2006 Prosthodontic Knowledge Co-Op

2006 Prosthodontic Knowledge Co-op Exam 2

Chapter 1: The Edentulist Predicament Edentulism is considered a serious emotional life issue. Patient responses and perceptions are an integral part of the clinical decision making paradigm for complete dentures. Many patients are considered to be “maladaptive” to dentures, and despite many of the dentists best efforts, some patients just can’t handle dentures. Patient’s ability to adapt to new dentures depends on many different things, both biomechanical as well as psychosocial. Patient’s mouths do change, both bones and other supporting tissues, plus their neuromuscular control. A patient’s mindset is also a major factor. Research has failed to take into account all these things to predict the best complete denture service.

Implant Prosthodontics:  Involves endosseous anchorage in mandible  Research in 1982 led the way, before there were many failed efforts o Greatly helps maladaptive denture wearers  As dentists, still very important to have knowledge of complete dentures without implants. Implants are not always the best option  For complete dentures, implant-supported overdentures are the endorsed the most

Chapter 2: Biomechanics of the Edentulous State  It is inaccurate to state caries and periodontal disease as sole cause of edentulism  Edentulism due to combinations of: Cultural, Financial, Past Treatment, and Dental Disease Determinants  In future, need for dentures will decline, partial tooth replacement increase o Older old people will be needing dentures, though o This means more difficult mounts for dentist  Patients look at edentulism as a handicap  Presents range of biomechanical problems for patient

Support Mechanisms for NATURAL DENTITION:  Masticatory system behaves quite differently from dentulous to edentulous  Teeth function properly only if adequately supported (periodontium)  PDL transmits forces to bone  Forces on teeth include mastication and deglutition (random biting) o Others by tongue and circumoral musculature o Lingual forces are greater than buccolabial forces  17.5 minutes/day teeth are subjected to FUNCTIONAL forces, that’s all o Within tolerance level of healthy periodontal tissues Support Mechanisms for COMPLETE DENTURES:  Normal arch has 45 cm2 of area to cope with forces  Mean denture-bearing area is 22.96 cm2 in Maxillary, 12.25 cm2 in Mandibular  44 lbs. of pressure for natural teeth during mastication, 13-16 lbs. with dentures  Maximal bite loads are 5-6 times less for dentures than natural dentition  Mucous membrane must serve identical purpose as PDL o Tolerance of mucous membrane can be even less if unhealthy

Residual Ridge:  Support for dentures includes: mucosa, submucosa, periosteum, and residual alveolar bone.  Alveolar process is subject to different forces with dentures than natural dentition and supporting tissues do not adapt to functional requirements as natural dentition adapts to certain forces  Bone reduction will occur with dentures  Complete dentures move causing mucosa to change  2 physical factors involved in denture retention: o Maximal extension of base o Maximal intimate contact of denture base and basal seat  Muscular factors from buccinator, orbicularis oris, and intrinsic and extrinsic muscles of tongue can help retention (dentist can use these)  Denture must also be modified to account for these forces  A psychological effect on salivary flow can also affect retention

Occlusion: Functional and Parafunctional Considerations:  Primary components of human dental occlusion: o Dentition o Neuromuscular system o Craniofacial structures  Dentition development is characterized by period of dental alveolar and craniofacial adaptability  Figure 2-5 is helpful (Development and adaptation of occlusion)  Healthy adult dentition, adaptation is limited to wear, extrusion, and drifting  When deterioration begins, fixed and RPDs are used to maintain occlusal equilibrium  In edentulous state, few adaptive processes left, remaining are only regressive  “Neutral Zone” is an area where functional balance of the orofacial and tongue muscles is obtained, these muscles play important role in stabilizing denture

