The development of jaw deformities in the human provides some of the most challenging issues of cause and effect relationships between muscle and bone. Genetic factors provide the underlying control for the development of the craniomandibular region, but the neuromuscular system is intimately woven with the bone. While genetic factors effect the muscle and bone, these two tissues can also interact to effect eachother. The best experimental data supporting this concept is presented. Asymmetrical mandibles can be developed in the experimental animal models when bilateral jaw muscles become unequal in the force across the craniomandibular skeleton (e. g., lesioning many trigeminal motoneurons unilaterally). Mutations that prevent fetal jaw muscle development or impairing muscle contraction in the fetal stage alter the shape and size of the cranioskeleton including the mandible. Clinically, systemic muscular diseases that include the jaw muscles (e. g., masseter, temporalis) lead to significant increases in vertical facial development and the development of a severe retrognathic. Jaw muscles must develop sufficient periodic forces on the craniomandibular skeleton, particularly the dentoalveolar and condylar regions, to control growth of the mandible. The neuromuscular system effects a third property of the craniomandibular bone, the mineralization of the tissue. The pattern of cortical bone mineralization may prove to be one of the effective methods to assess the actual forces developed in the craniomandi-bular skeleton by the jaw muscles.

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Functional impairment of mandibular movement after sagittal split osteotomy in 21 skeletal Class III patients was studied. Mandibular movement was recorded and analyzed by a six-degrees-of-freedom optoelectric mandibular motion recording system (Gnathohexagraph^®, JM-1000T, Ono Sokki, Japan). Mandibular movements were recorded preoperatively, and at 1, 2, 3, 6, and 12 month postoperatively. Mandibular movement was evaluated by analyzing the parameters of mandibular incisor paths. The subjects performed protrusive, lateral excursions and maximal open-close movement of the mandible and habitual open-close cycles of the mandible.
The values of protrusive and lateral excursions of the incisor at one month after surgery decreased by 25%, and functional recovery was significant at 12 months after surgery. The capacity of maximal opening of the jaw decreased by 43% at one month after surgery, and the opening capacity regained approximately 90% of the level at 12 months after surgery. A significant difference was found between males and females in the velocity of the open-close cycles. Male subjects showed a slight decrease in velocity one month after surgery, and the value reached 125% 12 months later. Female subjects showed a remarkable decrease in velocity one month after surgery and remained at 10% below the presurgical level. The results of this study indicated that functional impairment of mandibular movement after sagittal split osteotomy was achieved within one year, as well as restoration of the dentoskeletal morphology to its former condition.

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It has been reported that skeletal facial asymmetry is correlated with condyle path asymmetry on protrusive movement. In this article, we investigated the degree and the direction of the condyle path asymmetry on open, protrusive, and lateral movements, and their relationship with skeletal asymmetry in the frontal dimension.
The subjects were 35 patients with various facial patterns, (26 females, and 9 males ; mean age, 21.9±4. 8years). Standardized PA cephalograms were used for morphological analysis. The linear and angular measurements were based on the x-y coordinates, the Lo-Lo' plane as the x-axis, and the vertical line through Nc as the y-axis. Reference points, such as Mo, Mo', Go, Go', and Me, were chosen to analyze horizontal and vertical skeletal asymmetries. The measurements were used as skeletal asymmetry variables.
Condylar movements were recorded with a computeraided Axiograph (CADIAXR, Gamma). Both horizontal condylar inclination (HCN) on the sagittal plane and the Bennet angle (BEN) on the horizontal plane were measured 5 mm from a reference point (RP), and the shortest distance between RP and the most translated position of the condyle (DIS) on the sagittal plane was measured. The difference between the right and left condyles was calculated and used as a condylar path asymmetry variable. Stepwise linear regression analysis was performed to pick up a valid skeletal asymmetry variable for describing the condylar path asymmetry variable.
On open movement, stepwise linear regression analysis selected only deviation of Me as a valid parameter for the HCN difference between both condyles. Deviation of Me was also revealed to be a valid parameter for explaining the differences in HCN, BEN, and DIS on protrusive movement, and the differences in HCN and DIS on lateral movement. Upper dental arch asymmetry and horizontal cant of the occlusal plane were found to be effective parameters for HCN difference on protrusive movement. Upper dental arch asymmetry was also an effective parameter for BEN difference on lateral movement. These results indicated that horizontal and vertical skeletal facial asymmetry had a relationship with condylar path asymmetry in every mandibular movement.

