Postoperative Stability After Sagittal Split Ramus Osteotomies for Mandibular Setback With Monocortical Plate Fixation or Biocortical Screw Fixation

Scientific Poster Session Statement of the Problem: Distraction osteogenesis is a useful alternative to advance the maxilla in complicated cases of maxillary hypoplasia. Over a five year period, our institution has gathered data regarding the work-up, experience, and results of maxillary advancement using internal distractors in the treatment of maxillary hypoplasia. Materials and Methods: A retrospective chart review was conducted of patients that were treated for craniofacial and dentofacial abnormalities at the University of Kentucky Oral and Maxillofacial Surgery clinic over a five year period. In that time, over 300 patients have undergone surgery at our center to correct their skeletal discrepancies. Ten of the 300 patients were treated with maxillary distraction osteogenesis using internal distractors. All ten patients had cleft lip and palate and a variable number of previous surgeries. The primary indication for surgery with distraction osteogenesis was to correct moderate to severe maxillary hypoplasia. Followup of 6 months or greater was available for 8 patients. Stereolithographic models were used to blend distractors prior to surgery in 5 of them to facilitate placement of the hardware in the operating room. Method of Data Analysis: A retrospective chart review was performed. Data was gathered for observational analysis and significant clinical findings. Results: Latency prior to the start of distraction was 4-7 days and varied with the age of the patient. Distraction occurred at approximately 1 mm per day with an average distraction length of 8.5 mm (range 6-10 mm). Excellent occlusal results were obtained in 5 patients. Major complications including non-union and failure to achieve acceptable occlusal results were observed in 3 patients. Minor complications including pain and loosening of the distracter devices were observed in 2 patients, but did not appear to affect the esthetic and functional results. Conclusion: Distraction osteogenesis is a useful alternative to traditional orthognathic surgery to treat maxillary hypoplasia. Internal distracters appeal to patients because they are less visible than external distracter devices, but can be difficult to place and can cause discomfort to patients when trying to achieve an ideal primary vector of distraction. Stereolithographic models can help with placement of the device. Changes in design of distractors may help with patient discomfort.

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References

POSTER 16

Gateno J, Engel ER, Teichgraeber JF, Yamaji KE, Xia JJ: A new LeFort I internal distraction device in the treatment of severe maxillary hypoplasia. J Oral Maxillofac Surg 63(1):148, 2005 Polley JW, Figueroa AA: Management of severe maxillary deficiency in childhood and adolescence through distraction osteogenesis with an external, adjustable, rigid distraction device. J Craniofac Surg 8:181, 1997 Van Sickels, JE: Distraction osteogenesis versus orthognathic surgery. Am J Orthod Dentofac Orthop 118:482, 2000

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Retrospective Study of 50 Patients Who Underwent Maxillomandibular Advancement for the Treatment of Obstructive Sleep Apnea: An Evaluation of Subjective and Objective Data Ruben Cohen, DDS, 5432 Howe Street, Pittsburgh, PA 15232 (Dattilo DJ) Statement of the Problem: Surgical treatment using maxillomandibular advancement for Obstructive Sleep Apnea (OSA) has become increasingly popular in the past decade, but little research exists to show the longterm benefits of this procedure. Materials and Methods: Fifty patients were examined after a five-year period postoperatively. Both clinical and subjective data was evaluated to determine the success of the surgery. The parameters were evaluated and compared to preoperative values using conventional statistical methods. These parameters included Respiratory Disturbance Index (RDI), Low Oxyhemoglobin Desaturation (LSAT), cephalometric analysis, hypertension, Body Mass Index (BMI), tiredness, productivity, and restful sleep. Method of Data Analysis: The parameters were evaluated and compared to preoperative values using conventional statistical methods. Additionally, a survey was given to each patient to rate the subjective information requested. Results: Using the criteria indicated above, maxillomandibular advancement surgery produced a significant success rate in both subjective and clinical data. Not only was the skeletal position stable, but the physiologic and subjective improvements evaluated were maintained for the entire postoperative period during which the patients were followed. Long term complications were minimal and pertained mostly to residual paresthesia and some malocclusion. Conclusion: Maxillomandibular advancement surgery is an effective long term method of treating obstructive sleep apnea. References Riley RW, Powell NB, Li KK, Troell RJ, Guilleminault C: Surgery and obstructive sleep apnea: Long-term clinical outcomes. Otolaryngology – Head & Neck Surgery 122, No. 3, pp 415, 2000 Smatt Y, Ferri J: Retrospective study of 18 patients treated for maxillomandibular advancement with adjunctive procedures for obstructive sleep apnea syndrome. Journal of Craniofacial Surgery 16, No. 5 Sep 2005, pp 770-777

Postoperative Stability After Sagittal Split Ramus Osteotomies for Mandibular Setback With Monocortical Plate Fixation or Biocortical Screw Fixation Eun-Kyung Lee, DDS, Department of Oral and Maxillofacial Surgery, Seoul National University Boramae Hospital, Shindaebang 2-dong, Dongjak-gu, 69

