Implants

Treatment Planning and Soft-Tissue Management for Optimal Implant Esthetics: A Prosthodontic Perspective

Winston W.L. Chee, DDS Author:
Winston W.L. Chee, DDS, is the Ralph W. and Jean L. Bleak Professor of Restorative Dentistry, director of Implant Dentistry, and co-director of Advanced Education in Prosthodontics at the University of Southern California School of Dentistry. He also maintains a private practice limited to prosthodontics in Pasadena, CA.

Copyright 2003 Journal of the California Dental Association.

Esthetic restoration of implants in the anterior region of the mouth is one of the most difficult procedures to execute. This article discusses patient selection criteria. Implant position and its relationship to the esthetic outcome are also addressed. The importance of soft-tissue management in all phases of the surgical and restorative phases is emphasized. Guidelines are given for the successful delivery of this service for the patient.

Root-form cylindrical implants placed following surgical techniques described by Brånemark and colleagues are a predictable method to anchor prosthetic devices to the jaw bone.1-3 Currently, clinicians can prescribe the use of implants with the knowledge and confidence that they will predictably integrate into the jaw bone and provide lasting anchorage to restorations. The esthetic outcomes are not as predictable or consistent, however. This paper will discuss pitfalls from a prosthodontic perspective that are often encountered when restoring the anterior area of the mouth. It is the opinion of the author that achieving an esthetic outcome when restoring implants in the anterior region is one of the most difficult restorative goals to accomplish. To achieve optimal esthetics, each phase of treatment must be well-executed -- from preparation of the implant recipient site to provisional phases prior to implant placement, to implant integration and post-implant integration, implant placement, and fabrication of the definitive restoration.

Patient Selection

Patients who are candidates for replacement of an anterior tooth with an implant-supported restoration must understand the benefits of an implant restoration. They must also understand the additional time required for treatment and additional costs that will be incurred. They should also be informed of the additional difficulties in obtaining an esthetic result. This is especially important with respect to lip length.4 If the lip length is low and the patient understands that this situation will not reveal the more apical portions of the restoration, many additional steps can be avoided in reconstructing these areas (Figures 1 and 2). However, when there is a high lip line or a demanding patient, the limitations of implant-supported restorations must be discussed in detail prior to commencing treatment (Figure 3).

Bony Anatomy of the Implant Site

For successful integration of implants, sufficient bone must be available to stabilize and house the implant. If the bony anatomy is inadequate, a bone grafting procedure may be required. When these situations are encountered, patients must be made to understand that they are missing more than just a tooth. They must also understand that they are missing hard and soft tissue5-7 (Figure 4).

Soft-Tissue Thickness Over the Implant Site

One of the prerequisites for having an implant-borne restoration appear similar to a natural tooth is the contour of the restoration. However, the cross-sectional diameter of an implant is approximately 4 mm and the dimension of a central incisor is generally about 7 mm in the cervical region. Sufficient soft-tissue thickness must be present to allow this smooth transition from a circular 4.0 mm to a triangular 7 mm cross-section to create the proper emergence profile and esthetics for the restoration.8,9 This also pertains to the pontic areas of fixed partial dentures (Figures 5 and 6).

Implant Position

In most situations involving anterior implant restorations, the esthetic considerations are more important than functional considerations. As such, axial loading is not as critical as it is with posterior implant restorations. Implant position is critical to the final esthetic outcome, which must be considered in all three dimensions and in relation to the adjacent teeth.

What is usually strived for is to have the platform of the implant 3 to 5 mm apical to the cementoenamel junction of the intended replacement restoration and to have the implant as far to the labial as possible. This allows a smooth transition of contours from the narrow cross section of the implant to the natural contours of the replacement tooth6,7 (Figures 7 and 8).

With multiunit restorations, the mesiodistal positions of the implants are also critical -- errors resulting in interproximal placement of implants are difficult to manage esthetically (Figures 9 and 10).

It also must be noted that it is easier to control the esthetic outcome of the pontic area compared to an implant site in the cervical area -- use of too many implants may compromise the esthetic outcome of the restoration.

