A Multidisciplinary Approach to Single-Tooth Replacement
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A Multidisciplinary Approach to Single-Tooth Replacement Sergio Rubinstein, DDS* Alan J. Nidetz, DDS* Masayuki Hoshi, RDT** ver the last several decades, dentistry treatment, or pathology is, for some patients and O has focused on more conservative treat- dentists, a very aggressive treatment option. In- ment modalities and preventive tech- fection in any of these situations creates an envi- niques. This has been possible not only because ronment in the hard and soft tissues that makes of improved techniques and materials, but also regeneration procedures more difficult, thereby because of the understanding that tooth prepara- complicating the ability to create a natural ap- tion, regardless of how conservative it may be, is pearance in the definitive restoration. an irreversible procedure. While a conventional three-unit fixed partial den- A missing tooth in the anterior region is not ture is a predictable technique to replace a missing only a physical loss, but also may be an emotional tooth, the invasive nature of the treatment can lead experience for the patient as well. To remove to other complications throughout the life of the healthy tooth structure of adjacent teeth to re- restoration. Complications may include mechanical place a congenitally missing tooth or a tooth lost overload of the abutment teeth with weakening or to decay, trauma, root fracture, failed root canal fracture, risk of endodontic treatment, periodontal problems, decay, and cement failure. If any of these complications occurs on one of the abutment *Oral Rehabilitation Center, Skokie, Illinois, USA. teeth, the entire prosthesis will fail. Splinting teeth **Oral Rehabilitation Institute, Skokie, Illinois, USA. can overload the supporting structures because Correspondence to: Dr Sergio Rubinstein, Oral Rehabilitation Center, 64 Old Orchard, Suite 420, Skokie, IL 60077, USA. teeth function individually, and oral hygiene tech- E-mail: [email protected] niques become more cumbersome. QDT 2004 1 RUBINSTEIN ET AL HISTORY OF SINGLE-TOOTH structure that could be as thin as 0.2 mm. Use of a RESTORATIONS non-noble metal alloy significantly increases the mechanical retention of the etched framework and For more than 50 years, dentistry has sought a more easily prevents degradation of the luting more conservative approach to replacing a single resin in the oral cavity. Care must be exercised so missing tooth with a conventional fixed prosthesis, the framework does not involve the incisal third of which involves the cutting of sound tooth struc- the abutment teeth, since this could block translu- ture. Treatment possibilities have evolved from cency and result in a graying effect (Figs 2a to 2h). bonding a natural extracted tooth or composite While use of a resin-bonded retainer involves a resin restoration to the adjacent teeth,1–3 to the very conservative technique and preparation of Rochette bridge,4,5 to the Maryland bridge,6–8 and the enamel is minimal, the mechanical retentive currently to the single-implant–supported crown. properties of the prosthesis, by design, have a It is debatable which technique is the most con- wraparound effect of 180 degrees. Still, care must servative, and in many instances the patient’s pref- be exercised to prevent occlusal overload during erence dictates the restoration of choice. The clin- function. ician must also evaluate the advantages and Presently, the single-implant–supported crown disadvantages of such techniques in order to pro- is a predictable method of tooth replacement, vide the patient with the best clinical result since and it has several improvements over resin- not all patients should be treated with the same bonded prostheses: preparation of adjacent teeth restoration type or design. is not needed; the tooth replacement will function While the Rochette bridge replaced the miss- individually; a conventional oral hygiene tech- ing tooth without any tooth preparation, it was, at nique can be used; preservation and stimulation best, considered a temporary solution, and its of existing bone and soft tissues occur, including framework was designed with a gold substructure recreation of the interproximal papillae; and sta- and hence resulted in a thick metal framework. bility and function are improved because of the Such restorations were designed with macrome- implant supporting the crown. chanical retentions (Figs 1a to 1c) to lock the com- While osseointegration around implants is a posite into the gold and through the bonded lin- well-documented phenomenon, the implant de- gual surface. This technique met the patient’s signs will continue to undergo structural modifica- conservative requirements of replacing the miss- tions to fulfill the prosthetic requirements one ing tooth, even though it required the patient’s faces as the practice of dentistry evolves. Such compliance not to overload the prosthesis during changes include the transitions from the standard- masticatory function and necessitated a modified diameter implant to wider-diameter implants; flossing