SECTIONEDITORS
ent of edentulous
maxillae
with
osseointegrated
S. Lewis, DMD,a A. Sharma, BDS,b and R. Nishimura, DDW University of California-Los A.ngeles, School of Dentistry, Los Angeles, Calif. Edentulous maxillae can be restored with implant supported fixed restorations containing denture teeth on a metal framework, implant-retained removable overlay prostheses, or porcelain fused-to-metal fixed prostheses. Esthetics and hygiene access are two important factors in determining the restoration best suited for each patient. Treatment planning considerations and treatment procedures for the various techniques are discussed. (J PROSTHET DENT 1992;68:503-8.)
T reatment
of edentulous patients with fixed restorations supported by osseointegrated implants can provide excellent function1 with high levels of long-term success.2 Although the hybrid mandibular fixed prosthesis, or fixed bone-anchored bridge, can be designed with acceptable esthetics and good oral hygiene access, the restoration often presents problems in the edentulous maxillae. Achieving proper esthetics and maintaining adequate hygiene access may be difficult. Although hybrid fixed implant restorations may be successful esthetically and hygienically, implant-retained removable overlay prostheses are often the treatment of choice in the edentulous maxillae. In some instances, porcelain fused-to-metal restorations may be used in the edentulous maxillae and may provide optimum esthetics and hygiene access. This article discusses the considerations involved in determining the treatment of choice for the edentulous maxillae and the restorative techniques involved.
Hybrid
fixed
implant
restoration
The hybrid, maxillary fixed implant-supported prosthesis described by Lundqvist and Carlsson3 is a popular means of restoring edentulous patients. The restoration consists of denture teeth connected to ‘a metal framework with acrylic resin. By the incorporation of gold alloy cylinders into the framework, the restoration is supported by the titanium transmucosal abutment cylinders and is retained with gold alloy screws. ‘This restoration is not retrievable by the patient and must be designed to provide oral hygiene access around the abutment cylinders as they emerge through the mucosa. Exposing these cylinders for
Presented before the Pacific Coast Society of Prosthodontists, Victoria, British Columbia, Canada. aAssistant Professor, Removable Prosthodontics. bPrivate Practice, San Francisco, Calif. CAssistant Professor, Removable Prosthodontics. 10/l/39133
THEJOURNAL
OFPROSTHETIC DENTISTRY
hygiene access, however, may compromise esthetics. Because many edentulous patients present with at least moderate residual ridge resorption, the abutment cylinders are often out of sight and distant from the prosthetic teeth and the smile line. Because many patients show more maxillary teeth than mandibular teeth, visualization of the abutments resulting in poor esthetics is more common in the maxillae. The less ridge resorption and/or the higher the smile line, the greater is the likelihood of an esthetic problem because the abutment cylinders become visible. Making the abutments with a prosthesis flange compromises oral hygiene access (Fig. 1). When treatment is being planned, the patient should remove an existing maxillary denture and smile. The further away the maxillary residual ridge is from the smile line, the less likely it is that the transmucosal abutment cylinders will be visible during normal function (Fig. 2). Covering abutment cylinders with an acrylic resin flange, however, creates a significant hygiene problem. For this type of fixed prosthesis to be successful esthetically and hygienically, significant distance must be present between the smile line and the residual ridge (Fig. 3). Lip support without the maxillary denture in place must also be evaluated, because the fixed restoration does not contain a buccal flange. In severely resorbed states a flange may be needed to provide adequate facial contours. In some instances it may be difficult to determine the potential for success with this type of prosthesis. It may not be until the wax try-m that the final restorative choice is made. The wax trial prosthesis must be similar to the final restoration in design. The tissue surface must be convex and there can be no buccal flange covering the transmucosal abutment cylinders because they must be exposed for easy oral hygiene access. Only then can the esthetics be accurately determined by evaluating the visibility of the abutment cylinders and the lip support (Fig. 4). It is important to explain to patients at the initial consultation that, even if a fixed prosthesis is planned, the
503
LEWIS,
SHARMA,
AND
NISHIMURA
Fig. 1. Transmucosal abutment cylinders are disguised by ridge lapping, which results in contours that provide poor hygiene access.
Fig. 3. Moderate to severe resorption provides adequate space for teeth, denture base, metal framework, and hygiene access while not compromising esthetics.
Fig. 2. These abutment covered with a flange.