Function: Mastication and other Mandibular Movements  Mastication involves biophysical and biochemical processes  Sensory processes during mastication with natural teeth ensure no injury to soft tissues (proprioception, etc.), therefore teeth must be placed along this same arch to ensure functional balance of musculature and teeth (holding bolus in position during chewing)  Proper mastication of food is important in digestion, denture patient will end up chewing food less which will affect digestion of food  Tough food chewed in premolar region  Major differences between natural teeth and dentures: o Mucosal mechanism of support, opposed to periodontium o Movements of dentures during mastication o Changes in maxillomandibular relations and eventual migration of denture o Different physical stimuli to the sensor motor systems  During chewing, muscles flex, and soft tissues change shape, this changes occlusal relationships of dentures  Parafunction (Not directly related to mastication) include more horizontal forces as well as vertical forces

Changes in Morphological Face Height and TMJs:  Facial skeleton reduces in height in edentulous and denture-wearing patients  Dimensional changes of face due to edentulism transmit many forces to the TMJ  Mandibular process changes much more than Maxillary  There exists no single rest position in a patients life, it is constantly changing as a result of new and different forces exerting on it o This does NOT undermine using centric relation as a starting point for fabrication of dentures  Swallowing takes place at centric relation (unless you’re Napoleon Dynamite), this can be used to help identify exactly where centric relation is  Most functional natural tooth contacts occur in Mn position anterior to centric relation, called centric occlusion  Coincidence of centric relation and centric occlusion called centric relation occlusion

TMJ Changes:  TMJs are easier to restore in younger edentulous patients, older patients have had more factors in their life that have changed their TMJ o Shows degenerative joint disease as process more so than a disease entity  Joint disease much more prevalent in older patients, majority of edentulous patients  Good joint rest is imperative in complete denture fabrication

Esthetic, Behavioral, and Adaptive Responses:  Esthetic changes are not always due to edentulism, patient’s behavior plays a role  Morphological changes associated with edentulous state: o Deepening of nasolabial groove o Loss of labiodental angle o Decrease in horizontal labial angle o Narrowing of lips o Increase in columella-philtral angle o Prognathic appearance

 Communication with patient is extremely important then, determines what they want, what they will get with prosthodontics, and what is and is not related to edentulism

Behavioral and Adaptive Responses:  Willingness of patient plays a role  Subconsciously patient will notice that there is something strange in their mouth, causing new habits to form  If posterior Mn teeth are missing, tongue will move out to touch buccal mucosa, new denture will cause many problems with that tongue  Adaptation must take place in context of emotional, systemic, and psychological states  Harder to teach these older mouths new things  Patients hate dentures, a good relationship with the patient will really help

Chapter 3 – The Effects of Aging on the Edentulous State o Global pop. is aging at an unprecedented rate o There are nearly 2x’s as many older women than men, not sure why and not certain that women will continue to outlive men in the future o By the age of 75 nearly everyone is burdened by at least 1 chronic disorder that limits access to dental care and influences dental treatment. o Many older people are likely to be very concerned by unexpected dental costs, unless the need for treatment is explicit and reasonable to them o Prevalence of edentulism is declining (~1/3 – ½ of pop. over 65 are edentate) o More older men than women are likely to have teeth o Loss of teeth is associated with less affluent people o Oral cancer is higher among African Americans (probably socioeconomics) o Oral cancer is increasing among edentulous denture wearers who smoke and drink o Bone mass is maximal in midlife (men have more) and declines with age o bc osteoblasts less efficient, estrogen production down, reduced calcium absorption o osteoporosis – disorder causes by an accelerated loss of trabecular bone (usually in women after menopause) o type I – postmenopausal o type II – affects men and women, no obvious reason o saliva – lubricated, cleanses, protects mucosa, contributes to taste (minor glands help retain and lubricate the dentures) o xerostomia – can be caused by sjorgren syndrome and radiation therapy o with age: shorter chewing strokes, prolonged chewing time because they have poor motor coordination and weak muscles o sensitivity to taste declines with age (therefore more sugar and salt) o old likely to have inadequate calories, calcium and absorb vitamins poorly o wrinkles = sun causes melanocytes to enlarge, epidermis thickens, dermis thins out, collagen and elastin dissolved and then wrinkles appear when fat is lost o concavity of upper lip reduced, philtrum flattens, nasolabial grooves deepen, buccal pads hallow the cheeks, upper lip droops o teeth become brownish because of stains and dentin might be exposed o older persons worry just as much if not more about their appearance o the need for complete dentures in the western world will increase over the next quarter of a century o wounds heal more slowly and possibly less effectively in old people, this is bad if ill-fitting dentures cause trauma o new dentures are not accepted easily by older patients, so, whenever possible, modify the dentures that are familiar to the patient rather than make new dentures o if must make a new one, try to duplicate the general shape and tooth arrangement o every denture should have the patient’s identity embedded visibly

