 have addressed is the effect that parafunctional than a patient 70 years of age. Likewise, shown the first molar occlusal force to be habits may have on unhealthy dentition, in a young patient, delaying the fully strongly influenced by the cross-sectional i.e., periodontally involved teeth with edentulous state through the use of a area of the masseter muscle. The masseter mobility. The difficulty in addressing this partial denture or an implant-supported is readily evaluated clinically and accounts question scientifically is that mobile teeth prosthesis is preferable because the fourth for 66 percent of the occlusal forces the are difficult to manage; the quantifying or fifth set of full dentures will not be patient is capable of generating. The of mobility is controversial; and increases functionally ideal. Similarly, in medicine, role of these musculoskeletal factors in mobility may be caused by multiple the orthopedic surgeon will try every on the occlusion of teeth as opposed to factors, including failing periodontium, means to avoid placing hip implants in dental implants has been reviewed in increased occlusal trauma, parafunctional patient until he or she is well over 50. This detail by Curtis and colleagues (“Occlusal habits, extent of functional load, and is due to the limitation in the number Considerations for Implant Restorations existing dentition present to provide of successful hip implants that can be in the Partially Edentulous Patient,” in protection from occlusal load. Finding an placed. With technological advances, this issue). Though these occlusal factors answer to this question is complicated by osseointegration has improved the cannot be altered, the clinician must the fact that it would require a prospective situation in the partially dentate patient learn to appreciate their significance in study allowing a harmful destructive habit as well as patients requiring hip implants. determining prognosis. to persist. The need for control and the So as technological improves, these During normal occlusal activities, ethical issues involved are such that this limitations decrease and the prognosis

october 2000 761 prognosis

cda journal, vol 28, nº 10

Table 1. Factors Influencing Prognosis The prognosis of individual teeth • Mobility • Attachment level and relative bone support • Periodontal pockets • Tooth and root morphology be the need for root canal therapy, a post- assume that endodontically treated • Infrabony defects core, and a crown. The subsequent failure teeth are weakened and fracture-prone • Furcation involvement of this endodontically treated tooth may because of the desiccation of the tooth • Relationship to adjacent teeth and edentu- result in extraction and replacement with structure. This is not the case since lous area a . Due to the harsh environment photoelastic study indicates that there • Tooth vitality and endodontic status • Extent of restoration present of the oral cavity, there tends to be a is little difference in fracture resistance • Caries and root resorption need to replace existing restorations. between vital and nonvital teeth. Thus the age of the patient and the This section will review findings that The overall prognosis characteristics of the existing restorations suggest that increased susceptibility to • Age may influence the prognosis of the tooth fracture is associated with the role of • Medical and systemic background and subsequently the prognosis of the the endodontically treated tooth in the • Patient compliance • Individual tooth prognosis overall case. restorative design and the amount of • Strategic position and pulpal status of Age may also influence individual tooth structure removed. remaining teeth tooth prognosis. Traditionally, increased Several classical studies have • Present periodontal status (height of bone, incidence of attachment loss and gingival examined the relative amount of stress attachment level, mobility, inflammation) recession correlate with increasing age. placed on a tooth based on its role in a • Assessment of past periodontal response An excellent review5 on the epidemiology prosthetic design. Teeth that serve as to disease • Estimation of present level of disease of of periodontal disease among older fixed prosthetic abutments bear greater 7-8 activity adults indicates that moderate levels of stresses in function than a single crown. • Occlusion, malocclusion, and anatomical attachment loss, bone loss, and recession When teeth are used as a removable determinants of occlusal force are found in a high percentage of elderly partial abutment, the amount of stress • Number of remaining teeth adults, especially minorities. When one increases.9-10 It further increases when examines the various epidemiological a tooth serves as the distal abutment studies closely, one finds that the rate and tooth in a distal-extension partial denture pattern of disease was similar to other design.11-14 These stresses can fracture improves. This notion of considering age adult populations. Being older does not teeth weakened by endodontic therapy in the overall treatment prognosis needs increase the risk nor incidence, nor change and dowel space preparation. to be a more consistent theme in patient the episodic pattern of periodontal disease. A selected review of retrospective chart evaluation. The amount of periodontal disease is review studies confirms the increased Age also plays an important role in still based on individual risk factor and rate of fracture failure in endodontically the prognosis of individual teeth. With . And as people get older, the treated teeth. In a review of 6,000 patient age, the signs of attrition and accumulation of destructive events as records by Sorensen and Martinoff,15 root result in loss of tooth structures, the consequence of disease activity and fracture was shown to be up to five times crazing, and an increased presence of poor oral hygiene become more evident. more frequent in endodontically treated fracture lines (Figure 2). The limitation The amount of accumulated periodontal teeth than in healthy teeth. Further of restorations becomes more apparent disease in relation to the patient’s age analysis indicated that the failure rate of over time as amalgam expands, corrodes, should be factored into the prognosis. endodontically treated teeth in removable and fractures or as the composite seal partial dentures (22.6 percent) was twice is lost due to the differential expansion Role of Pulpal Health in Response to that of those in fixed prostheses (10.2 coefficient and restorative wear. All of Occlusal Force percent) and four times that of teeth with these events will dictate replacement and Although healthy teeth can withstand crowns (5.2 percent). The incidence of root additional removal of tooth structure as normal occlusal force, nonvital and/ fracture increases with age and occurs the restoration gets larger. This weakens or endodontically treated teeth have more frequently in posterior dentition.16 the tooth structure to functional occlusal an increased potential for root fracture Resistance to fracture increases when load so the probability of tooth fracture is (Figure 3). Based on the research of more tooth structure is available.17 In a increased. With tooth fracture, there may Helfer and colleagues,6 many dentists longitudinal five- to eight-year review of 299

762 0ctober 2000 prognosis

cda journal, vol 28, nº 10

patients who were treated for periodontal- Role of Periodontal Health in Response forces. Though clinical and radiographic prosthetic therapy, Nyman and Lindhe18 to Occlusal Force signs such as widening of the periodontal noted that 75 percent of the abutment teeth ligament space, angular bony defects, that fractured were endodontically treated Occlusion in Healthy Teeth vs. abnormal occlusal contacts, infrabony and serving as terminal abutments. Periodontally Involved Teeth pockets, crestal funneling, cervical The main risk factor of root fracture In evaluating the prognosis of notching, furcation rarefaction, vertical is the loss of dentin during endodontic individual teeth to occlusal forces, an bone loss, , condensation treatment. Excessive removal of dentin important determinant is the health of trabecular bone, and during access preparation, canal fill, and of the periodontium. This relationship, are frequently associated with occlusal post preparation weakens the tooth and termed “occlusal trauma,”26-27 describes trauma, the clinician must remember makes it prone to fracture.19-20 Therefore, it the pathologic alterations or adaptive their presence is only suggestive but not is important to minimize dentin removal changes in the periodontium in response pathognomonic of occlusal trauma.3,29-32 and post preparation. Since the placement to occlusal forces. Other terms used Many of these changes can be produced of a post does not reduce nor improve in the literature include “trauma from by a variety of other factors. the distribution of occlusal forces,21-22 occlusion,” “traumatizing occlusion,” and Increasing tooth mobility is the the use of posts should be limited to “occlusal overload.” The interrelationship hallmark of occlusal traumatism. situations where they are required to of occlusion and periodontal disease has Mobility, per se, is a reflection of past provide retention for a core.23 To achieve been recently reviewed.28 and present disease experience and/ optimal fracture resistance of crowns on Occlusal trauma can be classified as or adaptive changes of a tooth and endodontically treated teeth, Ketac-Silver either primary or secondary.26 Primary describes the ability of the tooth to cores have been shown to be superior to occlusal trauma is the effect of excessive withstand occlusal forces. This ability amalgam or bonded amalgam.24 Lastly, or abnormal forces acting on a normal and is highly influenced by past pathologic having at least 2 mm of crown margin healthy periodontium. Secondary occlusal conditions resulting in attachment loss, apical to a core buildup is important trauma refers to the effect of normal the height of the remaining alveolar bone, for retention and resistance to occlusal or excessive forces acting on a reduced and root morphology. These factors, forces.19,25 periodontium. While the literature and added together, give the crown-to-root These studies indicate the pulpal many textbooks emphasize this distinction, ratio, which dictates the mechanical status of the tooth and its relationship it is of little clinical relevance since the resistance of the tooth to an applied to the amount of occlusal stress may consequences of trauma from occlusion force. Though many clinicians emphasize significantly influence its prognosis. An are similar and independent of the height the importance of fremitus, it is not endodontically treated tooth may have a of the periodontium. The more important indicative of occlusal trauma. Fremitus fair prognosis in a fully dentate occlusion, fact is that occlusal trauma is dependent is simply a functionally induced form but the same tooth may have a guarded on how well the periodontium can of mobility that is reflective of past and prognosis in a partially dentate dentition. withstand and distribute the occlusal forces. present disease and/or adaptive changes. Furthermore, when this same tooth is With a reduced periodontium, it takes a The clinical dilemma is to decide if the the distal abutment in a long leverage comparatively small force to cause occlusal tooth movement observed is reflective of free-distal extensional partial denture trauma that will result in either adaptive or a past or ongoing pathologic condition. design, the prognosis is poor. This is pathologic compensatory changes. Determining detrimental change an example of how an individual tooth involves observation of increasing tooth may have a fair/guarded prognosis but Clinical Diagnosis of Occlusal Trauma mobility over time. Unfortunately, this is because of the overall treatment plan, the and Its Therapeutic Implications a clinically difficult task. It would require prognosis may be significantly worse. In The major clinical findings in patients multiple visits and a sensitive mobility- fact, the treatment plan may even dictate with occlusal trauma include the presence monitoring mechanism that can only be a poor/hopeless prognosis and result in of tooth mobility, fremitus, and pain provided with a periodontometer or a strategic extraction or the use of implant- from damaged supporting tissue when Periotest (Siemens). This is not clinically supported prosthesis. in the presence of excessive occlusal practical due to the time requirement

october 2000 763 prognosis

cda journal, vol 28, nº 10

Figure 2. With periodontal and endodontic health, heavy Figure 3a. A patient with signs of heavy attrition (photo Figure 3b. The heavy attrition shown in Figure 3A led occlusal stress is compensated with crazing, increase fracture courtesy of Dr. R. Gurrola). to the fracture of this endodontically treated tooth (photo lines, and attrition. This may lead to the loss of vertical provided by Dr. R. Gurrola). dimension. To withstand this type of constant occlusal stress, the compensatory requirement is good periodontal and endodontic health.

Figure 4. A history of increasing tooth mobility should Figure 5a. With the re-establishment of periodontal Figure 5b. Extraction of hopeless teeth and re- be investigated when there are signs of increase in diastema health, cross-arch splinting can be successful as demonstrated in establishment of periodontal health. spacing, shifting of teeth, and change in occlusion. this case. Pre-treatment photo.

Figure 5c. Coping placement for the abutment teeth. Figure 5d. The placement of a splinted cross-arch Figure 6a. With implant-supported prosthesis, prosthesis. biomechanical distribution of occlusal forces can be better distributed as exemplified in this case. Pretreatment photo.

Figure 6b. Removal of hopeless teeth and periodontal Figure 6c. Four implants were placed in the Nos. 5, 8, 9, Figure 6d. Radiographs of the final prosthesis. treatment. and 10 positions so biomechanical forces can be distributed. The prosthesis is also segmented into six pieces so repairs and obsolescence can be accommodated.

764 0ctober 2000 prognosis

cda journal, vol 28, nº 10

and the lack of sensitivity associated with term detrimental effect as long as good Clinical Management of Occlusal most clinically used mobility indices. oral hygiene is maintained. The problem Trauma and Tooth Mobility Operationally, the diagnosis of increasing with this study is that the compliance and Since occlusal trauma may result mobility is made based on patient history frequency of maintenance visits required from two concurrent etiologic factors – of changes in tooth positions, increase are not practical. excessive occlusal force and inflammatory in diastema, movement and shifting of Investigators at the University of periodontal disease – each problem is teeth, and change in occlusion (Figure 4). Michigan have published a series of treated separately. Occlusal therapy This is followed by an occlusal analysis studies addressing this issue with more is generally addressed following, or in of the resulting changes and existing realistic clinical conditions. The initial conjunction with, periodontal therapy. mobility pattern. From this information, report by Fleszar and colleagues34 focused Controlling or decreasing tooth mobility one can diagnose presumptive on a subpopulation of patients in the is the clinical measure for therapeutic situations of occlusal trauma. Due to University of Michigan longitudinal study success. The sequence for clinical the presumptive nature of the diagnosis, on periodontal response to therapy that management of occlusal trauma consists of treatment and outcome analysis needs included 72 patients who had undergone three basic strategies: the re-establishment to be performed over time. In extensive periodontal therapy and completed at of periodontal health, occlusal adjustment, restorative cases, evaluation of tooth least one year of recall. These cases were and dental splint therapy. mobility and suitability as abutment teeth followed for four additional years. At may require long-term provisionalization the end of that period, the investigators Re-establishment of Periodontal Health of the prosthodontic case. concluded that periodontal pockets Tooth mobility associated with Several factors can influence tooth associated with mobile teeth do not periodontally diseased tissue can be mobility. Mobility has been shown to respond as favorably to treatment decreased with periodontal therapy. influence clinical prognosis. If mobility is as compared to nonmobile teeth. Measurements with Muhlemann’s deemed clinically significant in treatment Furthermore, there was attachment periodontometer have demonstrated an outcome, there are several strategies to loss that occurred during the first two average decrease of mobility by 20 percent decrease mobility. years following surgical therapy. These within four months after plaque and conclusions were confirmed in another removal.38 Goldberg39 found a 25 The Influence of Mobility on subpopulation of the University of percent decrease in mobility shortly after Therapeutic Prognosis Michigan study by Wang and colleagues.35 scaling and curettage. Ferris40 showed a The clinical implication of tooth In examining 24 patients, they found that reduction in tooth mobility ranging from mobility and increasing tooth mobility molar teeth exhibiting mobility at baseline 13.6 percent to 77.3 percent two months has been the focus of several recent or during the first year of treatment had after initial therapy; the average reduction studies. Rosling and colleagues33 more attachment loss at the end of eight for the entire test group was 24.6 percent. investigated the importance of mobility years than molars without mobility. These Although periodontal surgical healing is in patients with advanced periodontal findings are consistent with findings by not influenced by tooth mobility, surgical disease. These patients were treated Wagner,36 which demonstrated that initial treatment can decrease tooth mobility by open flap curettage and placed on mobility, gingivitis, and mean probing by 40 percent to 50 percent.39-40 These supportive periodontal therapy. It was depth together were significant risk factors studies indicate that initial therapy can found that mobile and nonmobile teeth for predicting future attachment level decrease tooth mobility by approximately responded equally well to periodontal changes following periodontal treatment. 20 percent to 25 percent, whereas surgical therapy. The maintenance and survival Epidemiological data obtained by Ismail treatment can decrease mobility by an rates for treated mobile teeth were similar and colleagues36 confirmed that the additional 40 percent to 50 percent. to those of nonmobile teeth as long as presence of tooth mobility was a significant the patient complied with a rigorous risk factor for future attachment loss. Occlusal Adjustment two-week recall schedule during the These studies suggest tooth mobility, Since mobility is a risk factor for supportive periodontal therapy phase. especially when unmanaged, will increase future attachment loss, it is questioned This study suggests mobility has no long- the risk of attachment loss. whether occlusal equilibration should