Fig. 4. Tissue surface of restoration is convex for adequate oral hygiene access. A low smile line prevents visualization of space.
cylinders would be visible unless
treatment may be changed to a removable overlay prosthesis if the wax trial prosthesis is unacceptable. The other alternative is to make a separate buccal flange that is removable by the patient. If the only difficulty resulting from adequate oral hygiene space is poor phonetics, a removable palatal flange may also be a solution. Implant placement is somewhat critical for the fixed prosthesis. If placed buccally the screw access channels could exit through the facial aspects of the denture teeth, creating an esthetic problem. If placed too far palatally the restoration will become excessively wide in the buccal-topalatal dimension, causing a hygiene problem. Therefore, surgical stents are needed to ensure proper buccal-to-palatal placement. Mesial-to-distal relationship is not as critical for this prosthesis design because abutment cylinders positioned interproximally would be above the smile line and not visible during normal function.
504
Implant-retained
overlay
prosthesis
There are several advantages to the implant-retained overlay prosthesis in the edentulous maxillae. The buccal flange provides esthetic advantages that fixed restorations lack. With a flange there is no visible evidence of the titanium abutment cylinders emerging through the mucosa or the space required for proper hygiene. The flange also provides lip support, which is so often lacking with the placement of a hygienic fixed restoration. Moreover, phonetics may be improved because the hygiene space beneath a fixed prosthesis and the resulting escape of air during speech are no longer a factor with the presence of a flange. In addition to the esthetic and functional advantages of this restoration, oral hygiene is easy when the prosthesis is removed by the patient to expose the substructure. Two maxillary overlay prosthesis designs are commonly used. One type contains full palatal coverage comparable to
SEPTEMBER
1992
VOLUME
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NUMBER
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TREATMENT
OF EDENTULOUS
MAXILLAE
Fig. 6. Bar design has two distal resilient attachments that allow displacement toward the mucosa when posterior function occurs, rotating about the anterior clip.
Fig.
5. Correct (A) and incorrect (IB) design of tissue bar.
a maxillary complete denture. Two anterior implants may be used to retain the prosthesis, with a choice of various types of attachments. Full palatal coverage is needed for adequate support, stability, and retention. When a bar and clip retentive system is used, it is recommended that the bar be oriented parallel to the axis of rotation or perpendicular to the palatal suture. On posterior occlusal function, the clip will rotate around the bar, allowing the prosthesis to benefit from posterior soft tissue support. Clip wear will be minimized with this design, because the constant need to replace retentive clips is indicative of poor orientation of the tissue bar. Without the proper alignment, adverse forces will be placed on the retentive clips, the tissue bar, and the implant fixtures (Fig. 5). The second design is one with reduced palatal coverage. With full palatal coverage eliminated, the posterior palatal seal is removed. To regain this retention, retentive components must be placed posteriorly. Distal cantilevering from two implants is not recommended because of excessive loading; thus, four or more implants are needed when posterior implant retention is required. All other aspects of the prosthesis remain unchanged, providing improved esthetics, function, and hygiene access to the transmucosal abutments. Four implants may not be adequate to provide total
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 7. Master cast includes implant fixture analogs beneath the cast surface. Plastic UCLA abutments are connected to analogs in preparation of wax-up.
support for a maxillary prosthesis. Therefore it is important to ensure some mucosal support. The posterior retentive components should allow for vertical movement so that the denture displaces toward the mucosa for added support, rotating about the anterior clip, which is parallel to the axis of rotation (Fig. 6). With posterior mucosal support maintained, the length of the occlusal table is not limited. An initial treatment plan may include a fixed prosthesis on five or six implants that is changed to an overdenture at the wax try-in appointment, perhaps for esthetic or functional reasons. In this situation, the final overlay prosthesis can be totally implant-supported with tissue contact only to prevent food impaction. Vertical resiliency of the posterior retentive components is not needed. The functional abilities of this type of prosthesis should approach those of a fixed restoration while maintaining esthetic and
505
LEWIS,
Fig. 8. Finished restorations connect directly to implant fixtures and are retained with titanium alloy screws.
