The purpose of this study was to compare three different methods of measuring angular changes of the mandibular condyle in the horizontal plane. A cephalometer (Model C-166 R: Tokyo Emix Co. Ltd., Japan) along with an apparatus we developed were utilized to obtain submentovertex radiographs. The subjects were placed in a position where the central ray is perpendicular to the Camper plane.
In fifteen subjects with normal occlusion, two submentovertex cephalograms were obtained from each individual at two different times with the teeth in centric occlusion. The following are the three different measuring methods:
(A) “Best fit” method: The outlines of the condyles were traced and superimposed by the “Best fit” of the condyle. Then the angle between two inter-foramina spinosa lines was measured.
(B) “Caliper” method: To determine a condylar long axis by using a sliding digital caliper.
(C) “Perpendicular lines” method: The condylar long axis was determined by using tangent perpendicular lines from an inter-foramen spinosum line to the outline of the condyle. The tangents touch the outline of the condylar shape at the outermost point and the innermost point. A straight line that connects these two points is the condylar long axis.
The condylar long axis was determined by methods (B) and (C). The angle between the condylar long axis and the inter foramina spinosa line (condylar angle) was measured. Then the difference in the condylar angle between the two films was computed.
All films were traced, superimposed, and measured by the same examiner. The results were as follows:
1) The error of measurement of condylar rotation by the “Best fit” method was 1.0°±0.9°by the “caliper” method was 2.5°±2.1°and by the “perpendicular lines method” was 1.9°±1.5°Statistically significant (p<0.01) differences were found when the “Best fit” method was compared with the other two methods.
2) The condylar angle measured with the caliper was 15.7°±8.4°and with the perpendicular lines method was 10.1°±5.4°Statistically significant (p<0.01) differences were found between the two methods as determined by the t-test.
In conclusion, (1) the “Best fit” method was more suitable for measuring condylar rotation than the other conventional methods.(2) The “caliper” method of measuring the condylar angle in the horizontal plane was more suitable than the method using perpendicular lines.

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The activity indices of the masticatory and temporal muscles and the maxillofacial morphologies in patients with skeletal mandibular prognathism at the initial examination were compared with those in individuals with normal occlusion. The results were as follows:
1. The muscle activity index was significantly lower in the prognathic patients than in the normal individuals.
2. The items of maxillofacial morphometry that correlated with the muscle activity index were fewer and weaker in the prognathic patients than in the normal individuals.
These findings suggested that patients with skeletal mandibular prognathism have functional and morphological disturbances.

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During surgical treatment of the maxillofacial region, it is important to grasp the 3-dimensional structure, because the area has a physically complex structure consisting of many bones and soft tissue. Conventionally, diagnostic and therapeutical procedures were not commenced prior to rendering a 3-D image from the 2-D image. However, 3D-CT (3-dimensional Computed Tomography) has made it possible to easily monitor any morphologic shape as a 3-D image on a plane. This has heretofore been difficult to determine preoperatively.
So far, there has been a lack of investigation into the precision or accuracy of 3-D image analysis in the maxillofacial area. Therefore, a 3D-CT based reconstruction system was used for preoperative evaluation of mandibular diastrophism. 3-D imaging was carried out on the mandible both empirically and clinically to evaluate measurement accuracy and precision.
In this system, data scanned with a 3D-CT Hi-Speed Advantage (GE Yokokawa Medical Systems) were read by a Power Macintosh 8100/80 AV and the resulting image data were processed with a 3-D rendering software by Vox Blast (Image & Measurement Corp.). The measurement results demonstrated that the 3-D images met accuracy and precision requirements.
In addition, even more accurate measurements became possible by attaching markers to the skin surface of the maxillofacial area while scanning the 3D-CT images, which is an index of the reproductibility of this procedure.

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This study was conducted to compare pre-and post-surgical (mean 7.7 months) jaw functions in 18 patients (8 males and 10 females, mean age 23.1 years) with mandibular prognathism who underwent orthognathic surgery. Ten subjects (5 males and 5 females, mean age 26.1 years) were used as controls.
EMG power spectra and integrations of jaw-closing muscles (anterior temporal and masseter muscles) were analyzed during 10 tapping strokes and during 60 seconds of continuous maximum clenching in an intercuspal position.
1. Tapping
The integrations of EMG in temporal and masseter muscles were increased after orthognathic surgery as compared with those before surgery, but no significant differences were found.
The integrations of EMG in the patients before and after orthognathic surgery were both significantly lower as compared with the controls.
The median power frequencies (MPF) were lower, though not significantly, after orthognathic surgery as compared with those before surgery.
2. Continuous maximum clenching
The integrations of EMG in temporal and masseter muscles were increased after orthognathic surgery as compared with those before surgery, but no significant differences were found.
The integrations of EMG before and after orthognathic surgery were both significantly lower in the patients as compared with the controls.
MPF were lower after orthognathic surgery than before, but significant differences were not found.
The EMG power spectral and integration analyses during muscle fatigue were very useful to evaluate the stomatognathic function in mandibular prognathism.
The results of this study suggested the necessity of carrying out long-term observation for the evaluation of the function corrected by orthognathic surgery.