Chapter 4 – Sequelae Caused by Wearing Complete Dentures  placement of a removable prosthesis produces profound changes in oral environment o mechanical irritation, accumulation of microbial plaque, toxic or allergic Rxn  if function poorly could impair muscle function and lower nutritional status  irritations to mucosa may increase mucosal permeability to allergens or microbial  yeasts can use methylmethacrylate to degrade the denture resin  Direct Sequelae caused by wearing removable prostheses (complete or partial) o Mucosal rxns, oral galvanic currents, altered taste perception, burning mouth syndrome, gagging, residual ridge reduction, periodontal disease, caries  Denture stomatitis – pathological rxn of the denture-bearing palatal mucosa (about 50% of denture wearers have this condition) o Type I – localized simple inflammation o Type II – more diffuse erythema on part or entire denture-covered mucosa o Type III – granular type, commonly on central part of hard palate and alveolar ridges; usually associated with type I or II (usually surgical elimination of deep crypt formations are required for effective mucosal hygiene)  Candida albicans can cause denture stomatitis – mainly in patients who wear denture night and day  Predisposition to denture plaque  poor oral hygiene, high carb intake, lowered salivary flow, continuous denture wearing  Predisposition to host-parasite relationship (ie. Candida albicans)  aging, malnutrition, immunosuppression, radiation therapy, diabetes  Preventative measures = efficient oral and denture hygiene, and correction or denture- wearing habits o Scrub denture with soap after meals, mucosa cleaned and massaged with soft toothbrush and if recurrent infections then should take denture out at night  Flabby Ridge – due to replacement of bone by fibrous tissue (most commonly in anterior part of Maxilla), gives poor support for denture – sometimes removed  With ill-fitting dentures, sometimes tissue hyperplasia of mucosa in contact with denture border, result from chronic injury  Traumatic ulcers – usually show up 1-2 days after new denture  No definite proof of correlation b/t oral cancer and chronic irritation of mucosa  Burning Mouth Syndrome (BMS)  burning sensation of part or all structures in contact with denture o No mechanical irritation, oral mucosa appear healthy o Burning of supporting tissues or tongue common complaints of postmenopausal women  Causes for BMS: o LOCAL – friction, prolonged muscle activity, parafunctionality of tongue o SYSTEMIC – menopausal women (vitamin B12 or iron) o PSYCHOGENIC – anxiety and depression most common  Gagging – usually by stimulation of soft palate, usually get used to it in few days  Residual Ridge Reduction – process is chronic and irreversible; first year after becoming edentulous Mx loses 2-3 mm, Mn loses 4-5 mm; decreases after this but Mn reduces at a greater rate than Mx (women are usually more effected)  Overdenture abutments – selected teeth are preserved for abutments, treated endodontically and root surface and canal are filled with amalgam o High risk of caries and periodontal disease  Indirect Sequelae o Atrophy of Masticatory Muscles . Bite forces decrease with age (medial pterygoid and masseter have most atrophy and most often in women), this reduces masticatory function . Overdentures or implants usually cause improvement of mastication o Nutritional Deficiencies . Decease in energy needs, decrease in food intake, decrease in muscle mass . Four factors related to dietary selection  Masticatory function and oral health  General health  Socioeconomic status  Dietary habits  Consequences of wearing complete dentures: o Reduction of residual ridges . To prevent:  Try to retain some teeth for overdenture abutments (tooth roots in mandible is particularly important)  Regularly monitored to maintain acceptable fit and stable occlusal condition  Possibly implants o Pathological changes of oral mucosa . To prevent:  Patient must be monitored and come in on recall  Patient should abide by proper denture-wearing habits  “Finally, it is important to remind and to explain to our patients that treatment with complete dentures is not a “definitive” treatment and that their collaboration is important to prevent the long-term risks associated with the consequences of wearing complete dentures.”

