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Effect of dexamethasone on root resorption after delayed replantation of rat tooth.

The purpose of this study was to evaluate the effect of dexamethasone after delayed tooth replantation with specific regard to root resorption and ankylosis. In addition, the study was planned to elucidate further the usefulness of the model. Fifty-two maxillary first molar teeth were extracted from 26 Sprague-Dawley white female rats fed 0.4% beta-aminoproprionitrile for 3 days to facilitate the extraction. After extraction, the mesiobuccal root canals were endodontically treated under a microscope to prevent subsequent inflammatory resorption of pulpal origin and were assigned to three groups. Teeth in group 1, the dexamethasone group (n = 22), were demineralized in citric acid (1 min), washed, soaked in 1000 nM dexamethasone solution (3 min), air-dried, and replanted in the original sockets. Total extraoral treatment time for each tooth was controlled to 30 min. Teeth in group 2, the dried-only group (n = 22), were air-dried for 30 min after obturation without any surface treatment and replanted. Teeth in group 3, the immediate group (n = 8), were extracted, not root-filled and replanted immediately into their sockets. All experimental animals were killed at 3 weeks after replantation and evaluated histologically. Forty-three of the 52 teeth were available for histological interpretation. They consisted of six immediate, 18 dried-only, and 19 dexamethasone-treated teeth. The degree of progressive root resorption was significantly less in the dexamethasone-treated group than in the dried-only group (p < 0.05). The dexamethasone-treated group exhibited significantly more bone ankylosis than the dried-only group (p < 0.05). These results indicate that the topical use of dexamethasone may be of value in reducing the degree or rate of progressive root resorption secondary to traumatic avulsion and that the rat is a reasonable model for tooth replantation.

Administration, Topical↗

Immunohistochemical localization of receptor activator of nuclear factor kappaB (RANK) and its ligand (RANKL) in human deciduous teeth.

Osteoblasts and osteoclasts are involved in bone formation and resorption. RANK and RANKL [receptor activator of nuclear factor kappaB (ligand)], two cytokine-like proteins of the tumor necrosis factor superfamily, are localized on these bone cells and are crucial for the regulation of osteoclastic cell differentiation from hematopoietic precursors and also for the upregulation of mature osteoclasts mediated by cell-to-cell contact and a subsequent cascade of diverse intracellular signaling processes in the osteoclasts. It was the aim of this study to examine the sites of expression of RANKL and RANK in the corresponding cells of human dental hard and periodontal tissues using immunohistochemical light microscopical methods on tissue sections of 15 paraffin-embedded human deciduous teeth undergoing root resorption. We detected granular cytoplasmic RANKL-immunoreactivity in odontoblasts, pulp fibroblasts, periodontal ligament fibroblasts, and in single odontoclasts, the latter finding suggesting an autocrine/paracrine role. RANK-positive cells were identified as multinucleated odontoclasts localized near the dentine surface in resorption lacunae or as mononucleated precursors. These findings indicate that human dental cells express key mediators of hard tissue resorption and, though the RANK/RANKL-system may not be the sole regulator of tooth root resorption, these factors could at least contribute to this complex process under both physiological and pathological conditions.

Adsorption↗

Infraocclusion of primary molars. An epidemiological, familial, longitudinal clinical and histological study.

The aims of this thesis were to estimate the prevalence and familial tendencies of infraocclusion of primary molars and analyse the effect of extraction on occlusal development, and to characterise histologically the ankylosis in infraoccluded primary molars and recommend guidelines for treatment. The thesis is based on five investigations. In the prevalence and familial studies, 1059 children and 138 first-degree sibs were investigated. The three longitudinal clinical studies comprised 215 primary molars in infraocclusion and the children were subjected to clinical and radiographic examination and analysis of model casts every six months. The histological study comprised 62 teeth in infraocclusion and 40 in normal positions. In addition, bone biopsies were analysed histologically and by enzyme histochemical methods. The prevalence of infraocclusion of primary molars was found to be age-related and was significantly higher in sibs than in the studied population, which indicates a familial tendency. Infraoccluded primary molars with a successor present generally exfoliated normally. The permanent successors usually erupted six months later than on the normal contralateral side. Extraction of primary molars in infraocclusion meant definite space loss in some cases. With aplasia of the successor, the infraoccluded tooth did not exfoliate within the normal time range and the root resorption was found to be very slow, especially after 12-13 years of age. Very few of the previously reported negative effects of non-treatment of primary molars in infraocclusion on exfoliation, eruption and occlusal development could be confirmed in this study. Most infraoccluded primary molars were ankylosed histologically. No differences were found in the bone biopsies from the infraoccluded and control group. The results indicate that ankylosis in infraoccluded primary molars is not a static condition but part of a remodelling process following normal resorption of the roots. The general treatment policy should be to wait for normal exfoliation of infraoccluded primary molars to take place if the permanent successor is present and in cases with aplasia consider the aplasia per se, the degree of primary root resorption and the risk of progression of the infraocclusion.

Adolescent↗

Computed tomographic features of calcifying odontogenic cysts.

OBJECTIVES: To describe the CT appearances of 4 cases of the calcifying odontogenic cyst (COC) with particular reference to the effect of varying the window settings. METHODS: Conventional radiographs and CT scans of 4 calcifying odontogenic cysts were analyzed with respect to the presence of an impacted tooth, root resorption and calcification. In addition, increased attenuation by desquamated keratin was examined by varying the window settings on CT. RESULTS: All lesions were located in the maxilla and on conventional radiographs, had unilocular radiolucency with a well-defined margin. Calcifications and inclusion of an impacted tooth were seen in all cases. Root resorption was observed in two cases, but was not prominent. On CT, calcification was detected at the periphery of the lesion and/or around the impacted tooth in all cases. Varying the window setting revealed an increased attenuation area due to desquamated keratin. CONCLUSIONS: Varying the window setting on CT is useful as a means of identifying both desquamated keratin and peripheral calcification in COC.

Adolescent↗