Subcellular localization of vitronectin receptors (integrin αvβ3 subunits) in rat osteoblasts was examined by means of light and post-embedding, immuno-electron microscopy. The specific immunoreactivity for the cytoplasmic domain of integrin αv and β3 subunits, detected by using colloidal gold-conjugated secondary antibody, was clearly observed along the plasma membranes and in the cisterns of rough-surfaced endoplasmic reticulum and secretory granules of osteoblasts. Such immunoreactivity was hardly detected by a protein A-gold technique. Obtained results suggest that αvβ3 integrin has a role in osteoblast-bone matrix interactions including the induction of cytoplasmic polarity, cell differentiation, cell-matrix adhesion, and bone formation processes.

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The author examined the pathological mechanism underlying the lack of bone resorption in the osteoclasts of osteosclerotic oc/oc mice. Ultrastructural features of osteoclasts in oc/oc mice were different depending on the types of facing matrices. The osteoclasts on uncalcified cartilage matrix lacked both ruffled border and clear zone and contained many electron-dense vesicles, thus structurally resembled to septoclasts. The osteoclasts on calcified cartilage matrix formed short clear zone-like structure and contained both electron-dense and-lucent vesicles. The osteoclasts on bone matrix formed apparent clear zone and contained many electron-lucent vesicles, but still lacked in ruffled border. An immuno-electron microscopic analysis revealed that, in the osteoclasts of these mice, vacuolar-type H⁺-ATPase and cathepsin K were expressed in the cytoplasm and electron-lucent vesicles, but not on the apical plasma membranes facing the cartilage or bone matrix. These results suggest that osteosclerosis in oc/oc mice is possibly due to both the dissociation of H⁺-ATPase and cytoskeleton in osteoclasts and the lack of H⁺-ATPase and cathepsin K functions in their apical plasma membranes.

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This study was performed to analyze the defected layers on incisor dentin in magnesium-deficient rats. Young (5 wk) Wistar male rats were pair-fed semi-synthetic diets containing either control [0.5% calcium (Ca), 0.05% magnesium (Mg) and 0.35% phosphorous (P)] (n=8) or Mg deficient [0.5% Ca, 0.001% Mg and 0.35% P] ingredients (n=8) for 17. For the dentin formation rate, all animals were given three intraperitoneal injections of a 0.1 mol nitrilotriacetato lead and 0.1 mol nitrilotriacetato zinc (2 mg/kg body weight as lead) combination at days 0, 7 and 14. In addition, blood samples were obtained from the tail on days 10 and 17 during the experimental period to measure Ca, Mg, P and ALPase activity levels in the serum, and rats were confirmed to become hypomagunesemic and hypercalcemic. After the 17th day, the rats were sacrificed under anesthesia and the right and left maxillary and mandibular incisors were removed. After the designated treatment, right maxillary incisors were used to measure the incisor dentin formation rate and left maxillary incisors were used to measure the length (diameter). The right mandibular incisors were used to measure the Ca, Mg and P content in the ash, and the left mandibular incisors were used to detect Ca, P and Mg concentrations on the dentin by X-ray line scans using a wavelength dispersive X-ray spectrometer (WDS : Microspec). The results showed decreases in body weight, incisor dentin formation rate, length of incisor and content of Mg in the ash incisors in Mg-deficient rats. Metal concentrations on the dentin as measured by WDS indicated an increase of Mg content in the abnormal layers. This phenomenon of increase in Mg content suggests condensing of Mg content as the results of a decrease in dentin formation rate during Mg deficiency, and temporary increase in Mg by transportation of Mg with the stagnation of growth cells and soft tissues.

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The first objective of the present study was to compare the changes in occlusal force (OcFr) during retention in patients with various types of malocclusion using pressure-sensitive occlusal sheets (Dental Prescale). The second objective was to calculate the irregularity index before and after orthodontic treatment.
The final objective was to evaluate the correlation between the increase in OcFr during retention and the relapse rate in the lower incisors calculated by the study models at pre-and post-treatment.
The male subjects treated in Showa University Dental Hospital were selected according to the following criteria : 1) clinically normal function of the oral and maxillofacial region, 2) less than 4 mm deviation between the maxillary and mandibular midlines, 3) no congenital craniofacial anomaly such as cleft lip and/or palate and 4) first and second molars were all present and functioning without extensive defects. The subjects were divided into four types : Class I, II, III and surgical class III (S-Cl.III). All subjects completed active treatment with or without extraction of premolars. OcFr was recorded using Dental Prescale at both early and late retention stages. The irregularity index, defined by Dr. Little, was calculated using study models at pre-treatment and late retention stages.All subjects showed a positive correlation between the increase in OcFr during retention and the relapse rate in lower incisors. In particular, the positive correlation was statistically significant in Cl.I and Cl.III. OcFr at early retention stages among the four types of malocclusion ranked in the following order : Cl.III>Cl.I>Cl.II. The order changed to S-Cl.III>Cl.I>Cl.III>CUT in the late retention stage. Therefore, the increase in the rate of OcFr during retention ranked as follows : Cl.I>Cl.II= S-Cl.III>Cl.III.
The irregularity index during both pre-treatment and late retention stages, and the relapse rate of the lower incisors among the four types of malocclusion all ranked in the following order : Cl.II>Cl.I>Cl.III>These results suggest that Cl.I patients as well as S-Cl.III patients experienced an increase in OcFr during retention since S-Cl.III patients had diminished skeletal disharmony as the results of mandibular setback surgery. The relapse rate of the lower incisors in Cl.III patients tended to be greater than that in either Cl.III patients or S-Cl.III patients. The I.I. at the beginning of active treatment in Cl.II patients is relatively large due to undergrowth of the mandible. On the other hand, the I.I. at the beginning of active treatment in either WIT patients or S-Cl.III patients is relatively small due to sufficient mandible size.

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Maxillary protrusion with deep overbite due to undergrowth of the mandible and labial inclination of maxillary incisors was orthodontically treated by extracting the teeth in 5⊥4, and overcorrecting overjet and overbite. Although continuous prevention of periodontal disease, use of retainers, and instructions regarding lip biting habit had been performed, increases in overbite were noted two years after the initiation of retention. Even in cases with deep overbite, if stable tooth contact in the centric occlusion is present without functionally harmful actions, problems will not occur. However, if load is excessively applied to the temporomandibular joint and adverse actions on the periodontal tissue are caused due to anterior and lateral sliding movement restriction, the condition is not stable. In this case, since the mandibular angle was skeletally small, and the maxillary and mandibular canines, the lateral incisors, showed marked attrition, it was predicted that the masticatory pattern was excessive grinding. These functional problems were caused by decreases in the width between the mandibular canines, extrusion and lingual inclination of the mandibular anterior teeth, and the extrusion of the maxillary anterior teeth, resulting in the maxillary anterior teeth being pushed upward by the mandibular anterior teeth. This causes median diastema and an increase in overbite, an unstable condition. Therefore, it is suggested that, to prevent the relapse of overbite in deep overbite cases, not only overcorrection of the overjet and overbite, but also the establishment of more precise and stable quantitative treatment goals considering the mutual relationship among function, occlusion and morphology is important.

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