Chapter 15 Brought to you by Roy Krengel

Denture has 3 surfaces: 1) an impression surface 2) an occlusal surface 3) a polished surface Impression Surface: -rests on residual ridges and transmits forces directly to denture bearing tissues Occlusal surface: -consists of articulating surfaces of the prosthetic teeth that make contact during functional and parafunctional activity Polished surface: -non articulating part of teeth (Buccal/Lingual surfaces) as well as buccal, labial, lingual, and palatal parts of denture base -design and orientation of surface are determined by its relationship to the functional role of the tongue, lips, and cheeks -position of equilibrium among these muscle groups called “neutral zone” -get this neutral zone by making occlusion rims Occlusion Rims: -Records neutral zone first and then maxillomandibular relations -also records level of occlusal plane -most of these determinations cannot be made scientifically, more theoretical. However, clinical experience proves to be successful The preferred clinical sequence: 1) design the arch form on each wax occlusion rim 2) establish level/height of the occlusal place on mandibular rim 3) modify maxillary rim to meet the mandibular rim evenly at desired vertical dimension of occlusion (VDO) 4) make a preliminary centric relation (CR) record Arch Form: - the width of occluding surfaces and the contour of the arch form of the occlusion rims should be individually established for each patient - when natural teeth are replaced by artificial teeth, it is logical to set the artificial teeth in the same place where the natural teeth occupied - the same forces stabilize the artificial teeth/dentures - hard to do when patient is completely edentulous, clinical judgment needed - the best guide for determining and designing the arch form is to consider the pattern of bone resorption where the teeth are lost and the use of anatomical landmarks that are stable in position Mandibular Arch: - in lower jaw, more bone loss on labial side of anterior residual ridge - so, ridge is more lingually placed in anterior, but more buccally placed in posterior - corners of mouth used to determine position of canines Maxillary Arch: - no need to worry about tongue - residual ridge usually moved palatal, therefore the maxillary teeth must be placed labial and Buccal to the ridge to be in “neutral zone” - Maxillary Central Incisor incisal edge 8-10mm anterior to incisive papilla - Posterior teeth related to mandibular arch most of the time - The longer the period of edentulism, the weaker the muscle tone of the face Level of the Occlusal Plane: - some dentists find the occlusal plane by shaping the maxillary occlusal rim so that the incisal plane is parallel to the interpupillary line and is at a height that allows for the length of the natural tooth plus the amount of tissue resorption that has occurred - can also use the upper lip as guide - posteriorly, the occlusal plane is made parallel to the ala-tragus line on the basis of the position of most natural occlusal planes - for patients that this does not work, the dentist can establish the height of the occlusion plane by marking the corners of the mouth (modiolus-where 8 muscles meet pg. 263) on the rims to determine the height of the first premolars Tests to determine (VDO): 1) Judgment of the overall facial support 2) Visual observation of the space b/w the rims when the jaws are at rest 3) Measurements b/w dots on the fae when the jaws are at rest and when the occlusion rims are in contact 4) Observations when the “s” sound is enunciated accurately and repeatedly – the average speaking space (~1.5 -3 mm) Interocclusal centric relation (CR) Records: - interocclusal records are described as static, graphic, or functional - static records are made with a soft material between two rims used to make a “checkbite” record (preferred method) - graphic records are made with intraoral or extraoral tracing devices - functional records are made with pantographic tracing devices - List of how technique on bottom of page 265 if you guys really want to read it. Waste of time is my guess!

