[Difference of body movements accompanying mandibular movements in standing and sitting positions].

PURPOSE: To assess whether body movement accompanying jaw movement exists even in sitting position, and, if so, to investigate differences of body movements in the sitting and standing positions. METHOD: The subjects were six men (age, 25-29 years, mean, 27.0 years) without stomatognathic problems. During the measurements, their Camper's planes were kept horizontal. One measurement sequence consisted of 20 s of tapping preceded and followed by 10 s of intercuspation. Mandibular movements (lower incisor point) were measured by referring to a coordinate system located on the maxilla, and head movements (upper incisor, condyle, etc) with TRIMETII (Tokyo Sizaisya) and body movements (sternum point) in sagittal plane were measured by referring to a coordinate system located on the floor with Proreflex (Qualisys). RESULTS: Body movements accompanying jaw movements were detected even in sitting position. The ratio of body movements to jaw movements was significantly larger in standing position than in sitting position using Wilcoxon matched-pairs signed-rank test. Peak power of body movement at corresponding frequency to the open-close movement was significantly larger in standing position than in sitting position using Wilcoxon matched-pairs signed-rank test. On the other hand, there was no difference between sitting and standing position in probability of body movement detection by the original wave analysis using Wilcoxon matched-pairs signedrank test. CONCLUSION: Body movements accompanying jaw movements were detected even in sitting position, and were smaller than in standing position. However, the probability of movements detected in original wave had no difference between the positions. Thus we concluded that we can analyze body movements during mastication in natural sitting position.

A precise and useful method for coordinating computed tomography and jaw movement frames of reference.

PURPOSE: The aim of this study was to develop a means of coordinating helical computed tomography (CT)- based morphological data in 3 dimensions (3-D) with that pertaining to jaw movement as recorded by a device that measures jaw movement in six-degrees-of-freedom (6-DOF), thus producing multi-point movement analysis of the condyle. METHODS: The study sample was two volunteers. One of the subjects had erosive bony changes in both condyles, while the other had healthy condyles. We employed a customized facebow, which enabled us to coordinate jaw movement data and morphological volume data from CT. Total uncertainty of the coordination was computed, according to International Organization for Standardization (ISO). In order to demonstrate the effects of multi-point analysis for complex condylar movement, we tried to visualize the trajectory of the working condyle in lateral excursion. RESULTS: The overall uncertainty at a condylar center chosen as an example to illustrate the method was 0.38 mm, 0.19 mm, and 0.50 mm in antero-posterior, lateromedial, and supero-inferior directions, respectively, in terms of 95% coverage as defined by the ISO. CONCLUSION: We developed facebow-based X-ray markers with high clinical operability, which could correlate the helical CT's coordinate system with our 6-DOF jaw movement measuring system for precise analysis of 3-D condylar movements. In motion analysis of rotational condyle, even a small amount of measurement error cannot necessarily be neglected. Then, a multi-point approach such as that realized by our system presents the best option.

Condylar bone change and sagittal incisal and condylar paths during mandibular protrusive excursion.

This study showed significant differences in sagittal condylar and incisal path angles during mandibular protrusive excursion, as well as flattening of the condylar path related to the existence and type of condylar bone change. Twenty-eight (28) patients with signs and symptoms of TMJ disorders were studied, using a six-degrees-of-freedom measuring device and helical CT. Sagittal incisal and condylar path angles at two mm and three mm condylar path lengths (CPL) were significantly shorter in the bilateral condylar bone change (BBC), compared to the no bone change (NBC) group. Also, NBC incremental sagittal condylar path angles from three to five mm CPL and NBC condylar path curvature at five mm CPL were both significantly larger than in BBC. Comparing types of bone change, incremental sagittal condylar path angles from three to five mm CPL was significantly less in osteophyte than in NBC or erosion groups. Condylar path curvature at five mm CPL was also significantly less in osteophyte than in NBC.

The relationship between morphological changes of the condyle and condylar position in the glenoid fossa.

AIMS: To investigate whether condylar morphological changes influence the condyle position in the glenoid fossa as well as the amount of condylar movement from the intercuspal position (IP) to the reference position (RP). METHODS: Helical computed tomography was used for precise measurement of the joint spaces at IP and RP in 22 subjects (mean age 22.7 years). Subjects were divided into 2 groups, those without condylar bone changes (n = 11) and those with condylar bone changes (n = 11). The latter group was further subdivided into a flattening subgroup and an osteophyte subgroup, according to the type of condylar bone change. RESULTS: There were no significant differences in the width of the anterosuperior or posterosuperior joint spaces at IP between either the 2 groups or the 2 subgroups. On the other hand, during condylar movement from IP to RP, the condyles moved significantly more superiorly and posterosuperiorly in the bone-change group than in the no-bone-change group. There was also greater absolute horizontal condylar movement between IP and RP in the bone-change group. In addition, within the bone-change group, the type of condylar bone change influenced the amount of condylar movement. Joints with osteophyte formation showed the most superior, posterosuperior, and absolute horizontal movement from IP to RP. CONCLUSION: The findings that condyles of the bone-change group, especially those with osteophyte formation, were located significantly more anteroinferiorly in the glenoid fossa at IP than RP than the condyles of the no-bone-change group suggest that condylar IP-RP positional changes might be related to condylar shape alteration.

The relationship between retruded contact position and intercuspal position in patients with TMJ osteoarthritis.

This study was conducted to investigate the relationship between posterior mandibular excursion movement and temporomandibular joint osteoarthntis (TMJ OA) in 25 orthodontic patients with Angle Class I and Class II, using a six degrees-of-freedom measuring device and helical computed tomography. There were significant differences found in three-dimensional length, antero-posterior, absolute latero-medial and supero-inferior incisal, and condylar intercuspal position (IP)-retruded contact position (RCP) slides between bilateral, unilateral, and no condylar bone change groups. With respect to the types of condylar bone change, there were significant differences found in three-dimensional length, antero-postenor, and absolute latero-medial condylar IP-RCP slides between flattening, erosion and osteophyte groups. These results suggest that large three-dimensional, not only incisal but also condylar, IP-RCP slides might be related to the uni-/bilaterality and kind of TMJ pathosis, which might make such slides useful as clinical indices of TMJ OA.