Stability of Distraction Osteogenesis in Le Fort I Osteotomy Downfracture and Advancement

Scientific Poster Session ing type of movement, the fixation/mandible system had higher vertical loading values at 5 and 10 mm and higher lateral loading scores at 3, 5, and 10 mm for setback fixation when compared to same displacement values for advancement fixation. According to force direction, the three fixation techniques demonstrated higher peak load at any displacement point when lateral forces were compared to vertical forces for setback movements (P less than 0.05). Similar behavior for advancement movements only took place at 5 and 10 mm of displacement (P less than 0.05). Conclusion: Following the stated biomechanical environment, significant differences could be demonstrated regarding fixation technique, type of movement, force direction and amount of displacement. Plate group presented the inferior mechanical characteristics, while inverted-L group showed the most favorable outcomes. However, introduction of an additional bicortical screw to plate group (hybrid group) suggested significant biomechanical resistance improvement. Lateral forces and setback movements produced higher loading values over the fixation/mandible system than vertical forces and advancement movements respectively. References Hammer B, Ettlin D, Rahn B, Prein J: Stabilization of the short sagittal split osteotomy: In vitro testing of different plate and screw configurations. J Craniomaxillofac Surg 23:321, 1995 Murphy MT, Haug RH, Barber JE: An in vitro comparison of the mechanical characteristics of three sagittal ramus osteotomy fixation techniques. J Oral Maxillofacial Surg 55:489, 1997 Van Sickels JE, Peterson GP, Holms S, Haug RH: An in vitro comparison of an adjustable bone fixation system. J Oral Maxillofacial Surg 63:1620, 2005 Funding Source: CAPES—Brazilian Department of Education

POSTER 18 Stability of Distraction Osteogenesis in Le Fort I Osteotomy Downfracture and Advancement Alexander Rabinovich, DDS, MD, Kings County Hospital, Department of Oral and Maxillofacial Surgery, E-Bldg, 1st Floor, 451 Clarkson Ave, Brooklyn, NY 11203 (Cardoso A; Hoffman D; Lazow SK) Statement of the Problem: Distraction osteogenesis is a technique originally described by G. Ilizarov in 1951, where gradual separation of bony segments causes new bone formation within the osteotomy interface. This technique has recently been widely utilized in craniofacial/maxillofacial surgery, mostly using extraoral distraction devices. In this study we applied the concept of distraction osteogenesis using intraoral devices in association with a Le Fort I osteotomy for maxillary advancement in vertical and sagittal planes. AAOMS • 2006

Materials and Methods: Nine patients (5 females, 4 males), ages 14-45 (mean age 23.5); with severe A-P maxillary deficiency, as well as vertical maxillary deficiency due to various causes underwent Le Fort I osteotomy and maxillary advancement. Distraction osteogenesis using internal devices (Zurich distractor, KLS; Custom hourglass distractor, KLS) was used in all of the cases. Advancements were anterior, inferior or a combination of the two vectors. Movements ranged from 6 to 12 mm, with average movement exceeding 8 mm. One patient had a unilateral downfracture. All patients were treated with the same distraction protocol: one-week latency phase, followed by 0.5 mm advancement per day until a satisfactory position of maxilla was obtained, and a consolidation phase at least 3 times longer than the active phase. All distractors were removed 3 to 4 months after placement. None of the patients required a bone graft. Method of Data Analysis: Cephalometric radiographs were taken and Steiner cephalometric analysis was done at several stages of treatment: prior to placement of distraction devices, after distraction was completed, and finally at least 12 months after completion of treatment. Post-op follow-up varied in length from 12 months to 3 years. Data obtained during this study was compared to published data on stability of Le Fort I osteotomy with wire or plate fixation with bone grafting when necessary for anterior and downward movements of the same caliber. Results: All distraction cases had ⬍3 mm relapse, average being less then 10% based on preliminary data. The downward fractures had virtually no relapse and were stable at the 12 month interval. Anterior advancement cases had slight relapse and change in orientation at A point. There were no serious complications associated with the use of intraoral disractors in this study. Traditional method of bone grafting with rigid fixation had a 15% to 26% relapse with compatible movements. Bone grafting was necessary in most cases where movement exceeded 7 mm. Conclusion: Intra-oral distraction is an adequate procedure that can be used for downfracture or advancement of the maxilla. It allows for greater movements than traditional orthognathic surgery and does not require bone grafting. In addition, it appears to be a more stable procedure. References Green SA, Brownsr BD, editor: Gavriil Ilizarov and discovery of distraction osteogenesis. Skeletal Trauma: Basic Science, Management and Reconstruction, 3rd edition, St. Louis (MO), WB Saunders, 2003 Perez MM, Sameshima GT, Sinclair PM: The long term stability of LeFort I maxillary downsgrafts with rigid fixation to correct maxillary deficiency. Am J Orthodontics and Dentofacial Orthopedics 112, No. 1, Jul 1997, pp 104-118 Wagner S, Reyneke JP: The LeFort I downsliding osoetomy: A study

