Mandibular Body Osteotomy Research Articles

Mandibular Body Osteotomy Combined with Sagittal Split Ramus Osteotomy for the Treatment of Severe Skeletal Class Ⅲ Malocclusion with Ankylosed Teeth.

This study presents a combination of 2 different surgery procedures performed on the mandible as part of the treatment aiming to improve the facial profile and occlusal function of patients with severe skeletal class Ⅲ malocclusion and bilateral edentulous gaps. The teeth next to the edentulous gaps were found to be ankylosed. Mandibular setback by bilateral sagittal split ramus osteotomies and mandibular body osteotomies, combined with Le Fort Ⅰ level maxillary advancement were performed, since the chief complaint of the patient was a concave profile. As a result, the skeletal class Ⅲ malocclusion had been corrected, a satisfying facial profile had been achieved, and no apparent adverse effect was found. Thus, it has been proved that the combination of sagittal split ramus osteotomy and mandibular body osteotomy is available for correcting skeletal class Ⅲ malocclusion.

Aesthetic Enhancement of the Gonial Angle and Inferior Mandibular Border in the Chinese Population.

The current absence of a standardized mandibular body osteotomy design poses challenges in surgical planning. Traditional approaches may not suit patients with wider anterior mandibles, potentially resulting in unsatisfactory outcomes. Addressing this issue requires a rational design that combines mandibular angle and body osteotomies for improved clinical practice. In this retrospective cohort study we aimed to analyze mandibular computed tomography (CT) data with digital methods. The goal was to establish an integrated osteotomy design for both mandibular angle and body procedures and classify prevalent mandibular types in the Chinese Han population for surgical guidance. Included were 89 patients who underwent mandibular angle osteotomy without genioplasty between 2016 and 2022 at Peking University Third Hospital. Mimics 21.0 software facilitated CT data reconstruction and osteotomy planning. Postoperative effects were assessed through imaging, complications, and surveys, leading to mandibular type classification. Mandibular angles were categorized by 3 types, based on osteotomy range. Type I involved mandibular body osteotomy only, type II mandibular angle osteotomy only, and type III both mandibular angle and body osteotomies. Distribution within the cohort was 2.25%, 8.99%, and 88.76% for types I, II, and III respectively. Patient satisfaction was high, with minor and major complications at 47.19% and 1.12% by Clavien-Dindo classification. Utilizing Mimics software, we established an integrated osteotomy design and categorized mandibular types. Findings offer valuable guidance for mandibular angle surgery and contribute to understanding of Asian mandibular morphology.

MANDIBULAR BODY OSTEOTOMY FOR SKELETAL CLASS III MALOCCLUSION: A CASE-BASED REVIEW

Mandibular step body osteotomy has been out of favour since more stable ramus osteotomies were refined and used for jaw deformities. Mandibular body osteotomy still has certain indications for which it is preferable over ramus osteotomies. Mandibular body osteotomy is best suited to correct prognathism caused by mandibular body excess with a retained tooth or in presence of extraction space, with good posterior occlusion, when ramus osteotomies and setback will lead to loss of the last tooth and non-obtuse gonial angle. Other indications are apertognathia, mandibu­lar asymmetry and small advancements of the anterior mandible. Here we present a case 24 year male with a skeletal class III malocclusion managed with an intra­oral mandibular step osteotomy and setback of 8 mm. One-year followup has shown minimum neurosensory and odontogenic complications associated with mandibular step osteotomy and very high satisfaction among the patient. We also present a brief review of the indications, modifi­cations and refinement of the technique and summarize current published clinical usage. This is a very stable osteotomy with favourable fracture pattern and does not involve stripping or change in position of muscles of mastication thereby ensures long term stability and minimal risk of relapse. This surgery also has minimal effect on airway narrowing compared to the ramus osteotomy setback. For some specific indications not suited to a sagittal split ramus osteotomy, mandibular body step osteotomy still has relevance and usage.