Chapter 17 Part 1 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient

The goals for this phase of therapy are to construct complete dentures that: 1. function well 2. allow the patient to speak normally 3. are esthetically pleasing 4. will not abuse the tissues over residual ridges

Anterior Tooth Selection Based on theories that tooth shape relates to head shape, and tooth appearance is influenced by a patient’s age, sex and personality. The patient should be give the primary responsibility to determine the esthetic outcome, with guidance from the dentist. (a patient may want teeth to look older if they are older, so as to give them more of a natural look for someone their age). Prosthetic teeth are often smaller in size and lighter in color than the range of the natural dentition. Since anterior teeth are seen by everyone, give the patient what they want. Have the patient bring any models, old dentures, and photographs that show them happy and smiling. This type of care is termed the “conformative approach”, you are making the teeth as natural as possible to each individual patient. Use a “reoraganized approach” when you plan to change the prosthese to improve them, this is used when patients don’t like their teeth. When visualizing the teeth of a patient, it is important to use adequate light, and a mirror that shows the patient their entire face. Have patients pick the color. Suggest two options (method of pair comparison) if they want you to decide. Remove the option they don’t like, and bring in another in the same spectrum as the one they liked, you will slower get to the right shade. Steps 1. Listen to the patient 2. get records of existing tooth conditions, and the patients opinion 3. make it easy for your patient and yourself to visualize the samples 4. allow your patients to select the color 5. choose an appropriate size for the tooth 6. select a proper mold (crown taper, and labial curvature. Again, used paired comparison in selecting the size of tooth to use. Anterior tooth selection should be made early in the appointment process. Get confirmation of anterior teeth, including premolars, before final impressions are taken. This allows time for a change to be made if the patient is unsatisfied. It is a waste of money and time to have the laboratory set a second set of teeth.

Other Factors-  Patient preference, Porcelain vs. Acrylic  Highly visible gingival, select squarer teeth with a long contact point rather than highly tapered teeth. This will minimize the interproximal display of pink gingival acrylic, it is harder to make gingival look as natural as the teeth, so favor teeth over gingival space.  Limited interocclusal space, Use acrylic teeth. They can be ground thin and maintain attachment to denture base.  Opposing natural teeth, porcelain is abrasive, use acrylic teeth to oppose nature teeth.  Overdentures, over roots and implants, give the tooth a little extra volume for space. Tapered and curved teeth get too narrow, use more squared teeth.

Little things can be added to the denture to make it look more nature, i.e. wear or restorations.

Posterior Tooth Selection Goals: 1. properly fitted bases 2. correct jaw relation records that are transferred to an instrument capable of accepting what is recorded 3. the arrangement of the teeth for the best stability and other functional and nonfunctional activities Over the years, anatomy has taken a back seat to function.

Buccolingual width of posterior teeth---less than the width of natural teeth replaced. These narrower forms, especially in the lower denture, assist the cheeks and tongue in maintaining the dentures on the residual ridge.

Mesiodistal length of posterior teeth---vary to accommodate needs of a patient, a line from retromolar pad to canine on each side is made to assist placement on residual ridge. No teeth are placed on incline of retromolar pad. The distance between canine and beginning of incline determines if 3 or 4 teeth are used. Maxillary posterior teeth that extend too close to the posterior border of the maxillary denture may cause the patient to bite the cheek.

Vertical Height of the Facial Surfaces of Posterior Teeth---correspond to interarch space and to the height of the anterior teeth. 1st premolar=canine (Maxillary, for esthetics), the entire arch should mimick that of natural teeth.

