The purpose of the present study was to investigate postoperative stability of asymmetric mandible. We performed a cephalometric radiographic evaluation of postoperative stability on 11 patients who had undergone sagittal splitting ramus osteotomy of asymmetric jaw deformities at our clinic from 1989 to 1991.
The results were as follows:
1. Measurements of areas of right and left mandible by cephalometric radiograms, particulary those in the lower portion, were very useful to evaluate the postoperative change of mandibular asymmetry. The ratio of left area/right area in the lower portion of the mandible was turned to nearly 50/50 at one year after operation in 7 patients.
2. Four of 7 patients, who had a difference of over 7mm in setback between right and left of the mandible and had a horizontal movement of over 6mm at the center of both lower central incisors, exhibited less postoperative horizontal stability.
3. Only two of 9 patients, who were given preoperative orthodontic therapy, showed postoperative instability of the mandible.
4. The correlation between postoperative horizontal instability and posteroanterior instability of the mandible was not definitely confirmed.

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The purpose of this study was to evaluate the skeletal facial asymmetry in patients with facial deformity who needed surgical orthodontic treatment to correct their severe facial asymmetry.
Thirty adult patients with severe facial asymmetry who underwent surgical orthodontic treatment (Asymmetry group) and 30 adult patients with facial symmetry who underwent only orthodontic treatment (Control group) formed the basis of this study.
The skeletal facial asymmetry of the Asymmetry group was examined quantitatively both in the horizontal and the vertical dimensions, and compared with the dimensions of the Control group statistically.
The following results were obtained.
1. Horizontally, the Asymmetry group demonstrated significant facial asymmetry both in the mid face and the lower face, and the degree of this deformity increased gradually towards the lower face. Similarly, vertically, the Asymmetry group demonstrated facial asymmetry both in the mid face and the lower face, but the vertical degree of deformity was smaller than that horizontally.
2. Horizontally, the Asymmetry group demonstrated significant correlation among all facial components, while vertically, the Asymmetry group only demonstrated a significant correlation among the adjacent facial parts.
3. The classification of the Asymmetry group based on severely deformed facial parts revealed that 2/3 of the asymmetry cases had severe facial deformity not only in the mandible, but also in the mid face.

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In facial asymmetry cases, there seems to be a morphologic and functional imbalance related to the maxilla and mandible, TMJ and masticatory muscles. There have not been many reports on the relationship between the deformity of the cranial vault and mandibular deviation. The purpose of this study was to clarify the relationship between the deformity of the cranial vault and mandibular deviation by using submental-vertical radiograms.
Submental-vertical radiograms of 33 cases (patients from the Niigata University Dental Hospital, students of Niigata University and volunteers) were take and analyzed. The cases were divided into 2 groups which were compared with each other. Group1was composed of persons who had large mandibular deviation (|Dev.|≥4°). Group 2 was composed of persons who had smaller mandibular deviation.
The result shows that in group 1 the morphology of the temporal portion of the horizontal cranial vault was more concave on the side with deviation than the other side. It is suggested that cranial deformity is significantly related to mandibular deviation and cranial and mandibular deformity seems to be linked with asymmetry in condylar movement and functional imbalance of the masticatory muscles.

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For surgical correction of excessive transverse facial width in patients with masseter muscle hypertrophy or bony projection at the mandibular angle, we reported a technique for intraoral removal of bony exostoses at the mandibular angle. By our method, one block of the bony exostosis, which is extremely difficult to remove intraorally, can be removed easily and safely without damage to the inferior alveolar neurovascular bundle and surrounding tissue.
Our method is as follows.
A laminectomy bur is used to cut through the lateral cortical plate of the ramus on the line connecting suitable points on the posterior border of the ramus and the preangular notch. Next, a splitting chisel is directed and driven inward to the osteotomy line. Since the angle of mandible almost consists of mostly cortical bone and the medial cortical plate is thin, a triangle of the bone segment can be separated at the bone marrow and extirpated.

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Bilateral sagittal splitting osteotomy occasionally involve the paresthesia of the mental nerve area. In the present study, postoperative complication, especially neurosensory disturbance has been investigated after modificatioin of the surgical method and intra-postoperative care. According to patient questionnairing, the period of neurosensory disturbance was almost within 6 months for the participants who underwent the osteotomy, with the vertical line on premolar. But some of them suffered a neurosensory disturbance period of more than two years. After 1992, we changed the vertical osteotomy line from premolar to molar region. Recovery of thermoreception and nociceation were early, but most cases of nociceation was not abnormally shown. Mechanoreception recovered between 2 weeks and6months, and no patients suffered neurosensory disturbance longer than 6 months.
In addition, the amount of setback was found to be related to the recovery period of neurosensory disturbance.