technique because of the splinted pros- from the external-hexagon, antirotational device thesis (Fig 1d). to the internal morse taper connections; and from Proven over the years through the achievement the two-stage surgical approach to the now more of acceptable clinical results, such resin-bonded frequently used one-stage techniques that include prostheses continued to improve, and their evolu- immediate loading. These are just a few of the tion led to the development of the Maryland factors that complicate the analysis of implant de- bridge.6,7 For this technique, the tooth required a signs with respect to failure or success. The area conservative preparation in the enamel only8 with a often considered the most critical is the implant- gingival rest to create a definite seat. The prepara- abutment interface, and because of evolving de- tion design included an interproximal wraparound signs, this is where dentistry may see some signifi- to help prevent lingual displacement and to in- cant changes to obtain the best possible fit and crease stability on a bondable surface area improved tissue response. (enamel) with a solid, nonperforated, metal sub- 2 QDT 2004 A Multidisciplinary Approach to Single-Tooth Replacement Rochette Bridge 1a 1b 1c Fig 1a Lingual view of the waxup for the Rochette bridge. Fig 1b Cast framework on the stone model. Fig 1c Framework showing mechanical undercuts to lock the bonded pros- thesis. Fig 1d Buccal view of the bonded Rochette bridge. (Prosthetics and labora- tory work by Alexander H. Chan, DDS.) 1d Maryland Bridge Figs 2a and 2b The maxillary right central incisor and supporting bone Fig 2c A connective tissue graft was have been lost as a result of trauma. The rotation of the left central incisor placed to correct the soft tissue de- and the vertical bone loss required a multidisciplinary treatment approach. fect, and orthodontics corrected the rotation of the left central incisor. (Orthodontics by Sergio Rubinstein, DDS; surgery by Sergio Rubinstein and Patrick J. Pierre, DDS; 1981.) 2d 2e 2f Fig 2d Lingual view of the Mary- land bridge. The incisal extension required slight trimming to avoid blocking translucency. Figs 2e and 2f Views of the Mary- land bridge replacing the maxillary right central incisor. Figs 2g and 2h Views of the pa- tient’s smile. 2g 2h QDT 2004 3 RUBINSTEIN ET AL IMPLANT PROSTHODONTICS tion of the missing tooth (Fig 3e). Several clinical concerns need to be addressed: measurement of Since the endosseous implant was introduced in interproximal space and adjacent teeth, the oc- the United States, the prosthetic indications have clusal relationships, anterior and canine guidance, grown from the mandibular, fixed, bone-anchored and esthetic demands. The esthetic demands in- prosthesis to the single-tooth replacement.9–16 clude the lip profile, alveolar height and buccolin- While many clinicians still resist the application of gual dimensions, and the quality of the overlying endosseous implants, preferring the more tradi- gingiva.9 tional restorations, one could argue the relative There must also be enough mesiodistal clear- morbidity of preparing the adjacent teeth for fixed ance for the implant in order to avoid risk to adja- partial dentures compared with the two-stage, cent structures such as the nasopalatine or one-stage, or immediate-loading implant surgical mandibular nerve, nasal cavity, neighboring teeth, and prosthetic protocol. Clearly not only can im- or the maxillary sinus. In most cases, the implant plant prosthodontics offer excellent cosmetic out- and prosthetic components will require a mini- comes, but it also allows for bone preservation mum of 6 to 8 mm of mesiodistal clearance de- and stimulation, and the restoration most closely pending on the location in the dental arch.15–18 A resembles an actual tooth during function. congenitally missing tooth will most likely have a normal osseous ridge, both in height and width, whereas alveolar atrophy always follows the ex- DIAGNOSIS traction of teeth. Its severity depends on several factors, including (1) quantity and quality of bone, When a patient needs replacement of a missing (2) existing or previous pathology, (3) length of tooth (Figs 3a to 3c), the clinician must perform a time following tooth loss, and (4) trauma incurred series of clinical and radiographic evaluations (Fig during the extraction and the loading of the tis- 3d) to visualize and offer the available treatment sues. The collapse of the facial plate and alveolar options. The patient must be made aware of these height subsequent to tooth loss19 can impact the options, which generally include some form of re- position and angulation of an implant. The ideal movable partial denture, resin-bonded retainers, implant placement and how alternative positions fixed partial prosthesis, or an implant-supported affect prosthetic design and morphology has restoration. If a single-tooth implant restoration is been described at length; however, this will vary considered, the clinician must first determine from case to case and depending on the implant whether an adequate recipient bed, or site, for the system selected.