Figures 11 and 12 illustrate an implant restoration with implants in the Nos. 7, 8, 9 and 10 positions. This restoration does not require four implants to support it. A more esthetic result would have been possible without the implants placed in the Nos. 8 and 9 positions. Figures 13 and 14 show a fixed partial denture on implants in the Nos. 7 and 10 positions with Nos. 8 and 9 as pontics.

In addition, the depth of the more deeply placed implant will dictate the depth of the other implants placed, taking into account the final mucosal margins desired. Figure 15 illustrates uneven depths of implant placement for Nos. 7 and 10 resulting in uneven clinical crown lengths of Nos. 7 and 10.

Timing of Implant Placement and Site Development

If the tooth to be replaced has not yet been removed, several determinations should be made prior to the extraction. The bone surrounding the root should be evaluated; and, if it is deemed deficient, a decision must be made as to how the implant site can be improved. This can be done by orthodontic extrusion of the root fragment before extraction and/or bone grafts. Immediate placement of the implant should be attempted if the anatomical conditions are conducive; this is the most predictable method of preventing collapse of the buccal plate.6-9

Soft-Tissue Manipulation During Restoration

Assuming that the osseous anatomy is adequate to house the implant in an ideal position as described above and the soft tissue is of adequate quantity, then an excellent esthetic result is often possible with a little more effort on the part of the restorative dentist. The restorative dentist can shape and form the peri-implant soft tissue with provisional restorations to create the proper exit profile of the replacement teeth. The cross-section of the implant is only 4 mm in diameter, and the restorative dentist can use the provisional restoration to transition this to the more natural contours that will be required. The provisional restoration can likewise be used to form the pontic areas (Figures 16 and 17). This information must be communicated to the dental technician, who is a vital part of the team.10-12 The provisional restoration can be used as an impression device to transfer the shape and form of the soft tissue to the technician to allow the definitive restoration to be formed like the provisional restorations13,14 (Figures 18 through 20).

Conclusion

When a patient has a missing anterior tooth and desires replacement, a decision must be made by the dentist and patient as to the method of replacement. Common choices would include a conventional fixed partial denture, a resin-bonded fixed partial denture, or an implant-borne restoration. Each has its advantages and disadvantages. The conventional fixed partial denture has the advantages of being an established treatment procedure, having predictable esthetics, and being expedient. It has the disadvantage of requiring preparation of adjacent teeth and potential risk for periodontal and pulpal tissue. The resin-bonded partial denture has the advantages of preserving tooth structure, having predictable esthetics, and having reduced cost. It has the disadvantages of being technique-sensitive for the dentist and technician and often losing retention. The implant-supported restoration has the advantage of preserving tooth structure of adjacent teeth, being retrievable, having documented success in the long term, and allowing shorter spans of restorations. It has the disadvantages of having a long treatment time, requiring a provisional restoration during implant integration, requiring surgical placement of the implant, requiring a provisional after the implant is uncovered, and having higher cost.

Even with all the disadvantages listed, the implant-supported restoration can be successfully executed when all the factors discussed in this article are addressed. When one or more of the adjacent teeth are unrestored or in need of only a minor restoration, when a long-span fixed partial denture can be avoided, and when the abutment teeth are compromised and cannot support pontics, the implant-supported restoration should be considered the restoration of choice.

References

1. Adell R, Eriksson B, et al, A long-term follow-up study of osseointegrated implants in the treatment of totally edentulous jaws. Int J Oral Maxillofac Implants 5:347-59, 1990.

2. Naert I, Quirynen M, et al, A study of 589 consecutive implants supporting complete fixed prostheses. Part II: Prosthetic aspects. J Prosthet Dent 68:949-56, 1992.

3. Lekholm U, van Steenberghe D, et al, Osseointegrated implants in the treatment of partially edentulous jaws: A prospective 5-year multicenter study. Int J Oral Maxillofac Implants 9:627-35, 1994.

4. Teo CS, An evaluation of the smiling lip-line. Singapore Dent J 6(1):27-30, 1981.

5. Kan JY, Rungcharassaeng K, Site development for anterior single implant esthetics: the dentulous site. Compend Contin Educ Dent 22(3):221-6,228, 230-1, 2001.