october 2000 765 prognosis

cda journal, vol 28, nº 10

be performed to minimize these risks important factor for successful periodontal loss, these investigators noted that with and whether it is effective. There are disease management is plaque control, occlusal adjustment, initial tooth mobility differences in opinion over this issue. and most cases do not require occlusal did not affect attachment response during Occlusal adjustment has long adjustment or splinting. This is consistent this limited two-year period of study. been proposed as a method for the with this group’s experimental animal management of occlusal trauma. studies, which suggested occlusal trauma Dental Splint Therapy Muhleman27 reported that mobility values is not a co-destructive factor for further A dental splint is an appliance are 30 percent higher in hypofunctional attachment loss. Occlusal adjustment designed to stabilize mobile teeth and teeth than in hyperfunctional. With the was advocated only to improve a patient’s allow for “normal” function within the re-establishment of bilateral balanced comfort and function. limits of the reduced periodontium. The function by occlusal adjustment, mobility Caffessee,47 Ramfjord and Ash48 stated premise is that splinting will aid in the was reduced on the hypofunctional that occlusal therapy should be performed reduction of tooth mobility and create a side by 18.1 percent and on the as part of the initial preparation phase of more stable and favorable situation for hyperfunctional side by 8.7 percent. periodontal treatment whenever there periodontal repair. Splints are classified Vollmer and Rateitschak41 confirmed is a functional indication for it. After according to the length of service time that occlusal adjustment could result in the inflammation has been controlled, and the therapeutic objectives. Temporary mobility reductions of 18 percent to 28 appropriate occlusal management may splints are utilized in the short term to percent after seven to 30 days. While it is include occlusal adjustment, temporary help stabilize teeth during periodontal generally agreed that occlusal adjustment or long-term splinting, stabilization treatment. Provisional splints are used for can reduce tooth mobility, views differ appliances, orthodontic treatment, and limited duration, from months to several as to when in the therapeutic sequence restorative dentistry. The latter two years, for diagnostic purposes. Permanent occlusal adjustment is indicated. definitive treatments were recommended splints are for long-term use and may be Reflecting the European philosophy of to be performed at least one to two months of fixed or removable design. prosthetic rehabilitation of patients with or more after completion of periodontal Splinting has been advocated for advanced periodontal disease, Nyman and surgery. Splinting was advocated only stabilizing moderate to advanced tooth Lindhe42-45 demonstrated that splinting when mobility interferes with the health mobility. The goal of splint therapy is or occlusal equilibration is indicated and comfort of the patient or when the to reduce occlusal trauma and provide only if tooth mobility is extensive and mobility is progressively increasing. comfort during masticatory function. It may interfere with masticatory function This philosophy is supported by the may be a treatment of last resort, short or patient’s comfort. Additionally they findings by Burgett and colleagues49 of extracting the tooth. Restoratively, demonstrated that once mobility and who studied 50 treated patients in the permanent splinting is used to stabilize periodontal disease have been controlled, Michigan longitudinal periodontal study teeth after orthodontic treatment and teeth with secondary occlusal trauma and a who were placed into the periodontal to prevent extrusion of unopposed history of increased mobility can be used as maintenance phase. Of this total teeth. Dental emergency providers and abutments for fixed prostheses or splints. population, 22 patients received occlusal oral surgeons use splints to stabilize Teeth with severe attachment loss may adjustment and 28 patients were placed subluxated or avulsed teeth following still be used if inflammation is controlled. in the control nonadjustment group. acute trauma or transplantation It was advocated that these teeth be After two years, it was concluded that procedures. Periodontally, splinting is splinted cross-arch in prosthetic design those in the occlusal adjustment group used to stabilize the teeth and to facilitate for a favorable distribution of occlusal who received conventional periodontal therapy such as initial preparation, force. Conversely, teeth with persistently therapy, whether surgical or nonsurgical, occlusal adjustment, and surgery. increasing mobility are not acceptable had a more favorable clinical attachment The benefits of splinting teeth are abutments and should not be used. level and gain of attachment than those in based on clinical impressions rather Based on various studies performed at the nonadjustment group. In addressing than on scientific studies. Splinting has the Eastman Dental Clinics, Zander and the issue of whether initial tooth mobility not been shown to reduce individual Polson46 concluded that the single most is a risk factor for future attachment tooth mobility or enhance tissue

766 0ctober 2000 prognosis

cda journal, vol 28, nº 10

healing. Several studies50-52 indicate that reports, features contributing to the Conclusion although splinting teeth may temporarily success of the reported cases included The thesis of this paper is to discuss improve their mobility status, it does control of periodontal inflammation, good how individual tooth and overall not reduce their mobility once the splint oral hygiene in the presence of healthy treatment prognosis is affected by the has been removed. The splint, in effect, periodontal tissue, adequate number and occlusal harmony of the masticatory masks the mobility status. This results distribution of abutment teeth, cross- apparatus. In a healthy situation, the in making the accurate assessment of arch stabilization, and control of the masticatory apparatus – composed of individual tooth mobility a difficult task. occlusion. Though the success of these the teeth and its supporting structures, Renggli and Schwizer51 evaluated teeth cases is dramatic and impressive, it is temporomandibular joints, and associated splinted with copings and telescopic- important to recognize that these are case neuromusculoskeletal structures – designed prostheses. After 12 months, reports of highly motivated patients with operates in an integrated and dynamic no improvement was observed after a high degree of commitment toward oral manner. Loss of integrated function, the splint was removed. These findings hygiene and periodontal maintenance. such as the structural integrity of the have been supported by Rateitschak and Detail assessment of clinical findings as tooth through endodontic treatment or coworkers.50,52 Kegel and colleagues53 used well as patient compliance is critical for periodontal disease, can result in adaptive a split-mouth design to evaluate the effect success in defining the prognosis in this changes in response to occlusal force. the effect of splinting on tooth mobility type of advanced prosthetic treatment. Should the adaptive responses not be able during initial periodontal therapy. After The health of the periodontium greatly to compensate for the occlusal forces, the 15 weeks, the reductions in tooth mobility influences the ability of each tooth to prognosis may worsen significantly. observed in the splinted and unsplinted withstand occlusal force. Prognostically, it teeth were similar, and any reduction is important that there is a distribution of References 1. Proffitt WR, Equilibrium theory revisited. Factors influencing in mobility could only be attributed to occlusal stops with healthy periodontium. position of the teeth. Angle Orthod 48:175-86, 1978. improved occlusal relationships and A case in point is the dentition where 2. Hannam AG, Wood WW, Relationship between the size and reduction in inflammation. Galler and only maxillary and mandibular anteriors spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics. Am J colleagues54 designed a similar split- are present and the patient refuses to Phys Anthropol 80:429-45, 1989. mouth study to evaluate the effect wear a partial denture. The occlusal forces 3. Trenouth MJ, The relationship between bruxism and of splint on tooth mobility following can be such that all of these teeth may temporomandibular joint dysfunction as shown by computer analysis of nocturnal tooth contact patterns. J Oral Rehabil periodontal surgical procedures. After be mobile despite adequate periodontal 6:81-7, 1979. healing, postsurgical mobility was similar support. The good news is that with the 4. Shefter GJ, McFall WT, Occlusal relation and periodontal for both splinted and unsplinted teeth. elimination of periodontal inflammation status in human adults. J Periodontol 55:368-74, 1984. 5. Locker D, Slade GD, Murray H, Epidemiology of periodontal Despite the lack of objective improvement and the addition of posterior support, disease among older adults: a review. Periodontol 2000 in therapeutic response, it is reasonable there is often decreased mobility. 16:16-33, 1998. to splint teeth during periodontal therapy Additionally, with the wider acceptance of 6. Helfer AR, Melnick S, Schilder H, Determination of the moisture content of vital and pulpless teeth. Oral Surg 34:661- not only to reduce mobility, but also to dental implants, dental prostheses may 9, 1972. provide for patient comfort and normal provide occlusal support that previously 7. Reynolds JM, Abutment selection for fixed prosthodontics. J masticatory function during therapy. was not biomechanically possible based Prosthet Dent 19:483-90, 1968. 8. Shillingburg HT, Hobo S, Whitsett LD, Fundamentals of Fixed Despite the lack of scientific support on conventional prosthetic design Prosthodontics. Quintessence Books, Chicago, 1976, pp 17-28. for splinting, many clinicians are of the (Figure 6). Advances in dental implants 9. Kaires AK, Effect of partial denture design on bilateral force opinion that it is valuable in achieving and restorative materials have created distribution. J Prosthet Dent 6:373-9, 1956. 10. Kydd W, Dutton D, Smith D, Lateral forces exerted on therapeutic success. Clinical reports greater opportunities to better manage abutment teeth by partial dentures. J Am Dent Assoc 68:859- by Amsterdam,55 Cohen and Chacker,56 the distribution of occlusal forces. These 65, 1964. and Nyman and colleagues44 described advances can improve case prognoses in 11. Kratochvil FJ, Influence of occlusal rest position and clasp design on movement of abutment teeth. J Prosthet Dent periodontally handicapped patients with ways previously thought to be clinically 13:114-8, 1963. multiple missing teeth and advanced impossible. 12. Krol AJ, Clasp design for extension-base removable partial mobility who were treated successfully dentures. J Prosth Dent 29:408-14, 1973. 13. Shohet H, Relative magnitudes of stress on abutment teeth over the long term (Figure 5). In these with different design. J Prosthet Dent 21:267-72, 1969.

october 2000 767 prognosis

cda journal, vol 28, nº 10

14. Fenner W, Gerber A, Muhlemann HR, Tooth mobility Risk Factors for Response to Periodontal Treatment [thesis]. changes during treatment with partial denture prosthesis. J University of Michigan, Ann Arbor, 1992. Prosthet Dent 6:520-5, 1956. 37. Ismail Ai, Morrison EC, Burt BA, Natural history of 15. Sorensen JA, Martinoff JT, Endodontically treated teeth as periodontal disease in adults: Finding from the Tecumesh abutments. J Prost Dent 53:631-6, 1985. periodontal disease study, 1959-1987. J Dent Res 69:430-5, 16. Testori T, Badino M, Castagnola M, Vertical root fractures 1990. in endodontically treated teeth: A clinical survey of 36 cases. J 38. Fehr C, Muhlemann HR, Objecktive erfasung der wirkung Prosthet Dent 69:87-91, 1993. einer inernen parodontaltheapie. Parodontologie 4:152-62, 17. Tjann AHL, Whang SB, Resistance of root fracture of down 1956. channels with various thickness of buccal dentin walls. J 39. Goldberg HJV, Changes in tooth mobility during Prosthet Dent 53:496-500, 1985. periodontal therapy [abstract 2611]. J Dent Res 41:290, 1962. 18. Nyman S, Lindhe J, A longitudinal study of combined 40. Ferris RT, Quantitative evaluation of tooth mobility periodontal and prosthetic treatment of patients with following initial periodontal therapy. J Periodontol 37:190-7, advanced periodontal disease. J Periodontol 50:163-8, 1979. 1966. 19. Assif D, Gorfil C, Biomechanical considerations in restoring 41. Vollmer WH, Rateitschak KH, Influence of occlusal endodontically treated teeth. J Prothet Dent 71:565-7, 1994. adjustment by grinding on gingivitis and mobility of 20. Langer B, Stein SD, Wagenberg B, An evaluation of root traumatized teeth. J Clin Periodontol 2:113-25, 1975. resections: A ten-year study. J Periodontol 50:163-8, 1981. 42. Nyman S, Lindhe J, Persistent tooth hypomobility following 21. Assif D, Oren E, et al, Photoelastic analysis of stress completion of periodontal treatment. J Clin Periodontol transfer by endodontically treated teeth to the supporting 3:81-93, 1976. structure using different restorative techniques. J Prosthet 43. Nyman S, Lindhe J, Considerations on the design of Dent 61:535-43, 1989. occlusion in prosthetic rehabilitation of patients with 22. Assif D, Bitenski A, et al, Effect of post design on advanced periodontal disease. J Clin Periodontol 4:1-15, 1977. resistance to fracture of endodontically treated teeth with 44. Nyman S, Lindhe J, Lundgren D, The role of occlusion complete crowns. J Prosthet Dent 69:36-40, 1993. for the stability of fixed bridges in patients with reduced 23. Trabert KC, Cooney JP, The endodontically treated tooth. periodontal tissue support. J Clin Periodontol 2:53-66, 1975. Restorative concepts and techniques. Dent Clin North Am 45. Nyman S, Lang NP, Tooth mobility and the biological 28:923-51,1984. rationale for splinting teeth. Periodontol 2000 4:15-22,1994. 24. Barkhordar RA, Plesh O, Curtis DA, et al, Fracture 46. Zander HA, Polson AM, Present status of occlusion and resistance of endodontically treated teeth restored with occlusal therapy in periodontics. J Periodontol 48:540-4, 1977. bonded amalgam and full crowns. Gen Dent 47:404-407, 1999. 47. Caffesse R, Management of periodontal disease in 25. Barkhordar RA, Radke R, Abassi J, Effect of metal collars patients with occlusal abnormalities. Dent Clin North Am on resistance of endodontically treated teeth to root fracture. 24:215-30, 1964. J Prosthet Dent 61:676-8, 1989. 48. Ramfjord S, Ash MN, Significance of occlusion in the 26. Glossary of Periodontic Terms. American Academy of etiology and treatment of early, moderate, and advanced Periodontology, Chicago, 1986. periodontitis. J Periodontol 52:511-5, 1981. 27. Muhleman HR, Herzog H, Rateitschak, Quantitative 49. Burgett FG, Ramfjord S, et al, A randomized trial of evolution of the therapeutic effect of selective grinding. J occlusal adjustment in the treatment of periodontitis patients. Periodontol 28:11-6, 1957. J Clin Periodontol 19:381-7, 1992. 28. Kao RT, Role of occlusion in periodontal disease. In McNeill 50. Rateitschak KH, The therapeutic effect of local treatment C, Science and Practice of Occlusion, Quintessence Books, on periodontal disease assessed upon evaluation of different Chicago, 1997, pp 394-403. diagnostic criteria, I: Changes in tooth mobility. J Periodontol 29. Berimoulin J, Curilovic Z, Gingival recession and tooth 34:540-4, 1963. mobility. J Clin Periodontol 4:107-14,1977. 51. Reggli HH, Schwizer H, Splinting of teeth with removable 30. Jin LJ, Cao CF, Clinical diagnosis of trauma from occlusion bridge-biologic effects. J Clin Periodontol 1:43-9, 1974. and its relation with severity of periodontitis. J Clin 52. Wust BP, Rateitschak KH, Muhlemann HR, Influence of Periodontol 19:92-7, 1992. local periodontal treatment on tooth mobility and gingival 31. Joshipura KJ, Kent RL, DePaola PF, Gingival recession: inflammation. Helv Odontol Acta 4:58-61, 1960. Intra-oral distribution and associated factors. J Periodontol 53. Kegel W, Selipsky H, Philips C, The effect of splinting on 65:864-71, 1994. tooth mobility, I: During initial therapy. J Clin Periodontol 32. Philstrom BL, Anderson KA, et al, Association between 6:45-58,1979. signs of trauma of occlusion and periodontitis. J Periodontol 54. Galler C, Selipsky H, Phillips C, et al, The effect of splinting 57:1-6, 1986. on tooth mobility, II: After osseous surgery. J Clin Periodontol 33. Rosling B, Nyman S, Lindhe J, The effect of systematic 6:317-20, 1979. plaque control on bone regeneration infrabony pockets. J Clin 55. Amsterdam M, Periodontal prosthesis. Alpha Omegan Periodontol 3:38-53, 1976. 67:21, 1974. 34. Flaszar TJ, Knowles JW, et al, Tooth mobility and 56. Cohen DW, Chaker F, Criteria for the selection of one periodontal therapy. J Clin Periodontol 7:495-505, 1980. treatment over another. Dent Clin North Am 8:33-41, 1964. 35. Wang H, Brugett FG, et al, The influence of molar furcation To request a printed copy of this article, please contact: involvement and mobility on future clinical periodontal Richard T. Kao, DDS, PhD, 10440 S. DeAnza Blvd., Suite #D-1, attachment loss. J Periodontol 65:25-9, 1994. Cupertino, CA 95014 or at [email protected]. 36. Wagner R, Tooth Mobility, Probing Depth, and Gingivitis as