hygienic advantages. Maxillary cantilever guidelines of 10 to 15 mm beyond the distal implants must be considered with this implant-supported design. Posterior resilient attachments provide soft tissue support and eliminate these restrictions. For maxillary overdentures, whether they are conventional on two implants or with reduced palatal coverage on four or more implants, the placement of the anterior clip is critical for stability. Because the maxillae resorb palatally, the anterior teeth are often placed anterior to the residual ridge. This placement might be quite significant the more prognathic the ridge relationship becomes. The more anterior the teeth are, relative to the retentive clip, the more anterior rotation will be evident during incising. The resulting prosthesis instability could be decreased by placement of the bar and clip more anteriorly beneath the teeth. This position places the forces closer to the fulcrum line. Duplicating an existing denture or a wax trial denture in a clear acrylic resin stent that fits over the cast during bar fabrication is helpful in determining how far anteriorly the bar and clip may be placed. It must be remembered, however, that an anteriorly cantilevered bar is more limited with two implants than with four implants. An extremely stable and retentive implant-supported overdenture prosthesis is the “spark erosion” restoration (Dental Arts Laboratories, Inc., Peoria, Ill.) whereby the prosthesis fits with great precision over a two-degree tapered milled bar. The final prosthesis is totally implantsupported, virtually as stable and retentive as a fixed prosthesis, but may have a buccal flange for optimum esthetics. Retrievability by the patient allows for oral hygiene access. Thus, the benefits of both fixed and removable prostheses are obtained. Cantilevering guidelines must be followed with this implant-supported restoration.
Fixed partial
denture
design
Edentulous patients with minimal ridge resorption may be treated in a manner similar to the treatment for a par-
SHARMA,
AND
NISRIMURA
tially edentulous patient. Fixed prostheses can be made similar to those for restoring partially edentulous residual ridges where minimal resorption exists. In these situations porcelain fused-to-metal fixed implant-supported restorations may be used. Before implant placement, a wax trial complete denture can be made on a preliminary cast for initial evaluation of bone resorption and its effect on lip support. The buccal flange is removed before the trial because the final porcelain fused-to-metal restoration would not have a buccal flange. If acceptable esthetics are achieved with this flangeless prosthesis, the trial denture may be converted into a surgical stent. Porcelain fused-to-metal fixed prostheses should be designed to appear as if natural teeth are emerging through the mucosa. For this reason implant placement is critical. The implants must be placed as close to the facial aspects of the restoration as possible without necessitating a facial screw access channel. This position allows for proper bucCal-to-lingual dimension of the restoration. The implants must also be placed properly mesiodistally. Interproximal implant placement results in poor esthetics. Vertically, the implant fixture must be placed apically (approximately 4 mm below the projected cementoenamel junction) so that adequate space exists mucosally to create a gradual and natural emergence profile as the restoration exits through the mucosa.” This apical placement improves esthetics and promotes oral hygiene. To achieve such demanding implant placement, surgical stents must be used. If moderate to severe resorption has occurred, the teeth of the final prosthesis may appear unusually long with large interproximal spaces; and because the maxillae resorb palatally, the prosthesis may also appear flared laterally. Because of these considerations and possible problems with precise implant placement, it is recommended that an implant-supported and retained fixed provisional restoration be made. If successful esthetically and functionally, and if proper oral hygiene can be maintained, then the definitive restoration can be made. Patients must know during the initial workup that if there are esthetic or hygiene compromises with a fixed provisional restoration of this type, an alternative approach might be needed. That approach would most often be a removable overlay type of prosthesis, perhaps utilizing spark erosion technology. Therefore, the final decision to fabricate a porcelain fused-to-metal prosthesis is often made only after the successful use of a fixed provisional restoration, long after the patient has committed to treatment. There are two popular techniques to fabricate esthetic porcelain fused-to-metal restorations on Branemark implants (Nobelpharma USA, Chicago, Ill.). Both involve restorations that begin subgingivally so that porcelain can emerge through the mucosa with a smooth, gradual, and natural profile. These techniques use either the UCLA abutment5v6 or the esthetic titanium conical abutments such as the Nobelpharma Est,hetiCone (Nobelpharma
SEPTEMBER
1992
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NUMBER
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TREATMENT
OF EDENTULOUS
MAXILLAE
Fig. 9. Maxillary UCLA abutment restoration provides a smooth and gradual emergence profile through the mucosa. Fig. 10. Final porcelain fused to metal restoration uses EsthetiCone system (Nobelpharma USA, Chicago, Ill.) and provides an esthetic and hygienic restoration. Fig. 11. Provisional restoration contains gold alloy cylinders for each EsthetiCone abutment. Esthetics, phonetics, and oral hygiene access are evaluated intraorally before fabrication of a definitive restoration. Fig. 12. Maxillary fixed provisional restoration is used to evaluate phonetics, esthetics, hygiene access, aad patient acceptance. A tissue bar and overdenture was eventually determined to be the treatment of choice.