Scientific Poster Session Seoul, 156-707 South Korea (Yoo CK; Han KD; Ihm JA; Hwang KG; Chung IH) Statement of the Problem: This comparative study was an analysis of a mandibular stability following bilateral sagittal split ramus osteotomies for mandibular setback with monocortical titanuim plate fixation or bicortical screw fixation. Materials and Methods: A total of 57 patients with skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in this study. Of these patients, 29 patients were osteosynthesized monocortically with titanium plate, and 28 patients were osteosynthesized bicortically with positioning screws. Method of Data Analysis: This retrospective study utilized cephalometric radiographs, which were taken preoperatively, and 1 week, and 1 year postoperatively. Cephalometric parameters – gonial angle (GA), mandiblular plane angle (MPA), SNB, upper facial height ratio (U/F) were measured. Postoperative changes in the mandibular shape were analyzed by Wilcoxon signed-rank test to determine the stability of fixation methods. Results: The postoperative changes in gonial angle and mandibular plane angle tended to increase in both monocortical (changes in GA: 2.20, MPA: 1.19) and bicortical fixation group (changes in GA: 2.18, MPA: 1.17). In addition, the upper facial height ratio showed decrease in both monocortical (⫺0.64) and bicortical fixation group (⫺0.25). However, SNB showed decrease in monocortical fixation group (⫺0.62), and increase in bicortical fixation group (0.30). In statistical analysis, there was no significant difference in postoperative changes in gonial angle, mandibular plane angle, SNB, upper facial height ratio in both patient groups. Conclusion: These findings suggested there was no significant difference in postoperative changes in mandibular shape in both monocortical and bicortical fixation group after sagittal split ramus osteotomy. It was concluded that monocortical osteosysnthesis using miniplate could be used to obtain stable postoperative changes after mandibular setback. References Ueki K, Nakagawa K, Takathuka S, Yamamoto E: Plate fixation after mandibular osteotomy. Int J Oral Maxillofac Surg 30:490, 2001 Rubens BC, Stoelinga PJW, Blijdorp PA, Schoenares JHA, Politis C: Skeletal stability following sagittal split osteotomy using monocortical miniplate fixation. Int J Oral Maxillofac Surg 17:371, 1988

POSTER 17 An In Vitro Biomechanical Evaluation of Fixation Techniques for Sagittal Split Ramus Osteotomy: Mandibular Advancement and Setback Luis Augusto Passeri, DDS, MS, PhD, Av Limeira, 901, Piracicaba Dental School, Unicamp, Piracicaba, SP 13414-903, Brazil (Brasileiro BF; Grempel RG) 70

Statement of the Problem: The clinical effectiveness of internal fixation plates and bone screws in orthognathic surgery is well accepted and documented. To better understand the biomechanics of sagittal split ramus osteotomy fixation and to develop improved fixation devices and techniques, experimental investigations are often used to quantify and evaluate function in an in vitro environment prior to their clinical use. Thus, the goal of this investigation was to compare biomechanical resistance of 3 fixation techniques for mandibular sagittal split osteotomy in vitro. Materials and Methods: The study was conducted at Piracicaba Dental School – State University of Campinas, by the Division of Oral and Maxillofacial Surgery. One hundred twenty polyurethane synthetic hemi-mandible replicas (Nacional, Jau, Sa˜o Paulo, Brazil) were used. Replicas were fabricated in a pair of pieces divided by a standardized sagittal split ramus osteotomy and submitted to 5 mm advancement and 5-mm setback. Fixation techniques included a 4-hole plate and 4 monocortical screws (plate group), a 4-hole plate and 4 monocortical screws with one additional bicortical positional screw (hybrid group), and 3 bicortical positional screws in an inverted-L pattern (inverted-L group). All screws were 2.0 mm in diameter, fabricated of titanium and selftapping (MDT, Rio Claro, SP, Brazil). The system was secured in a custom fabricated jig and subjected to linear vertical loads at the incisal edge and linear lateral forces at the molar region by an Instron 4411 servohydraulic mechanical testing unit (Instron Corp, Norwood, MA). Testing machine developed a linear displacement at a rate of 1 mm per second, and a 50 KN load cell measured the resultant force. Method of Data Analysis: Twelve groups of 10 hemimandibles were analyzed according to fixation technique (n ⫽ 3), type of movement (n ⫽ 2) and force direction (n ⫽ 2). Loading test data analysis was based on peak load values regarding systems mechanical deformation at 1 mm, 3 mm, 5 mm and 10 mm of displacement, and stiffness (load/displacement slope curve) for each group. Means and standard deviations were derived and compared for statistical significance using ANOVA with a confidence level of 95% (P values less than 0.05). Multiple comparisons were analyzed using Tukey test for type of movement and fixation technique, and for force direction and fixation technique. Results: The designed study demonstrated the plate group achieved significant lower load (P less than 0.01) regarding type of movement, force direction or amount of displacement when directly compared to other fixation techniques, except when peak load was calculated under lateral forces in advancement with displacement values of 1 mm and 3 mm. Also, inverted–L group showed higher resistance to vertical forces for advancement movements at 3 and 5 mm of displacement when compared to the hybrid group (P less than 0.01). RegardAAOMS • 2006