Posterior teeth and materials---porcelain was the favorite because the rapid wear of acrylic resin. With the tendency for porcelain to chip, acrylic gained popularity. In the past two decades improved resin and composite resin teeth have been used because they were more wear resistant.

Cusp inclines and posterior teeth---based on the type of occlusion to be developed, the philosophy of occlusion to be fulfilled, and the accomplishment of both of these goals with the least complicated approach. Blah Blah Blah

Arranging Teeth for Complete Denture Occlusion Occlusion rim wax is used, helps determine the desired amount of lip support and the technician arranges the teeth using the rims as a guide. These are adjusted at the try-in appointment. Incisive Papilla is a valuable guide to anterior tooth placement because it has a constant relationship to the natural central incisors, it positions the midline, it should be noted that it works most of the time, not always. The labial surfaces of the central incisors are usually 8 to 10 mm infront of the papillae.

The anterioposterior position of the dental arch should be governed chiefly by consideration of the orbicularis oris muscle and its attaching muscles: the auadratus labii superioris, caninus, zygomaticus, quadratus labii inferioris, risorius, triangularis, and buccinator. (this my be to specific) The muscles are affected by the anteroposterior position of teeth and denture base. Basically, too far forward or backward will be baaaaad. So, if the residual ridge is resorbed, setting the teeth on it will lead to them being to posterior and will give the patient an aged look. The wax occlusion rims, will be the ultimate guide for the positioning of the teeth. A try-in of these rims will give the dentist a good idea if the arch fits well with the space of the oral cavity and muscles. The wax can be adjusted due to the try-in.

Arranging Anterior Teeth Refer to the lab manual, this material seems different from what we have been taught in lab. So, I will talk to the teacher on Monday about what we should follow.

Occlusal Schemes : 2nd Half of Ch. 17 (p314-328)

Key points:

*3 Schools of Thought on articulation: 1-bilateral balance -anatomical molds(teeth) are selected for bilateral balanced articulations; however nonanatomical teeth can be used if you also use the concept of compensating curves. 2-monoplane (nonanatomical) nonanatomical teeth are usually used, but you can apparently use anatomical as well (stupid) 3-lingualized –Maxillary lingual cusp functions as the main supporting cusp in harmony with the occlusal surfaces of the lower teeth. This is typically a combination of anatomical maxillary teeth and lower nonanatomical molds

*Usually 3 posterior teeth (1 premolar, 2 molar) are set. Mandibular 2nd premolar is most often selected as it provides greater occlusal surface area for grinding. Maxillary 1st premolar is typically selected for esthetic reasons

*2 compensating curves: p. 319, 323 Anteroposterior compensating curve- developed to provide the needed tooth structure for balancing contacts in Protrusive movement Mediolateral compensating curve – needed to provide the needed tooth structure to achieve balanced articulation during lateral movements

*Posterior teeth are only set to the point at which the mandibular ridge begins to curve upward toward the retromolar pad

*2 posterior tooth molds available 1- Controlled contact (CC) –these teeth are suggested for pts. Who have trouble reproducing centric jaw relation position. The teeth are less anatomical and allow more freedom of movement in maximum intercuspation. i.e. cusp heights are flatter/lower

2- Maximum contact (MC) –for patients who don’t have trouble repeating occlusal position. The MC teeth are more anatomical in appearance with greater cusp heights. Some occlusal reshaping is often necessary to establish maximum intercuspation i.e. MC is more work for us

Just a note: The second half of Ch. 17 deals with a lot of step-wise processes such as a paragraph or two on setting each posterior tooth and processes on adjusting contacts and establishing max intercuspation. This is what we covered for the 2nd exam, and much of it is common sense ( Where would you find working interferences…A: on the lingual inclines of maxillary facial cusps and on the facial inclines of mandibular facial cusps) I just tried to pull out the information I felt was more important or more apt to be tested on. The two paragraphs on compensating curves (p323) would be worth 5 min of your time. If you have any questions please let me know Brandon Kelly [email protected]

