Features in subjects with the frontal occlusal plane inclined toward the contralateral side of the mandibular deviation.

INTRODUCTION: The frontal occlusal plane of the maxilla generally inclines toward the ipsilateral side of the mandibular deviation in subjects with facial asymmetry; however, a few patients with facial asymmetry have their frontal occlusal planes inclined toward the contralateral side. We aimed to investigate the morphologic and functional features of such patients. METHODS: The subjects were 40 patients with facial asymmetry divided into 2 groups based on the inclination of the frontal occlusal plane toward the ipsilateral or the contralateral side. We analyzed lateral and posteroanterior cephalometric radiographs and occlusal variables and evaluated temporomandibular joint symptoms. Statistical comparisons were performed between the 2 groups (P <0.05). RESULTS: The posteroanterior cephalometry significantly differed between the ipsilateral and contralateral groups. Occlusal force and occlusal contact area were significantly larger, and temporomandibular joint symptoms were more frequently found on the side of the upward-inclined frontal occlusal plane than on the opposite side in both groups. CONCLUSIONS: The features in the contralateral group in terms of occlusal force and temporomandibular disorders were clinically significant. Clinicians should note that the conditions associated with the contralateral group require less presurgical decompensation.

The imbalance of masticatory muscle activity affects the asymmetric growth of condylar cartilage and subchondral bone in rats.

OBJECTIVE: To examine the effects of imbalance of masticatory muscle activity of the rat mandible on the condylar cartilage and subchondral bone during the growth period. DESIGN: Forty 5-week-old male Wistar rats were randomly divided into experimental (n=20) and control (n=20) groups. In the experimental group, the left masseter muscles were resected. The rats were sacrificed at 7 or 9 weeks of age in both groups. Microcomputed tomography was used to determine the three-dimensional morphology and cancellous bone structure. For histological and histochemical examination, 5-µm-thick serial frontal sections of the condyle were stained with toluidine blue and immunostained with asporin and TGF-ß1 to evaluate the promotion and inhibition of chondrogenesis. RESULTS: In the experimental group, microcomputed tomography analysis showed asymmetric growth; the resected side condyles showed degenerative changes. Histological analysis showed that the total cartilage in the central region of the resected side was significantly thinner than in the non-resected side in the experimental group, as well as in the control group. Compared with the control group, the expression of asporin was significantly higher in the resected side, and significantly lower in the non-resected side. In contrast, the expression of TGF-ß1-immunopositive cells in the non-resected side was significantly higher than in the resected side and the control group. CONCLUSIONS: These findings imply that lateral imbalance of masseter muscle activity lead to inhibition of chondrogenesis and induce asymmetric formation of the condyle during the growth period.

Mechanical loading leads to osteoarthritis-like changes in the hypofunctional temporomandibular joint in rats.

OBJECTIVES: Temporomandibular joint (TMJ) hypofunction secondary to feeding a liquid diet in the growing period leads to morphological hypoplasia. However, few studies have evaluated the results of mechanical loading on the hypoplastic TMJ. This study investigated whether TMJ hypofunction in rats causes osteoarthritis (OA)-like changes when exposed to mechanical loading. DESIGN: Male 21-day-old Wistar rats were divided into four groups. The first group (C) served as the control. In the second group (W), mechanical loading was applied to the TMJ by continuous steady mouth opening (3h/day for 5 days) from 63 days of age. A jaw-opening device was used to hold the mandible open in the maximal mouth-opening position with a cobalt-chromium (Co-Cr) wire (φ: 0.9mm). Groups C and W both received a normal hard diet. The third group (L) and fourth group (LW) were fed a liquid diet and group LW were subjected to the same loading as group W. We evaluated the TMJ using micro-CT, toluidine blue staining and immunohistochemistry of matrix metalloproteinase (MMP)-13. RESULTS: In group LW in the superior and posterior regions of the condyle, bone volume fraction, trabecular thickness and trabecular number were significantly decreased and trabecular spacing was significantly increased. The ratio of MMP-13 immunopositive cells was significantly higher than in the other groups. OA-like changes were also observed, including reduced thickness of the cartilage, irregularities in the chondrocytic layer, and cell-free areas. CONCLUSIONS: TMJ hypofunction in rats is likely to lead to OA-like changes when exposed to mechanical loading.

