Vestibular Sulcus Approach to Anterior Maxillary Reconstruction With Transmucosal Implants

Scientific Poster Session with the polyurethane resin derived from the castor bean oil (poliquil). The control defects were filled with the blood of the animal. Seven animals in each group were killed at 7 and 15 weeks. Method of Data Analysis: Once dead, the entire cranial vault was removed from each animal, leaving the pericranium intact. The specimens were visually examined by optic microscope for signs of inflammation, new bone formation, and resorption of the bioimplant from both the cranial and dural sides. This analysis was done by an oral pathologist. This professional had no contact with others of the research. Results: The histological analysis revealed that all groups (control and experimentals), presented increased bone regeneration with the time, but this reparation was faster in the control group, even showing important decrease on the thickness of the defect. All materials were biologically compatible; however the polyurethane was resorbed more slowly and considerate with better results than demineralized bone matrix. Conclusion: The results showed that all groups repaired completed, the materials that were tested repaired more slowly than the control group, but with higher quality in the experimental groups. References Burg KJL, Porter S, Kellam JF: Biomaterial developments for bone tissue engineering. Biomaterials 21:234, 2000 Urist MR: Bone morphogenetic protein, bone regeneration, heterotopic ossification and the bone-bone marrow consortium, in Peck W (ed): Bone and Mineral Research. New York, NY, Elsevier Science Publishers BV, 1989, pp 57-112 Biocompatibility of the polyurethane resin of the castor bean inserted into the alveolar bone of the dog.

POSTER 17 Vestibular Sulcus Approach to Anterior Maxillary Reconstruction With Transmucosal Implants Cesar Guerrero, DDS, Santa Rosa, Centro Integral Santa Rosa, Ofic. 105, Caracas 01061, Venezuela (Gonzalez M; Henriquez M; Dominguez E; Fernandez MJ) Statement of the Problem: Ideal anterior maxillary reconstruction remains a challenge for dental implant placement. Post-surgical architectural progressive remodeling, poor blood supply, soft tissue scars, and treatment time are the most important drawbacks when preservation of the natural bony and gingival contour is the main goal. Materials and Methods: Thirty patients (17 males, 13 females) with ages ranging from 24 to 57 years of age were evaluated. This study was designed to evaluate the results of anterior maxillary reconstruction after three different alveolar surgical techniques and implant placement. The principles consisted of avoiding any crestal AAOMS • 2005

incisions, utilizing a vestibular sulcus approach for grafting, and trans-mucosal (no-flap surgery) implant placement. The sample (n⫽30) was divided in three groups; Group (1): Implant ⫹ connective tissue graft, Group (2): Implant ⫹ bone graft, and Group (3): alveolar distraction ⫹ second stage no-flap implants. Group 1 (n⫽10): When only soft tissue A-P projection was needed, connective tissue was placed through the vestibular approach into the pocket with trans mucosal dental fixtures. Group 2 (n⫽10): Through a vestibular sulcus incision, a bone graft from the mandibular ramus was fixed with titanium screws to the defect area; then the fixtures were placed trans-mucosally. Group 3 (n⫽10): Same incision to performed the osteotomy for distraction, and appliance activation at the alveolar crest 7 days later, at a rate of 1⁄2 mm twice a day. Removal of the distraction rod 8 to 12 weeks later by unscrewing the head and, at the same time dental fixtures were placed through the mucosa. Method of Data Analysis: This retrospective, single examiner, randomized, clinical evaluation of the three groups was conducted following these criteria: 1) Minimum postoperative follow-up of 12 months; and 2) Same surgeon. Clinical records (gingivitis by gingival index of LOE and sillness, intra oral photographs, dental models, panoramic and periapical radiographs) of all three groups were reviewed up to the longest follow-up of 24 months. The specific events were recorded and classified as: (a) Alveolar bone graft exposure; (b) Complete bone graft resorption; (c) 50%-70% bone graft resorption; (d) 30%-50% bone graft resorption; (e) 1-3mm gingival apical migration; (f) more than 3mm gingival and bone apical migration. Results: The thirty surgical sites had a gingival index average of 0 to 1 at 12-months follow-up and at 24 months, where 0 was normal gingiva, and 1 was mild inflammation with no bleeding on probing. No moderate or severe inflammation, ulceration, or spontaneous bleeding was recorded with no gingival or bone apical migration from any of the groups. There were no significant specific events for Group 1: no vertical or horizontal alveolar bone resorption was observed, and good soft tissue A-P projection was reported for this group. In Group 2, three fixation screws from the bone graft had to be removed due to perforation of the mucosa. A-P bone resorption was recorded as 30% to 50% at 12 months follow-up and 0% at 24 months. For Group 3, no bone resorption was observed after 12 months or at 24 months, three distraction chambers had to be opened at the time of implant surgery for distraction plate removal, and three needed extra bone grafts for A-P projection. Conclusion: Group 1 had the most stable and esthetic results, which might be related to the low complexity of the cases, where only soft tissue was needed. Group 2 had the highest bone resorption of the three groups, correlated with some results from previous studies; while Group 3 had some other technical problems, rep85