Chapter 18: The try In Appointment I. Perfection and Verification of Jaw Relation Records -Patients should be advised to leave the existing or previous denture out of the mouth for a minimum of 24 hours before jaw records are perfected and verified at the time of try in -this can distort soft tissue and will not be as accurate Direct relation to accuracy of jaw relation records 1. appearance and comfort 2. occlusion 3. health of the soft tissues Factors of the final determination of the vertical dimension – Combinations of these may help in determining vertical dimension 1. Preextraction records 2. The amount of interocclusal distance to which the patient was accustomed, either before the loss of natural teeth of with old dentures 3. Phonetics and esthetics 4. The amount of interocclusal distance between teeth when the mandible is in resting position 5. Study of facial dimensions and facial expressions 6. Lip length in relation to the teeth 7. The interarch distance and parallelism of the ridges as observed from mounted casts 8. Condition and amount of shrinkage of the ridges Verifying Centric Relation 1. Intraoral Observation Of Intercuspation - Dentist guides Centric Relation with thumb into the most retruded position of the mandible - Patient stops at the slightest “feather touch” of the posterior teeth - Hard to detect by visualization, so dentist feels with index fingers for movement 2. Extraoral Articulator Method - To determine whether the position of the teeth on the articulator is the same as that in the patients mouth - 1st take CR of teeth on the articulator using wax - 2nd place Aluwax on the Mn posterior teeth, heat wax in a 130 degrees F water bath to get soft, and place in patients mouth to get CR - The dentist guides CR by hinge movement like the articulator, but do not apply enough pressure to go through the wax and hit the tooth - After CR has been taken, the trial denture should be chilled and placed on the articulator to confirm the CR II. Eccentirc Jaw Relation Records -Incisal guidance is more influential in controlling movements of the Mn than the condylar paths are because condylar paths are further away from the cusp inclines, which both the incisal angle and the condyle angle influence (on the articulator) -Establishment of the posterior palatal seal (of the denture) is determined by the vibrating line on the soft palate - The dentist can have the patient pinch their nose and attempt to blow through it creating a vibrating line, accentuating the foveae palatinae - The posterior limit of the baseplate should extend laterally 3mm beyond the crest of the hamular notch - Hamular Notches – appear between the maxillary tuberosities and the hamular processes of the medial pterygoid plates - To prevent displacement of the denture, a bead is placed at the posterior of the denture - This bead is 1 - 1.5mm high, 1.5mm broad at its base and sharp at its apex (Triangular shaped), across the posterior of the denture running laterally through the center of the hamular notches - This pushes up into the soft palate to create suction so that the denture does not displace - If the bead is too wide, the denture will be pushed downward and defeat the purpose of having the denture seal - The bead should run 2mm anteriorly to the posterior edge of the denture baseplate III. Creating Facial and Functional Harmony with Anterior Teeth - The facial landmarks of the lower third of the face have a direct relationship to the presence of the natural teeth - The two buccinators and the obicularis oris from a functional unit that depends on the position of the dental arches and the labial contours of the mucosa or the denture base for effective action - With the loss of teeth the obicularis, buccinators and attaching muscles are impaired - Three factors affect the face in repositioning the obicularis oris with complete dentures: 1. The thickness of labial flanges of both dentures 2. The anteroposterior position of the anterior teeth 3. The amount of separation between the mandible and the maxillae Guides in determining Facial and Functional Harmony 1. Preliminary selection of the teeth – size, form, and color; same color as face so that it isn’t the main focus 2. Horizontal orientation of the teeth – must correspond to the ridge relation 3. Vertical orientation of the teeth – determined by the length of the upper lip, long or short 4. Inclination of the anterior teeth – the inclination of the anterior teeth parallels the profile line of the face 5. Harmony in the general composition of anterior teeth I. Harmony of the dental arch form and the form of the residual ridge - Arches and ridges described as square, tapering or ovoid; they show facial characteristics as described - Central incisors are more forward from the canines in a tapering arch than any other, resulting in crowding; then ovoid and then square II. Harmony of the long axes of the