Effect of functional shift of the mandible on lubrication of the temporomandibular joint.

Lubrication of synovial joints reduces the coefficient of friction of the articular cartilage surface. To investigate the effect of malocclusion on the lubrication of the temporomandibular joint (TMJ), we evaluated lubricin expression in the rat TMJ immunohistochemically, under conditions of functional lateral shift of the mandible, during period of growth. Thirty 5-week-old male Wistar rats were divided into experimental, recovery, and control groups. Each rt in the experimental and recovery groups was fitted with an acrylic-plate guiding appliance. The rats in the experimental and control groups were killed at 14 and 28 days after the appliance was attached. Each rat in the recovery group was detached from the appliance at 14 days, and was killed 14 days after the appliance was removed. In the experimental group, the expression of lubricin staining in TMJ cartilage was significantly decreased during the experimental period. In the recovery group, the expression of lubricin staining in TMJ cartilage was significantly greater than in the experimental group, and there was no significant difference at 28 days between the control and recovery groups. Analysis of these data suggests that a functional lateral shift of the mandible during the growth period influences lubrication of the TMJ.

Intermittent posterior displacement of the rat mandible in the growth period affects the condylar cancellous bone.

OBJECTIVE: To examine whether intermittent posterior condylar displacement causes changes in cancellous bone in the mandibular condyle during the growth period. MATERIALS AND METHODS: Sixteen 5-week-old male Wistar rats were divided into experimental and control groups. In the experimental group, an appliance was attached to the maxillary incisors to induce posterior displacement of the condyles in the occluded condition. Untreated rats served as the control group. Animals were sacrificed at 14 days, and the condyles were removed to analyze the three-dimensional cancellous bone structure by microcomputed tomography (micro-CT). Serial sagittal paraffin sections of the condyles were used for hematoxylin and eosin staining to investigate histomorphological changes and for tartrate-resistant acid phosphatase (TRAP) staining to identify osteoclastic cells. RESULTS: Micro-CT analysis showed that in the experimental group, the bone volume fraction and the degree of anisotropy were significantly decreased compared with those in the control group in the anterior region of the condyle. Moreover, the number of TRAP-positive cells was significantly greater in the same region in the experimental group than in the control group. CONCLUSION: Intermittent posterior displacement of the mandible can cause region-specific changes in the profile and microarchitecture of the condylar cancellous bone.

Health management of adults with Turner syndrome: an attempt at multidisciplinary medical care by gynecologists in cooperation with specialists from other fields.

AIM: Since women with Turner Syndrome (TS) have various complications, they require comprehensive medical evaluation and multidisciplinary treatment. Although TS patients receive adequate care in childhood, many adults with TS do not. Since most TS adults attend gynecologists for hormone replacement therapy, we suggest gynecologists take primary responsibility for their management. In an attempt to provide TS patients with a comprehensive treatment regimen, we started multidisciplinary medical management in the Reproductive Health Clinic at Yokohama City University Hospital. To evaluate the efficacy of this medical care system, a retrospective analysis was conducted. METHODS: The clinical profiles of 57 TS patients were examined. The past histories, complications and clinical data of these patients were extracted from their medical records and examined clinically. Bone mineral density measurements of lumbar vertebrae (L(2-4)), anti-thyroid antibody titer measurements, hearing tests and cardiovascular MRI were also performed. RESULTS: Mean follow-up duration was 5.1 years (range, 1-8 years). At the time of transition, patients with complications developed in childhood, such as amenorrhea, osteopenia/osteoporosis, otitis media, thyroid dysfunction and cardiovascular disease were identified. All these complaints were successfully followed up in our adult care system. Several complications common to TS adults, such as glucose intolerance, liver dysfunction, hyperlypidemia and hypertension could be identified by our screening system. Patients were referred to specialists when necessary. CONCLUSION: Multidisciplinary health management in our Reproductive Health Clinic improved the status of medical care for TS adults.