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Anterior Implant-Supported Reconstructions

A Prosthetic Challenge

Interdisciplinary treatment planning and the development of a comprehensive surgical and restorative approach are critical factors in the final aesthetic success of a clinical case. Complete reconstruction of tooth- and gingiva-related aesthetics that match the appearance of the natural healthy tissues remains the ultimate objective of any treatment.

To a large extent, the predictability of aesthetic success depends on the degree of tissue loss present at the initiation of the treatment. Consequently, the use of single-unit implant-supported restorations have a high degree of predictability, since the adjacent natural teeth--with intact bone and soft tissue attachment--can provide the morphological substructure that is required to restore natural gingival and papillary architecture. The objective of this article is to discuss contemporary techniques utilized to replace a single missing tooth in the anterior maxilla.

 

Treatment Planning

In order to gain complete information on the site indicated for restoration, comprehensive facial, dental, and periodontal analysis should be performed. Facial analysis should provide information about a patient's general aesthetic physiognomy and smile line. The dental analysis is performed to evaluate the size, shape, and position of the patient's anterior teeth. Finally, the degree of bone and attachment loss in the area of the site and the adjacent natural teeth is evaluated during periodontal analysis (Figures 1 and 2). Based on these evaluations, a diagnostic waxup—which allows the anticipated restorative result to be previewed—can be used for the fabrication of an accurate surgical stent that offers additional information on the three-dimensional position of the implant at surgery.

 

Surgical Considerations

General surgical considerations include atraumatic tooth removal, bone and soft tissue management, and ideal implant placement. The restorative team should also contemplate the use of autogenous bone grafts, barrier membranes of nonresorbable or resorbable material, and tension-free flap closure. It is also necessary to prevent pressure on the surgical site during the healing period and to carefully monitor soft tissue health around implant and reconstructive sites. The degree of bone and attachment loss and the desired arch position of the implant determine whether a one-stage, two-stage, or three-stage surgical approach should be selected.1

A one-stage implant procedure with or without flap elevation is possible in patients who have sufficient bone and soft tissue present to place an implant in the ideal restorative position with 360˚ bone surrounding the implant. The advantage of this procedure is that it is minimally invasive and a second surgery for the abutment connection is unnecessary. An additional benefit is that the gingival and papillae profile are not changed, and this results in ideal soft tissue harmony.2

A two-stage implant procedure with full flap elevation is necessary in patients who have insufficient gingival tissue and bone support in the horizontal and vertical plane to place an implant in an ideal aesthetic position. These sites require augmentation simultaneously with implant placement to allow bone and soft tissue to regenerate in the deficient regions around the ideally placed implant.3 The implant site is completely closed to promote an uneventful healing period. To allow ideal bone and soft tissue harmony around the definitive implant crown, it is necessary to over-contour the augmentation site during the surgical procedure. The second surgery for the abutment connection is minimally invasive and utilizes a palatal approach for access, short buccal vertical incisions, and soft tissue grafts as necessary. This allows rapid healing around the abutment with minimal scar tissue. An under-dimensioned provisional restoration can be placed 2 to 3 weeks postoperatively.

A three-stage implant procedure is indicated for patients who have a severe deficiency of horizontal and vertical bone that prevents the installation of an implant.4 These severe deficiencies are treated with a staged augmentation and implant procedure. The first stage involves the augmentation of the ridge defect with an autogenous bone graft, with or without membrane, for horizontal and vertical reconstruction. A soft tissue graft can also be harvested and added to this bone reconstructive procedure to allow for increased volume of soft tissue. Following a healing period of approximately 6 to 8 months, the implant can be placed in its ideal position. If a ridge defect is still present around the implant, a simultaneous implant and bone and soft tissue augmentation procedure can be performed. In this instance, an additional healing period of 6 months must be permitted. The third stage involves soft tissue management during the abutment connection surgery, which is approached from the palate to prevent any trauma and recession of the buccal tissues.

           

Prosthetic Considerations

In the natural dentition, interproximal contacts and a tissue attachment that follows the scalloped outline of the cementoenamel junction are responsible for the shape of the gingiva, which results in well-formed and aesthetically pleasing interdental papillae. 5,6 Since implant necks are flat, a specific prosthodontic approach is necessary to match the desired contour of the marginal tissues to the natural shape of a healthy papilla. To improve predictability, a conservative approach in which pressure is applied on marginal tissues should be utilized rather than unpredictable (ie, electrosurgical) means.7-9 Treatment options for such a conservative approach consist of anatomically shaped healing abutments that may be machined or customized, and accordingly shaped provisional and definitive restorations.

 

Case Presentation

A 30-year-old female patient presented with a failing implant at the site of tooth #8 (Figures 3 and 4). A comprehensive treatment plan that required the removal of the implant fixture and bone reconstruction with a monocortical bone graft and a barrier membrane at stage I was designed by the restorative team (Figures 5, 6, and 7). At stage II (nine months after the completion of the initial surgery), implant placement (Figure 8) was followed by surgical augmentation of the site with a connective tissue graft (Figure 9) to permit the development of optimal ridge architecture during the subsequent provisionalization phase.