USA). 7~8 Both result in an esthetic and hygienic restoration, even when the patient shows the cervical third of the tooth. The UCLA abutment technique provides a restoration that fits directly to the implant fixtures. A master cast with implant fixture analogs must be made (Fig. 7). The wax pattern incorporates plastic UCLA abutments that fit directly to the fixture analogs (Fig. 7). The resulting castings then fit directly to the implant fixtures, a solder relationship is made, porcelain is applied, and the final restoration is completed (Fig. 8 and 9). Soft tissue casts are useful for this or any technique where the subgingival contours are critical. The Nobelpharma EsthetiCone (Nobelpharma USA) titanium abutment is designed to provide emergence profiIes similar to the UCLA abutment with similar esthetic and hygienic results. This abutment provides for a titanium-
THE JOURNAL
OF PROSTRETIC
DENTISTKY
to-mucosal interface subgingivally and a titanium-to-titanium interface at the level of the implant fixture. Gold alloy cylinders (Nobelpharma USA) become part of the wax pattern and ultimately part of the restoration, providing the fit of the restoration to the abutments. Gold screws (Nobelpharma USA) retain the restoration (Fig. 10). A soft tissue cast is also recommended here. Both techniques, the UCLA abutment and EsthetiCone abutment, provide the ability to fabricate fixed provisional restorations. As stated, this concept is important before fabrication of a definitive restoration (Fig. 11). Although it may appear to most clinicians that fixed restorations are the most ideal method of replacing missing teeth, this assumption is not always true. Many patients are more satisfied with a removable prosthesis in the edentulous maxillae because these prostheses may better achieve proper esthetics, adequate lip support, normal speech patterns,
507
LEWIS,
and oral hygiene access. Even patients who initially appear to be good candidates for a porcelain fused-to-metal restoration because of adequate ridge form and lip support must be further evaluated in the provisional stage (Fig. 12).
There are several treatment options for the edentulous maxillae with osseointegrated implants. The classic hybrid prosthesis was initially the most common approach, but, because of esthetic and hygienic compromises most often noted with limited interarch distance or high smile lines, this restoration is losing its popularity. Removable implant-retained overlay prostheses are perhaps the most predictably satisfying restorations for edentulous maxillae because esthetics and hygiene access can easily be achieved in most patients. Treatment options for this type of restoration include full palatal coverage if only two implants are placed or a restoration without palatal coverage when four or more implants are present. The option used may be dependent on patient preference or bone availability. Another prosthesis approach includes porcelain fusedto-metal restorations. This treatment is best achieved if only minimal residual ridge resorption has occurred. Both flangeless wax trial dentures before implant placement and implant-supported fixed provisional restorations after abutment connection are recommended to determine the feasibility of this approach before beginning the definitive
508
SHARMA,ANDNISfIIMbiRA
restoration. The UCLA abutment or esthetically designed titanium abutments such as the Nobelpharma EsthetiCone system may be used to achieve maximum esthetic results. The spark erosion prosthesis provides comfort and function similar to that of a fixed prosthesis while maintaining the esthetic and hygienic advantages of a removable prosthesis. REFERENCES 1. Cm AB, Laney WR. Maximum occlusal force levels with osseointegrated oral implant prostheses and patients with complete dentures. Int J Oral Maxillofac Implant 1967;2:101-8. 2. Adell R, Lekholm U, Rock&B, Branemark P-I. A 15-year study of osseaintegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;6:387-416. 3. Lundqvist S, Carlsson G. Maxillary fixed prostheses on osseointegrated dental implants. J PROSTKETDENTI~~~;~~:Z~~-~O. 4, Pare1 S, Sullivan D. Esthetics and osseointegration. Dallas: Taylor Publishing, 1989;29-96. 5. Lewis S, Beumer J, Moy P, Hornburg W. The UCLA abutment. Int J Oral Maxillofac Implant, 1988;3:183-9. 6. Lewis S, Llamas D, Avera S. The UCLA abutment: a four-year review. J PROSTHETDENT 1992;6'7:509-15. 7. Lewis S. An esthetic titanium abutment: report of a technique. Int J Oral Maxillofac Implant 1991;6:195-201. 8. Pare1 S, Lewis S. Esthetic implant restorations. Esthetic Dentistry Update 1991;2:29-31.