COMPARISON OF BONE HEALING AFTER THE USE OF A THREE DIMENSIONAL MINIPLATE AND A CONVENTIONAL MINIPLATE IN MANDIBULAR BODY OSTEOTOMY (AN EXPERIMENTAL STUDY)

Introduction: Mandibular fractures comprise most of the traumatic injuries treated by an oral and maxillofacial surgeon. The aim of fracture treatment is to restore the architecture and function of bone. Many techniques for treating mandibular fractures have evolved over the years. The design of the three dimensional (3D) plate is conceptually that of 2 linear plates connected by reinforcing vertical struts providing greater resistance against gap opening at the inferior border with biting forces. Objectives: To compare histologically bone healing of mandibular body osteotomy after using either a 3D miniplate or conventional miniplates. Materials and methods: This study was conducted on twelve healthy dogs. An iatrogenic osteotomy defect was performed intra-orally between the mandibular 3rd and 4th premolars using a surgical micro reciprocating saw. The fragments will be reduced bimanually and stabilized: Group A (six dogs): 3D miniplates. Group B (six dogs): conventional miniplates. The dogs were euthanized at 2 and 6 weeks postoperatively and the osteotomy sites were excised, divided into three thirds (Tension Third, TT; Intermediary Third, IT; Compression Third, CT) and prepared for histological analysis. Results:The osteotomy site was completely filled with parallel-fibred bone, with more newly formed Haversian systems in Group A compared with Group B, bone repair did not reach the typical aspects of the parent lamellar bone. The percentages of newly formed bone at 2 weeks in group A according to thirds (TT, IT and CT) that reported have a statistically significant difference in comparison with group B. At 6 weeks, there were no statistically significant differences between the two groups among the TT and CT but there was a statistically significant difference (p4 = 0.039) in the IT. Conclusions: 3-D plates could be a better option than conventional miniplates.

Histological Analysis of Bone Repair in Mandibular Body Osteotomy Using Internal Fixation System in Three Different Gaps without Bone Graft in an Animal Model.

The aim was to analyze histologically the bone repair in a mandibular osteotomy model with different gaps between the segments. Nine male rabbits who underwent osteotomies on the mandibular body were fixed with a 1.5 system plate and no bone graft; group 1 (2 mm gap between segments), group 2 (5 mm gap between segments), and group 3 (8 mm gap between segments) were included. After 8 weeks they were euthanized and the sample was processed for histological analysis. Group 1 showed advanced bone repair with cartilaginous tissue and cancellous bone, showing osteoblasts and type III collagenous fibers. In group 2, a more delayed ossification was observed, with an extensive area of peripheral ossifying cartilage and chondrocytes in greater number at the center of the defect; group 3 showed no evidence of ossification with fibrous tissue, a very low level of chondrocytes, and some bone sequestrate. We can conclude that, in this animal model, 2 or 5 mm gap in the osteotomy could be repaired as bone when fixation is used. The size of the gap is an important factor for the use of bone grafts considering endochondral ossification. This model can be used for graft analysis and related technologies.

0890 INDIVIDUALIZED THERAPY FOR TREATING OBSTRUCTIVE SLEEP APNEA IN PEDIATRIC CROUZON SYNDROME PATIENTS

Pediatric patients with Crouzon syndrome have great possibilities in suffering from obstructive sleep apnea (OSA), which is mainly due to midfacial hypoplasia and facial deformities. For most patients, a multi-disciplinary and sequential treatment plan is necessary to make for Crouzon syndrome often has different phenotypes of different severity in OSA and facial deformities. Typical patients were selected in this study to illustrate the necessity of individualized therapy for treating OSA. In the study, four Crouzon syndrome children of different severity in suffering from OSA and maxillofacial deformities were introduced. Detailed information in individualized treatment options was given including clinical manifestations, radiological findings, polysomnography detectings and treatment combinations. Based on the above findings, different but effective treatment options for these children’s OSA problems were adopted, either by surgeries including distraction osteogenesis and craniomaxillofacial surgeries with or without tonsillectomy, or by noninvasive continuous positive airway pressure (CPAP) therapy. Patient 1 was performed with LeFort IIIosteotomy and external distraction osteogenesis. Patient 2 was given LeFort IIIosteotomy and external distractor fixation and concurrent bilateral mandibular body osteotomy and internal distractor fixation for bimaxillary distraction. Patient 3 received LeFort I osteotomy for maxillary advancement with concurrent bilateral tonsillectomy. Differently, patient 4 with mild OSA disturbance adopted initial continuous positive airway pressure (CPAP) with good adherence and body development. Six years later, he began orthodontic treatment for preparing for orthognathic surgery. Recently bimaxillary surgery was performed on him to enlarge upper airway anatomically as well as improve facial profile. Follow-up studies showed problems of OSA and nocturnal hypoxia of those four patients were all alleviated greatly, as well as maxillofacial deformities. Combined with preoperative and postoperative orthodontics, patient 1 and 4 also got optimal results in better facial profile and dental occlusion. Thus, given Crouzon patients had great possiblilities in suffering from OSA and hypoxia problems, individualized therapy should be made and performed carefully to obtain optimized treatment results based on adequate clinical evaluations and patients’ conditions including age, disease severity and esthetic considerations. This work was supported by the National Natural Science Foundation of China (Grant number: 81470786).