768 0ctober 2000 implants

cda journal, vol 28, nº 10

Occlusal Considerations for Implant Restorations in the Partially Edentulous Patient

By Donald A. Curtis, DMD, Arun Sharma, BDS, MS; Fredrick C. Finzen, DDS; and Richard T. Kao, DDS, PhD

abstract The type and frequency of complications associated with dental implants has changed during the past decade. As more-successful rates of osseointegration have resulted from improved surgical protocols and materials, the major complications have become restorative-related rather than surgery- related. Recent studies indicate that restorative complications with implant-retained restorations occur at rates of 10 percent to 77 percent over a three-year period. Many of the restorative complications can be minimized with careful treatment planning and coordination of care. However, because implants lack the stress release associated with a periodontal ligament, impact loading to restorative materials and the crestal bone remains potentially more damaging with implant-supported restorations. This article discusses the biomechanical implications of implant restorations and outlines occlusal considerations designed to decrease restorative complications.

authors mplant-retained prostheses have physiologic and functional benefits of an Donald A. Curtis, Fredrick C. Finzen, become a well-established option to implant-supported prosthesis, restorative DMD, is a professor DDS, is an associate treat the partially edentulous patient complications often occur.4-7 in the Department clinical professor in and often represent an improvement Those complications occur with a of Preventative and the Department of Restorative Dental Preventative and over traditional removable partial reported frequency of 10 percent to 4-9 Sciences at the University Restorative Dental Identures. Improved support, a more 77 percent over a three-year period. of California at San Sciences at UCSF School of stable occlusion, preservation of bone, Complications are more common in Francisco School of Dentistry. and improved patient acceptance are screw-retained implant crowns rather Dentistry. Richard T. Kao DDS, PhD, reasons an implant-supported prosthesis than cemented restorations,8 and they is in private practice in 1 Arun Sharma, BDS, Cupertino, Calif. should be considered. Additionally, occur more frequently with single-tooth MS, is an assistant long-term oral health is often improved implant crowns than with multiple- clinical professor in by using an implant because less-invasive splinted units.6 Reasons for the high the Department of restorative procedures are required for complication rate include anatomic Preventative and the remaining dentition.2,3 Despite highly limitations such as bone volume or Restorative Dental Sciences at UCSF School of predictable techniques for achieving quality, spacing issues such as excessive Dentistry. osseointegration and the recognized or inadequate horizontal or vertical october 2000 771 implants

cda journal, vol 28, nº 10

restorative space, and the unique Normal masticatory forces are mostly during a night for periods up to an hour. biomechanical loading that occurs with vertical and vary with age, gender, muscle Electromyographic studies have shown endosseous implants. Because implants mass, skeletal form, and measured that bruxing forces are generally at the lack the stress release associated with position in the arch.13 Occlusal contact level of the patient’s maximal biting force, a periodontal ligament, impact loading time totals about 17 minutes a day, eight approximately seven to eight times that to restorative materials and the crestal of which occur during mastication.14 Most of normal masticatory forces.18 In a study bone is potentially more damaging.10-11 normal masticatory forces are vertical of 4,045 implants followed during a five- As a result of anatomic limitations and along the long axis of the dentition and year period, all patients with fractured biomechanical differences, ideal implant average less than 70 Newtons with a implants (eight patients, or 0.2 percent) placement and biomechanical loading is typical Western diet.15 In general, the had parafunctional habits; and bone loss not always possible. Follow-up problems greatest forces would be expected in the preceded the implant fractures.19 In a can include reversible complications first molar area of a young stressed male three-year study of 1,279 fixtures, Quiryen such as screw loosening, screw fracture, with a square-angle jaw chewing on a determined that 27 percent of the fixtures or porcelain or acrylic resin fracture. hard substrate. Conversely, lesser forces in a high-risk group of individuals with Irreversible complications can include would be expected in a sedate elderly parafunctional habits either failed or had loss of bone, loss of osseointegration, or female with a long midface measured in more than 1 mm of bone loss during the implant fracture. the incisor area when chewing on a soft second or third year of loading.20 For the This article will outline occlusal substrate. low-risk group, without parafunctional considerations in the partially edentulous Non-axial masticatory forces are habits, the percent with failure or patient when using dental implants. The generally much less than vertical forces and bone loss greater than 1 mm was 2.7 emphasis will be on posterior occlusion are generated from elliptical jaw motion percent.20 Bruxing is not an absolute because molars are the most commonly and contact on inclines of cusp teeth. contraindication to implant restorations, replaced teeth and posterior quadrants Non-axial masticatory forces vary with the but caution and careful treatment are the most common areas of restorative chewing stroke and location in the mouth planning would be essential in such cases. complications with implants. Masticatory but are generally less than 50 Newtons in forces, types of restorative complications the buccolingual direction and 20 Newtons Complications From Overloading seen with overloading implants, and the in the anterior-posterior direction.15 Implants ways in which occlusal considerations can Patients lacking anterior disclusion, lacking Complications from overloading decrease restorative complications will be proximal contacts for support, having implants are often a result of reviewed. a cross-bite, or having limited posterior unanticipated forces on restorations not natural tooth contacts would be at higher designed to tolerate either the static or Masticatory Forces on Teeth and risk for generating great horizontal and cyclic loading of the patient’s normal Implants anterior-posterior forces. masticatory forces and/or parafunctional Understanding normal masticatory habits. Complications from overloading forces is important when treatment High-Risk Patients implants are more common in posterior planning with dental implants. Masticatory Patients at high risk for excessive restorations and increase dramatically forces developed by a patient with a forces would be those with bruxing habits, when a prosthesis is nonpassive.6 quadrant restored with an implant- defined as a nocturnal grinding that can Complications are more common in supported fixed prosthesis are equivalent to include both a vertical and horizontal the maxilla than mandible and occur those of a patient with natural dentition.12 component.14 More than 20 percent more frequently in screw-retained than However, forces passed to crestal bone of the population are clinically active in cemented restorations.8 The most and impact forces are greater with implant bruxers at some point in their lives.16,17 serious biologic response to overloading restorations than with natural teeth.10,11 Identification of bruxers is important is crestal bone loss. The most common Occlusal modifications and restorative before treatment planning with implants. restorative complications of overloading changes can decrease the stress on crestal Studies have shown that bruxism often are screw loosening, screw fracture, and bone and restorative materials. results in horizontal forces several times porcelain fracture.

772 0ctober 2000 implants

cda journal, vol 28, nº 10

Crestal Bone Loss Screw loosening occurs when compressive fracture are often warning signs that Crestal bone loss around endosseous occlusal forces are higher than the tension more-serious complications – such as implants is not fully understood but likely in the screw-implant assembly that holds implant fracture or bone loss – may occur. occurs for several reasons, some of which the components together (the clamping In a retrospective study, Rangert showed are related to occlusal loading.21,22 Crestal force).32 Forces tending to separate the that reversible complications such as bone is susceptible to bone loss because screw-implant assembly can be related to screw loosening occurred in more than of the difference between implant and prosthesis design or misfit, excessive or off- 60 percent of the restorations before bone elasticity. Because titanium is so axis forces that can occur from a premature irreversible complications such as implant much stiffer than bone, a stress gradient occlusal contact or contact on a cantilever, fracture occurred.6 When screw loosening occurs at the interface of the bone and an offset, or a steep cusp angle. The or screw fracture have occurred, the use of implant, placing the crestal bone at risk clamping force will also be decreased when a nightguard should be considered. for resorption. Additionally, the crestal an implant restoration is nonpassive.32 bone is often immature at the time of When an abutment screw to an Screw Fracture initial prosthetic loading and susceptible implant restoration loosens, it is important Screw fracturing usually occurs to osteoclastic activity. In addition, the to check the fit of the implant/restoration for different reasons than does screw flex of the tooth or dampening effect from interface with a radiograph. It is also loosening. While screw loosening most the periodontal ligament is not equivalent important to verify that a proximal contact often occurs when occlusal compressive with a rigid implant or metal restoration, is not so tight that the restoration is forces are beyond the threshold of so more force is passed to the crestal not completely seated because of lateral clamping forces, screw fracturing usually bone. Human trials, animal studies, and pressure. The internal of the hex and screw occurs from excessive shear forces34 finite element analysis studies support threads should be inspected for damage. (Figures 1A, B, and C). Screw fracturing often the theory that repetitive overloading Occlusal considerations and restorative indicates that excessive lateral forces beyond a physiologic threshold can cause modifications can decrease the incidence of are occurring and should be considered microfractures and osteoclastic activity to screw loosening (Table 2). When checking a major warning sign of more-serious crestal bone, resulting in bone loss.6,19,23-27 the occlusion, make sure a prematurity complications. Studies have shown a Overloading of an implant can occur does not exist. If steep cusp angles are higher incidence of bone loss associated more easily, with fewer symptoms, and found, they should be flattened, which with restorations where screw fractures with more permanent damage than will decrease the potential for exceeding have occurred.6 A verification of fit and overloading of teeth. This is because the clamping force of the screw-implant an optimization of occlusal factors should implants do not have a surrounding assembly.32,33 If the occlusal table is wide, be completed as would be done for a supportive ligament that can provide narrowing it will decrease both the patient with screw loosening. Careful increased proprioception, better offset and the potential for exceeding consideration should also be given to distribution of forces, sharper pain the clamping force of the screw-implant major changes in the prosthesis. The perception, or adaptations to overloading, assembly. Screw loosening occurs less sectioning of a cantilever, the addition such as thickening of the periodontal frequently when a wide-diameter implant of an implant and fabrication of a new ligament28-29 (Table 1). and a machined gold cylinder rather than prosthesis, or a prosthesis with a new a narrow diameter implant or castable wax design should be considered. Screw Loosening sleeve is utilized. Replacing the titanium Screw loosening has been reported screw with a gold-alloy screw is reported Materials Fracture to occur with a three-year frequency of to increase the clamping force or pre-load Materials fracture on implant-retained from 3 percent to 38 percent in screw- and has been found to be helpful but has restorations is one of the more common retained posterior restorations.4,5,8,30,31 not been documented by clinical studies. complications that leads to refabrication of Screw loosening is more likely in single- Additionally, a torque driver can be helpful a prosthesis.35 Material fractures can occur unit restorations, occurs more often in to standardize the torque level. soon after loading but can also occur years the molar than premolar area, and can Repeated complications such as screw after delivery because of material fatigue often be related to excessive loading. loosening, screw fracture, or porcelain and deformation (Figures 2A and B). The

october 2000 773 implants

cda journal, vol 28, nº 10

Table 1 The Advantages of a Periodontal Ligament Natural dentition with a PDL allows: Restorative modification with implants: Better tactile and sensory proprioception, 10X Patient feedback less reliable for occlusal ad- better acuity at low levels of biting force26 justment, with perception of force stimulation duller and more difficult to locate.27 and/or restorative complications. Important considerations include how Better stress distribution to alveolar bone with Ankylosed and rigid implant results in 80% patients have lost teeth and whether they suspensory ligament of occlusal forces passed to crestal bone, so have a history of bruxism, clenching, consider a rigid framework for better stress or parafunctional habits. If a patient distribution and progressive loading. has lost teeth due to fracturing, he or Signs and symptoms of overload, including Few warning signs or symptoms of overload. she is at higher risk for overloading thickened ligament, tooth mobility, wear see screw loosening, screw fracture, abutment implants than if teeth were lost due to facets, fremitis and pain fracture, or bone loss. periodontal disease.39 Additionally, if a patient’s maxillomandibular relationship Easier delivery of restoration because of PDL Ankylosed implant makes it more time- con- includes excessive anterior-posterior movement suming for adjustment of contacts, and non or lateral discrepancies, e.g., a skeletal allowance for supereruption class II patient, he or she would be at increased risk for non-axial loading. Clinical signs or symptoms that warrant careful consideration include a square- incidence of materials fracture is higher fractures to abutments and screws when angle jaw, large masseter muscles, lack of with implant-retained restorations than the using acrylic resin,38 the rate of acrylic anterior disclusion, wear facets, fremitis, equivalent restoration on natural dentition resin fracture and the need for repair is periodontal ligament thickening, or few for three major reasons. First, because significantly higher than when porcelain is posterior tooth-to-tooth stops. implants lack the stress release possible with used.35 An important consideration is wear a periodontal ligament, impact forces are compatibility between the opposing arches. Restorative and Occlusal higher on implant-retained restorations; and Considerations fatigue, creep, and permanent deformation Strategies to Minimize Overloading of The fabrication of an implant- are more likely to occur. Second, with Implants and Implant Components supported restoration in a posterior the small base for implants (3 to 6 mm) quadrant requires several modifications compared to the wider base of natural Treatment Planning to the equivalent procedures on natural teeth (10 to 12 mm), even a well-designed Complications with dental implants dentition. Reduction of stress to metal frame for a porcelain-fused-to-metal are most often the result of inadequate implants and restorative components restoration can have areas of unsupported treatment planning and lack of is recommended and may be necessary porcelain that can fracture. Third, higher coordination of care. Considerations of even though the equivalent step is not stresses within the implant-retained bone density and volume, anticipated as critical with natural dentition. A restoration can occur close to the screw- loads, and planned restorative design definitive restoration that includes a retained access hole resulting in fractures. are all important to review before the narrow occlusal table and shallow cusp When selecting materials for an number, length, and diameter of implants anatomy is likely to decrease the forces implant-retained prosthesis, options are determined. Treatment planning for on prosthetic components and crestal include various acrylic resins, gold, or an implant-supported restoration also bone34 (Figures 3a and b). Indexing and porcelain. Transient shock absorption is includes identification of patients at high soldering have also been shown to best with a softer material like an acrylic risk for developing excessive force to the decrease stress to crestal bone.40 Splinting resin, but static loading is not influenced implants, restorative designs and occlusal of single units in patients at risk for high significantly by the veneering material.36,39 considerations to minimize and broadly occlusal loading should be considered In individuals at low risk for bruxism distribute stresses, and an awareness that as should judicial use of cantilevering. or excessive force transmission, gold, careful follow-up is required. These recommendations apply to use of porcelain, or acrylic resin are all viable A complete history and detailed the traditional 3.75 mm diameter implant options. Although some authors have examination is important to identify with an external hex and would be determined that there is a reduced rate of patients at high risk for occlusal overload modified if wider platform or internal hex