At stage III, following an additional maturation phase of 6 months, the patient demonstrated tissue that was similar to the adjacent natural dentition in the vertical and sagittal dimensions (Figure 10). Once a standard healing abutment had been placed, the palatal position of the seated implant fixture--as dictated by the compromised bone volume--was associated with a considerably undercontoured labial emergence profile (Figures 11 and 12). A standard coping was then utilized to make an impression, and a silicon reproduction of the gingiva surrounding the implant was fabricated on the master model (Figure 13). In order to preview the correct emergence profile, a provisional restoration was fabricated to match the ideal emergence profile of a natural incisor. Prior to its first insertion, the cervical contour of the provisional restoration was reduced 30 percent in volume as a transition between the emergence profile of the healing abutment and the ideal shape of the previewed definitive contour (Figure 14). This process prevented overtraumatization of the gingival tissues due to the mismatch of the contour of the gingival margin around the neck of the fixture and the ideal contour. To prevent additional palatal overcontour, acrylic resin was added to a metal abutment on the proximal and labial aspects only.

Following a 2-week period, the marginal tissues adapted to the initial impulse, and the cervical volume was increased to the ideal triangular cross-sectional shape of a natural central incisor (Figure 15). The patient consented to the aesthetic correction of the malpositioned right lateral incisor with composite, which preserved the option for subsequent orthodontic treatment (Figure 16). To transfer the developed emergence profile into the master model (Figure 17), a standard impression coping was modified with acrylic (Figure 18). A putty key of the waxup on the master model allowed the casting of an individualized abutment structure that would properly support the porcelain-fused-to-metal (PFM) restoration. The definitive restoration exhibited an acceptable marginal tissue contour and formation of proximal papillae when compared with the adjacent natural teeth (Figure 19).

 

Discussion

With comprehensive treatment planning and a careful surgical and restorative approach, a relatively predictable aesthetic result can be achieved even in patients with compromised implant sites. Single-tooth implant sites with adjacent natural teeth that present a healthy periodontal ligament (i.e., full papilla, scallop-shaped bone, and soft tissue) can be restored and maintained with an ideal aesthetic outcome as the periodontium of the natural teeth will support the bone level superior to the implant-abutment interface. If the periodontium of the natural teeth is compromised and gingival recession is present, however, the aesthetic outcome of the single-tooth implant restoration will exhibit similar features as multiple-implant sites and demonstrate an unpredictable aesthetic result.

 

Conclusion

Treatment of the anterior maxilla with implant-supported restorations remains a challenge and requires thorough treatment planning between the oral surgeon and the prosthodontist, particularly if the area of the deficient teeth is compromised by additional tissue loss. Fabrication of a waxup and a detailed stent for the implant placement appear to be helpful initial steps. A conservative treatment using primarily pressure to form the marginal tissues to the desired shape appears to improve the predictability of achieving an aesthetic result - even with compromised patients. In order to improve the long-term stability of such results, however, the interface between implants and abutments may require reconsideration.

  

References

  1. Jovanovic SA. Bone rehabilitation to achieve optimal implant aesthetics. Pract Periodont Aesthet Dent 1997;9(1):41-52.
  2. Simion M, Jovanovic SA, Trisi P, et al. Vertical ridge augmentation around dental implants using a membrane technique and autogenous bone or allografts in humans. Int J Periodont Rest Dent 1998;18(1):8-23.
  3. Wohrle PS. Single-tooth replacement in the aesthetic zone with immediate provisionalization: Fourteen consecutive case reports. Pract Periodont Aesthet Dent 1998;10(9):1107-1114.
  4. Buser D, Dula K, Hirt HP, Schenk RK. Lateral ridge augmentation using autografts and barrier membranes: A clinical study with 40 partially edentulous patients. J Oral Maxillofac Surgery 1996;54(4):420-433.
  5. Kois JC. Altering gingival levels: The restorative connection. Part 1: Biologic levels. J Esthet Dent 1994;6(1):3-9.
  6. Saadoun AP, Le Gall MG. Periodontal implications in implant treatment planning for aesthetic results. Pract Periodont Aesthet Dent 1998;10(5):655-664.
  7. Azzi R. Electrosurgery in periodontics: A literature review. J West Soc Periodontol 1981;29(1):4-10.
  8. Azzi R, Kenney EB, Tsao TF, Carranza FA. The effect of electrosurgery on alveolar bone. J Periodontol 1983;54(2):96-100.
  9. De Vitre R, Galburt RB, Maness WJ. Biometric comparison of bur and electrosurgical retraction methods. J Prosthet Dent 1985;53(2):179-182.
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