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Surgical correction of severe mandibular protrusion had been frequently performed by the Obwegeser II surgical procedure or combined mandibular osteotomy. Although clinically acceptable results had been achieved by applying the former method, certain problems such as intraoperative complication and postoperative stability had not been completely solved. The latter method had been considered to solve the problems. There were few articles discussing it, despite combined mandibular osteotomy used for the treatment of mandibular deformity in Japan.
The purpose of this paper was to discuss the clinical problems of the Obwegeser II method and to elucidate the surgical criteria for producing better results.
Case 1 was a 22-year-old man, who had protrusion of the upper lip and mandible. W e treated him with maxillary anterior segmental osteotomy and sagittal splitting ramus osteotomy combined with mandibular anterior segmental osteotomy.
Case 2 was a 20-year-old woman, who had severe mandibular protrusion. We treated her with intraoral vertical ramus osteotomy combined with mandibular anterior segmental osteotomy.
Results of both cases were excellent, and literature was cited in our report.

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The purpose of treatment of jaw fracture and deformities is to improve the appearance and stomatognathic function of the oral and maxi ilofacial region. Morphological examination has been performed extensively in the orthodontic field; however, objective functional assessment methods for the masticatory system are few.
The patient, a 19-year-old female, was referred to us and complained of occlusal discomfort and man-dibular deviation. We performed open reduction of the malunion fracture and evaluated the stomato-gnathic function, i. e., occlusal contacts in intercuspal position and muscle contraction pattern during gum chewing, by means of medical engineering instruments pre and post operatively.

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A 23-year-old female with skeletal mandibular prognathism was scheduled for orthognathic surgery. Since she had moderate asthma, consideration was given to avoidance of respiratory complications before, during and after surgery.
1. Preoperatively, reversibility of bronchial constriction was evaluated with a spirogram before and after inhalation of a bronchodilator. The patient had been prescribed bronchodilators and bronchodilator aerosols, and antibiotics were administered to prevent postsurgical infections.
2. Anesthesia was induced with intravenous administration of midazolam and ketamin. During surgery, the patient was maintained in anesthesia with nitrogen oxide, oxygen and sevoflurane. Aminophyline was administered intravenously to avoid an asthma attack. The patient underwent sagittal split ramus osteotomy. Rigid fixation with titanium screws and intermaxillary traction with elastics after surgery were performed to avoid complications after surgery.
3. One day after surgery, despite receiving intravenous aminophylline, this patient had an asthma attack, but it was successfully recovered in fifteen minutes with bronchodilator aerosols after removing the nasogastric tube. Stimulation of the larynx by the nasogastric tube may have induced the attack.
4. Orthognathic surgery can be performed on an asthmatic patient if the attending physician is able to prevent asthma attacks or takes proper measures against the occurrence of attacks in close consulation with an asthmatic medical specialist.

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In this case, widening and scissors bite of left upper dental arch was observed as a complication after fracture. Le Fort I type osteotomy of the left maxilla and palatine suture osteotomy were performed and the constriction of the upper dental arch by using a rapid maxillary contraction appliance was rendered. As compared with before the treatment, 2.0mm reduction of maxillary arch on P-A cephalogram, and 3.3mm reduction of the distance of central incisors, 3.9mm reduction of the distance of first bicuspids and 2.6mm reduction of the distance of first molars were observed in the model. Following treatment, the occlusions and aesthetic feeling were recovered satisfactorily in a short time.

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We treated a case of jaw deformity with pernicious biting habit and other symptoms.
The patient was a 48-year-old female, who had been attempting to improve prognathism with conscious edge-to-edge occlusion. Consequently, she had some physical symptoms, that is unstable occlusion, mandibular malposition, headache and pain of the lingual margin. Analysis of the integration of electromyogram (tapping and clenching) had shown that she could bite stronger with the anterior position of the mandible than with edge-to-edge occlusion. She used a modified, inclined bite plate which guided the mandible forward. After one month, she acquired stable occlusion and lingual pain was cured. After that, 44 were extracted and anterior segmental osteotomy by modified Kole's method was performed. The integration of electromyogram was similar to controls, at three months after operation. Now, she has been followed up without symptoms for10months since operation.