774 0ctober 2000 implants

cda journal, vol 28, nº 10

Table 2 How Restorative Considerations and Prosthetic Procedures Differ Between Teeth and Implants for a Posterior Fixed Restoration in the Partially Edentulous Patient Variable Natural dentition Implants implants binds as it is tightened, it is Shallow cusps Not as important because PDL Decreases lateral stress to im- often a sign that indexing and soldering able to absorb forces plant restoration and crestal bone is needed to provide passivity of the Narrow occlusal table Not as important because tooth Improves access for cleaning, restoration. when restoring poste- starts from wider base, has decreases stress to bone, and Cantilevers significantly increase rior quadrant PDL to absorb forces, and has decreases potential fracture from easier and more predictable metal unsupported porcelain stresses to the crestal bone, and caution design should be especially high when they are used opposite natural dentition. Lindquist Splinting Not usually necessary Often important in posterior quadrants for force distribution and Ahlqvist found more bone loss around fixtures with long cantilevers.21,22 Indexing and soldering Often not required because mar- Necessary because more difficult ginal fit can be evaluated and the to evaluate fit. Also, better fit Although traditional bone-anchor bridges PDL provides movement results in decreased stresses to used 10 to 20 mm cantilevers opposing crestal bone an edentulous arch, modern research has Cantilevers Only after careful consideration Increases complications because shown stresses to be significant when of increased potential for non- opposed by the increased forces possible axial loading and concentrates in natural dentition. stress at crestal bone level The cantilever length possible is Occlusal offset Usually not a problem Often a problem in maxillary influenced by biomechanical factors. The (buccal-lingual) posterior due to normal resorp- location of the cantilever, anticipated tion patterns occlusal load, diameter, number, and Restorative material Usually do not have to consider Better dampening effect with surface characteristics of the implant, dampening effect because of PDL acrylic resin but higher wear and anterior-posterior spread, bone quality, and fracture rate rigidity of the superstructure should be considered before cantilevers are planned (Figures 5a and b). If there is not sufficient components were used. table would invite tooth migration, but with rigidity, the anchorage unit closest to the A posterior implant-supported an ankylosed implant restoration, that is load will be excessively loaded. Likewise, if prosthesis with flat cusp angles stresses not a problem. A narrower occlusal table the fit between the implant and prosthesis the bone, implant components, and also facilitates easier access for home care. is not accurate, some of the implants will restorative materials less than the The splinting of posterior implants be excessively loaded while other units will equivalent prosthesis with steeper is important to consider for patients not be loaded. cusp anatomy. The more complex the requiring distribution of forces. Although The delivery of an implant-retained occlusal surface, the greater the potential the total force passed to crestal bone posterior restoration involves first checking for wedging of food and increased will remain the same for a given load, the proximal and occlusal contacts. It is lateral force transmission.41 Therefore, stress distribution can be manipulated by imperative that contacts be adjusted until wide occlusal groves and fossae are splinting.41 Implant fractures as well as light proximal contacts occur so that the recommended to decrease the potential screw loosening occur less frequently when restoration is fully seated and the seating for the wedging of food (Figures 4a and implants are splinted together.6 When is verified with a radiograph. Occlusal b). Additionally, anterior disclusion is splinting posterior units, indexing and contacts are checked next and the opposing easier to develop when posterior occlusal soldering improves the fit and decreases dentition adjusted if it is believed that the anatomy is shallow and the posterior the stress to the prosthetic components centric contact can be brought closer to occlusal plane is flat. and crestal bone. It is often difficult to the long axis of the implant. The centric A narrower occlusal table should be clinically evaluate the subgingival marginal contacts are adjusted with light occlusal considered in the diagnostic wax-up, adaptation of implant castings, so indexing contact for two reasons. First, the opposing provisional, and definitive restoration. and soldering is highly recommended. If natural dentition is often compressed; and, Normally, a flatter and narrower occlusal the abutment screw on a multiple-splinted secondly, progressive loading is possible

october 2000 775 implants

cda journal, vol 28, nº 10

Figure 1a. A radiograph of a 3.75 mm diameter implant Figure 1b. A radiograph showing the fractured implant Figure 1c. The fractured implant. Screw loosening and, in replacing a molar in a patient with a bruxing habit. after several appointments to tighten loose or broken screws. particular, screw breaking are warning signs that more serious problems may occur.

Figure 2a. Clinical example of fractured porcelain due to Figure 2b. Laboratory example. Figure 3a. Clinical example of a posterior restoration poor metal design that did not provide porcelain support. with a slight offset, shallow occlusal morphology, and a narrow occlusal table. The major benefits of a restoration with a narrow and shallow occlusal anatomy are improved access for oral hygiene and decreased potential for lateral loading.

Figure 3b. Another view. Figure 4a. Laboratory example of a posterior Figure 4b. Clinical example. restoration where shallow occlusal anatomy allowed anterior disclusion by natural dentition.

Figure 5a. Example of a patient with a cantilever. Figure 5b. Another view. Anterior cantilevers are generally less problematic than a distal cantilever.

776 0ctober 2000 implants

cda journal, vol 28, nº 10

when starting with light occlusion on an screw-retained restoration because it is is a priority, and the use of an all-gold implant. Any occlusal prematurity will result often easier to create a narrow occlusal table restoration is recommended when esthetics in increased vertical and horizontal loading. without the restriction in dimensions of a do not indicate a ceramo-metal restoration. Lateral contacts are then evaluated. screw access hole. In the maxillary anterior, Whenever possible, anterior natural teeth lateral movements are often smoother Monitoring and Follow-up should disclude the posterior implant if not interrupted by a screw access hole. More follow-up is needed with crowns. When anterior disclusion is not Wear compatibility to the opposing arch is implants than with traditional fixed possible, and lateral forces will knowingly often easier to establish with a cemented prosthetic work. When a screw loosens, be placed on the posterior implant crowns, restoration because occlusal contacts are it is important to document the event it is advisable to treatment plan additional often directly over the screw access hole that so that appropriate steps can be taken wide-diameter implants. A wider diameter is covered by composite and opposed by if repeated screw loosening occurs. implant is almost always an advantage porcelain or metal. Likewise, it is important to monitor the due to increased surface area contact In patients where a cantilever, bone level with bitewing radiographs (approximately 25 percent for each 1 wide off-set, or future modification in twice in the first year because other signs mm increase in diameter) and a broader prosthetic design or prosthetic needs and symptoms of potential overload occlusal platform. If lateral forces cannot are planned or anticipated, a retrievable are unlikely to be evident. The occlusion be eliminated, they should be designed to restorative option such as a screw- should also be evaluated yearly to make equally distribute over as many teeth and retained prosthesis should be strongly sure prematurities do not exist and that implants as possible. If excessive forces considered. Additionally, a screw-retained the anterior dentition has not worn, are anticipated, either an alternative to prosthesis is often necessary when which could place more lateral stress on an implant-supported prosthesis or a minimal interocclusal space is present. posterior implant restorations. removable overpartial can be considered. Although reported complications are more A nightguard should be fabricated Posterior implant restorations that common in screw-retained prostheses as for patients at high risk for occlusal follow an arc are less prone to implant opposed to cemented restorations, many overload. These would include patients fracture and certain other restorative of the reported complications represent with a history of bruxism or clenching, complications than a posterior quadrant the clinician’s early learning curve and patients with lateral offsets or cantilever, that is restored in a linear configuration.6 product development. With improved or implant restorations that do not have a It has also been shown that restorative machining of implant components, the proximal natural tooth. complications decrease when three rather improved pre-load possible with gold- than two implants are used to restore a plated screws, and an increased awareness Conclusion posterior quadrant.6 It therefore makes of component limitations, screw-retained Implant restorations are a “high sense that when a posterior quadrant is restorations have become very predictable stakes” treatment requiring a substantial restored, three implants in a nonlinear and preferable to cemented restorations financial and time commitment. configuration be considered. Use of in many clinical situations. Unanticipated restorative complications wide-diameter implants will often provide When complications such as abutment can be disheartening for both patient and an equivalent benefit to the nonlinear screw loosening occurs with a cemented clinician. It is important to educate the configuration. crown, a new restoration may be required. patient about potential complications Restorations can be cemented, screw- Additionally, soft tissue complications before starting an implant restoration. retained, retained with a lingual set screw, or resulting from excess cement have been Many of the complications are related to retained with substructure and attachment. reported42 and are especially problematic force transmission and can be controlled Each method for retaining an implant when an implant-supported crown with careful treatment planning, which restoration has indications, and occlusal is cemented on an abutment with a often leads to a better distribution of relationships can influence the prosthetic subgingival margin where inflamed and/ forces. It is important to identify patients choice. For example, the occlusion is often or unattached tissue is proximal to the likely to overload the planned restoration easier to control and axial loading more implant. A screw-retained prosthesis and to be aware of warning signs that favorable with a cemented rather than is recommended when retrievability overloading may be occurring.

october 2000 777 implants

cda journal, vol 28, nº 10

References 22. Ahlqvist J, Borg K, et al, Osseointegrated implants in 41. Cibirka RM, Razzoog ME, et al, Determining the force 1. Zarb G, Schmitt A, Edentulous predicament, I: A prospective edentulous jaws: a 2-year longitudinal study. Int J Oral absorption quotient for restorative materials used in implant study of the effectiveness of implant supported fixed Maxillofac Implants 5:155-63, 1990. occlusal surfaces. J Prosthet Dent 67:361-4,1992. prostheses. J Am Dent Assoc 127:59-72, 1996. 23. Frost HM, Vital biomechanics: proposed general concepts 42. Pauletto N, Lahiffe BJ, Walton JN, Complications 2. Wilding R, Reddy J, Periodontal disease in partial denture for skeletal adaptations to mechanical usage. Calcif Tissue Int associated with excess cement around crown on wearers -- a biologic index. J Oral Rehab 14:111-24, 1987. 42:145-56, 1988. osseointegrated implants: a clinical report. Int J Oral 3. Wetherell J, Smales R, Partial dentures failure: a long-term 24. Hoshaw SJ, Brunski JB, et al, Theories of bone remodeling Maxillofac Implants 14: 865-8, 1999. clinical survey. J Dent 8:333-40, 1980. and remodeling in response to mechanical usage: experimental To request a printed copy of this article, please contact: 4. Goodacre CJ, Kan JYK, Rungcharassaeng K, Clinical investigation of an in vitro bone interface. In Goldstein SA, Donald A. Curtis, DMD, UCSF School of Dentistry, Department complications of osseointegrated implants. J Prosthet Dent ed, 1990 Advances in Biomechanical Engineering. American of Preventive and Restorative Dental Sciences, 707 Parnassus 81:537-52, 1999. Society of Mechanical Engineers, New York, 1990, p 391-4. Ave., 5. Becker W, Becker BE, Replacement of maxillary and 25. Brunski JB, Biomechanical factors affecting the bone San Francisco, CA 94143-0758. mandibular molars with single endosseous implant interface. Clin Materials 10:153, 1992. restorations: a retrospective study. J Prosthet Dent 74:51- 26. Isidor F, Loss of osseointegration caused by occlusal load 5,1995. of oral implants. A clinical and radiographic study in monkeys. 6. Rangert B, Eng M, et al, Bending overload and implant Clin Oral Impl Res 7:143-52, 1996. fracture: a retrospective clinical analysis. Int J Oral Maxillofac 27. Hurzeler MB, Quinones CR, et al, Changes in peri implant Implants 10:326-34, 1995. tissues subjected to orthodontic forces and ligature 7. Wie H, Registration of localization, occlusion and occluding breakdown in monkeys. J Periodontal 69:396-404, 1998. materials for failing screw joints in the Branemark implant 28. Ulrich R, Mühlbradt L, et al, Qualitative mechanoperception system. Clin Oral Impl Res 6:47-53, 1995. of natural teeth and endosseous implants. Int J Oral Maxillofac 8. Parein AM, Eckert SE, et al, Implant reconstruction in Implants 8:173-8, 1993. the posterior mandible: a long-term retrospective study. J 29. Mühlbradt L, Ulrich R, et al, Adaptive Bestimmung der Prosthet Dent, 78:34-42,1997. Tatstschwellen bei natürlichen Zähnen und enossalen 9. Behr M, Lang R, et al, Complication rate with prosthodontic Implantaten. Z Zahnärztl Implant 5:101-7, 1989. reconstructions on ITI and IMZ dental implants. Clin Oral 30. Parcin AM, Eckert SE, Wollan PC, Implant reconstruction Implants Res 9:51-8, 1998. in the posterior mandible: A long-term retrospective study. J 10. Papavasiliou G, Kamposiova P, et al, Three dimensional Prosthet Dent 78:34-42, 1997. finite element analysis of stress-distribution around single 31. Skalak R, Aspects of biomechanical considerations. tooth implants as a function of bony support, prosthesis type, In, Branemark PI, Zarb GA, Albrektsson TA, ed, Tissue and loading during function. J Prosthet Dent 76:633-40, 1996. Integrated Prostheses Osseointegration in Clinical Dentistry. 11. Hoshaw SJ, Bronstii JB, Cochran GU, Mechanical loading of Quintessence, Chicago, 1985, pp 117-28. Branemark implants affects interfacial bone remodeling and 32. McGlumphy EA, Mendel DA, Holloway JA, Implant screw remodeling. Int J Oral Maxillofac Implants 9:345-59, 1994. mechanics. Dent Clin N Am 42:71-89, 1998. 12. Carr AB, Laney WR, Maximum occlusal force levels in 33. Kaukinen JA, Edge M J, Lang B, The influence of occlusal patients with osseointegrated oral implant prosthesis design on simulated masticatory forces transferred to and patients with complete dentures. Int J Oral Maxillofac implant-retained prosthesis and supporting bone. J Prosthet Implants 2:101-8, 1987. Dent 76:50-5, 1996. 13. Graf H, Occlusal forces during function. In, Rowe NH, 34. Weinberg LA, The biomechanics of force distribution in Occlusion: Research on Form and Function. University of implant-supported prosthesis. Int J Oral Maxillofac Implants Michigan, Ann Arbor, 1975, pp 90-111. 8:19-31, 1993. 14. Graf H, Bruxism. Dent Clin N Am 13:659-65, 1969. 35. Carlson B, Carlsson GE, Prosthodontic complications 15. Graf H, Grassel H, Aeberhard HJ, A method for the in osseointegrated dental implant treatment. Int J Oral measurement of occlusal forces in three directions. Helv Maxillofac Impl 9:90-4, 1994. Odont Scand 18:7-11, 1974. 36. Gracis SE, Nicholls JI, et al, Shock-absorbing behavior of 16. Thompson BA, Blount BW, Krumholtz TS, Treatment five restorative materials used on implants. Int J Prosthodont approaches to bruxism. Am Fam Physician 49:1617-22, 1994. 4:282-91, 1991. 17. Glaros AG, Incidence of diurnal and nocturnal bruxism. J 37. McGlumphy EA, Campagni WU, Peterson LJ, A comparison Prosthet Dent 45:545-9, 1981. of the stress transfer characteristics of a dental implant with 18. Rugh JD, Harlan J, Nocturnal bruxism and a rigid or a resilient internal element. J Prosthet Dent 62:586- temporomandibular disorders. Advances in Neurology 49:329- 93, 1989. 41, 1988. 38. Jent T, Lekholm U, Adell R, Osseointegrated implants in 19. Balshi TJ, An analysis and management of fractured the treatment of partially edentulous patients: A preliminary implants: A clinical report. Int J Oral Maxillofac Implants study on 876 consecutively placed fixtures. Int J Oral 11:660-6, 1996. Maxillofac Implants 4:211-7, 1989. 20. Quiryen M, Naert I, van Steenberhe D, Fixture design and 39. Renouard F, Rangert B, Risk Factors in Implant Dentistry. overload influence marginal bone loss and fixture success in Simplified Clinical Analysis for Predictable Treatment. the Branemark system. Clin Oral Impl Res 3:104-11, 1991. Quintessence, Chicago, 1999. 21. Lindquist LW, Rochler B, Carlsson GE, Bone resorption 40. Clelland NL, Carr AB, Gilstat A, Comparison of strains around fixtures in edentulous patients treated with transferred to a bone simulant between as-cast and mandibular fixed tissue-integrated prostheses. J Prosthet postsoldered implant frameworks for a five-implant- Dent 59:59-63, 1988. supported fixed prosthesis. J Prosthod 5:193-200, 1996.