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Orthognathic surgery was performed on a total of 118 patients from 1989 to 1995 in our clinic. The ratio of male to female was 1: 2.2 and the mean age was 20.6 years. In most of the patients (95.7%), mandibular prognathism with or without another type of jaw deformity was diagnosed. Sagittal splitting ramus osteotomy (SSRO) was performed on 113 patients (95.8%). The average time of operation and the average blood loss during operation were 3 hr 47min and 558.2ml for SSRO and 6 hr 44min and1090 ml for two jaw surgery, respectively. Fixation of the bone fragment for SSRO was done asfollows: 58 patients by semi-rigid fixation with titanium miniplate, 50 patients by circumferential wiring, and 5 patients by other methods. The average period of intermaxillary fixation in SSRO was 8.2 days for miniplate fixation and 20.2 days for circumferential wiring. Seventy-five of 90patients (76.3%) who received blood transfusion received autotransfusion.

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The frequency of TMJ disorders in patients with jaw deformities was surveyed by questionnaires and dental casts. TMJ disorders in 174 patients (84 males and 90 females, mean age of 22.0 years) were evaluated by questionnaire. Dental casts were evaluated and classified into occlusomorphologic types such as mandibular prognathism, asymmetry, open bite, maxillary prognathism, and composite of these according to previously described criteria. All variables such as gender, age, potential etiologic factors and histories, and occlusomorphology, were analyzed for association with symptoms by Fisher's exact probability test.
The frequency of reported present or past TMJ disorders was 77.6%. No difference due to gender was observed. When the frequency of TMJ disorders in different age groups was examined, the youngest being 15 years old followed by the others at increasing age intervals of 5 years, there was no significant difference between age groups. Among 135 symptomatic patients, 49 patients (36.3%) reported only one symptom of TMJ disorders, while 86 patients (63.7%) reported two or more symptoms. As for potential etiologic factors and historical events, poor posture and experience of trauma were more frequently observed among symptomatic patients than asymptomatic patients (p<0.05). There was no significant difference in the frequency of TMJ disorders between different occlusomorphologic types.

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Sagittal splitting ramus osteotomy is widely used for the correction of mandibular prognathism. There are various procedures for fixation of segments that underwent osteotomy. One of the aims of fixation is to reduce a skeletal relapse after operation. At present, rigid fixations using screw and/or plate are employed in many institutions. However, it has been suggested that these rigid fixations may cause a temporomandibular disorder.
The purpose of this investigation was to compare postoperative positional change and function between screw and plate fixation. The subjects were fifteen patients in whom segments that underwent osteotomy were fixed with positioning screws and fifteen patients in whom segments that underwent osteotomy were fixed with mini-plates. Radiographs which were taken before, immediately after, after three months, six months, and twelve months were analyzed for estimation of positional change. Lateral cephalograms were analyzed for angle of SN-MP, SNB, SN-Pog and ANB. Frontal cephalograms were analyzed for ramus angulation. Submental radiographs were analyzed for condylar angulation. Initial interincisal distance at the releasing time of intermaxillary fixation and trismus (less than 35mm) duration after surgery were also evaluated. Every analytical result was not significantly different between the plate fixation group and the screw fixation group. Therefore, plate fixation of bone segments in sagittal splitting ramus osteotomy may be a useful procedure.

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A case of unilateral ankylosis of the temporomandibular joint, which caused micrognathia with facial asymmetry, was reported. A 3-year-old female visited our department because of facial asymmetry She was placed on conservative therapy using a functional appliance to improve facial asymmetry and occlusal relationship. Because of mandibular trismus, condylectomy was performed at the age of 13 years 10 months. Interincisal distance increased to 38mm, but micrognathia with facial asymmetry remained. Therefore, Le Fort I osteotomy combined with extraoral vertical ramus osteotomy on the affected side and sagittal split ramus osteotomy on the opposite side was performed at the age of 16 years 10 months. In addition, augmentation genioplasty with a porous hydroxyapatite block was performed at the age of 17 years 6 months. Four years later, the patient was satisfied with recovery of jaw opening and improvement in facial appearance.

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For correction of skeletal open bite with Angle class I, sagittal splitting of body of mandible has been performed.
This surgical method can preserve the integrity of the inferior aspect of the mandibular body and alveolar crest and has obviated the necessity of bone grafting and making the precise model needed for conventional mandibular body ostectomy. In addition, the excellent interface of bone has promoted early consolidation of the proximal and distal segments.Therefore, sagittal splitting of the body of the mandible is an effective surgical procedure for skeletal open bite.

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In this paper, three cases treated with functional genioplasty to improve function and esthetics were presented, and the functional genioplasty was discussed.
The chin deformities demonstrate not only esthetic but also functional problems caused by positional disharmony of suprahyoid and labiomental muscles. The obstructive sleep apnea syndrome due to the severely retruded chin as well as lip incompetence with open mouth and flattening of the anterior surface of the chin when closing forcibly lip in excessively vertical chin were presented.
In this study, broad soft tissue pedicle genioplasty was found to be useful for surgical correction of chin deformities to improve function and esthetics.

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Unusual skeletal patterns are often seen in patients with facial asymmetry and in those with Class III malocclusion. In such cases, treatment based solely on skeletal analysis does not necessarily bring about satisfactory improvement in the morphology of integumental soft tissue.
In this study, soft tissue analysis was conducted in order to better understand the facial asymmetry of a patient. Then this information was used in conjunction with hard tissue analysis of the same facial area when determining a treatment regimen. By using this method, the problems of facial asymmetry became clear, and an it was found that appropriately adjusted treatment plan leads to improvement in occlusion and facial esthetics. This case shows the importance of considering information from both soft and hard tissue analyses when developing a suitable procedure for orthognathic surgery in order to achieve facial symmetry for the patient. In addition, this case suggests the effectiveness of using the relative position of the subnasal as a standard when considering treatment to improve the profile.

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