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Temporomandibular joint (TMJ) ankylosis in infancy may affect the growth of the mandible and lead to a micrognathia. Bilateral TMJ ankylosis may result in bird face appearance and unilateral TMJ ankylosis may result in an asymmetrical face. In this article, we report a case of micrognathia with unilateral TMJ ankylosis from 6 to 19 years old.
A 6-year-old girl visited our clinic with a complaint of mouth opening disturbance. As an initial therapy, she underwent training of mouth opening with a mouth gag. When she was 10 years old, she had increased in interincisal distance up to 10mm. There after, she did not visit our clinic. When 16 years old, she visited us with severe disturbance of mouth opening and an asymmetrical face. At that time, TMJ ankylosis was diagnosed, and condylectomy and coronoidectomy were performed. In order to improve facial asymmetry and occlusal relationship in anticipation of orthognatic surgery, preoperative orthodontic treatments were performed. In a 3-year follow-up, she exhibited mouth opening disturbance and micrognathia. When19years old, simultaneous TMJ mobilization and sagital splitting osteotomy of the ramus were performed. The patient had satisfactory mouth opening movement and improvement in facial symmetry.

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Simultaneous bimaxillary orthognathic surgery, which can alter an occlusal plane, is employed for correction of varying maxillomandibular dentofacial deformities. Since positioning of the maxillary segment is inherently considerable to improve both facial esthetics and occlusion, a systematized and ensured procedure is needed to obtain stable results.
The authors describe here the bimaxillary surgical procedures with special reference to a newly devised “Two-Step positioning” of the maxillary segment utilizing face bow transfer and an occlusal plane indicator.
The Two-Step positioning technique is summarized as follows:
1) An altered occlusal plane of the maxilla in model surgery is recorded in a Quick mount face bow (Whip-mix Co.). Beforehand the dental arch impression made with self-curing resin and small hooks at bilateral premolars is attached to the bite fork, which securely holds the mobilized maxillary segment on the bite fork during surgery.
2) Step 1: After mobilizing the mandible and maxillary segment, the maxillary occlusal plane is transfered to the patient by means of face bow transfer. The maxillary segment is immobilized with two low profile miniplates (Leibinger Co.).
3) Step: The occlusal plane indicator having an upper dental arch impression is applied to the dental arch, which enables easy assessment of the occlusal plane three-dimensionally. In case indicating additional correction of the plane, loosening some screws of the miniplate allows versatility in repositioning of the segment.
This technique has been applied to 30 cases without incidence, and it has been our experience that positioning of the maxillary segment is ensured and the surgical procedures are systematized with this technique.

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Orthognathic surgery under general anesthesia was performed on 255 patients from April 1982 through December 1992 at the First Department of Oral and Maxillofacial Surgery, Osaka Dental University. Based on preoperative examinations of those patients, the following prevalence rates of diseases were obtained, reinforcing the need for preoperative examinations:
1. Anemia was found in21patients (8.2%); two (2.3%) of them were male and19 (10.9%) were female.
2. Abnormality of liver function was found in 17 patients (6.7%); nine (11.1%) were male and eight (4.6%) were female.
3. Arrthythmia was found in 6 patients (2.4%); one (1.2%) was male and five (4.6%) were female.
4. Allergic disease was found in 47 patients (18.4%); 15 (18.5%) were male and 32 (18.4%) were female. Eighteen out of 47 patients suffered from asthma.
5. Hyperthyroidism was found in two patients (0.8%).

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A clinical evaluation was carried out on 284 patients who underwent orthognathic surgery from October 1975 for 19 years and 6 months at our hospital.
The results were as follows.
1) The male-female ratio was 1: 2.3.
2) The average age was 21.0 years.
3) Most of the patients (81.7%) came from Kumamoto Prefecture.
4) Mandibular prognathism was the predominant diagnosis (74.3%).
5) Sagittal splitting ramus osteotomy (Obwegeser-Dal Pont method) was performed on 268 patients.
6) The average operation time and the average bleeding amount during the operation were 2hr. 43min.±38min. and 192ml.±143ml. respectively for sagittal splitting ramus osteotomy.
7) From 1975 to 1993, 241 patients underwent circumferential wiring with 6-week intermaxillary fixation.
From 1993, 27 patients underwent rigid fixation by screws without intermaxillary fixation.
8) It was found that the incidence of temporomandibular joint symptoms in patients who underwent screw fixation was not much different from that of patients underwent circumferential wiring after surgery.

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