Reprint requests to: DR.STEVENLEWIS AO-156 CHS 10833 LECONTEAYE. Los ANGELES,CA~OOZ~
SEPTEMBER
1992
VOLUME
68
NUMBER
3
ent of edentulous
maxillae
with
osseointegrated
S. Lewis, DMD,a A. Sharma, BDS,b and R. Nishimura, DDW University of California-Los A.ngeles, School of Dentistry, Los Angeles, Calif. Edentulous maxillae can be restored with implant supported fixed restorations containing denture teeth on a metal framework, implant-retained removable overlay prostheses, or porcelain fused-to-metal fixed prostheses. Esthetics and hygiene access are two important factors in determining the restoration best suited for each patient. Treatment planning considerations and treatment procedures for the various techniques are discussed. (J PROSTHET DENT 1992;68:503-8.)
T reatment
of edentulous patients with fixed restorations supported by osseointegrated implants can provide excellent function1 with high levels of long-term success.2 Although the hybrid mandibular fixed prosthesis, or fixed bone-anchored bridge, can be designed with acceptable esthetics and good oral hygiene access, the restoration often presents problems in the edentulous maxillae. Achieving proper esthetics and maintaining adequate hygiene access may be difficult. Although hybrid fixed implant restorations may be successful esthetically and hygienically, implant-retained removable overlay prostheses are often the treatment of choice in the edentulous maxillae. In some instances, porcelain fused-to-metal restorations may be used in the edentulous maxillae and may provide optimum esthetics and hygiene access. This article discusses the considerations involved in determining the treatment of choice for the edentulous maxillae and the restorative techniques involved.
Hybrid
fixed
implant
restoration
The hybrid, maxillary fixed implant-supported prosthesis described by Lundqvist and Carlsson3 is a popular means of restoring edentulous patients. The restoration consists of denture teeth connected to ‘a metal framework with acrylic resin. By the incorporation of gold alloy cylinders into the framework, the restoration is supported by the titanium transmucosal abutment cylinders and is retained with gold alloy screws. ‘This restoration is not retrievable by the patient and must be designed to provide oral hygiene access around the abutment cylinders as they emerge through the mucosa. Exposing these cylinders for
Presented before the Pacific Coast Society of Prosthodontists, Victoria, British Columbia, Canada. aAssistant Professor, Removable Prosthodontics. bPrivate Practice, San Francisco, Calif. CAssistant Professor, Removable Prosthodontics. 10/l/39133
THEJOURNAL
OFPROSTHETIC DENTISTRY
hygiene access, however, may compromise esthetics. Because many edentulous patients present with at least moderate residual ridge resorption, the abutment cylinders are often out of sight and distant from the prosthetic teeth and the smile line. Because many patients show more maxillary teeth than mandibular teeth, visualization of the abutments resulting in poor esthetics is more common in the maxillae. The less ridge resorption and/or the higher the smile line, the greater is the likelihood of an esthetic problem because the abutment cylinders become visible. Making the abutments with a prosthesis flange compromises oral hygiene access (Fig. 1). When treatment is being planned, the patient should remove an existing maxillary denture and smile. The further away the maxillary residual ridge is from the smile line, the less likely it is that the transmucosal abutment cylinders will be visible during normal function (Fig. 2). Covering abutment cylinders with an acrylic resin flange, however, creates a significant hygiene problem. For this type of fixed prosthesis to be successful esthetically and hygienically, significant distance must be present between the smile line and the residual ridge (Fig. 3). Lip support without the maxillary denture in place must also be evaluated, because the fixed restoration does not contain a buccal flange. In severely resorbed states a flange may be needed to provide adequate facial contours. In some instances it may be difficult to determine the potential for success with this type of prosthesis. It may not be until the wax try-m that the final restorative choice is made. The wax trial prosthesis must be similar to the final restoration in design. The tissue surface must be convex and there can be no buccal flange covering the transmucosal abutment cylinders because they must be exposed for easy oral hygiene access. Only then can the esthetics be accurately determined by evaluating the visibility of the abutment cylinders and the lip support (Fig. 4). It is important to explain to patients at the initial consultation that, even if a fixed prosthesis is planned, the
503
LEWIS,
SHARMA,
AND
NISHIMURA
Fig. 1. Transmucosal abutment cylinders are disguised by ridge lapping, which results in contours that provide poor hygiene access.
Fig. 3. Moderate to severe resorption provides adequate space for teeth, denture base, metal framework, and hygiene access while not compromising esthetics.
Fig. 2. These abutment covered with a flange.