6. Nowzari H, Esthetic implant dentistry. Compend Contin Educ Dent 22(8):643-50, 2001.

7. Schincaglia GP, Nowzari H, Surgical treatment planning for the single-unit implant in aesthetic areas. Periodontol 2000 27:162-82, 2001.

8. Becker W, Becker BE, Hujoel P, Retrospective case series analysis of the factors determining immediate implant placement. Compend Contin Educ Dent 21(10):805-8, 2000.

9. Wagenberg BD, Ginsburg TR, Immediate implant placement on removal of the natural tooth: retrospective analysis of 1,081 implants. Compend Contin Educ Dent 22(5):399-404, 2001.

10. Chee WW, Provisional restorations in soft tissue management around dental implants. Periodontol 2000 27:139-47, 2001.

11. Chee WW, Nowzari H, Kaneko L, Esthetic replacement of the anterior tooth with an implant-supported restoration. J Calif Dent Assoc 25(12):860-5, 1997.

12. Neale D and Chee WWL, Development of soft tissue emergence profile: A technique J Prosthet Dent 71:364-8, 1994.

13. Chee WW, Cho GC, et al, A technique to replicate soft tissues around fixed restoration pontics on working casts. J Prosthodont 8(1):44-6, 1999.

14. Chee WW, Cho GC, Ha S, Replicating soft tissue contours on working casts for implant restorations. J Prosthodont 6(3):218-20, 1997.

To request a printed copy of this article, please contact/Winston W.L. Chee, DDS, USC School of Dentistry, 925 W. 34th St., Room 4374, Los Angeles, CA 90089-0641, (213) 740-1537, wchee@usc.edu.

Legends

Figure 1. Anterior view of patient smile showing display of implant-supported restoration from No. 6 through No. 10.

Figure 2. View of restoration in Figure 1 with lips retracted (note uneven clinical crown lengths, which are not visible with this patient’s lip mobility).

Figure 3. Anterior view of patient smile displaying loss of papilla between teeth Nos. 8 and 9 with implant restoration. With these patients, it is much more difficult to achieve a satisfactory result.

Figure 4. Retracted view of anterior implant-supported fixed partial denture from No. 6 through No. 10 with No. 7 implant in poor restorative position due to insufficient bone.

Figure 5. Illustrating the transition in contour required from the implant to the emergence of the clinical crown from the mucosa.

Figure 6. Occlusal view of peri implant soft-tissue contours and ridge anatomy under ovate pontics for an implant-supported fixed partial denture.

Figure 7. Anterior view illustrating ideal depth of implant in relation to restoration (note smooth transition in contours).

Figure 8. Sagittal view illustrating smooth transition from implant to labial surface with proper implant placement.

Figure 9. Illustrates implants placed in interproximal area with surgical guide in place.

Figure 10. Restoration with implant positions in Figure 9 with non-ideal esthetics.

Figure 11. Occlusal view of four implants placed to restore teeth Nos. 7 through 10 (note reverse arch form of implants).

Figure 12. Labial view of restoration of implants in Figure 11 -- note poor relation of mucosal margins.

Figure 13. Occlusal view of implant restoration from Nos. 7 through 10 with implants in Nos. 7 and 10 area.

Figure 14. Anterior view of restoration in Figure 13 -- Nos. 8 and 9 are pontics, control of esthetics is easier with pontics than implants.

Figure 15. Anterior view of implant-supported restoration from No. 7 through No. 10 with implants in Nos. 7 and 10 (note asymmetry of Nos. 7 and 10 due to uneven implant depth).

Figure 16. Provisional restoration for implant-supported restoration from No. 7 though No. 10.

Figure 17. Soft-tissue morphology with provisional restoration in Figure 16 removed.

Figure 18. Provisional restoration “picked up” as impression coping in impression tray.

Figure 19. The soft-tissue morphology developed by the provisional restoration in Figure 16 is communicated to the dental laboratory.

Figure 20. Labial view of completed restoration.