Bone healing after biodegradable mini-plate fixation.

To compare bone healing in mandibular vertical body osteotomies (MVBO) after fixation with a resorbable 2.0mm-profile fixation system in the first and third postoperative months in rabbits. Twenty hemimandibles of ten rabbits were divided into two groups according to duration of resorbable fixation-one or three months. The MVBOs were performed and one four-hole, resorbable, 2.0mm mini-plate fixation system was used on each side. The computed tomography (CT) scans, scanning electron microscopy (SEM), and histomorphometric outcomes of groups I and II were compared. Significant differences were found between the one- and three- month assessments in terms of newly formed bone ratio values (p<0.05). There was more new bone formation at the third month on both the CT and histomorphometric examinations. A better adaptation of the bone tissues to the resorbable mini-plate and screws was observed on SEM at three months. The resorbable mini-plates provided a fixation stable enough to allow immediate oral alimentation and callus formation in both groups.

Histologic and Histometric Analysis of Bone Repair at the Site of Mandibular Body Osteotomy and at the Bone-Screw Interface After Using a Biodegradable 2.0-mm Internal Fixation System.

The aim of the study was to evaluate histologically and histometrically the bone repair at the mandibular body osteotomy and at the bone-screw interface after using a biodegradable 2.0-mm internal fixation system. Six dogs were subjected to an osteotomy in the mandibular body, which was stabilized by applying a fixation device manufactured with poly-L-DL-lactic acid (70:30). The dogs were euthanized at 2 and 18 weeks. Each screw was sectioned along its long axis, and the osteotomy sites were divided into 3 parts: the upper part was labeled the tension third (TT); the lower part, compression third (CT); and the part between the TT and CT, intermediary third (IT). Histologic analysis showed areas of direct contact between the screw surface and the parent lamellar bone at 2 weeks. At 18 weeks, 3 microscopically distinct layers at the bone-screw interface were noted. At the osteotomy sites, union between the bone fragments was observed at 18 weeks. Statistically significant differences in the newly formed bone among TT, IT, and CT (P = 0.019) were observed. In conclusion, the biomechanical environment created by the biodegradable IF system used in this study facilitated bone repair at the osteotomy site.

Attachment Rate of the Inferior Alveolar Nerve to Buccal Plate During Bilateral Sagittal Split Osteotomy Influences Self-Reported Sensory Impairment

This study was aimed to investigate a modified buccal osteotomy technique and whether the integrity of the lingual part of the lower border influences the attachment of the neurovascular bundle to the proximal segment of the mandible during a sagittal split osteotomy without increasing the number of bad splits. The presence of self-reported sensibility disturbance in the lower lip at the last follow-up visit was assessed. This study included 220 and 133 patients with bilateral sagittal split osteotomy undergoing the classical and the new modified buccal osteotomy techniques, respectively. In the new technique, the lower border is divided into a lingual fragment that remains incorporated in the tooth-bearing fragment and a buccal fragment that comes with the proximal fragment (buccal plate). In the classical technique, the inferior alveolar nerve was attached to the proximal segment of the mandible in more than one third of operation sites (36.36% on the right and 40.91% on the left) compared with less than one fourth of the operation sites using the new technique (9.73% on the right and 23.01% on the left). The overall figure of self-reported changed sensibility was 09.40% (12/128) in the new technique compared to 15.12% in the classical technique. We present a suitable improvement to the classical buccal osteotomy technique that allows less manipulation and injury of the inferior alveolar nerve with consequent reduction in self-reported postoperative changes in lower lip sensation