Fig. 4. Tissue surface of restoration is convex for adequate oral hygiene access. A low smile line prevents visualization of space.
cylinders would be visible unless
treatment may be changed to a removable overlay prosthesis if the wax trial prosthesis is unacceptable. The other alternative is to make a separate buccal flange that is removable by the patient. If the only difficulty resulting from adequate oral hygiene space is poor phonetics, a removable palatal flange may also be a solution. Implant placement is somewhat critical for the fixed prosthesis. If placed buccally the screw access channels could exit through the facial aspects of the denture teeth, creating an esthetic problem. If placed too far palatally the restoration will become excessively wide in the buccal-topalatal dimension, causing a hygiene problem. Therefore, surgical stents are needed to ensure proper buccal-to-palatal placement. Mesial-to-distal relationship is not as critical for this prosthesis design because abutment cylinders positioned interproximally would be above the smile line and not visible during normal function.
504
Implant-retained
overlay
prosthesis
There are several advantages to the implant-retained overlay prosthesis in the edentulous maxillae. The buccal flange provides esthetic advantages that fixed restorations lack. With a flange there is no visible evidence of the titanium abutment cylinders emerging through the mucosa or the space required for proper hygiene. The flange also provides lip support, which is so often lacking with the placement of a hygienic fixed restoration. Moreover, phonetics may be improved because the hygiene space beneath a fixed prosthesis and the resulting escape of air during speech are no longer a factor with the presence of a flange. In addition to the esthetic and functional advantages of this restoration, oral hygiene is easy when the prosthesis is removed by the patient to expose the substructure. Two maxillary overlay prosthesis designs are commonly used. One type contains full palatal coverage comparable to
SEPTEMBER
1992
VOLUME
68
NUMBER
3
TREATMENT
OF EDENTULOUS
MAXILLAE
Fig. 6. Bar design has two distal resilient attachments that allow displacement toward the mucosa when posterior function occurs, rotating about the anterior clip.
Fig.
5. Correct (A) and incorrect (IB) design of tissue bar.
a maxillary complete denture. Two anterior implants may be used to retain the prosthesis, with a choice of various types of attachments. Full palatal coverage is needed for adequate support, stability, and retention. When a bar and clip retentive system is used, it is recommended that the bar be oriented parallel to the axis of rotation or perpendicular to the palatal suture. On posterior occlusal function, the clip will rotate around the bar, allowing the prosthesis to benefit from posterior soft tissue support. Clip wear will be minimized with this design, because the constant need to replace retentive clips is indicative of poor orientation of the tissue bar. Without the proper alignment, adverse forces will be placed on the retentive clips, the tissue bar, and the implant fixtures (Fig. 5). The second design is one with reduced palatal coverage. With full palatal coverage eliminated, the posterior palatal seal is removed. To regain this retention, retentive components must be placed posteriorly. Distal cantilevering from two implants is not recommended because of excessive loading; thus, four or more implants are needed when posterior implant retention is required. All other aspects of the prosthesis remain unchanged, providing improved esthetics, function, and hygiene access to the transmucosal abutments. Four implants may not be adequate to provide total
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 7. Master cast includes implant fixture analogs beneath the cast surface. Plastic UCLA abutments are connected to analogs in preparation of wax-up.
support for a maxillary prosthesis. Therefore it is important to ensure some mucosal support. The posterior retentive components should allow for vertical movement so that the denture displaces toward the mucosa for added support, rotating about the anterior clip, which is parallel to the axis of rotation (Fig. 6). With posterior mucosal support maintained, the length of the occlusal table is not limited. An initial treatment plan may include a fixed prosthesis on five or six implants that is changed to an overdenture at the wax try-in appointment, perhaps for esthetic or functional reasons. In this situation, the final overlay prosthesis can be totally implant-supported with tissue contact only to prevent food impaction. Vertical resiliency of the posterior retentive components is not needed. The functional abilities of this type of prosthesis should approach those of a fixed restoration while maintaining esthetic and
505
LEWIS,
Fig. 8. Finished restorations connect directly to implant fixtures and are retained with titanium alloy screws.
