The purpose of this study was to investigate the effects of sleep bruxism on periodontal sensation and tooth displacement in the molar region. Twenty-eight (28) subjects lacking objective or subjective abnormalities in stomatognathic function were divided into two groups representing bruxers (n=14) and controls (n=14). Sleep bruxism was confirmed based on the nocturnal electromyography activity of the masseter muscle. Periodontal sensation was assessed based on interocclusal tactile threshold (ITT), which refers to the minimal thickness that can be detected between the occlusal surfaces of the teeth. ITT was measured in the first molar region. Displacement of teeth during clenching was measured using a two-dimensional tooth displacement transducer. Statistical analysis of the differences in ITT and tooth displacement between the bruxers and controls was performed by Mann Whitney U-test (p < 0.05). Mean ITT for bruxers was significantly lower than that for controls (p < 0.01). The mean displacement of both the maxillary and mandibular first molar for the bruxers was significantly larger than that for the controls (p < 0.05). The results of this study suggest that sleep bruxism affects both periodontal sensation and tooth displacement.

No abstract

The processes of bone wound healing after maxillary molar extraction in ovariectomized aged rats were examined by means of quantitative backscattered electron image analysis and energy-dispersive X-ray microanalysis. Six-month-old female rats were either sham-operated or underwent bilateral ovariectomy (OVX), and 60 days postoperatively, the maxillary first molars were extracted. On post-extraction days 7, 30, and 60, the dissected and resin-embedded maxillae were micromilled in the transverse direction through the extracted alveolar sockets, and new bone formation on the buccal maxillary bone surface and within the extracted alveolar sockets was examined. In both sham-operated control and OVX rats, new bone formation was recognized on the buccal bone surface, as well as within the extracted sockets, and increased daily through to day 60. In comparison to sham-operated controls, new bone formation in OVX rats was significantly decreased both on the buccal bone surface and within the extracted sockets. Our results suggest that bone wound healing by new bone formation after maxillary molar extraction is significantly decreased in OVX-induced osteoporosis.

We studied bone wound healing processes after maxillary molar extraction in ovariectomized (OVX) aged rats, as an experimental model of postmenopausal osteoporosis, by means of scanning electron microscopy. Six-month-old female rats were either sham-operated or bilaterally OVX; and at 60 days postoperatively, the maxillary first molars were extracted. On postextraction days 4, 7, 30 and 60, the dissected maxillae were fixed and the alveolar bone surfaces around the extracted alveolar sockets were examined. In sham-operated controls, new bone formation was recognized on the buccal-side bone surfaces on day 4 and then increased in extent daily through day 60 mainly on the buccal and mesial sides. On day 60, the extracted sockets were filled with new bone mass and the surrounding alveolar bone surfaces had become smooth, indicating decreased bone metabolism. Bone resorption was prominent throughout the bone surfaces around and within the extracted sockets, increased in extent through day 7, but had decreased by day 60. In comparison to sham-operated controls, new bone formation in OVX rats was slightly increased in the early phase but subsequently showed a marked decrease. Bone resorption in OVX rats was greatly stimulated and was comparatively long-lasting. These results suggest that, under the present experimental conditions, in bone wound healing after maxillary molar extraction, (i) ovariectomy stimulates sustained bone resorption and (ii) bone formation and resorption both take place at specific sites on alveolar bone surfaces.

Postmenopausal oestrogen deficiency results in bone loss (osteoporosis) in humans and experimental animals. The loss of trabecular bone in the ovariectomized (OVX) rat provides a useful experimental model of post-menopausal osteoporosis. At 5 months after ovariectomy of 3-month-old female rats, the mid and distal femurs and maxillae were dissected and processed for quantitative backscattered electron microscopic examinations. Histomorphometric analysis of femurs in OVX rats showed significant loss in metaphyseal trabecular bone areas compared with sham-operated controls; no significant bone loss was observed in the cortical bone areas of mid-diaphyses in OVX rats. Net bone areas in the maxillae of OVX rats was similar to that of sham-operated controls. Bone structure of maxillae in OVX rats was also similar to that in controls. Our results suggest that, in this animal model of osteoporosis, prominent bone loss occurs mainly in the bone areas formed by endochondral ossification such as distal femurs, but those areas formed by intramembranous ossification such as mid-femurs and maxillae sustained less effects by OVX.