Comparison and validation of finite element analysis with a servo-hydraulic testing unit for a biodegradable fixation system in a rabbit model

The aim of this study was the biomechanical validation of three-dimensional finite element analysis (FEA) with a servo-hydraulic testing unit (STU) for a resorbable fixation system (RFS) in a rabbit model. Bilateral mandibular vertical body osteotomies (BMVBO) were performed in 15 female New Zealand rabbits. The animals were divided into three groups. The STU and FEA tests were done immediately after surgery in group 1 (1day), at the first postoperative month in group 2, and at the third postoperative month in group 3. Both stress tests were carried out by applying vertical forces at the lower incisal edge, loading from 0N force and increasing this until breakage occurred at the bone. The maximum forces that the hemimandibles could stand and the amount of deformation were recorded and analysed with the FEA and STU tests. We found the STU and FEA test results to be similar and that they could be used interchangeably for groups 1 and 3. However, the FEA results differed most from the real STU values in group 2 because of callus formation that had not ossified at the osteotomy line.

Functional improvements after orthodontic-surgical reconstruction in a patient with multiple maxillofacial fractures

Patients with multiple craniofacial fractures often suffer from stomatognathic problems after their primary treatment, because administering emergency care is the clinician's highest priority. Therefore, optimal bone repositioning is sometimes difficult because bone fixation is delayed. Moreover, neither an adequate radiographic examination nor an evaluation of primary occlusion is available during the repair of fractured bones. The lack of these assessments can also lead to occlusal dysfunction after bone fixation. As a result, patients with craniofacial fractures often require occlusal reconstruction. This report describes the successful occlusal reconstruction with orthodontic-surgical treatment of a patient with multiple maxillofacial bone fractures. Combined surgery, including an intraoral vertical ramus osteotomy and a mandibular body osteotomy, was performed to reposition the deviated mandible after 3 months of preoperative orthodontic treatment. The total active treatment period was 25 months. After treatment, both the facial asymmetry and the anterior open bite caused by the skeletal disharmony were significantly improved. Additionally, the range of condylar motion, maximum occlusal force, and occlusal contact area during maximum clenching were also increased. These stomatognathic functions were further enhanced by 2 years of retention. Orthodontic-surgical reconstruction appears to improve both facial esthetics and occlusal function in patients with facial asymmetry caused by severe traumatic maxillofacial fractures.

Comparative study of bone repair in mandibular body osteotomy between metallic and absorbable 2.0 mm internal fixation systems. Histological and histometric analysis in dogs: a pilot study

The objective of this study was to compare the bone repair along a mandibular body osteotomy stabilized with 2.0mm absorbable and metallic systems. 12 male, adult mongrel dogs were divided into two groups (metallic and absorbable) and subjected to unilateral osteotomy between the mandibular third and fourth premolars, which was stabilized by applying two 4-hole plates. At 2 and 18 weeks, three dogs from each group were killed and the osteotomy sites were removed and divided equally into three parts: the upper part was labelled the tension third (TT), the lower part the compression third (CT), and the part between the TT and CT the intermediary third (IT). Regardless of the treatment system, union between the fragments was observed at 18 weeks and the CT showed more advanced stages of bone repair than the TT. Histometric analysis did not reveal any significant differences among the 3 parts or systems in the distance between bone fragments at 2 weeks. Although at 18 weeks the proportions of newly formed bone did not differ among TT, IT and CT, significantly enhanced bone formation was observed in all sections for the metallic group. The patterns of repair were distinct between treatments.

Poster 49: Assessment of Biomechanical Stability, Stress Distribution and Resorption Patterns of Biodegradable 2.0mm Inion® CPS Fixation System in a Rabbit Model

To evaluate biomechanical stability of resorbable 2.0 mm INION CPS fixation system in a servohydraulic testing unit (STU) and stress distribution of resorbable screws, miniplates and cortical/cancellous bone in bilateral mandibular vertical body osteotomies (BMVBO) immediately after surgeries, at the postoperative first and third months healing periods using 3-D finite element analysis (FEA) in a rabbit model. Additionally, patterns of resorption process were monitored by SEM analyses at first and third months' intervals.

