Volume 78 • Number 2
Peri-Implant Bone Loss Around Posterior Mandible Dental Implants Placed After Distraction Osteogenesis: Preliminary Findings Wilson C.K. Polo,* Ney Soares de Araujo,† Ynara B.O. Lima,‡ Julio Cesar Joly,§ Wilson R. Sendyk,* and Patricia R. Cury§
Background: The present study evaluates implant survival and peri-implant bone loss around posterior mandible dental implants placed at sites of distraction osteogenesis. Methods: On removal of the distraction devices, 34 dental implants were inserted into 14 posterior mandible sites in 10 healthy, non-smoking female patients. Prosthetic treatment was performed 4 months after implant placement using fixed implant prostheses. After 6 to 16.5 months, periapical radiographs were taken and evaluated for peri-implant bone loss and radiolucency. The distance between the implant margin and the first visible bone–implant contact was measured on the mesial and distal aspects of the implants using imaging software. Radiographic dimensional distortion was corrected as a function of the known true dimension of the implant. Results: Of the 34 implants placed, two (5.9%) failed to integrate at reentry surgery. Both were replaced and restored during the course of the study so that a total of 34 implants was followed for 12.1 – 3.8 months post-restoration and 16.1 – 3.8 months post-insertion. Mean loss of marginal bone height was 2.6 – 1.0 mm. During the follow-up period, radiolucent lines along the implant surface were absent. Conclusions: The mean peri-implant bone loss in areas of alveolar bone distraction was 1.9 mm/year. A high implant survival rate was observed. J Periodontol 2007;78:204-208. KEY WORDS Atrophy; bone; distraction osteogenesis; mandible.
* Department of Periodontics and Implantology, School of Dentistry, University of Santo Amaro, Sa˜o Paulo, SP, Brazil. † Department of Oral Pathology, University of Sa˜o Paulo, Sa˜o Paulo, SP, Brazil. ‡ Department of Biochemistry, Sa˜o Leopoldo Mandic Dental Research Institute, Campinas, SP, Brazil. § Department of Periodontics, Sa˜o Leopoldo Mandic Dental Research Institute.
D
istraction osteogenesis is a biologic process that stimulates the formation of new bone and soft tissue following the gradual separation of two bone segments. The concept of bone lengthening was described first by Codivilla,1 who reported the lengthening of a femur. The technique of generating new bone by stretching or lengthening a callus was popularized by Ilizarov et al.2 in 1980. Subsequently, distraction osteogenesis was applied to the craniofacial region3-6 and used for alveolar ridge augmentation.7,8 Alveolar distraction osteogenesis is an extremely promising technique used to correct alveolar ridge deformities and atrophies prior to implant placement. Clinical studies showed a significant gain in bone height using this technique, with implant success rates of 88% to 100%.9-19 Bone height stability is one of the most important and reliable factors used when considering implant success criteria. To our knowledge, only two studies have examined bone height stability following prosthetic reconstruction for dental implants inserted into areas of distraction osteogenesis.9,12 However, qualitative bone evaluations have been performed by other investigators.11,15,16 Chiapasco et al.9 showed bone resorption of 1.3 – 0.3 mm 12 months after prosthetic loading doi: 10.1902/jop.2007.060202
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in eight patients with vertically deficient anterior and posterior mandibles treated by distraction osteogenesis. However, only panoramic radiographs were evaluated, and the measurements were made to the nearest 0.5 mm. Jensen et al.12 reported stable bone levels (1.0 – 1.3 mm bone loss) for at least 3 years post-restoration in 28 patients with anterior maxillary vertical defects treated by distraction osteogenesis. These authors used computer-based radiography. The present study evaluates bone stability radiographically following prosthetic reconstruction for posterior mandible dental implants inserted into areas of distraction osteogenesis. MATERIALS AND METHODS The present study’s protocol was approved by the Institutional Ethics Committee of the University of Santo Amaro, and informed consent was obtained from all subjects. Between January 2002 and June 2004, 10 partially edentulous female patients, aged 21 to 60 years, were selected, and distraction and implant surgeries were performed. Criteria for inclusion were good systemic health, no medications, no contraindication for surgery, non-smokers, and atrophic posterior mandible presenting 6 to 10 mm of bone above the inferior alveolar nerve. Preoperative diagnoses and treatment planning, based on clinical, radiographic, and diagnostic waxup evaluations, were performed on all patients prior to distraction surgery, which has been described previously.14 After the planned distraction had been obtained, the mobile segment was held in place for 8 to 12 weeks allowing bone consolidation. Following this period, the alveolus was exposed by an incision, the distractor was removed, and the implants were placed into the augmented bone. Thirty-four implantsi with acid-etched surfaces were inserted at 14 surgical sites on the posterior mandibles, at or slightly below the alveolar bone crest, and extending into the basal bone. Surgery was performed by the same operator under local-regional anesthesia, using appropriate aseptic and sterile procedures. Prosthetic treatment was performed 4 months after implant insertion, using fixed, implant-supported prostheses, by a group of clinicians in an institutional environment. Oral hygiene instructions were given, and the patients were recalled after 6 months and once a year thereafter. During the final patient consultation, between 6 and 16.5 months post-restoration, a periapical radiograph was obtained of all implants in all patients, applying the long-cone parallel technique. A radiographic holder¶ was employed to place each film parallel to the implant long axis and perpendicular to the central