778 0ctober 2000 0cclusion

cda journal, vol 28, nº 10

Occlusion: An Orthodontic Perspective

Paul M. Kasrovi, DDS, MS; Michael Meyer, DDS; Gerald D. Nelson, DDS

abstract In recent years, orthodontists have examined their concepts of occlusion. In current literature, at professional meetings, and in continuing education courses, one hears an ongoing discussion of condylar position and mandibular border movements in relation to occlusion. There is a wide variation in opinion as to whether dental occlusion and TMJ function are interdependent. The authors have adopted a dynamic concept of dental function to replace the traditional static view of molar relationship and incisor overlap. This article discusses how occlusion has evolved in orthodontics and reviews Andrews’ six keys to ideal static occlusion, the goals of ideal dynamic occlusion, and the six signs of developing malocclusions. The authors also review the literature on the relationship between orthodontics, occlusion, and TMD.

authors dward H. Angle, the father of focused on cusp contact during functional modern orthodontics, is credited movements.4-6 The dynamic concept was Paul M. Kasrovi, DDS, Gerald D. Nelson, DDS, MS, is an assistant clinical is an associate clinical with the definition of normal readily adopted by prosthodontists and professor in the Division professor in the Division occlusion as well as classification restorative dentists whose challenge of Orthodontics at the of Orthodontics at UCSF of malocclusions.1 According to was to restore teeth to ideal anatomic University of California at and a diplomate of the EDr. Angle, normal occlusion exists when form. The dynamic concept of occlusion San Francisco. American Board of the mesiobuccal cusp of the upper first provided practical guidelines for building Orthodontics. Michael Meyer, DDS, molar occludes with the buccal groove of cusp heights and placing grooves to is an associate clinical the lower first molar. This definition of facilitate functional jaw movements professor in the Division occlusion, based on a static position of the without functional interferences. of Orthodontics at UCSF teeth in closure, launched orthodontics There is more acceptance than ever for School of Dentistry. as the specialty dedicated to treating a dynamic concept of occlusion; however, deviations from Angle’s definition of the concept remains controversial. normal occlusion.2 There is no scientific evidence to show B.B. McCullum, the father of whether such a concept is valid. In such modern occlusion, and the founder of circumstances, one must be guided by the Gnathological Society, introduced a clinical judgment. It seems prudent when more dynamic concept of occlusion.3 His planning and executing orthodontic concept of occlusion, along with that of treatment to include a consideration of Stallard, Stuart, Huffman, and Regenos, mandibular movements. Producing fine 780 october 2000 0cclusion

cda journal, vol 28, nº 10

orthodontic results is a major technical Each maxillary tooth is distal and facial any orthodontic treatment. The six challenge, and producing an occlusion to the mandibular counterpart (Figure characteristics, which are referred to as the that coordinates with temporomandibular 3). Mandibular buccal cusps contact six keys to normal occlusion, are as follows: joint function increases the complexity. maxillary embrasures. Maxillary lingual nnThe first key: molar relationship. The introduction of pre-adjusted cusps are in a fossa relationship with the The distobuccal cusp of the upper orthodontic brackets, new wires with mandibular counterpart (except for the first molar contacts the mesiobuccal remarkable range of motion and distolingual cusps of the maxillary first cusp of the lower second molar. The resiliency, and the diagnostic techniques and second molars). mesiobuccal cusp of the upper first to relate occlusion to skeletal landmarks It is useful that there is a mesiodistal molar falls in the groove between the and mandibular movements have range for a nicely functioning occlusion. mesiobuccal and middle-buccal cusps increased the sophistication of treatment Anatomic considerations of teeth (e.g., of the lower first molar. The proper goals and the ability to achieve them. tooth size discrepancies, atypical teeth, relationship allows the cuspids and and over-retained primary teeth in place bicuspids to enjoy a cusp-embrasure Cusp-Fossa vs. Cusp-Embrasure of congenitally missing teeth), skeletal relationship buccally and a cusp-fossa Occlusion disharmonies, and atypical extraction relationship lingually (Figure 5a). Charles Stuart5 stated that there patterns may favor one occlusal scheme nnThe second key: crown angulation (tip). was a mesial and distal limit to a well- (Figure 4). The terms distal-normal, The gingival portion of the crowns of all functioning occlusion. The mesial limit mesial-normal, and median-normal (an the teeth is more distal than the incisal was referred to as a “tooth-to-tooth” and occlusal relationship midway between the or occlusal portion of the crowns. The the distal limit was referred to as the other two) have been used to describe long axis of all teeth, except molars, “tooth-to-two-teeth” occlusion. Huffman a satisfactory finished orthodontic is the mid-developmental ridge of the and Regenos6 later summarized the two occlusion.8 facial surfaces of the teeth. The long types of occlusion described by Stuart, Current orthodontic goals of incisor axis of the molar is considered to be the referring to them as “cusp-fossa” and overlap and overjet and of interincisal buccal groove and its extension to the “cusp-embrasure” occlusion. angle lead the orthodontist to prefer gingival (Figure 5b). In a cusp-fossa occlusion, as also cusp-embrasure as the goal. This scheme nnThe third key: crown inclination advocated by Thomas,7 each mandibular provides for freedom of movement in (torque). This refers to labiolingual buccal cusp occludes into the fossa of the lateral and protrusive excursions with inclination of the anterior teeth maxillary counterpart and each maxillary protective cuspid and incisor function. or buccolingual inclination of the lingual cusp occludes into the fossa of the posterior teeth. The upper incisors mandibular counterpart (Figure 1). This Six Keys to Ideal Static Occlusion have a labial crown inclination (positive occlusal scheme, which places maxillary As discussed above, from a static torque). The lower incisors have a slight teeth slightly mesial of Angle Class I occlusal standpoint, Stuart’s distal limit lingual inclination (negative torque). relationship, very effectively directs (tooth-to-two teeth), also referred to as The upper cuspids and posterior forces along the long axis of teeth, an the Angle Class I occlusion, is the typical teeth have lingual crown inclination arrangement that encourages positional goal in orthodontic treatment. In a 1972 (negative torque). The inclination is stability. Furthermore, food impaction landmark article, Andrews9 described similar for upper cuspids and bicuspids between teeth is minimized since no cusp six significant characteristics in his study and slightly more pronounced in the tips strike opposing embrasures, and of 120 cases of non-orthodontic normal molars. Lingual crown inclination there is less tendency for wear of cusp tips occlusions that have since become (negative torque) also exists in the and occlusal attrition. additional goals for a well-finished lower cuspids and posterior teeth In a cusp-embrasure occlusal orthodontic case. It is important to note and progressively increases from the scheme, all teeth, with the exception that the subjects in Andrews’ study all cuspids through the second molars of mandibular central incisors and had naturally straight teeth with pleasing (Figure 5c). maxillary third molars, have a tooth- smiles; their casts occluded in a generally nnThe fourth key: no rotations. Rotated to-two teeth relationship (Figure 2). ideal position, and they had never received teeth occupy more space within the

october 2000 781 0cclusion

cda journal, vol 28, nº 10

dental arch (Figure 5d). lower teeth are closed into MI. It has of the maxillary incisors to the facial nnThe fifth key: no spaces. All contact been shown that the displacement of the surfaces of the mandibular incisors points are tight (Figure 5e). condyles from the above position caused and 1 mm of overjet from the tip of the nnThe sixth key: the occlusal plane. The by intercusping of teeth (i.e., CR-MI maxillary canine to the facial surface of occlusal plane may vary from generally discrepancy) should ideally be less than 1 the mandibular canine. flat to a slight curve of Spee F( igure 5f). mm vertically and horizontally and less These important findings gave than 0.5 mm transversely.11,12 Mounted Models in Diagnosis and rise to pre-adjusted orthodontic nnTo achieve optimal functional Treatment Planning brackets, incorporating specific built- occlusion, the teeth should be For diagnosis and treatment planning, in adjustments that produce ideal tip, positioned so that they create what orthodontists have traditionally relied on torque, in/out, and rotational tooth has been termed a mutually protected hand-held study casts trimmed with an positions, significantly reducing the need occlusal scheme. In this scheme, MI interocclusal wax registration (Figure for archwire adjustments throughout the posterior teeth protect anterior teeth 8). Many orthodontists analyze the course of orthodontic treatment. from lateral stress at full closure; and functional status of the patient’s occlusion the anterior teeth protect posterior as part of their diagnosis and treatment Goals of Ideal Dynamic Occlusion teeth from lateral stress during plan. To that end, study casts are Dynamic occlusion requires that the mandibular movements, as long as mounted on a semi-adjustable articulator teeth function during jaw movements the condyles are permitted a gliding with a CR interocclusal wax registration. free from premature contacts and movement along the eminentia. In To produce such a wax registration, the interferences. To achieve this, one must MI, there are simultaneous occlusal operator must guide the mandible into pay particular attention to static tooth contacts around centric cusps of centric relation by seating the condyles positions, to condylar position upon posterior teeth directing the closure in a superior-anterior direction within closure into occlusion, and to mandibular stress along their long axes. In the glenoid fossa (Figure 6). This is border movements as determined by the addition, there is no actual contact of accomplished by supporting the angles temporomandibular joints. Roth10 has the anterior teeth in MI, but a slight of the mandible in a superior direction demonstrated that if the orthodontist is clearance detectable by a 0.0005-inch while pushing gently down on the chin able to finish cases to Andrew’s six keys thickness shimstock. Upon movement and asking the patient to relax and close and establish maximum intercuspation of the mandible in any direction from slowly (Figure 9a). Although different CR in harmony with centric relation, then full closure (left and right lateral interocclusal wax registration techniques Stuart’s goals of ideal functional occlusion excursions and straight protrusion), have been proposed, the two-piece “power can be achieved. Although still not the anterior teeth and canines provide centric” technique has shown merit in universally accepted and practiced by all a gentle guide ramp that allows the seating the condyles as close to CR as orthodontists, many of these functional condyles to traverse the eminentia, possible (Figure 9b).12-14 The term power occlusion principles have received and disclude the posterior teeth on the centric refers to the use of the patient’s significant recognition in the specialty. working and balancing sides (Figures closure muscles (masseter, medial Essential to the stability of an ideal 7a through d). The condylar guidance pterygoid, and the superior head of the occlusion is the relationship between expressed by the morphology of the lateral pterygoid) to seat the condyles in centric relation (CR) and maximum joints is the major determinant of the desired direction.11 intercuspation (MI). Centric relation will the overbite-overjet relationship of Using centric relation mounted study permit seating of the condyles into the anterior teeth and canines, and the casts (Figure 9c), one can evaluate the glenoid fossa against the articular discs major determinant of posterior tooth following aspects of the dental-orthopedic at the most superior position against positioning and archform.11 Generally complex: the eminentia and also centered in the speaking, when teeth are in MI with nnRelate the position of the maxilla to the transverse plane of space (Figure 6). In the condyles seated in CR, there must cranial base; an ideal orthodontic finish, this condylar be 4 mm of vertical overbite and 2 to nnRelate the mandible to the maxilla with position should occur when upper and 3 mm of overjet from the incisal edges the condyles seated in centric relation;

782 0ctober 2000 0cclusion

cda journal, vol 28, nº 10

and the condyle is balanced or stable, without strain or stress within the Figure 1. Cusp-fossa (tooth-to-tooth) occlusion (From McNeill C, ed, Science and Practice of Occlusion. Quintessence articular fossa.20 It is critical to identify the Publishing, Chicago, 1997, p 408). patient’s proper CR before any orthodontic treatment is initiated, rather than see it surface halfway through the treatment. As the position of teeth is altered with orthodontic appliances, the patient’s MI adapts continuously, and the only reliable reference point is centric relation. There are, however, times when capturing a reliable CR record on a patient is unlikely, due to muscular interventions. In such Figure 2. Cusp embrasure occlusion (tooth-to-two-teeth). cases, a period of splint (orthotic) therapy, prior to active orthodontic treatment, can deprogram the patient’s muscular and proprioceptive influences, allowing position indicator and mandibular uninhibited condylar seating (Figure 11). position indicator are instruments used with the Panodent and SAM articulators, Developing Malocclusions: Six Warning respectively. They are designed to Signs in a 7-Year-Old record the position of the condylar Most referrals for orthodontic axis and measure CR/MI discrepancy treatment are occlusion-related.21 Many in three planes of space and have been warning signs of developing malocclusions demonstrated to be both accurate and appear in the early mixed dentition. reliable (Figures 10A and B).16-19 One can Ideally, children should be screened for bring this information to the lateral orthodontic treatment no later than age cephalogram, which is typically taken in 7, when the posterior occlusion has been Figure 3. Cusp-fossa (above) vs. cusp-embrasure MI, and correct the mandibular position established by the eruption of the six-year occlusion (From McNeill C, ed, Science and Practice of Occlusion. Quintessence Publishing, Chicago, 1997, page 315). to CR on the tracing of the cephalogram molars. This allows the orthodontist to prior to cephalometric analysis (Figure evaluate anteroposterior and transverse 10c). This, in addition to the CR mounted relationships of the occlusion, as well as models, will allow the orthodontist to any functional mandibular shifts. The nnPlan treatment to a reproducible develop a diagnosis and treatment plan presence of permanent maxillary and condylar position, allowing while accounting for centric relation. mandibular central and lateral incisors examination of excursive mandibular Mounted study casts are only as reveals arch length discrepancies, habit movements; and accurate as the interocclusal and facebow patterns, and vertical dimension problems nnDetect the point of initial tooth record that was used to construct the such as deep bite, open bite, or gummy contact, unmasking occlusal mounting. The accuracy of the interocclusal smile. Most facial asymmetries appear by interferences and evaluating the cant of record (wax bite registration) is only as age 7. To raise the awareness of the public the occlusal plane.15 good as the ability of the practitioner and establish an easy-to-follow set of The degree of discrepancy between in registering the patient’s bite. The guidelines for general practitioners, the CR and MI can not only be qualitatively possibility of correctly registering that California Association of Orthodontists assessed, but also quantitatively measured bite is directly dependent on whether has introduced a brochure called “Bite in three dimensions of space using the patient’s muscles of mastication are Down Early” that outlines the six warning additional instrumentation. The condylar relaxed (i.e., without spasm or splinting), signs in 7-year-olds (this brochure may

october 2000 783 0cclusion

cda journal, vol 28, nº 10

be ordered by calling the California underlying habit such as tongue thrust, asymmetries (Figures 12h and i). Association of Orthodontists at [415] finger sucking or mouth breathing due Close attention to these early 441-2416). 22 to respiratory dysfunctions or blocked warning signs and timely referral to airways (enlarged tonsils and adenoids) the orthodontist can prevent more Six Warning Signs (Figure 12e). complicated later treatments for the nnIs there excessive horizontal overlap nnIs there spacing/crowding between the patient. Many unfavorable growth (overjet)? Protrusion of the upper front teeth? Teeth are overlapped and rotated patterns may be altered if early treatment teeth (Figure 12A). or there are noticeably large gaps is rendered with growth-modification nnIs there excessive vertical overlap (deep between them (Figures 12f and g). appliances. Arch development with bite)? Lower incisors near the palatal nnDo the upper and lower midlines expansion devices can be provided in the tissue (Figure 12B). coincide? The maxillary and mandibular early mixed dentition to correct crossbites nnIs there a crossbite of the anterior or midlines should be coincident and and relieve crowded arches and in some posterior teeth? The upper teeth fit should both also align with the facial cases prevent extraction of permanent inside the lower teeth (Figures 12c and d). midline (mid-sagittal plane). If the teeth. Elimination of habits is also nnIs there an open bite? The child can midlines do not coincide, there may be significantly more successful and stable if stick his/her tongue between the upper many causes, including impacted teeth, addressed in the early mixed dentition. and lower front teeth when back teeth functional mandibular shift, uneven Referral for an orthodontic screening are together. This may indicate an mandibular growth, and midface at age 7 does not always result in immediate treatment but allows the orthodontist to determine how and when a child’s particular problem should be treated for maximum improvement with the least amount of time and expense. Many orthodontic problems will best await treatment until the late mixed dentition or permanent dentition.