O.397 Osseodistraction in 67 patients with mandibular asymmetry

Piezo-osteotomy feasibility as a substitute for the conventional saw in orthognathic surgery was evaluated regarding operative technique, blood loss, time requirement, and nerve and vessel integrity.Fifty patients had orthognathic surgery procedures in typical distribution using piezosurgical osteotomy: 22 (44%) monosegment, 26 (52%) segmented Le Fort I osteotomies; 48 (48%) sagittal split osteotomies, 6 (12%) symphyseal, and 4 (4%) mandibular body osteotomies. Controls were 86 patients with conventional saw and chisel osteotomies: 57 (66%) monosegment, 25 (29%) segmented Le Fort I osteotomies, 126 (73%) sagittal split, and 4 (5%) symphyseal osteotomies.Piezosurgical bone osteotomy permitted individualized cut designs, enabling segment interdigitation after repositioning. Angulated tools weakened the pterygomaxillary suture; auxiliary chisels were required in 100% of cases for the nasal septum, and lateral nasal walls as 46% pterygoid processes. After downfracture, the dorsal maxillary sinus wall and pterygoid processes were easily reduced. Hemorrhage was successfully avoided with average blood loss of 541 ± 150 mL versus 773 ± 344 mL (P = .001) for a conventional bimaxillary procedure. Sagittal mandibular osteotomy required considerable time (auxiliary saw in 13%); the lingual dorsal osteotomy was mostly performed tactile. Time investment remained unchanged: 227 ± 73 minutes per bimaxillary standard osteotomy versus 238 ± 61 minutes (P = .5); clinical courses and reossification were unobtrusive. Alveolar inferior nerve sensitivity was retained in 95% of the study collective versus 85% in the controls (P = .0003) at 3 months postoperative testing.Piezoelectric osteotomy reduced blood loss and inferior alveolar nerve injury at no extra time investment. Single cases require auxiliary chiseling or sawing. Piezoelectric drilling for screw insertion and complex osteotomy designs may be developed to maintain bone contact or interdigitation after repositioning and minimize need for osteofixation.

Piezoosteotomy in orthognathic surgery versus conventional saw and chisel osteotomy

Piezoosteotomy was assessed as alternative osteotomy method in orthognathic surgery regarding handling, time requirement, nerve and vessel impairment. In this comparative clinical experience, 90 patient's orthognathic surgery procedures were performed in typical distribution prospectively by piezoosteotomy: 34 (38%) monosegment, 47 (52%) segmented LeFortI osteotomies, 94 (52%) sagittal split osteotomies, 11 (12%) symphyseal, and 4 (2%) mandibular body osteotomies. As controls served 90 retrospective patients with conventional saw and chisel osteotomy: 58 (64%) monosegment, 27 (30%) segmented LeFortI osteotomies, 130 (72%) sagittal split, and 4 (4%) symphyseal osteotomies. Piezoosteotomies were individually designed to interdigitate the jaw segments after repositioning. The pterygomaxillary suture weakened angulated tools; auxiliary chisels were required in 100% of cases for the nasal septum and lateral nasal walls, in 33% for pterygoid processes. The dorsal maxilla as the pterygoid process were easily reduced; 15% mandibular osteotomies required sawing, while the lingual dorsal osteotomy was performed by manual feedback due to limited visibility. Bloodloss decreased from average 537 +/- 208 ml vs. 772 +/- 338 ml (p = 0.0001). Operation time remained unchanged: 223 +/- 70 min vs. 238 +/- 60 min (p = 0.2) for a conventional bimaxillary procedure. Clinical courses and reossification were unobtrusive. Alveolar inferior nerve sensitivity was retained in 98% of the piezoosteotomy collective versus 84% of controls (p = 0.0001) at 3 months postoperative testing. Piezoelectric osteotomy did not prolong the operation and reduced blood loss as alveolar nerve impairment. A few patients required additional sawing or chisel. Piezoelectric screw insertion as complex osteotomies may be initiated to simplify the procedure and increase segment interdigitation after repositioning as to minimize the osteofixation time and dimensions.