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The accuracy of positioning the osteotomized maxilla during orthognathic surgery was assessed in 26 patients, comparing the use of an external reference point placed on the forehead skin (SERP), and an external reference point consisting of a bone screw placed at the forehead bone (BERP). In all cases, the unoperated mandible was used to provide an anteroposterior and transverse maxillary position, through use of an intermediate splint. In 14 cases, the distance between the SERP and the maxillary central incisor was measured, to determine the maxillary vertical dimensions. In 12 cases, measurements between the BERP the and maxillary central incisor were made.
All preoperative lateral cephalometric radiographs were traced by one investigator, and these tracings were superimposed on postoperative lateral chephalograms (3 to 6 days after surgery), respectively. The actual changes in the vertical and horizontal position of U1 were measured perpendicular and parallel to the Frankfort horizontal plane. The actual change of the palatal plane angle was also measured. These values of actual change were compared with the prediction tracings made by measurements obtained from model surgery, and the difference between planned and actual movements was calculated.
The mean difference of U1 anteroposterior movement was 1.5±2.0mm in the SERP group, and 1.2±1.1 mm in the BERP group. The mean difference of U1 vertical movement was 1.8 ±2.8mm in the SERP group, and 0.5±0.3mm in the BERP group. And the mean difference of palatal plane angle rotation in the SERP group was 2.7±6.2°, and 1.6±1.8° in the BERP group. Statistical analysis showed a significant difference between the SERP group and the BERP group in the U1 vertical difference (t-test, p<0.05).
The results of this investigation revealed less accuracy in the actual three-dimensional maxillary movements of the SERP group, compared with the BERP group. And this study also showed that use of the BERP will allow accurate three-dimensional control of the maxillary position, especially in the vertical dimension. However, the maxillary repositioning technique using BERP still remains subject to operator error, and other numerous possible sources of error were identified, which may lead to an incorrect result.

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AIM: The purpose of this study is to introduce our newly developed 3D integration system for computed simulation of facial, skeletal, and occlusal changes with orthognathic surgery, and its clinical application.
MATERIAL AND METHOD: The system is composed of the following three non-contact measuring units: a facial analyzer using coded pattern projection (OGIS, RFX IV), an X-ray CT machine (SIEMENS, SOMATOM PLUS S), and a dental model analyzer using laser scanning (UNISN, VMS250R). To construct common 3D coordinates, the face bow having three ceramic balls used as standard points was set on the maxillary dental arch for obtaining 3D information from each measuring unit. The 3D coordinate values were sent to the workstation (KUBOTA, Titan 2) and integrated into the common 3-D coordinate system by superposition based on the standard points of the face bow.
RESULT: 1) Compared with measured values by a contact 3D measuring unit (MITSUTOYO, MXF203), the measuring reliability in the 3D distance was 1.61±0.81mm in the facial analyzer, 0.56±0.25mm in the X-ray CT machine, and 0.13±0.08mm in the dental model analyzer. 2) Measurement reliability of the predicted skeletal change based on the occlusal change was 1.20±0.36mm in the 3D distance.
In clinical application, 3D skeletal and facialgraphics could be simulated based on predicted occlusal changes.
CONCLUSION: 3D information from the different measuring units could be integrated with high accuracy into our 3D integration system, and its clinical applicability was satisfactorily confirmed.

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Various methods for testing sensory disturbance after sagittal splitting ramus osteotomy have been reported, but no standardized testing method exists. In the present investigation, which was conducted at multiple sites, the authors investigated the presence and degree of sensory disturbance after sagittal splitting ramus osteotomy. Identical test apparatuses (Semmes-Weinstein pressure aesthesiometer) were used in the sensory tests. Furthermore, the time of observation, the location measured, and the evaluation method were standardized, in order to compare the data.
The data indicated that the one-week postoperative incidence of sensory disturbance was 43.2%, 72.2%, 62.5%, and 71.4% at hospitals A, B, C, and D, respectively. The total rate of incidence among the four hospitals was 56.5%. It was therefore possible to identify the incidence rate numerically. In addition, by employing Bell's interpretation scale, the degree of sensory disturbance was classifiable.
The standardization of factors, such as test equipment, measurement method, and data evaluation, will increase the accuracy of comparative studies that involve different hospitals and previous reports.

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A case of hemifacial microsomia treated by orthognatic surgery is reported. The patient was a 14-year-old male who complained of facial asymmetry and dental crowding. After preoperative orthodontic treatment with the extraction of the four first premolars, a Le Fort I osteotomy and sagittal split ramus osteotomies (two-jaw surgery) were carried out, when the patient was 16 years old. Facial asymmetry and occlusion were improved dramatically. No marked clinical changes in occlusion were found after 12 months' follow-up. The patient has been wearing retainers full-time. He is pleased with the occlusion and his facial appearance.

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