hygienic advantages. Maxillary cantilever guidelines of 10 to 15 mm beyond the distal implants must be considered with this implant-supported design. Posterior resilient attachments provide soft tissue support and eliminate these restrictions. For maxillary overdentures, whether they are conventional on two implants or with reduced palatal coverage on four or more implants, the placement of the anterior clip is critical for stability. Because the maxillae resorb palatally, the anterior teeth are often placed anterior to the residual ridge. This placement might be quite significant the more prognathic the ridge relationship becomes. The more anterior the teeth are, relative to the retentive clip, the more anterior rotation will be evident during incising. The resulting prosthesis instability could be decreased by placement of the bar and clip more anteriorly beneath the teeth. This position places the forces closer to the fulcrum line. Duplicating an existing denture or a wax trial denture in a clear acrylic resin stent that fits over the cast during bar fabrication is helpful in determining how far anteriorly the bar and clip may be placed. It must be remembered, however, that an anteriorly cantilevered bar is more limited with two implants than with four implants. An extremely stable and retentive implant-supported overdenture prosthesis is the “spark erosion” restoration (Dental Arts Laboratories, Inc., Peoria, Ill.) whereby the prosthesis fits with great precision over a two-degree tapered milled bar. The final prosthesis is totally implantsupported, virtually as stable and retentive as a fixed prosthesis, but may have a buccal flange for optimum esthetics. Retrievability by the patient allows for oral hygiene access. Thus, the benefits of both fixed and removable prostheses are obtained. Cantilevering guidelines must be followed with this implant-supported restoration.
Fixed partial
denture
design
Edentulous patients with minimal ridge resorption may be treated in a manner similar to the treatment for a par-
SHARMA,
AND
NISRIMURA
tially edentulous patient. Fixed prostheses can be made similar to those for restoring partially edentulous residual ridges where minimal resorption exists. In these situations porcelain fused-to-metal fixed implant-supported restorations may be used. Before implant placement, a wax trial complete denture can be made on a preliminary cast for initial evaluation of bone resorption and its effect on lip support. The buccal flange is removed before the trial because the final porcelain fused-to-metal restoration would not have a buccal flange. If acceptable esthetics are achieved with this flangeless prosthesis, the trial denture may be converted into a surgical stent. Porcelain fused-to-metal fixed prostheses should be designed to appear as if natural teeth are emerging through the mucosa. For this reason implant placement is critical. The implants must be placed as close to the facial aspects of the restoration as possible without necessitating a facial screw access channel. This position allows for proper bucCal-to-lingual dimension of the restoration. The implants must also be placed properly mesiodistally. Interproximal implant placement results in poor esthetics. Vertically, the implant fixture must be placed apically (approximately 4 mm below the projected cementoenamel junction) so that adequate space exists mucosally to create a gradual and natural emergence profile as the restoration exits through the mucosa.” This apical placement improves esthetics and promotes oral hygiene. To achieve such demanding implant placement, surgical stents must be used. If moderate to severe resorption has occurred, the teeth of the final prosthesis may appear unusually long with large interproximal spaces; and because the maxillae resorb palatally, the prosthesis may also appear flared laterally. Because of these considerations and possible problems with precise implant placement, it is recommended that an implant-supported and retained fixed provisional restoration be made. If successful esthetically and functionally, and if proper oral hygiene can be maintained, then the definitive restoration can be made. Patients must know during the initial workup that if there are esthetic or hygiene compromises with a fixed provisional restoration of this type, an alternative approach might be needed. That approach would most often be a removable overlay type of prosthesis, perhaps utilizing spark erosion technology. Therefore, the final decision to fabricate a porcelain fused-to-metal prosthesis is often made only after the successful use of a fixed provisional restoration, long after the patient has committed to treatment. There are two popular techniques to fabricate esthetic porcelain fused-to-metal restorations on Branemark implants (Nobelpharma USA, Chicago, Ill.). Both involve restorations that begin subgingivally so that porcelain can emerge through the mucosa with a smooth, gradual, and natural profile. These techniques use either the UCLA abutment5v6 or the esthetic titanium conical abutments such as the Nobelpharma Est,hetiCone (Nobelpharma
SEPTEMBER
1992
VOLUME
68
NUMBER
3
TREATMENT
OF EDENTULOUS
MAXILLAE
Fig. 9. Maxillary UCLA abutment restoration provides a smooth and gradual emergence profile through the mucosa. Fig. 10. Final porcelain fused to metal restoration uses EsthetiCone system (Nobelpharma USA, Chicago, Ill.) and provides an esthetic and hygienic restoration. Fig. 11. Provisional restoration contains gold alloy cylinders for each EsthetiCone abutment. Esthetics, phonetics, and oral hygiene access are evaluated intraorally before fabrication of a definitive restoration. Fig. 12. Maxillary fixed provisional restoration is used to evaluate phonetics, esthetics, hygiene access, aad patient acceptance. A tissue bar and overdenture was eventually determined to be the treatment of choice.