central incisors and the face - Incisal plane should be in line with the interpupillary line - The long axes of the central incisors should be parallel to the long axis of the face and the midline should of the dental arch should be located near the middle of the face - The Mn central incisors are aligned with the Mx central incisors - May be modified to meet individual needs III. Harmony of the teeth with the smiling line of the lower lip - The vertical position of the upper canines is responsible for the shape of the smiling line, if canines are placed to low this gives a reverse smiling appearance (teeth look like they are frowning) IV. Harmony of the opposing lines of the labial and buccal surfaces - Asymmetry is the objective so that the dentures don’t look fake - Asymmetrical symmetry - dissimilarities in the inclination, rotation, and position of the teeth on each side of the midline - The teeth should have opposing equivalent angles away from a midline V. Harmony of the teeth and profile line - The Mx central incisors should parallel the face; ie: if the Mn is retracted the cervical portion of the tooth should be out the furthest anterior and the incisal portion posterior, whereas if the Mn is protracted the incisal portion of the tooth should be the furthest anterior and the cervical portion posterior VI. Harmony of the incisal wear and age - The teeth in a denture should be ground down to simulate the wear surfaces at the age of the patient; ie: older equals more wear - Developing incisal wear on artificial teeth during balance and correcting of occlusion is a logical approach to this phase of esthetics - The artificial teeth of an older person should not have small ball point interproximal contacts with large interproximal spaces because this would be characteristic of a younger person 6. Refinement of individual tooth positions – set with the appropriate inclinations and rotations; this is why patients should have a preextraction record that helps the dentist set the teeth in the right position - A study of common irregularities to Mx teeth that should be added to a denture 1. A slight lapping of the mesial surfaces of the lateral incisors over the central incisors 2. A depressing of the lateral incisors lingually so the distal surface of the central and the mesial serface of the canine are labial to the mesial and distal surfaces of the lateral 3. A rotating of the mesial incisal corner of each lateral incisor lingual to the distal surface of the central while the distal surface of the lateral remains flush with the mesial surface of the canine 4. Placement of the incisal edge of each lateral higher than that of the central incisor and canine - Harmony of Spaces and Individual Tooth Position – spaces can be used as an irregularity between teeth to look more natural and to provide more proper balance in the overall composition 7. The concept of harmony with sex, personality, and age of the patient - Feminine: curved surfaces, roundness and softness in the form of the dentition, and a prominent smiling line of the anterior teeth - Masculine: boldness, vigor and squareness and a straightness to the incisal line - Size and position of the central incisors dominate the arrangement of the six upper anterior teeth - Smaller lateral incisors and rotation of these teeth give a softer more feminine look - Rotation of the distal central incisors gives a more vigor look 8. The correlation of esthetics and incisal guidance - no vertical overlap (overbite) of anterior teeth while posterior teeth are in Centric Occlusion - To compensate for this there needs to be overjet to make esthetically pleasing Patient Acceptance of the Arrangement of the Anterior Teeth - Patients should be given opportunity to observe and approve the final arrangement of the anterior teeth at the time of the appointment, the denture should not be completed until approval is given - Patient should not be able to observe trial dentures in their mouths until the dentist is satisfied with the composition - The patient should first observe how the teeth look in their mouth and second stand 3-4 feet back from a mirror and observe how they look in a normal conversation because other people will be looking at them more than they will - Patient should bring along the most critical family member or friend at the time of try in - The dentist should listen to all the concerns and comments of the patient and not dismiss them as silly - The dentist can make some changes, but other suggestions may not be advisable because it is not anatomically feasible and may prevent the muscles in cheeks and lips to properly move the face - When everyone is in agreement, the dentist should have the patient sign a statement that protects the dentist. This statement claims that the patient was given the opportunity to view the teeth while arranged in wax or that requested changes were not done.