Accurate surgical planning is essential in surgery of jaw deformity. Though recently simulated operations utilizing 3-D CT have been reported, they are still unsatisfactory for surgical planning because the images are displayed on a 2-D basis.
In this paper, simulated surgery for jaw deformities with 3-D life-size solid models, produced by millling polyurethane forms on the basis of CT data (ENDOPLAN system), are reported. These models are very valuable for simulated surgery, preoperative evaluation, and explanation of the surgical procedure to patients.

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The purpose of this study was to examine the cephalometric changes of mandibular and condylar position during preoperative orthodontic treatment. The materials in this study were lateral cephalograms and lateral radiographs of the temporomandibular joint from18cases of mandibular protrusion undergoing orthognathic surgery. These were taken at the initial (A) and the end (B) of the preoperative orthodontic treatment. Linear and angular measurments were made and analyzed statistically, and superimpositions of the condyle in the condylar fossa were also performed.
The results were as follows:
1. During preoperative orthodontic treatment, the Menton moved anterosuperiorly or anteroinferiorly or posteroinferiorly. The SN-Mandibular plane angle increased in some cases, but decreased in other cases.
2. Condylar positions also changed in many cases, but the extent of the change was much less thanthat of Menton. Superimpositions of the condyle in the condylar fossa showed complicated changes which consisted of anteroposterior and superoinferior movement combined with rotation of the condyle.
3. There was a statistically significant correlation in the rotation of the mandible and condyle. But here was no statistically significant difference in the horizontal and vertical movements of the Menton and condyle.
These results strongly suggest that the mandibular position has changed in preoperative orthodontic treatment. Therefore, it is worthwile to examine the changes of the mandibular position including condyle prior to determination of external bone fragments during the surgical procedures of sagittal split osteotomy of the ascending ramus and screw fixation.

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Changes in lateral soft tissue profile were investigated in 18 mandibular prognathism patients treated with sagittal splitting osteotomy. Further, prediction of the changes and postoperative positions of 21 soft tissue points was carried out based upon 11 hard tissue points before treatment, changes of four measurement items for the skeleton and 5 anatomic soft tissue positions by means of stepwise multiple regression analysis.
1. The amount of mandibular setback had the most substantial influence on the prediction of horizon -tal soft tissue changes, whereas vertical mandibular change exerted a great influence on the prediction of verticalones. In addition, factors other than the amount of mandibular set back some what influ-enced the soft tissue profile prediction.
2. Soft tissue profile prediction is possible with enough precision for clinical use by this method.

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Morphological features of the mandible were evaluated by cephalometric analysis of 44 patients with surgically operated skeletal mandibular protrusion. The results were as follows:
1. The mandibular condyle was narrow and long and the condyle was high in the mandibular protrusion. Mandible and mandibular body were long, mandibular notch was deep, gonial angle was wide and the ramus inclined forward.
2. The small anteroposterior diameter of the mandibular condyle were related to the long mandibular length, the long mandibular body length, the high ramus height and the forward inclined ramus. High condylar height was related to the long mandibular length, the short anteroposterior diameter of the ramus, the wide gonial angle and the forward inclined ramus.
3. From these findings, it might be suggested that the mandible in patients with surgically operated skeletal mandibular protrusion had the characteristics of underdevelopment.

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The purpose of this study was to clarify the correction of facial asymmetry through the orthognathic surgery. The subjects were operated by bilateral sagittal splitting ramus osteotomies (SSRO group) and the unilateral sagittal splitting ramus osteotomy combined with the body ostectomy (SSRO-BODY group). Skeletal and soft tissue outlines were obtained from the frontal cephalogram before and after surgery. These outlines were normalized, and changes of those outlines in the two groups were compared with each other.
As for soft tissue outline, asymmetry of both groups were corrected much better after surgery.
In skeletal outline of the SSRO group, there were significant changes in the region of bilateral mandibular angle after surgery, but change of the outline was a little on the deviation side. In the SSRO-BODY group, however, outline in regions of bilateral mandibular angle and ramus on the deviation side changed significantly after surgery. Facial asymmetry seemed to be corrected much more in the SSRO-BODY group than the SSRO group.

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The purpose of this study was to investigate the positional changes of the hyoid bone following surgical correction of mandibular prognathism. The materials consisted of cephalograms of 10 patients before surgery and one and five years after surgery. To eliminate the influence of head posture, the position of the hyoid bone was revised on cephalogram with SH and C3H before surgery. The results as follows:
1. In the stable group after surgery, the position of the hyoid bone changed back-and downward. In the relapse group, the hyoid bone position did not change back-and downward. However, there were two cases which the hyoid bone position changed back-and upward, and three cases showed a forward and downward change.
2. The same result was apparently observed in the stable group and relapse group in one year after surgery.
3. In the stable group, the hyoid bone position also changed back-and downward five years after surgery. In the relapse group, the hyoid bone position changed back-and downward in three cases, and returned to the preoperative position in one case.