Critical Evaluation of Piezoelectric Osteotomy in Orthognathic Surgery: Operative Technique, Blood Loss, Time Requirement, Nerve and Vessel Integrity

Piezo-osteotomy feasibility as a substitute for the conventional saw in orthognathic surgery was evaluated regarding operative technique, blood loss, time requirement, and nerve and vessel integrity. Fifty patients had orthognathic surgery procedures in typical distribution using piezosurgical osteotomy: 22 (44%) monosegment, 26 (52%) segmented Le Fort I osteotomies; 48 (48%) sagittal split osteotomies, 6 (12%) symphyseal, and 4 (4%) mandibular body osteotomies. Controls were 86 patients with conventional saw and chisel osteotomies: 57 (66%) monosegment, 25 (29%) segmented Le Fort I osteotomies, 126 (73%) sagittal split, and 4 (5%) symphyseal osteotomies. Piezosurgical bone osteotomy permitted individualized cut designs, enabling segment interdigitation after repositioning. Angulated tools weakened the pterygomaxillary suture; auxiliary chisels were required in 100% of cases for the nasal septum, and lateral nasal walls as 46% pterygoid processes. After downfracture, the dorsal maxillary sinus wall and pterygoid processes were easily reduced. Hemorrhage was successfully avoided with average blood loss of 541 +/- 150 mL versus 773 +/- 344 mL (P = .001) for a conventional bimaxillary procedure. Sagittal mandibular osteotomy required considerable time (auxiliary saw in 13%); the lingual dorsal osteotomy was mostly performed tactile. Time investment remained unchanged: 227 +/- 73 minutes per bimaxillary standard osteotomy versus 238 +/- 61 minutes (P = .5); clinical courses and reossification were unobtrusive. Alveolar inferior nerve sensitivity was retained in 95% of the study collective versus 85% in the controls (P = .0003) at 3 months postoperative testing. Piezoelectric osteotomy reduced blood loss and inferior alveolar nerve injury at no extra time investment. Single cases require auxiliary chiseling or sawing. Piezoelectric drilling for screw insertion and complex osteotomy designs may be developed to maintain bone contact or interdigitation after repositioning and minimize need for osteofixation.

Bone repair in mandibular body osteotomy after using 2.0 miniplate system – histological and histometric analysis in dogs

The objective of this study was to evaluate the bone repair along a mandibular body osteotomy after using a 2.0 miniplate system. Nine adult mongrel dogs were subjected to unilateral continuous defect through an osteotomy between the mandibular 3rd and 4th premolars. Two four-hole miniplates were placed in accordance with the Arbeitgeimeinschaft für Osteosynthesefragen Manual. Miniplates adapted to the alveolar processes were fixed monocortically with 6.0-mm-length titanium alloy self-tapping screws, whereas miniplates placed near the mandible bases were fixed bicortically. At 2, 6 and 12 weeks, three dogs were sacrificed per period, and the osteotomy sites were removed, divided into three thirds (Tension Third, TT; Intermediary Third, IT; Compression Third, CT) and prepared for conventional and polarized light microscopy. At 6 weeks, while the CT repaired faster and showed bone union by woven bone formation, the TT and IT exhibited a ligament-like fibrous connective tissue inserted in, and connecting, newly formed woven bone overlying the parent lamellar bone edges. At 12 weeks, bone repair took place at all thirds. Histometrically, proportions of newly formed bone did not alter at TT, IT and CT, whereas significantly enhanced bone formation was observed for the 12-week group, irrespective of the third. The results demonstrated that although the method used to stabilize the mandibular osteotomy allowed bone repair to occur, differences in the dynamics of bone healing may take place along the osteotomy site, depending on the action of tension and compression forces generated by masticatory muscles.