USA). 7~8 Both result in an esthetic and hygienic restoration, even when the patient shows the cervical third of the tooth. The UCLA abutment technique provides a restoration that fits directly to the implant fixtures. A master cast with implant fixture analogs must be made (Fig. 7). The wax pattern incorporates plastic UCLA abutments that fit directly to the fixture analogs (Fig. 7). The resulting castings then fit directly to the implant fixtures, a solder relationship is made, porcelain is applied, and the final restoration is completed (Fig. 8 and 9). Soft tissue casts are useful for this or any technique where the subgingival contours are critical. The Nobelpharma EsthetiCone (Nobelpharma USA) titanium abutment is designed to provide emergence profiIes similar to the UCLA abutment with similar esthetic and hygienic results. This abutment provides for a titanium-
THE JOURNAL
OF PROSTRETIC
DENTISTKY
to-mucosal interface subgingivally and a titanium-to-titanium interface at the level of the implant fixture. Gold alloy cylinders (Nobelpharma USA) become part of the wax pattern and ultimately part of the restoration, providing the fit of the restoration to the abutments. Gold screws (Nobelpharma USA) retain the restoration (Fig. 10). A soft tissue cast is also recommended here. Both techniques, the UCLA abutment and EsthetiCone abutment, provide the ability to fabricate fixed provisional restorations. As stated, this concept is important before fabrication of a definitive restoration (Fig. 11). Although it may appear to most clinicians that fixed restorations are the most ideal method of replacing missing teeth, this assumption is not always true. Many patients are more satisfied with a removable prosthesis in the edentulous maxillae because these prostheses may better achieve proper esthetics, adequate lip support, normal speech patterns,
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and oral hygiene access. Even patients who initially appear to be good candidates for a porcelain fused-to-metal restoration because of adequate ridge form and lip support must be further evaluated in the provisional stage (Fig. 12).
There are several treatment options for the edentulous maxillae with osseointegrated implants. The classic hybrid prosthesis was initially the most common approach, but, because of esthetic and hygienic compromises most often noted with limited interarch distance or high smile lines, this restoration is losing its popularity. Removable implant-retained overlay prostheses are perhaps the most predictably satisfying restorations for edentulous maxillae because esthetics and hygiene access can easily be achieved in most patients. Treatment options for this type of restoration include full palatal coverage if only two implants are placed or a restoration without palatal coverage when four or more implants are present. The option used may be dependent on patient preference or bone availability. Another prosthesis approach includes porcelain fusedto-metal restorations. This treatment is best achieved if only minimal residual ridge resorption has occurred. Both flangeless wax trial dentures before implant placement and implant-supported fixed provisional restorations after abutment connection are recommended to determine the feasibility of this approach before beginning the definitive
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restoration. The UCLA abutment or esthetically designed titanium abutments such as the Nobelpharma EsthetiCone system may be used to achieve maximum esthetic results. The spark erosion prosthesis provides comfort and function similar to that of a fixed prosthesis while maintaining the esthetic and hygienic advantages of a removable prosthesis. REFERENCES 1. Cm AB, Laney WR. Maximum occlusal force levels with osseointegrated oral implant prostheses and patients with complete dentures. Int J Oral Maxillofac Implant 1967;2:101-8. 2. Adell R, Lekholm U, Rock&B, Branemark P-I. A 15-year study of osseaintegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;6:387-416. 3. Lundqvist S, Carlsson G. Maxillary fixed prostheses on osseointegrated dental implants. J PROSTKETDENTI~~~;~~:Z~~-~O. 4, Pare1 S, Sullivan D. Esthetics and osseointegration. Dallas: Taylor Publishing, 1989;29-96. 5. Lewis S, Beumer J, Moy P, Hornburg W. The UCLA abutment. Int J Oral Maxillofac Implant, 1988;3:183-9. 6. Lewis S, Llamas D, Avera S. The UCLA abutment: a four-year review. J PROSTHETDENT 1992;6'7:509-15. 7. Lewis S. An esthetic titanium abutment: report of a technique. Int J Oral Maxillofac Implant 1991;6:195-201. 8. Pare1 S, Lewis S. Esthetic implant restorations. Esthetic Dentistry Update 1991;2:29-31.
Reprint requests to: DR.STEVENLEWIS AO-156 CHS 10833 LECONTEAYE. Los ANGELES,CA~OOZ~
SEPTEMBER
1992
VOLUME
68
NUMBER
3