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This study was undertaken to extract characteristics of dento-facial vertical changes following orthognathic surgery in mandibular prognathic patients with open bite and to clarify morphological factors that affect the stability of postoperative occlusion.
Lateral cephalometric radiographs were taken in a sample of adult mandibular prognathic patients with (Open bite group) and without (Control group) open bite. Each group consisted of 12 subjects who underwent mandibular setback osteotomy with the sagittal split technique requiring intermaxillary fixation with circumferential wiring. There were no significant differences in the A-B difference and overjet in the pretreatment stage between the two groups.
Dento-facial vertical changes were divided into three subgroups changes in denture and skeletal patterns, as well as in an anterior occlusion (a combination of denture and skeletal patterns). These changes were analyzed and compared between the two groups in five stages: Pretreatment, immediately before and after surgery, posttreatment, and under retention (more than one year after posttreatment). The results were as follows:
1. During the preoperative orthodontic treatment period, the Open bite group showed an elongation of upper incisors (P<0.01), an upward displacement of the Menton (P<0.01) and an increase in overbite (P<0.001) as compared with those of the Control group.
During the intermaxillary fixation period, both groups showed an elongation of upper and lower incisors, an upward displacement of the Menton and an increase in overbite. The Open bite group revealed a smaller overbite than the Control group immediately after surgery (P<0.05).
During the postoperative orthodontic treatment period. the Open bite group showed an elongation of lower incisors (P<0.05). The Menton was displaced mainly downward in the Open bite group. The overbite decreased in the both groups.
During the retention period, there were no changes in the denture pattern in both groups. The Open bite group showed a downward displacement of the Menton and a decrease in overbite.
2. No significant effects on dento-facial patterns in the pretreatment stage were observed, dentofacial changes followed preoperative orthodontic treatment and osteotomy on the postoperative dentofacial changes were demonstrated in both groups. However there was a correlation between the overbite in the pretreatment stage and its change during the retention period in the Control group (P<0.01). Regarding the relevancy of each subdivided dento-facial change in the postoperative stage, there were correlations between the skeletal pattern and the anterior occlusion in both the Open bite (P<0.001) and Control (P<0.05) groups during the retention period.

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Orthognathic surgery was performed on 180 patients from 1984 to 1993 in our clinic. There were 42 male and 138 female patients with a mean age of 20 years. 154 patients (85.5%) were diagnosed with mandibular prognathism. 160 patients (88.9%) underwent sagittal splitting ramus osteotomy (Obwegeser-Dal Pont's method). 29 patients underwent Le Fort I osteotomy. The average time of operation and the average blood loss during operation were 3 hr 41 min and 583 ml for sagittal splitting ramus osteotomy with tongue reduction, 3 hr 13 min and 580 ml for sagittal splitting ramus osteotomy, 4 hr 51 min and 926 ml for Le Fort I osteotomy, 5 hr 49 min and 1, 091ml for two jaw surgery. Tongue reduction (Egyedi-Obwegeser's method) was carried out on 113 patients (62.8%) 169 patients (93.9%) received autologous blood transfusion, and 72% of blood loss was replenished by autologous blood transfusion.

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Sagittal splitting ramus osteotomy is widely performed for correction of mandibular skeletal dentofacial deformities. W e retrospectively studied 325 patients treated with bilateral sagittal splitting ramus osteotomies in order to investigate perioperative unfavorable fracture, and found eight episodes of fracture in eight patients (2.4% of incidence). The most predominant fracture site was the distal segment with vertical and horizontal fracture line. All fractured segments were sufficiently repositioned and fixed in appropriate positions. Slight extension of the intermaxillary fixation period was noted, however, no severe postoperative complication was found.
It was considered that incomplete osteotomy, misdirection of horizontal medial osteotomy, and violent bone split caused unfavorable fractures.