Polo, de Araujo, Lima, Joly, Sendyk, Cury
beam. The radiographs were digitized# at 512 · 480 pixels and 8 bits. The digitized radiographs were examined for peri-implant radiolucency and bone height. The distance between the top of the implant shoulder (abutment interface) and the first visible bone–implant contact was measured on the mesial and distal aspects of the implants using image analysis software.** The radiographic measurements were performed by two independent examiners. All measurements were reviewed for consistency, and any inconsistent reading was reassessed by the examiners. The differences between the readings were 0.05). DISCUSSION Osseointegrated implants have been used successfully to restore partially edentulous ridges.20,21 However, clinicians frequently encounter alveolar ridge atrophy, which impedes the placement of implants 206
Marginal Bone Loss (mm)
of favorable length; in the posterior mandible, bone grafting or nerve repositioning often is necessary prior to implant placement. Bone grafting has been the most commonly used technique to increase the height of the alveolar ridge.22,23 However, bone grafting has various limitations: grafting does not always ensure the desired bone regeneration, particularly in the case of large bone defects, a secondary donor site is necessary, and the soft tissue may be unable to cover
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J Periodontol • February 2007
the bone graft. Nerve repositioning may result in neurosensory disturbances from nerve manipulation, although a high implant survival rate is likely.24 In the present study, two (5.9%) implants failed to integrate; both were positioned at the vertical osteotomy site, which likely is associated with the failures. Both implants were replaced and restored during the course of the study so that an implant survival rate of 100% was obtained. All implants were used in the prosthetic rehabilitation. Comparable implant success rates have been reported by others using inferior alveolar nerve repositioning (87.0% to 93.6%)12,25-27 or in areas of posterior mandible where regeneration was not necessary (92.2% to 98%).20,28,29 Jensen et al.12 reported a 10% implant failure rate for areas of distraction osteogenesis, which they attributed to insufficient bone for osseointegration or the traumatic nature of the cases. In the present study, the removal of the distractor device and implant insertion were performed concomitantly 8 to 12 weeks after distraction. Early implant placement has the advantage of increased blood supply and provides bone transport segment stability by the implants.13 Vascularity increases several fold during active distraction,16 which is desirable for the osseointegration process. Further, earlier implant insertion seems to have a positive effect on the structure of the newly formed bone.14 However, when the implants are to be inserted at vertical osteotomy sites, a delayed approach should be used.13 At the end of the consolidation period, considerable mineralization (77.8%) of the bone regenerated by distraction osteogenesis has been reported.30 However, in the present study, regardless of whether the implants extended through the regenerated bone into the basal bone, primary stability of the implants, similar to that obtained when placing implants in native bone, was difficult to achieve; this limitation is in agreement with the literature.12 This may be associated with the reduced height of the transported segment (mean, 4 mm) and its poor stability, the presence of poorly mineralized areas in the distraction gap, and the presence of small bone defects in the facial regeneration zone. However, this clinical finding does not seem to influence osseointegration. Block et al.31 reported that implants extending only into the regenerated bone, and then loaded for 1 year, also maintained stability and were well integrated. A bone loss of between 0.03 and 2.5 mm (mean, 0.9 – 0.6 mm) above the upper mini-plate was measured in all patients;14 this limited the implant height used in the present study (10.4 – 1.0 mm). Two 8.5mm-high implants were used, one of which was inserted into an area associated with infection during distraction osteogenesis. Following implant insertion, an additional vertical bone loss was measured (2.6 –