Figure 4. A finished orthodontic case, which required extraction of upper bicuspids and a lower incisor, presents with an atypical, yet functionally acceptable, occlusion.

Figure 5a. The first key: molar relationship (courtesy of Figure 5b. The second key: crown angulation (tip). Figure 5c. The third key: crown inclination (torque). GAC International).

Figure 5d. The fourth key: no rotations. Figure 5e. The fifth key: no spaces. Figure 5f. The sixth key: the occlusal plane.

784 0ctober 2000 0cclusion

cda journal, vol 28, nº 10

Orthodontic Treatment and many opinions on these topics. Most Temporomandibular Disorders reports suggest the lack of any correlation Does orthodontic treatment cause between occlusion, orthodontic temporomandibular dysfunction (TMD)? treatment, and TMD. Signs and Is occlusion an etiologic factor in signs symptoms of TMD after orthodontic Figure 6. Centric relation allows seating of the condyles and symptoms of TMD? Do occlusal treatment were found to occur in some superiorly and anteriorly within the glenoid fossa (From changes created by orthodontic treatment cases, but no connection was observed McNeill C, ed, Science and Practice of Occlusion. Quintessence Publishing, Chicago, 1997, Page 507). predispose an individual to increased between TMJ-related functional risk for TMD? Several studies have been disturbances and a well-planned and well- conducted to answer these questions, but executed orthodontic therapy.29 Several may benefit from a period of behavior there is still a great deal of controversy. long-term research studies have indicated modification, physical therapy, and even Many studies conducted have suffered that orthodontics is not a cause of TMD.30- CR-positioning splint therapy before any from flaws in research technique. This 32 Conversely, no data exist to support active orthodontic treatment begins. combined with the complexity and the notion that orthodontic treatment the multifactorial nature of TMD has of children or adults prevents or lowers The Importance of Occlusion in contributed to some uncertainty. the risk of subsequently developing Orthodontic Treatment One particular shortcoming is the TMD.33 Further, studies have found that Can the orthodontist achieve good lack of quantitative information at the orthodontic treatment does not appear functional occlusion routinely with condylar level. Most measurement criteria to pose an increased risk for development orthodontic treatment? Yes, in most have been based on changes at the occlusal of TMJ sounds or symptoms, regardless cases. Is it easy to achieve? No. Striving level, either intraorally or with hand-held of whether extraction or non-extraction for excellence in treating each case to study casts, or on tomographic assessment treatment has been rendered.34 functional ideals is challenging. The goals of the condyles. Researchers have looked Orthodontic patients are not more likely are excellent functional occlusion, stable at the tooth end of the mandible and to develop TMD signs and symptoms tooth position, periodontal health, and have examined anatomical factors such while undergoing treatment.35 Post- a beautiful smile with balanced facial as molar classification, overjet, overbite, orthodontic patients have been shown features, but they are not always possible crowding and subjective clinical inspection to have no more signs and symptoms to achieve. to determine a correlation with TMD of TMD than those with untreated Do ideal occlusion goals apply to signs and symptoms. Such occlusal malocclusion or those with normal the adult patient? Yes, but treatment characteristics are poor indicators of occlusion.33 Studies have failed to connect planning for the adult patient is more condylar position.23-25 Tomography has a period of orthodontic treatment to complicated and requires input from been shown to be unreliable in evaluating either the onset of TMD or a change in the patient’s dentist and perhaps condylar position.26,27 In most studies that TMD signs and symptoms.36 other specialists. Orthodontists view have shown a lack of correlation between If TMD arises during orthodontic freeway space in the growing patient as occlusion and TMD, no instrumentation treatment, observation and palliative care an important ally, allowing changes in has been used to evaluate condylar should precede irreversible treatment the dentition not possible in the adult. position as dictated by the occlusion. approaches. The onset of pain during The lack of jaw growth in adults means Conclusions have been based on chin point treatment will lead the orthodontist to that goals requiring a change in jaw manipulation, intraoral inspection and modify active therapy, reduce forces, shape or size must involve orthognathic hand-held study casts. In a recent study,28 stop headgear wear, eliminate distalizing surgery. Adolescents are quite resistant Crawford showed a reduction in TMD signs forces, minimize or eliminate interarch to periodontal damage in the face of and symptoms using a mutually protected elastics use, or eliminate gross occlusal patient neglect. Adults are not. However, occlusal scheme with CR and MI relatively interferences by occlusal coverage splint with careful interdisciplinary planning, coincidental as measured by condylar therapy.33 Patients who present with TMD remarkable improvements are possible position indicator readings. signs and symptoms, a significant CR/ for the adult patient, and ideal occlusion A review of the literature reveals MI shift, or with severe postural habits, goals need not be set aside.

october 2000 785 0cclusion

cda journal, vol 28, nº 10

Although there are conflicting views Figure 7a. Maximum intercuspation. on the role of malocclusion as a potential risk factor for TMD,32,37,38 there are other reasons for orthodontists to be concerned with functional occlusion. Collision of cusps, if allowed to occur, will cause trauma with potential sequela of , Figure 7b. Left working, right balancing. tooth mobility, attrition, and periodontal breakdown.39 Muscles can fatigue if the neuromuscular protection mechanism must restrict mandibular movement to avoid cusp collision. Such working and/or balancing interferences during mandibular border movements are also Figure 7c. Right working, left balancing. major culprits for significant deviation of MI from CR. Orthodontists want to detect such interferences and eliminate them during orthodontic therapy. Is an ideal functional orthodontic result stable? If only that were so. Patients have to be told that teeth Figure 7d. Left and right protrusive. shift throughout their lives, whether or not there has been orthodontic Figure 9a. treatment, and that the changes are Proper manipulation typically inconsequential. Orthodontic of the mandible to seat the condyles treatment cannot prevent these changes. in a superior- Orthodontists try to evaluate the stability anterior direction of the cases after treatment and make (From McNeill C, ed, Science and decisions about which patients should Practice of Occlusion. indefinitely continue with some sort of Quintessence retention devices. Publishing, Chicago, 1997, Page 507). Conclusion As technologic advances in Figure 8. Hand-held study casts. orthodontic therapy have evolved, orthodontists have widened their diagnostic criteria and treatment goals to include an accurate determination of mandibular position and function. The treatment goal of an ideal static occlusion remains important but is now considered only part of a broader view of an ideal final result. An ideal final result will also include the functional criteria of mutually protected occlusion with centric Figure 9b. Taking a “power centric” relation wax Figure 9c. Study casts mounted in centric relation. relation closely coincident with maximum registration.

786 0ctober 2000 0cclusion

cda journal, vol 28, nº 10

intercuspation. Ideal final results are not always possible. Orthodontic screening

Figure 10b. For this patient, the measurements indicate by age 7 allows good planning for ideal that when in maximum intercuspation, the right condyle is correction of a malocclusion. Correction displaced 2 mm downward and 2 mm backward and the left of many orthodontic problems in the condyle is displaced 2.5 mm downward and 1 mm backward from their respective centric relation positions. There is very developing or adolescent dentition is Figure 10a. Determination of CR-MI discrepancy minimal transverse shift between CR and MI. preferable to waiting until the adult using a condylar position indicator (CPI). dentition. Treatment during this younger period improves the chance of achieving excellent results and better post-treatment stability. In adults, lack of growth and periodontal risk present the orthodontist some diagnostic challenges, but ideal functional occlusion remains a workable goal. The relationship Figure 10c. CR converted lateral cephalogram tracing between occlusion and TMD is still based on the CPI measurements. Figure 11. Full arch hard plastic CR repositioning splint unclear. Research has not established (orthotic). a connection, but reliable analysis of

Figure 12a. Excess overjet. Figure 12b. Deep bite. Figure 12c. Anterior crossbite.

Figure 12d. Posterior crossbite. Figure 12e. Anterior open bite. Figure 12f. Dental spacing.

Figure 12g. Crowding. Figure 12h. Midline displacement. Figure 12i. Midline displacement causes blocked canine.

october 2000 787 0cclusion

cda journal, vol 28, nº 10

22. Bite down early: A parent’s guide to detecting bite condylar position has not been addressed problems. Brochure by the California State Society Of Orthodontists, 1993. in such research. Excellent static occlusal 23. Lundeen HC, Gibbs CH, Advances in Occlusion. John Wright goals and functional goals are now PSG, Boston, 1982, pp 2-32. understood to be critical elements in long- 24. Shildkraut M, Wood DP, Hunter WS, The CR-CO discrepancy and its effects on cephalometric measurements. Angle Orthod term stability of orthodontic treatment. 64(5):333-42, 1994. 25. Wood DP, Elliot RW, Reproducibility of the centric relation References bite registration technique. Angle Orthod 64(3):211-20, 1994. 1. Angle EH, Classification of malocclusion. D Cosmos 41:248, 26. Hatcher DC, Blom RJ, Baker CG, Temporomandibular joint 1899. spatial relationships: Osseous and soft tissues. J Prosthet 2. Aronowitz HI, Orthodontics and occlusion: a historical Dent 56(3):344-53, 1986. perspective. J Cal Dent Assoc 24(10):16-8, 1996. 27. Roth RH, Occlusion and condylar position. Am J Orthod 3. McCollum BB and Stuart CE, A research report. California Dentofac Orthop 107(3):315-8, 1995. Scientific Press, South Pasadena, 1955. 28. Crawford SD, Condylar axis position, as determined by the 4. Stallard H and Stuart CE, Concepts of occlusion. Dent Clin N occlusion and measured by the CPI instrument, and signs and Am 1963:591-606. symptoms of temporomandibular dysfunction. Angle Orthod 5. Stuart CE, Good occlusion for natural teeth. J Prosth Dent 69(2):103-15, 1999. 14:316-24,1964. 29. Keb K, Bakopulos K, Witt E, TMJ function with or without 6. Huffman RW, Regenos JW, Principles of Occlusion, orthodontic treatment. Eur J Orthod 13:192-6, 1991. Laboratory and Clinical Teaching Manual. Department of 30. Baker RW, Catania JA, Baker RW, Occlusion as it relates to Operative Dentistry, Ohio State University, 1973. TMJ: A study of the literature. NY State Dent J 57:36-9, 1991. 7. Thomas PK, Syllabus on full mouth waxing technique for 31. Sadowsky C, Poulson AM, TMD and functional occlusion rehabilitation: tooth-to-tooth cusp fossa concept of organic after orthodontic treatment: Results of two long-term studies. occlusion, 2nd ed. Instant printing services, 1967, pp. 1-10. Am J Orthod 86:386-90, 1984. 8. Moore T, Gnathology and orthodontics. Unpublished thesis, 32. Sadowsky C, BeGole E, Long-term status of TMJ function Angle Society Of Northern California. and functional occlusion after orthodontic treatment. Am J 9. Andrews LF, The six keys to normal occlusion. Am J Orthod Orthod 78:201-12, 1980. 62:296-309, 1972. 33. Greene CS, Orthodontics, orthodontists and TMD. 10. Roth RH, Functional occlusion for the orthodontist. J Clin Summarized by Crouch DL. Pacific Coast Society of Orthod part 1, 15:32-51; part 2, 15:100-23, part 3, 15:174-98; part Orthodontists Bulletin, Winter 1990, 33-5. 4, 15:246-65, 1981. 34. Sadowsky C, Theisen TA, Sakols EI, Orthodontic treatment 11. Roth RH, The Roth functional occlusion approach to and TMJ sounds -- A longitudinal study. Am J Ortho Dentofacial orthodontics, Roth/Williams Center for Functional Occlusion. Orthop 99:441-7, 1991. Course syllabus, 1999. 35. Hirata RH, Heft NW, Hernandez B, Longitudinal study 12. Williamson EH, Steinke RM, et al, Centric relation: A of signs of TMD in orthodontically treated and nontreated comparison of muscle-determined position and operator groups. Am J Orthop Dentofacial Orthop 101:35-40, 1992. guidance. Am J Orthod 77(2):133-45, 1980. 36. Rendell JK, Norton LA, Gay T, Orthodontic treatment and 13. Wood DP, Floreani KJ, et al, The effect of incisal bite force temporomandibular joint disorders. Am J Orthod Dentofacial on condylar seating. Angle Orthod 64(1):53-62, 1994. Orthop 101:84-7, 1992. 14. Lundeen HC, Centric relation records: The effect of muscle 37. Righellis EG, Commentary: Condylar axis position and action. J Prosthet Dent 31(3):244-53, 1974. temporomandibular dysfunction, Angle Orthod 69(2):115-6, 15. Kasrovi PM, Mounted models, tomorrow’s technology? 1999. Pacific Coast Society of Orthodontists Bulletin, pp 43-44, 38. McNamara JA, Okeson SA, Occlusion, orthodontic Fall 1999. treatment, temporomandibular joint disorders: a review. J 16. Slavicek, R, Part 4 instrumental analysis of mandibular Orofacial Pain 9:73-90, 1995. casts using the mandibular position indicator. J Clin Orthod 39. Burgett FG, Trauma from occlusion, periodontal concerns. 22:566-575, 1988. Dent Clin N Am 39(2):301-11, 1995. 17. Utt TW, Meyers CE, Wierzba TF, A three-dimensional To requested a printed copy of this article, please contact: comparison of condylar position changes between centric Paul M. Kasrovi, DDS, MS, 8201 Edgewater Drive, Suite 101, relation and centric occlusion using the mandibular position Oakland, CA 94621. indicator. Am J Orthod Dentofacial Orthop 107:298-308, 1995. 18. Wood DP, Korne PH, Estimated and true hinge axis: a comparison of condylar displacements. Angle Orthod 62(3):167-75, 1992. 19. Lavine DS, Kulbersh R, Bonner PT, Reliability of the condylar position indicator. University of Detroit, In press. 20. Lundeen HC. Centric relation records: The effect of muscle action. J Prosthet Dent 31(3):244-253, 1974. 21. Nurminen L, Pietilea T, Motivation for and satisfaction with orthodontic-surgical treatment: a retrospective study of 28 patients. Eur J Orthodont 21(1):79-87, 1999