Scientific Poster Session resenting the more complexes cases, where bone and soft tissue had to be corrected in three dimensions. The use of trans mucosal implant placement is recommended as a favorable technique to preserve the vertical bone projection and architecture. References Brånemark P-I, Gro ¨ ndahl K, Worthington P: Osseointegration and Autogenous Onlay Bone Grafts: Reconstruction of the Edentulous Atrophic Maxilla. Illinois, Quintessence, 2001 Chin M, Toth BA: Distraction osteogenesis in maxillofacial surgery using internal devices: Report of five cases. J Oral Maxillofac Surg 54:45, 1996

bone formation after distraction osteogenesis. It can be clinically applied in the future. References Fredericks DC, Piehl DJ, Baker JT, et al: Effects of pulsed electromagnetic field stimulation on distraction osteogenesis in the rabbit tibial leg lengthening model. J Pediatr Orthop 23:478, 2003 El-Hakim IE, Azim AMA, El-Hassan MFA, et al: Preliminary investigation into the effects of electrical stimulation on mandibular distraction osteogenesis in goats. Int J Oral Maxillofac Surg 33:42, 2004 Park SH, Silva M: Neuromuscular electrical stimulation enhances fracture healing: Results of an animal model. J Orthop Res 22:382, 2004 Funding Source: The Korea Health 21 R& D Project, Ministry of Health & Welfare, ROK

POSTER 18

POSTER 19

Electrical Stimulation for Early Bone Formation After Distraction Osteogenesis

Unilateral Use of the Zygomatic Implant: A Preliminary Report

Soon-Jung Hwang, MD, DDS, Dept of OMFS Seoul National University Dental Hospital, 275-1, YeongeonDong Jongro-Gu, Seoul, 110-768, Republic of Korea (Kim DK; Hwang KG; Cho TH; Zhang YL; Song YM; Lee JH; Kim IS; Hwang SJ) Statement of the Problem: Distraction osteogenesis is widely used for bone lengthening in patients with maxillofacial deformity and alveolar bone atrophy. One of the main problems in distraction osteogenesis is the long consolidation period for 2-3 months, in which the devices have to be fixed on the bone to prevent relapse. This results in scar formation on the face and disturbance of mastication and speech. This study was performed to evaluate the effect of electrical stimulation on the early bone formation in distraction osteogenesis. Materials and Methods: A total of 10 rabbits were used (5 for control group, 5 for experimental group). A vertical osteotomy in the mandibular body on both sides was performed and the distraction device was fixed. After 5 days distraction was done 1mm per day for 7 days. A pulsed electromagnetic field (38 Gauss, 100 Hz) was applied for 8 hours per day and it continued for 5 days immediately after distraction in the experimental group. Both groups were sacrificed after 1 week and 2 weeks. Method of Data Analysis: Histological specimens with H&E and Masson trichrome staining were made and histomorphometrically analysed with image analyser. Results: In both groups, a new bone formation was observed in the distracted area after 2 weeks. A new bone formation could be observed already after 1 week in the experimental group, whereas only organized osteoid was seen in the control group. The bone formation was enhanced in the experimental groups (22%) compared with control group (12%). Conclusion: This study suggests that electrical stimulation with electromagnet field is effective in the early 86

Anna Lu, DMD, 1411 E. 14th St, Oakland, CA 94602 (Bedrossian E; Indresano AT) Statement of the Problem: The use of the Zygomatic Implant, in conjunction with premaxillary implants for the restoration of the fully edentulous maxilla, has been reported by different authors. The predictable use of this implant is favorably mentioned. The existing protocol for the use for the restoration of the Zygomatic implants recommends cross arch stabilization of these implants at Stage II. The use of this implant for the partially resorbed edentulous area has not been studied. This investigation studies the use of the Zygomatic implant in the unilateral edentulous posterior maxilla. Materials and Methods: The protocol used requires the placement of the Zygomatic implant in conjunction with a minimum of two implants to allow for tripoding. All implants were placed by the same surgical team, adhering to the protocol designed by Bedrossian, et al. Five patients were treated. A total of 7 posterior maxillary quadrants were included in this study. Eight Zygomatic implants and 15 comventional implants were placed. After a 6 month osseointegration period, the implants were uncovered and restored with ceramometal bridges. Method of Data Analysis: The patients were seen 1 week after phase I surgery. After the 6 month osseointegration period, the implants were uncovered. The implants were examined for signs of mobility and/or pain. Failure of the implant was defined as mobility, sensitivity to percussion, and persistent pain. Results: All Zygomatic implant and regular platform implants osseointegrated and were restored with ceramometal bridges. The success rate of the prosthesis was 100%. Conclusion: The preliminary data suggest that the use of the zygomatic implant for the restoration of the partially edentulous resorbed posterior maxilla in a tripod manner is a viable alternative to the sinus lift procedure. AAOMS • 2005