1.0 mm) on the mesial and distal aspects of the implant, resulting in a mean peri-implant bone loss of 1.9 mm/year. Regardless of the bone loss observed here, distraction osteogenesis permitted the use of an increased implant length. Less marginal bone loss (1.0 to 1.3 mm) has been obtained in other studies,9,12 which may derive from methodological limitations because panoramic radiographs were evaluated using a millimeter ruler.9 Jensen et al.12 did not describe the methodology employed in their computer-based radiographic evaluation. Less than 1.5 mm of vertical bone loss in the first year and less than 0.2 mm after the first year of loading, similar to the present results, have been considered compatible with healthy conditions; this suggests that implants inserted in areas of distraction osteogenesis exhibit a behavior similar to implants in other bone areas. Longer follow-up analyses should be performed to evaluate the stability of the alveolar bone height and eventual bone resorption. Despite the limited number of implants evaluated in the present study, this technique seems to be very reliable in correcting vertical defects of the posterior mandible for implant-supported prosthetic rehabilitation. Compared to bone grafting and guided bone regeneration, the present technique offers many advantages: the opportunity to provide natural bone formation over a short interval, soft tissue following elongation of the underlying bone, surgery performed using local anesthesia, and a minimal risk for nerve damage compared to displacement of the alveolar nerve. However, distraction osteogenesis of the alveolar ridge also has disadvantages. The distraction device must remain in place for a considerable period, which may cause some discomfort to the patient, particularly during speech and eating. Further, because the distraction device is transmucosal, the risk for dehiscence and infection through the soft tissue cannot be ignored. CONCLUSIONS Within the limits of the present study, dental implants in areas of alveolar bone distraction exhibited a mean peri-implant bone loss of 1.9 mm/year, together with high survival rates following prosthetic loading. However, longitudinal follow-up of the implants at the sites of distraction osteogenesis should be performed to evaluate their long-term success. REFERENCES 1. Codivilla A. On the means of lengthening in the lower limb the muscles and tissues which are shortened through deformity. Am J Orthop Surg 1904;2:353-369. 2. Ilizarov GA, Devyatov AA, Kamerin VK. Plastic reconstruction of longitudinal bone defects by means of compression and subsequent distraction. Acta Chir Plast 1980;22:32-41. 207
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3. Klein C, Howaldt HP. Lengthening of the hypoplastic mandible by gradual distraction in childhood – A preliminary report. J Craniomaxillofac Surg 1995;23: 68-74. 4. McCarthy JG, Schreiber J, Karp N, Thorne CH, Grayson BH. Lengthening the human mandible by gradual distraction. Plast Reconstr Surg 1992;89:1-8. 5. Molina F, Ortiz Monasterio F. Mandibular elongation and remodeling by distraction: A farewell to major osteotomies. Plast Reconstr Surg 1995;96:825-840. 6. Snyder CC, Levine GA, Swanson HM, Browne EZ Jr. Mandibular lengthening by gradual distraction. Preliminary report. Plast Reconstr Surg 1973;51:506-508. 7. Chin M, Toth BA. Distraction osteogenesis in maxillofacial surgery using internal devices: Review of five cases. J Oral Maxillofac Surg 1996;54:45-53. 8. Block MS, Chang A, Crawford C. Mandibular alveolar ridge augmentation in the dog using distraction osteogenesis. J Oral Maxillofac Surg 1996;54:309-314. 9. Chiapasco M, Romeo E, Vogel G. Vertical distraction osteogenesis of edentulous ridges for improvement of oral implant positioning: A clinical report of preliminary results. Int J Oral Maxillofac Implants 2001;16: 43-51. 10. Gaggl A, Schultes G, Rainer H, Karcher H. The transgingival approach for placement of distraction implants. J Oral Maxillofac Surg 2002;60:793-796. 11. Gaggl A, Schultes G, Karcher H. Vertical alveolar ridge distraction with prosthetic treatable distractors: A clinical investigation. Int J Oral Maxillofac Implants 2000; 15:701-710. 12. Jensen OT, Cockrell R, Kuhike L, Reed C. Anterior maxillary alveolar distraction osteogenesis: A prospective 5-year clinical study. Int J Oral Maxillofac Implants 2002;17:52-68. 13. McAllister BS. Histologic and radiographic evidence of vertical ridge augmentation utilizing distraction osteogenesis: 10 consecutively placed distractors. J Periodontol 2001;72:1767-1779. 14. Polo WC, Cury PR, Sendyk WR, Gromatzky A. Posterior mandibular alveolar distraction osteogenesis utilizing an extraosseous distractor: A prospective study. J Periodontol 2005;76:1463-1468. 15. Rachmiel A, Srouji S, Peled M. Alveolar ridge augmentation by distraction osteogenesis. Int J Oral Maxillofac Surg 2001;30:510-517. 16. Robiony M, Polini F, Costa F, Politi M. Osteogenesis distraction and platelet-rich plasma for bone restoration of the severely atrophic mandible: Preliminary results. J Oral Maxillofac Surg 2002;60:630-635. 17. Urbani G. Alveolar distraction before implantation: A report of five cases and a review of the literature. Int J Periodontics Restorative Dent 2001;21:569-579. 18. Laster Z, Rachmiel A, Jensen OT. Alveolar width distraction osteogenesis for early implant placement. J Oral Maxillofac Surg 2005;63:1724-1730 (erratum 2006;64:566). 19. Enislidis G, Fock N, Millesi-Schobel G, et al. Analysis of complications following alveolar distraction osteogenesis and implant placement in the partially eden-
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Correspondence: Dr. Patricia R. Cury, Department of Periodontics, Sa ˜ o Leopoldo Mandic Dental Research Institute, Rua Jose´ Rocha Junqueira no. 13, Ponte Preta, Campinas/ SP 13045-610, Brazil. Fax: 55-19-3237-3611; e-mail:
[email protected]. Accepted for publication September 20, 2006.