788 0ctober 2000 gp guide

cda journal, vol 28, nº 10

A Practical Guide to Occlusal Management for the General Practitioner

Gordon D. Douglass, DDS, MS; Larry Jenson, DDS; and Daniel Mendoza, DDS

abstract The general dentist has a unique role as the gatekeeper of dental care. In this role, the generalist is called upon to be the primary diagnostician and is charged with the responsibility for triaging patients. Classification systems devised by many of the dental specialties are valuable tools for the diagnosis of diseases and conditions specific to the specialty, but no classifications have been directed to the general dentist. This paper describes a system being used at the University of California at San Francisco School of Dentistry that enables the general dentist to classify a patient’s stomatognathic system as either physiologic or nonphysiologic and then guides the clinician toward appropriate treatment decisions.

authors otwithstanding years of acceptance of the restoration. Gordon D. Douglass, DDS, Larry Jenson, DDS, is an research, the role of occlusion A recent review of experimental MS, is a clinical professor assistant clinical professor in the Department of in the Department of in a broad spectrum of diseases occlusal interference studies by Clark 5 Preventive and Restorative Preventive and Restorative still seems to be an area of and colleagues suggests a reason dental Dental Sciences at the Dental Sciences at UCSF. disagreement, confusion, practitioners have a strong regard for University of California at Nand misunderstanding.1-4 Although the the importance of occlusion. When San Francisco School of Daniel Mendoza, DDS, is an give-and-take of experienced academics Clark and colleagues assessed studies Dentistry. assistant clinical professor in the Department of and clinicians is healthy and will in time on the effects of experimentally induced Preventive and Restorative lead to a meeting of the minds, in the real occlusal interferences on the periodontal Dental Sciences at UCSF. world of clinical dentistry, most general and pulpal tissues of affected teeth, they dentists would argue that occlusion is a found a definite correlation between significant consideration in their care of those interferences and deleterious patients. For the clinician, this respect for tissue changes. This suggests that an the subject began in dental school, when, induced occlusal prematurity will most with his or her first placement of a cast likely lead to patient discomfort and occlusal restoration, a significant amount tissue deterioration. But, they also of clinical time was spent adjusting found these traumatic and inflammatory the occlusion to obtain the patient’s changes to be transient. In other 792 october 2000 gp guide

cda journal, vol 28, nº 10

words, if a patient can tolerate an literature offers little to guide the general occlusal stability. The Braly classification artificially induced occlusal prematurity, practitioner in the assessment and system has since been modified, accommodation is likely to occur. The management of occlusion. For example, expanded, and incorporated into the problem in dental practice is that most the Lytle and Skurow classification6 teaching program at UCSF to be used as patients will not just “stand it,” so clinical uses the complexity of periodontal an aid in teaching comprehensive patient procedures must be planned to avoid and restorative needs to identify four care to students of general dentistry. creating an occlusal prematurity or, classes: operative dentistry, crown and This paper will use a portion of the UCSF worse, creating a prematurity to which a bridge, occlusal reconstruction, and Braly-type classification and draw from patient’s stomatognathic system may not periodontal prosthesis. It allows the the clinical experience of the authors accommodate. clinician to determine a restorative class in presenting a guide for assessing and The general dentist is unique among and treatment protocol for the patient. managing occlusion in the daily care of dental professionals in his or her However, differentiation between the general dental patients. It will be divided responsibility for seeing a diverse population classes is based upon the technical into three sections: diagnosis, treatment of patients where the assessment of dental difficulty of the anticipated restorations, planning, and treatment procedures. health is frequently done as a routine not on the diagnosis of existing occlusal procedure, not associated with specific abnormality. Diagnosis patient complaints. The chronic nature The popular Angle classification of As health care providers, dentists of the conditions and diseases treated by “malocclusions” is used extensively in should all subscribe to the basic logic of dentists is akin to beginning a comic strip orthodontics. This classification is based patient care: Data acquisition through in the middle, trying to hypothesize what upon morphological differences between examination and history must necessarily came before, and then predicting the finish. patients. However, when taken in context precede a diagnosis, which in turn What the general practitioner must do is with other measures of dental health for must necessarily precede treatment evaluate signs and symptoms of chronic a given individual, Angle’s classes may be recommendations. Adherence to this change of the stomatognathic system and found to be physiologically sound. At the simple scheme helps ensure that dentists ask the question: Is the stomatognathic University of California at San Francisco develop the most appropriate treatment system healthy (stable) or unhealthy School of Dentistry, Angle’s classification plans for their patients. Yet dentists often (unstable). For example, a symptom-free is considered to be of morphologic place more emphasis on their examination 20-year-old patient with severe attrition of variations not malocclusions.7 findings and treatment recommendations the occlusal surfaces should give more cause Another classification system, developed than on the diagnoses. For example, for concern than an 80-year-old patient by Helkimo,8 classifies dysfunction of the it is a rare dental chart that has a with the same amount of occlusal wear, temporomandibular joint in three types designated area for diagnoses. And, unlike because a system suffering from premature according to the scoring of a dysfunction physicians, dentists are not accustomed to destruction must be considered unhealthy. index with five parameters. The parameters determining and providing the appropriate Following the discovery phase, the dentist are impaired range of motion, impaired diagnostic codes to insurance companies must determine the appropriate care of the TMJ function, muscle pain, TMJ pain for reimbursement of completed system and whether that care is within his to palpation, and pain upon mandibular procedures. Perhaps this is not surprising or her capabilities. The purpose of this paper movement. This classification is a valuable when one considers that the diagnoses is to offer a useful classification system to tool for the assessment of TMD, but it does dentists generally make are, for the most support the general dentist’s evaluation and not address intraoral findings. None of the part, unproblematic. The findings that care of patients. aforementioned classifications addresses the lead to a diagnosis of caries or periodontal situation of the general dental practitioner. disease are usually obvious and rarely Existing Classifications A more broadly based system directed suggest competing diagnoses that require Although classifications have proven toward the general dentist was initially careful differential analysis. Occlusion- to be useful tools in the assessment published by Braly9 in 1972. Braly based associated, degenerative processes in the and management of dental problems his classification on patient data and the stomatognathic system, however, are not in a number of specialty areas, the need to maintain, modify, or re-establish as straightforward. While dentists may all

october 2000 793 gp guide

cda journal, vol 28, nº 10

do a good job of examining the occlusion unopposed super-erupted third molar). for the Case Type I is to avoid affecting and recording their findings, it is the next Finally, a Type C patient might present the stomatognathic system adversely step – making the diagnosis – that often with a severe retrognathic mandible and by whatever restorative or preventive proves troublesome. dysfunctional TMJs requiring complex (sealants, etc.) procedure is required as a Periodontal specialists have provided multidisciplinary evaluation and care. part of routine dental care. Some would a good model to diagnose destructive Case Types I-III are related to findings argue this is technically the hardest of the processes and direct appropriate care.10 The for which treatment will require dental case types to manage (Figures 1a and b). now-standard case-type designations (I-IV) restorations. Since, at present, general Case Types II and III define a system for periodontal disease aid the general dentistry is primarily restoration-based, that is not functioning within the dentist in arriving at a diagnosis and this paper’s focus has been limited to Case expected norms and is, therefore, termed possible treatment. , Types I-III. nonphysiologic (Figures 2a and b, 3a and increased pocket depth, attachment loss, For purposes of this article, the b). Typical findings associated with a and other findings now lead to a particular stomatognathic system is defined as nonphysiologic system may include case-type designation based on accepted the combination of structures involved unrestored missing teeth; limited TMJ criteria. Treatment recommendations in speech; receiving, mastication, and function; tissue inflammation; pain; tooth can then follow logically from a given deglutition of food; and parafunctional hypermobility; a loss or replacement of diagnostic type (e.g., a diagnosis of actions.11 Evaluation of this system tooth structure beyond that expected gingivitis [Case Type I] necessarily excludes involves both an examination of these for the age of the patient (e.g., a young root planing from the list of treatment structures and an examination of patient with extensive caries, multiple recommendations and necessarily includes the functional relationship between root canals, crowns, fixed and removable oral hygiene instruction). them. Occlusion is defined as the static partial dentures, and/or severe occlusal At the UCSF School of Dentistry, a relationship between the incising or wear); and an “abnormal” RCP to ICP modified Braly9 classification system masticating surfaces of the maxillary or shift. An “abnormal” shift is defined is used to establish a “physiologic” or mandibular teeth or tooth analogues.12 as one in which a causal relationship “nonphysiologic” designation for the To be designated physiologic, the with clinical findings such as mobile stomatognathic system in a manner stomatognathic system must be healthy, teeth, tooth fracture, and tooth wear is similar to the one used by periodontists. stable, and functioning within the suspected. Case Type II is distinguished The system designates six Case Types expected norms, i.e., no detectable from Case Type III by the absence of TMD (A-C and I-III) that allow for treatment tissue degeneration nor pain in or other dysfunctional findings. decisions based upon a thorough associated structures. To be designated evaluation of the stomatognathic system. nonphysiologic (unhealthy, unstable), Treatment Planning Restorative Case Types A-C are related to findings the system must display evidence of Procedures for which treatment will not involve past or present unexpected degenerative Treatment planning with the goal of the restoration of tooth structure. For processes. Findings are the clinical maintaining or acquiring a physiologic example, a Case Type A patient might evidence needed to support a diagnosis system requires the perspective present with soft tissue pathology such and, ultimately, treatment decisions. that there is not just one restorative as , candida infection, or As described by Stroud,13 shifts material, technique, or procedure that is cancer. For this case type, no restorative from RCP to ICP found in symptom- appropriate for every case type. Each case procedure is necessary; and the goal free patients are subject to considerable type must be addressed individually and of treatment should be to maintain an “normal variation” without evidence to the materials, techniques, and procedures otherwise physiologic stomatognathic suggest an etiology in temporomandibular tailored to the goal for that type. system. A Type B patient might present joint dysfunction. For this classification, a with occlusal discrepancies causing normal shift is described as one for which Case Type I discomfort in individual teeth for which a causal relationship with clinical findings As described above, the goal in the treatment might include occlusal cannot be found (tooth mobility, fracture, treating the stomatognathic system of a adjustment or extraction (such as an excessive occlusal wear, etc.). The goal patient diagnosed as a Case Type I is to

794 0ctober 2000 gp guide

cda journal, vol 28, nº 10

render necessary care that will maintain a system found to be functioning in a physiologic fashion. Treatment planned for the Case Type I patient should not Figure 1a. A Case Type I patient: This 35-year-old patient Figure 1b. A Case Type I patient: This 42-year-old alter the physiologic health of the existing presents with a complaint of poor anterior bridge esthetics. patient presents with a complaint of pain upon chewing Clinical evaluation reveals the stomatognathic system to on the left side. Clinical evaluation reveals a fracture of system, so the clinician must choose be physiologic. Treatment procedures should, therefore, be the distolingual cusp of the lower left first molar due to an materials and techniques that are least directed toward techniques and materials that will maintain extensive undermining restoration. Other than this finding, the likely to adversely affect the system. As the healthy function of the existing system. stomatognathic system is physiologic. Treatment procedures in this case should be directed toward the selection and use clinicians, however, dentists frequently of a restorative material that will not compromise the normal fail in this regard. For example, it is not physiology of the existing system. uncommon to see as many as four or five different materials (porcelains, resins, alloys, and hybrid materials) used to restore occlusal surfaces and interspersed around a patient’s dentition. One of the best materials for maintaining a physiologic occlusion is gold. Unfortunately, gold is not tooth- colored; and the result is that for the sake of esthetics many young dentitions have been started on the road to destruction Figure 2a. A Case Type II patient: This 38-year-old Figure 2b. A Case Type II patient: This 42-year-old with the placement of a highly abrasive patient presents with a complaint of an inability to chew patient presents with a complaint of worn teeth and anterior feldspathic porcelain restoration.14-17 efficiently. Clinical evaluation reveals extensive loss of esthetics. Clinical evaluation reveals heavy attrition and Hopefully, the development of new, more teeth, loss of alveolar support, large restorations, and an chipping of the anterior teeth, but no evidence of craniofacial ill-fitting removable partial denture, but no evidence of a pain, TMD, nor other dysfunctional relationship. Treatment physiologic materials with acceptable dysfunctional craniomandibular relationship. The severity procedures should, therefore, be directed toward modifying esthetic properties will result in less of the oral conditions, however, suggests a nonphysiologic the factors contributing to the destructive process prior to destruction. stomatognathic system. Treatment procedures should, initiating restorative care. therefore, be directed toward modifying the factors contributing to the destructive process. Case Type II Once a diagnosis of a nonphysiologic Case Type II has been made, appropriate treatment might include occlusal adjustment, orthodontics, restorations, or other procedures that directly address the causative element in the destructive process. Examples include adjustment of an occlusal prematurity to correct individual tooth mobility, an orthodontic procedure to correct tipping or drifting teeth, a fixed Figure 3a. A Case Type III patient: This 52-year-old Figure 3b. A Case Type III patient: This 50-year-old partial denture to stabilize the arches, patient presents with a complaint of pain on chewing. Clinical patient complains of tipping teeth and an inability to incise. placement and restoration of implants, evaluation reveals extensive loss of teeth, drifting and Clinical evaluation reveals a need for multiple restorations or the use of various modalities (occlusal super-eruption of the remaining teeth, deep anterior vertical but healthy gingival tissues. The lower right posterior teeth overlap, and TMJ pain. This patient is diagnosed as having are flaring facially, and the posterior bite is opening. Further splints, nightguards, biofeedback therapy, a nonphysiologic dysfunctional stomatognathic system. analysis reveals a severely deviated swallow, suggesting etc.) to modify destructive-habit patterns. Treatment must, therefore, be directed toward re-establishing a nonphysiologic dysfunctional stomatognathic system. The determination that a system is a functional stomatognathic system. Treatment for this patient must be directed toward correcting the dysfunctional relationships before restorative procedures not or has not functioned physiologically can be undertaken.