Nicotine impairs distraction osteogenesis in the rat mandible

Distraction osteogenesis (DO) has gained clinical acceptance as a surgical technique for treatment of congenital craniomaxillofacial deficiencies requiring skeletal expansion. The use of this technique elsewhere requires more information on overcoming difficult clinical settings, for which new animal models will be needed. The aim of this study was to develop and validate a model of impaired DO of the rat mandible with nicotine. Twenty rats underwent a right vertical mandibular body osteotomy, after which distraction began with custom-made percutaneous devices and a 3-day latency period, 6-day distraction (0.25 mm twice daily) and 30 days of neutral fixation. Rats received either nicotine or placebo slow-release pellets. Specimens were analysed after removal of the devices for quantitative radiographic bone fill, amount of bone advancement and histological features. The mean radiographic bone-fill score with nicotine treatment was 75% of that with placebo ( P = 0.0036). The nicotine-treated rats had less (49%) elongation than the placebo-treated controls ( P = 0.0008). Histological analysis demonstrated less bone, vascularity and cellular activity in nicotine-treated rats. This study shows that nicotine reproducibly inhibits osteogenesis, vascularity and bone lengthening in mandibular DO.

M636: Orthognathic Surgery: Treatment Planning and Surgical Techniques

Surgical techniques in orthognathic surgery have and will continue to undergo modifications and change in an effort to improve the quality of patient care and outcome. This program will present state–of–the–art surgical techniques and research results substantiating the efficacy of these surgical methods. The following modifications will be discussed:1. Genioplasty A. Augmentation B. Tenon and mortise osseous genioplasty2. Anterior mandibular subapical osteotomy3. Mandibular body osteotomy4. Mandibular ramus sagittal split osteotomy modifications A. Ramus and inferior border osteotomy B. Rigid fixation5. Maxillary osteotomy modification A. Maxillary step osteotomy and rigid fixation B. Porous block HA grafting6. Double jaw surgery A. Selective alteration of the occlusal plane B. Surgical sequencing of the maxilla and mandible C. Model surgery modifications7. TMJ factors affecting orthognathic surgery outcomesImplementation of these techniques by the experienced, skilled surgeon, coupled with accurate diagnosis and treatment planning, should provide optimal functional and esthetic outcomes for our patients. Surgical techniques in orthognathic surgery have and will continue to undergo modifications and change in an effort to improve the quality of patient care and outcome. This program will present state–of–the–art surgical techniques and research results substantiating the efficacy of these surgical methods. The following modifications will be discussed: 1. Genioplasty A. Augmentation B. Tenon and mortise osseous genioplasty 2. Anterior mandibular subapical osteotomy 3. Mandibular body osteotomy 4. Mandibular ramus sagittal split osteotomy modifications A. Ramus and inferior border osteotomy B. Rigid fixation 5. Maxillary osteotomy modification A. Maxillary step osteotomy and rigid fixation B. Porous block HA grafting 6. Double jaw surgery A. Selective alteration of the occlusal plane B. Surgical sequencing of the maxilla and mandible C. Model surgery modifications 7. TMJ factors affecting orthognathic surgery outcomes Implementation of these techniques by the experienced, skilled surgeon, coupled with accurate diagnosis and treatment planning, should provide optimal functional and esthetic outcomes for our patients.

Poster 206: Revisit of Mandibular Body Osteotomy for Correction of Mandibular Prognathism: A Case Report

Mandibular body osteotomy became less common recently for correction of mandibular prognathism because of complications such as inferior alveolar nerve injury and developing more effective surgical procedures such as mandibular sagittal split ramus osteotomy. However, there are several cases which seemed to be an indication of this operation. In this paper, we report a case of mandibular prognathism which we performed the body osteotomy with inferior alveolar neurovascular bundle decompression in order to minimize damage to this structure. An eighteen year old man showed mandibular prognathism but the occlusion in the molar region was normal. After preoperative orthodontic treatment, the body osteotomy was performed in the missing second premolar space. Mucoperiosteal finger flap was reflected at the crest of the space to expose the inferior border of the mandible and around the mental foramen. 0.1 × 0.2 cm shaped lateral cortical plate was removed around the mental foramen and incisal branch of neurovascular bundle was severed. After that, osteotomy was performed and bone segments were fixed with mini plates. Inter maxillary fixation continued for a week after operation. One year after operation, his occlusion is stable and sensory disturbance of lower lip is not recognized. We consider this method should be a candidate for patients with mandibular prognathism, who have normal occlusion in the molar region, although decompression of the neurovascular bundle is necessary to minimize damage to this structure.