71

Scientific Poster Session of long term hard tissue stability. Int J Adult Orthodontics and Orthognathic Surgery 15, No. 1, Spr 2000, pp 37-49

POSTER 19 Comparison Between Panoramic and Cone Beam Computed Tomography (CBCT) for Dental Use for the Assessment of Inferior Alveolar Canal in 500 Extracted Third Molars Yutaka Akiyama, DDS, Nihon University School of Dentistry, Department of Oral and Maxillofacial Surgery, 1-8-13, surugadai, Kannda, Chiyodaku, Tokyou 1018310, Japan (Matumoto M; Hashimoto K; Arai Y) Statement of the Problem: In this study, the positional relationship between the mandibular canal, through which the inferior alveolar nerve passes, and the third molar was observed in detail in patients who underwent CBCT imaging. The same information was obtained from panoramic radiographs and compared. Materials and Methods: The materials used were radiographs of 500 third molars from 366 patients (159 males, 207 females; aged 15 to 79 years, mean 32.5 years) who were treated at the Dept of Oral Surgery, Nihon University School of Dentistry in the 6 years between 1998 and 2004, and who underwent Cone-beam computerized tomography (CBCT) imaging (3DX, MORITA Cop Kyoto Japan, US name 3D Accuitomo). The distance and positional relationship between the third molar and the mandibular canal, buccolingual position, and mandible width were observed using the CBCT images. The positional relationship between third molar and mandibular canal and the status of the white line defining the superior wall of the mandibular canal were observed using panoramic radiographs. Method of Data Analysis: From the contiguous parallel slices of the dental arch (cross-sectional view of the arch) that were acquired, the image in which the third molar and mandibular canal were closest was selected and classified as follows. Classification based on distance: Relationship between third molar and mandibular canal on CBCT images Separated by more than 1 mm (Grade I), separated by less than 1 mm or in contact, and walls of mandibular canal seen as white lines (Grade II), Separated by less than 1 mm or in contact, and walls of mandibular canal not seen as white lines (contiguous with periodontal membrane space) (Grade III). The distance was measured using the 3DX system software (Morita Co, Kyoto, Japan). Classification based on location: Located on buccal side of third molar (B), Mandibular canal in contact with root apex (I), Located on lingual side of third molar (L), Located in the area of the ramus (R). 72

Classification of panoramic radiographic findings: Third molar and mandibular canal in contact or overlapping and Superior wall of mandibular canal seen as a continuous white line (Type A). Third molar and mandibular canal in contact or overlapping and Superior wall of mandibular canal not clearly seen as a continuous white line (Interruptions of the cortical white line) (Type B). Downward displacement of the mandibular canal in the area of the third molar (Diversion of the canal) (Type C). Patients were examined for postoperative dysesthesia of the lower lip. Results: Among the 366 patients (500 teeth) in whom CBCT imaging was performed, the mandibular canal was in buccal position in 252 patients, inferior position in 139 patients, lingual position in 95 patients, and in the ramus region in 14 patients. Based on the distance, 167 patients were Grade I, 194 were Grade II and 139 were Grade III. The panoramic radiographic findings were as follows: Type A; 230 patients, Type B; 175 patients, and Type C; 95. Grade III distances were seen in CBCT images of 28 of 230 (12.1%) patients with Type A panoramic radiographic findings, 30 of 175 patients (17.3%) with Type B findings, and 81 of 95 patients (85.2%) with Type C findings. Postoperative dysesthesia of the lower lip occurred in 5 patients (1.0%), all of whom were classified as Grade III. Conclusion: Diversion of the mandibular canal in the area of the third molar in panoramic radiographic images indicates a tendency for proximity of the third molar and mandibular canal, which would help to determine the risk of dysesthesia after extraction. References Bart F, Blaeser, MA, August R, Donoff B, et al: Panoramic radiographic risk factors for inferior alveolar nerve injury after third molar extraction. J Oral Maxillofac Surg 61:417, 2003 Westesson PL, Carlsson LE: Anatomy of mandibular third molars. A comparison between radiographic appearance and clinical observations. Oral Surg Oral Med Oral Pathol 49:90, 1980

POSTER 20 Endotracheal Tube Fixation in the Edentulous Facial Burn Patient W. Stephen Barnes, II, DMD, 2500 MetroHealth Drive, Department of Oral and Maxillofacial Surgery, MetroHealth Medical Center, Cleveland, OH 44109 (Ash C; Bradrick J) Statement of the Problem: Securing of the endotracheal tube (ET) in the facial burn patient is a challenge in the intensive care setting. There have been significantly higher reports of accidental extubation due to inadequate stabilization of the ET tube in burn ICU compared AAOMS • 2006