october 2000 795 gp guide

cda journal, vol 28, nº 10

must lead the clinician to a careful the average general practice and should however, is one of the biggest challenges assessment of those factors contributing be referred to an appropriately trained to indirect restorative techniques. to the degenerative processes. In addition individual capable of managing the Douglass19 described two variables to the usual patient data, one of the most necessary multidisciplinary care. Proper that influence the clinician’s ability valuable tools for assessment of the Case treatment might include long-term to accurately register interocclusal Type II patient is an arcon articulator TMD management, orthodontics and relationships. Those described were with casts mounted in RCP (a.k.a. centric orthognathic surgery, periodontics, fixed the movement of teeth within their relation). To hand-hold or mount casts in or removable prosthodontics, or other periodontal ligaments that is necessary ICP (a.k.a. centric occlusion) for diagnostic complex procedures. for any dentulous patient to achieve ICP20 purposes is much like looking out from and the narrowing of the mandible that the home plate of a baseball diamond and Treatment Procedures can occur when the mandible is opened not realizing that a lot of the action in the beyond 25 percent of its maximum.21-23 game takes place behind you. The use of Case Type I The “double-bite” (a.k.a. triple-tray) is casts accurately mounted in RCP allows Treating a stomatognathic system that an example of a closed-mouth quadrant the diagnostician to evaluate the entire is physiologic without the potential for technique that effectively addresses playing field from the backstop. From this destabilizing the existing stability is not the variables described by Douglass. perspective, articulated casts can be used easy. Direct restorative procedures must First, the teeth are impressed while the to assess the relationship between the be carefully performed to avoid altering patient is closed in ICP, and second, the dentition and the supporting structures the occlusion. Occlusal restorations closed mouth impression decreases the and determine the proper procedures should be of minimal widths and designed distortion of the mandible that can occur required to correct any degenerative around occlusal contacts. Areas of restored during an open-mouth impression. The processes a clinician may suspect are occlusion must be carefully adjusted to advantage of a closed-mouth impression associated with the occlusion.13 ensure simultaneous occlusal contacts that technique is the accuracy of the ICP that When the degenerative processes have fit properly into the existing system. can be achieved. been controlled or corrected, subsequent Clinicians should use techniques Quadrant techniques utilizing care of the Case Type II patient can that have the best chance of delivering open-mouth impressions and closed- proceed in a fashion similar to the Case an accurately fitting restoration. The mouth occlusal registrations are subject Type I patient. The same careful selection use of some quadrant techniques and to serious errors, due not only to the of materials, techniques, and procedures bite registration materials that deliver a distortions of the casts but also to is required to maintain the newly acquired restoration in hyper- or hypo-occlusion artifacts inherent in all casts (e.g., relationship. will allow teeth to drift, result in an bubbles, tears). Numerous materials altered functional relationship, and are available for registering interarch Case Type III potentially destabilize a healthy system. relationships. Among these are wax, The most difficult to manage is Will the placement of a restoration acrylic, zinc oxide-eugenol pastes, and the Case Type III. This case type has that is in hyper-occlusion result in a elastomeric materials. All materials dysfunctional problems plus chronic nonphysiologic system? The answer, used to register jaw relationships have disease processes that with current as cited by Clark and colleagues,5 is problems unique to themselves, but knowledge will probably only be managed an emphatic “yes,” but most systems any of these materials used to record a and not cured. Exceptional diagnostic eventually accommodate to the error. closed-jaw relationship will not accurately skills and clinical judgment must be Similarly, a restoration in hypo-occlusion fit a cast made from an open-mouth used to determine the proper approach may result in uncontrolled hyper-eruption impression. Regardless of how meticulous to treatment. Like the complex cancer of opposing teeth and lead to an altered the technique may be, restorations made patient, the Case Type III will likely be functional relationship.18 with direct or indirect techniques must treated by a multidisciplinary team. For Indirect quadrant techniques that always be carefully adjusted clinically to this reason, the Case Type III is NOT utilize ICP are best for the Case Type I. avoid creating an occlusal instability. an appropriate patient for treatment in Recording an accurate jaw relationship,

796 0ctober 2000 gp guide

cda journal, vol 28, nº 10

october 2000 797 gp guide

cda journal, vol 28, nº 10

Case Type II by McNeill requires that the clinician responsibility to the patient to properly Treatment of the Case Type II, by consider restoring to an RCP jaw assess, diagnose, and manage any chronic definition, requires modification of an relationship, for it is this relationship conditions and/or diseases. When it unhealthy stomatognathic system. The that will most predictably achieve comes to diagnosing occlusion-related clinician, therefore, must have a goal the objectives for axial loading and problems, however, few guidelines exist. toward which to work. McNeill20 describes nondeflective contacts.23 This does not This article has presented a classification the objectives for occlusal treatment as: mean that all Case Type II patients should system used at the University of nnMaximum symmetric distribution of have their dentitions modified to close in California at San Francisco to assist the centric contacts in the intercuspal an RCP maxillomandibular relationship the general dentist in the diagnosis, position; if treatment goals can otherwise be treatment planning, and management nnAxial or near-axial loading of the teeth; achieved. As with the Case Type I, of problems associated with the nnAcceptable occlusal plane; procedures must be followed carefully to stomatognathic system. nnGuidance contacts allowing for freedom avoid creating an occlusal prematurity and in closing and excursive gliding the potential for destabilizing the system. References 1. Kao RT, Role of occlusion in periodontal disease. In, McNeill mandibular movements without C, ed, Science and Practice of Occlusion. Quintessence deflection; and Case Type III Publishing, Chicago, 1997, pp 394-403. nnAcceptable vertical dimension of The treatment goal for a patient 2. Okeson JP, Management of Temporomandibular Disorders and Occlusion, 4th ed. Mosby-Year Book, St. Louis, 1998, pp occlusion and interocclusal resting diagnosed as a Case Type III is to re- 149-54. range. establish the stability of a severely 3. Stohler CS, Clinical decision-making in occlusion: A paradigm The more extensive procedures dysfunctional system. This can be an shift. In, McNeill C, ed, Science and Practice of Occlusion. Quintessence Publishing, Chicago, 1997, p 298. generally required in the treatment of intimidating experience for an uninitiated 4. Roth RH, Gnathologic considerations for orthodontic diagnostic Case Types II will most likely clinician. Certainly, novice general therapy. In, McNeill, ed, Science and Practice of Occlusion. force the clinician to utilize open-mouth practitioners would be well-advised to Quintessence Publishing, Chicago, 1997, p 503. 5. Clark GT, Tsukiyama Y, et al, Sixty-eight years of impression, full-arch techniques. But a refer these patients to those with more experimental occlusal interference studies: What have we procedure that utilizes an open-mouth experience and expertise. Developing learned? J Prosthet Dent 82(6):704-13, 1999. impression is subject to distortions the expertise, however, does not require 6. Lytle JD and Skurow H, An interdisciplinary classification of restorative dentistry. Int J Perio Rest Dent 3:9-16, 1987. in the casts as described above for formal graduate programs. Many general 7. Douglass G and DeVreugd R, The dynamics of occlusal quadrant techniques, and, therefore, to practitioners gain valuable experience and relationships. In, McNeill C, ed, Science and Practice of an inability to accurately place these casts expertise through continuing education Occlusion. Quintessence Publishing, Chicago, 1997, pp 69-78. 8. Mandibular function and dysfunction. In, Shaw E, ed, into occlusal registrations made from lectures and interactive study groups. Orthodontics and Occlusal Management. Butterworth- teeth that moved while in the process of As the dentist from whom the Heinemann, Oxford, 1993, pp 259-60. achieving an ICP. majority of patients first seek dental 9. Braly BV, Occlusal analysis and treatment planning for restorative dentistry. J Prosthet Dent 27:168-71, 1972. To best address the limitations care, the general dentist must have the 10. Academy of Periodontology, Dental Insurance Workshop: inherent in the use of full-arch casts, skills to collect data and make a diagnosis Reporting Periodontal Procedures to Third Parties. Scientific, registrations should be restricted to the and the wisdom to recognize his or her Clinical and Educational Affairs Department, Academy of Periodontology: 18, 1992 prepared teeth and carefully trimmed limitations. For the care of patients, and 11. The Academy of Prosthodontics, Glossary of Prosthodontic to limit interarch registrations to very the well-being of the practitioner, it is Terms. J Prosthet Dent 81:101, 1999. small and strategic areas of the casts. The important the general dentist be able to 12. The Academy of Prosthodontics, Glossary of Prosthodontic Terms. J Prosthet Dent 81:88, 1999. purpose of an occlusal registration is to recognize Case Type III patients and the 13. Stroud L, Mounted study casts and cephalometric stabilize the working cast horizontally and complexities associated with their care. analysis. In, McNeill C, ed, Science and Practice of Occlusion. to accurately record the vertical dimension Quintessence Publishing, Chicago, 1997, pp 331-41. 14. Kelley JR, Nishimura I, Campbell SD, Ceramics in dentistry: between the arches. Any material that can Conclusion historical roots and current perspectives. J Prosthet Dent be trimmed and adjusted to best achieve The vast majority of adult patients 75(1):18-32, 1996 this purpose for a specific case should be begin their care with a general dentist. 15. Hacker CH, Wagner WC and Razzoog ME, An in vitro investigation of the wear of enamel on porcelain and gold in the choice of the clinician. As the primary diagnostician, the saliva. J Prosthet Dent 75(1):14-7, 1996. Achieving the objectives as described general practitioner has an enormous 16. Ramp MH, Suzuki S, et al, Evaluation of wear: enamel

798 0ctober 2000 gp guide

cda journal, vol 28, nº 10

opposing three ceramic materials and a gold alloy. J Prosthet Dent 77(5):523-30, 1997. 17. Hudson JD, Goldstein GR, Georgescu M, Enamel wear caused by three different restorative materials. J Prosthet Dent 74(6):647-54, 1995. 18. Okeson JP, Management of temporomandibular disorders and occlusion, 4th ed. Mosby-Year Book, St. Louis, 1998, p 578. 19. Douglass G, The cast restoration -- Why is it high? J Prosthet Dent 34(5):491-5, 1975. 20. Goto T, An experimental study on the physiologic mobility of a tooth. Shikwa Gakuho 71:1415-44, 1971. 21. McDowell JA and Regli CP, A quantitative analysis of the decrease in width of the mandibular arch during forced movements of the mandible. J Dent Res 40:1183-5, 1961. 22. Regli CP and Kelly E K, The phenomenon of decreased mandibular arch width in opening movements. J Prosthet Dent 17:49-53, 1967. 23. McNeill C, Selective tooth grinding and equilibration. In, McNeill C, Science and Practice of Occlusion. Quintessence Publishing, Chicago, 1997, pp 404-15. To request a printed copy of this article, please contact: Gordon D. Douglass, DDS, MS, UCSF School of Dentistry, San Francisco, CA 94143-0758 or at [email protected].

october 2000 799 Dr. Bob cda journal, vol 28, nº 10

A Breath of Fresh Air

ashington, D.C. – The L.A. city fathers have vowed to regain American Geophysical the title this summer. Union warns that ozone nnDetroit – The Detroit News reports depletion, particularly that Toronto’s O2 Spa Bar is North over the Northern America’s first oxygen bar and quotes WHemisphere, is more severe than had Lissa Charron, co-owner, as stating, been previously thought. Much of this is “Literally, people come here to get a attributed to the Senate race in New York. breath of fresh air.” nnwww.oxygentherapy.com – Air pollution What’s going on here? While we in the remains a major threat to Americans, dental profession have been concentrating , Robert E. contributing substantially to the on the hazards of biofilm in our Horseman, nation’s ill health burden. Scientists waterlines and whether the emergence DDS expect no improvement in air quality angle of our veneers is correct, the world until political air time is severely has been running out of oxygen, and the restricted. ozone layer is thinning and developing nnwww.lungusa.com – More than 132 holes like a lace doily. million Americans live in areas that Let’s get our priorities right here, received an “F” for air pollution in an people! The Red Cross and various city, annual report by the American Lung county and state emergency agencies have Association. Perrier, progenitor of the thus far failed to mobilize. The governor bottled water craze, is about to mount has declared no crisis and Rosie O’Donnell a massive ad campaign for its new has been uncharacteristically mute on bottled air product (OxyMoxie), due the subject. Barbara Walters has yet to out this fall. interview a single anoxia victim. But nnLos Angeles – For the first time since without official sanction, enterprising and record keeping began, Houston’s level civic-minded citizens are opening oxygen- of ozone concentration exceeded the dispensing facilities all over the continent. levels of former champ Los Angeles. Dentists -- who, by federal edict,

812 october 2000

dr. bob

cda journal, vol 28, nº 10

have oxygen available at all times in their his or her 20-minute limit, become over- component. That would be Dr. Norman offices -- seemingly have ignored this euphoric and demand one more whiff H. Edleman, medical affairs consultant for vital adjunct to their practice for reasons for the road, the oxygen barkeep has the the American Lung Association. that are not quite clear. Instead, we have same moral obligation to refuse service as “From a purely scientific point of blithely glossed over blue-tinged lips and a regular liquid-bar attendant. Naturally, view,” he says, “it’s hard to substantiate indigo fingernails, incorrectly assuming designated drivers will soon be the norm what the benefits could be. Maybe they were Revlon’s new summer hues. for inebriates who experience an oxy-kiwi restricted to 20 minutes of consumption, Patients’ odd and sometimes high, and, inevitably, 12-step programs the risks could be minimal, but pure eccentric behavior has been diagnosed as will have to be formed for oxyholics. oxygen can be an irritant; taking it could postmenopausal, mid-life crisis-oriented, Meanwhile, avant garde dentists are be dangerous to people with severe or pure cussedness when the real reason offering the oxygen-deficient public Smile chronic bronchitis or emphysema.” was right before our eyes. Underwater Clinics and Halitosis Centers. Without Obviously oxygen can be addictive. divers readily recognize the phenomenon even a health factor to justify their Accurate figures on how many people are as “rapture of the deep” or nitrogen existence, these enterprises emerge as already dependent on the gas just to make narcosis. This condition was heretofore opportunistic at best. Is this pathetic, or it through their day are not available. confined to divers going too deep what? We are not suggesting that they It should also be noted that going “cold underwater and staying too long. be abandoned, important as they are to turkey” is not a recommended treatment This is exactly what is happening the economy and national defense, but if modality since addicts seldom live more now on the surface as our O2/nitrogen dentists are to continue to merit the trust than 10 minutes upon withdrawal. ratio drops. So says Mr. Ed McCabe (Mr. and loyalty of their patients, they must You might as well tell patrons of Oxygen), who can be found endorsing rethink their office air. Biofilm in the Starbucks that coffee will keep them a product called Hydroxygen Plus on water can wait. awake, especially if they drink $16 worth the Web. McCabe, who was recently Here’s what you do: O2 Consulting, in 20 minutes. There will be those few foot released from 547 days in jail on an which can be found on the Net at www. draggers who think 80 cents a minute unrelated matter, states that the product oxygen4u.com, will aid in setting up an for something they’ve been getting for synergistically combines oxygen, oxygen bar in your office; or, as a sort of free up till now is excessive. We can only hydrogen, minerals and 34 metabolic getting-your-feet-wet introduction, they remind them of some of the innovative and digestive enzymes to alleviate “this will cater an oxygen party for you. ideas that have made America what it is problem.” An oxygen party sounds like loads of today, such as the Tucker automobile; the This problem, he says, seems to be fun. Matt or Bran of party@oxygen4u. new, improved Coca Cola; sitcom laugh that we are simply not getting enough com describe it this way: “You sit next tracks; and the Nehru jacket. oxygen. Ed confirms that most viruses, to a large hookah with four sprawling So dust off that O2 tank in your office parasites, bacteria, fungus and pathogens tentacles like an industrial octopus and that’s been waiting for a dental emergency are anaerobic and therefore cannot live flasks of water bubbling at the end of for years. Don’t be caught waiting at the in oxygen. Ed is pretty sure about this each limb. The oxygen’aperitif’ comes in post when that first über-hip patient and so are a lot of others. Thus, the orange, mint, or lemon flavors (you can demands a couple liters of the pure stuff, proliferation of oxygen bars where, for $16 even come away feeling happy, focused, even if it’s not a covered benefit. for 20 minutes of refreshment, you can or invigorated by the addition of ‘special’ pop in off the street, insert a canula up aromatherapies). The gaseous cocktail your nasal passages and “chat, drink juice, bubbles away as the tubing is wrapped relax, whatever.” around your ears and put up your nose.” Ninety-nine percent pure oxygen may Just the ticket to abort that appear to be short of the mark to some bloato feeling after a spree among individuals who are used to nothing but the carbohydrates. As described, this the best. Even Ivory soap is 99 44/100 party would seem to be an even greater percent pure. They can be appeased by attraction than the popular sensory ordering flavored air -- orange, kiwi or deprivation tank soiree. lemon-lime -- as an extra cost upgrade. Exciting as all this is, somebody Should a customer inhale more than was bound to pop up with a gloom

october 2000 813