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Questionnaires were sent to oral and maxillofacial surgery, orthodontic, and anestheisology departments where board members of Japanese Association of Oral and Maxillofacial Surgeons, Japan Orthodontic Society, or Japanese Dental Society of Anestheology are working. Questionnaires included questions cocerning surgical procedures applied to mandibular deformities, fixation methods between segments, the duration of postoperative intermaxillary fixation, complications of perioperative phase and preoperative and postoperative orthodontic treatments. This paper presented the results of the survey on surgical procedures, fixation methods between segments and the duration of intermaxillary fixation based on the replies from 99 oral and maxillofacial surgery departments.
Results
1. Sagittal splitting ramus osteotomy is widely used for the treatment of mandibular deformities in oral and maxillofacial surgery departments of Japan, and 89 out of 93 oral and maxillofacial surgery departments apply this procedure to the most of their mandibular deformity cases.
2. Three departments use vertical ramus osteotomy for the treatment of mandibular deformities in more than 50% of their cases and 18 departments use this procedure in the second largest number of their cases.
3. Intermaxillary fixation is used postoperatively in most departments. Some departments apply it for more than six weeks even if rigid bone fixation methods are used.
4. Most of all oral and maxillofacial surgery departments have been trying to reduce the duration of intermaxillary fixation by applying more rigid methods for securing segments.

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This is a case report on treatment of skeletal psalidodont deformity with simultaneous maxillary and mandibular posterior segmental osteotomy. Operation was performed through only buccal mucosal incision for the preservation of blood supply to the osteotomized segments and the fixation of fragments were done using acrylic resin splint without using miniplate-screwing to avoid injuring the tooth root. Soon after the operation, temporary segmental mobility was observed. However, the usually reported postoperative complications such as relapse and disturbance of the segment or the teeth were not remarkable. Finally. the fine occlusal relationship and function were obtained.

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The purpose of this study was to evaluate the changes of the external segments after Obwegeser-Dal Pont's sagittal splitting ramus osteotomy. Condylar angulation, ramus angulation, distance between rami and position of point Ar of 6 cases were measured before operation and 1, 3, 6 and 12 months after operation.
The results were as follows:
1. The condylar angulation immediately after sagittal splitting ramus osteotomy increased.
2. The condylar angulation had a tendency to return to the preoperative status and the distance between rami became shorter until 12 months postoperatively. It was considered that the external segments were moved inside by rotation.
3. It was suggested that the condylar angulation on the side of deviation in the case of facial asymmetry was increasing.

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Face bow headgear is an extraoral anchorage appliance used for distalization of maxillary molars, controlling growth of the maxilla, reinforced anchorage and so on. In preoperative orthodontic treatment, face bow headgear was used to treat mandibular protrusion in two siblings. Face bow headgear was used to prevent labial tipping of the maxillary incisors during leveling. Their maxillary premolars were not extracted.
Case 1 was a female, 19 years 2 months at the initial examination. She was diagnosed with skeletal mandibular protrusion and facial asymmetry. After preoperative orthodontic treatment, the maxillary incisors slightly tipped labially. After surgical orthodontic treatment, facial asymmetry was improved.
Case 2 was a male, 19 years 1 month at the initial examination. He was diagnosed with skeletal mandibular protrusion and slight facial asymmetry. After preoperative orthodontic treatment, the maxillary incisors did not tip labially. After surgical orthodontic treatment, facial asymmetry was improved.
Since face bow headgear was used in preoperative orthodontic treatment, labial tipping of the maxillary incisors during leveling could be prevented. Face bow headgear also had an effect on facial asymmetry. These cases were treated in a comparatively short time.

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Varying amounts of skeletal relapse have been reported following the surgical correction of dentofacial deformities by Le Fort I osteotomy.
Modified Le Fort I osteotomy was introduced to reduce relapse. This procedure was designed by Kaminishi to enhance stability and provide a more solid bony base for rigid skeletal fixation of the mobilized segment.
Two of our cases are presented in this study. This modification has given us greater control and stability, especially in combined maxillary and mandibular osteotomies.

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Superior surgical techniques by oral and maxillofacial surgeons should be required for obtaining stability on patients' prognoses. Furthermore, the coordination between the maxillary and mandibular arch forms should be attained by preoperative orthodontic treatment, that would enable smooth osteotomy.
However, many different factors of each patient would sometimes make the preoperative orthodontic treatment difficult to obtain an ideal relationship between the maxillary and the mandibular arch forms.
In the present study, a patient with a skeletal Class III malocclusion and severe deep overbite was treated by surgical orthodontic treatment. In this case, a prominently narrow mandibular arch and closed occlusion was made to interrupt preoperative orthodontic treatment in order to attain coordinated arch widths between the maxilla and the mandible. Furthermore, we discussed the procedures for rasing vertical dimension, correcting arch form disharmony between the maxilla and the mandible, and obtaining stability on patients' prognoses, as in this case.

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