Dental Implant Repositioning by Osteotomy in the Esthetic Zone
A step back can be incautious too.
Implant placement following dental extraction with immediate provisional restoration has often led to late-term gingival recession, resulting in an unesthetic, relatively long crown.1,2 When dehiscence of the facial surface of the implant occurs, the restoration presents as a dark shadow beneath the soft tissue.3 If the dehiscence is severe, screw threads become exposed, and a chronic peri-implant infection may develop.4 The natural progression of a chronically infected implant is further bone loss that can extend circumferentially around the implant and involve supporting bone of adjacent teeth.5 When bone loss progresses, subpapillary bone is lost, and soft tissue ablation with papillary loss generally follows.6,7
The choice of treatment in these situations, especially when they arise in the esthetic zone, is controversial and unclear.8 Many clinicians choose to perform various salvage procedures such as resubmergence of the implant after disinfection with citric acid, followed by bone or soft tissue grafting.9–11 Other clinicians prefer to remove the implant and bone graft the site to develop a foundation for implant retreatment.12,13 Apical repositioning flaps have been used in attempts to cover exposed implant surfaces, but these measures are generally unsuccessful.14–16
When peri-implant bone loss is severe and chronic infection is present, each treatment alternative represents a very difficult course of treatment with a high incidence of failure. The question arises: What should be done and under what criteria? No definitive parameters have been established; in particular, no systematic approach has been developed to determine what is most important and what is least important in retreatment of an esthetically failed dental implant restoration. This chapter proposes a decision tree algorithm that ranks criteria, that is, pertinent questions regarding treatment for a “failed” implant restoration in the presence of osseointegration.
Question 1: Is the implant osseointegrated sufficiently to warrant salvage treatment?
When the implant is painful or bone loss exceeds one-third to one-half of bone support, the implant should be considered as not integrated, even if it is immobile. The process of “reintegration” of a contaminated titanium surface has been demonstrated in animal models but is still unproven clinically and probably should be considered a dubious practice.17–21 An implant can be submerged successfully with a soft or hard tissue overgraft, but often the overgraft becomes infected, and a fistula develops from inadequate hygiene of the contaminated implant surface.22
Another reason it is important to consider the presence of implant osseointegration is the prospective decision to remove the implant. When an implant is to be removed and the apical portion is still osseointegrated, damage to the bone can extend laterally to include adjacent tooth roots, which are often only 1 or 2 mm away. This makes trephine removal of the implant impossible without damage to adjacent tooth structure. If the implant is not well osseointegrated, it can be “unscrewed,” and the socket can be grafted without extending morbidity.
Question 2: Is the implant malpositioned?
When the implant is integrated over most of its surface (two-thirds or more) but presents with facial dehiscence and exposed screw threads, the clinician must then ask the second question in the decision tree. Most frequently, the implant will be well integrated but malpositioned so that the implant body extends facial to the buccal line, that is, buccally inclined relative to the axial line angle.23,24 When the implant is malpositioned facially, it is placed outside the osseous envelope and not easily covered by soft or hard tissue grafts. Apical repositioning flaps are not helpful, so in this setting most clinicians are forced to seek a prosthetic solution.23 This may or may not be satisfactory, and bone loss may progress.
A further issue with malpositioned implants is implant size.25 Sometimes, an implant that is too large for the quantity of alveolar space has been placed, a situation that is almost impossible to address.
Question 3: What is the depth of implant placement?
The implant body should be placed slightly below the alveolar plane.26 In the anterior maxilla this would correspond to a position at or near the facial marginal bone or about 3 mm below the facial marginal gingiva.27 When the implant is placed very deep, such as 5 mm or more below the marginal bone level of the adjacent tooth, as can happen in immediate postextraction placement,28 then the platform-abutment interface leads to a long junctional epithelial attachment; this attachment eventually migrates apically, exposing the cervical portion of the restoration, the implant platform, and even screw threads.29
Question 4: Is 2 mm of facial bone present over the surface of the implant?
The next question to consider concerns facial bone volume. Obviously, with an esthetically compromised maxillary implant restoration, the bone has generally been lost either prior to or subsequent to implant placement. It is a moot question. However, to obtain a successful long-term esthetic restoration, 2 mm of facial bone thickness need not always be present over the implant surface but, when present, almost always guarantees successful esthetics.26,28 The level of the marginal bone should be assessed. If a full facial dehiscence extending to the implant apex is present, the implant should be removed. If not, alternatives can be considered.
Question 5: Is adjacent subpapillary bone compromised or threatened by the failing implant?
Once bone is lost from adjacent root surfaces, the papilla will soon be lost, and esthetic reconstruction may be impossible .30 Sometimes adjacent teeth are lost from failure of a single-tooth implant.31 Therefore, it is important to closely observe subpapillary bone.
Question 6: Is apical bone present above the implant?
Sometimes in a short anterior maxilla, the implant penetrates the nasal cavity, thereby possibly eliminating apical bone for primary stabilization on retreatment and more importantly making implant repositioning surgery more difficult, if not impossible, to accomplish.
Question 7: Is there room to reposition the implant platform toward the alveolar crest?
The final question is one of interocclusal space. A single-tooth implant can only be moved 4 or 5 mm vertically by osteotomy.32 This is a significant distance that often satisfies the esthetic demand but could place the implant platform too close to mandibular incisors if a deep bite is present.33 Furthermore, if the implant platform is already located near the alveolar plane, crestal movement will only expose the implant more and may reduce inter-restorative space to the point of nonrestorability.34
These questions serve as a decision tree that establishes whether or not bodily movement of an implant in the esthetic zone can be accomplished (Fig 20-1). The diagnostic parameters that must be assessed include the degree of osseointegration, the extent of implant malpositioning, the depth of the implant platform, the presence of facial bone integrity, the proximity to adjacent subpapillary bone, the presence of apical bone above the implant, and the existence of adequate interarch space. All criteria must be judged to be favorable before the implant can be repositioned vertically by an osteotomy procedure.
Although the algorithm provides a rationale for surgical repositioning of an implant, the decision to proceed with an osteotomy should not be taken lightly; there is already a significant complication present that can be compounded further by an osteotomy procedure that is difficult to perform even for those who are experienced with single-tooth osteotomy surgery. A complete loss of the osteotomy segment caused by poor surgical technique would probably require iliac bone graft reconstruction or grafting with bone morphogenetic protein 2 as well as other secondary procedures. For these reasons, orthognathic surgeons have avoided single-tooth osteotomies because the blood supply is easily disturbed when limited to palatal flap vascularity.
Case 1: Malpositioned maxillary right central incisor implant
A 38-year-old patient had a 6-mm-diameter implant placed 2 years prior to presentation for treatment (Fig 20-2a). Multiple infections had been treated intermittently with antibiotic therapy. Infections had become more frequent.