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PubMedDate not supplied

Cytokine expression in feline osteoclastic resorptive lesions.

Feline osteoclastic resorptive lesions (FORL) of the teeth are common in cats, and lead to pain, destruction of the periodontal ligament, and tooth loss. The expression of interleukin (IL)-1 beta and IL-6 mRNA was higher in teeth with FORL than in normal teeth (P<0.01 and P<0.001, respectively), but no such differences were found between pathological and normal gingival tissue samples. There were no differences between teeth affected with FORL and normal teeth in respect of the expression of receptor activator of NF kappa B ligand (RANKL) mRNA or osteoprotegerin (OPG) mRNA. However, OPG mRNA expression was higher in gingival tissue associated with teeth affected with FORL than in normal gingival tissue (P<0.05), whereas the reverse was true of RANKL mRNA expression (P<0.05). OPG mRNA expression was significantly higher in teeth than in femoral and alveolar bone (P<0.001). RANKL and OPG mRNAs were detected in all tissues examined. The data suggest that the elevated expression of IL-l beta and IL-6 mRNA plays a role in the mediation of osteoclast activity in advanced FORL. In contrast, OPG and RANKL do not appear to regulate osteoclasts in advanced disease. The results also suggest that OPG and RANKL mRNA play a role in mediating inflammatory responses in gingival cells, and that OPG has an inhibiting effect on tooth resorption.

Animals↗
PubMed1976

[Light microscopic presentation of the morphological behavior of the nerves of deciduous teeth during tooth exfoliation deciduous and after loss of the dentition].

Structural changes in the nerve can hardly be demonstrated in nerve sections located intradentally, i.e. away from the area of tooth resorption. pseudohypersegmentation, however, is found intradentally in nerve sections of the radical pulp close to the resorption area. Serious lesions of the nervous substance are found extradentally, in the direct neighborhood of the erupting permanent tooth. If the deciduous tooth was lost more than 12 months ago, intraosseously the final stage of physiological degeneration is reached.

Child↗
PubMed1993

Fracture of tooth by internal resorption: case report.

A case of extensive internal resorption of the left mandibular first premolar in a 24 year old man is reported. The case presented with slight discolouration and mobility of the tooth. On radiological examination extensive internal resorption and a fracture line at the cemento enamel region was observed, separating the crown and root. The case was treated endodontically after surgical removal of the fractured fragment of the crown.

Adult↗
PubMed1989

[Bone resorption in orthodontic tooth movement: an attempted schematization].

The osteoclast is the major cellular agent of bone resorption. Hormonal stimulation of bone resorption is indirect and depends on the osteoblastic function. Protease production is the final common pathway through which osteoblastic cells initiate osteoclastic resorption. Exposition of the mineralised matrix and contact with the osteoclasts always comes before resorption, regardless of the stimulating agent involved in the resorption process. In orthodontic conditions, production and activation of osteoclasts may be attained through different ways. Inflammation subsequent to tissue damage and bioelectric perturbations associated to alveolar bending can be considered as two major events which may lead to increase bone resorption and orthodontic tooth displacement. The precise transduction mechanism of an orthodontic force into cellular resorbing activity is still obscure.

Alveolar Process↗
PubMed1989

Early responses by osteoclasts in vivo and dentinoclasts in vitro to corticosteroids.

The results of previous investigations examining the association between corticosteroids and bone resorption in vitro have been conflicting. Recent studies have shown that application of a triamcinolone-containing medicament to the dental pulp cavity inhibits dentinoclast-mediated tooth resorption in vivo and in vitro. The aims of this study were to quantitate early ultrastructural changes in osteoclasts in vivo in response to a single steroid dose, and to examine the attachment of dentinoclasts grown in steroid-supplemented cultures in vitro. Resorbing bone around erupting rat molars was examined using TEM and morphometrically quantitated for changes in ruffled border and clear zone areas 1 and 4 h after injections of NaCl, calcitonin, hydrocortisone and prednisolone. Dentinoclasts were harvested from resorption areas in mature rat molars, grown in cultures with calcitonin, hydrocortisone or prednisolone, and fixed and viewed with SEM after 30 min and 2 h. Results of TEM studies showed a significant reduction in areas of resorbing structures in osteoclasts treated with calcitonin at 1 and 4 h, and prednisolone at 4 h. At 1 and 4 h, hydrocortisone showed an increase in resorbing structure areas. SEM results indicated all experimental substances reduced dentinoclast spreading and attachment. It was concluded that the direct effect of steroids on clastic cells may be one of inhibition (the degree of which depends on the nature and dose of the steroid) whereas, in vivo, systemic administration may cause more secondary effects (such as PTH stimulation) to compete with this inhibition. The efficacy of steroid-containing medicaments in inhibiting dentinoclastic resorption may be due to their relatively localized area of application.

Adrenal Cortex Hormones↗
PubMed2000

Development and fine structure of pharyngeal replacement teeth in juvenile zebrafish (Danio rerio) (Teleostei, Cyprinidae).

Teeth are commonly used model systems for the study of epithelial-mesenchymal interactions during organogenesis. We describe here the ultrastructural characteristics of developing pharyngeal replacement teeth in juvenile zebrafish, an increasingly important model organism for vertebrate development. Replacement teeth develop in close association with the dental organ of a functional tooth. Morphogenesis is well advanced prior to the start of cytodifferentiation. Fibrillar enameloid matrix is formed first, followed by the deposition of predentine. Initial mineralization of the enameloid proceeds quickly; maturation involves the presence of ruffled-bordered ameloblasts. Dentine mineralization is inotropic and is mediated by matrix vesicles. Woven-fibred attachment bone matrix is deposited before completion of dentine mineralization. Eruption of fully ankylosed teeth is a fast process and may involve degenerative changes in the pharyngeal epithelium. Mononucleated osteoclasts and clastic cells located in the pulp cavity intervene in tooth resorption prior to shedding. Structural differences with larval, first-generation zebrafish teeth include the presence of dentinal tubules and the absence of an electron-dense covering membrane. Part of these differences may relate to size differences of the teeth. Others, like the site of the replacement tooth bud, suggest that initiation may take place in already committed epithelium from the first initiation event in the larval stage.

Amelogenesis↗
PubMed1989

[Histopathological observation of periodontal tissue by tipping movement toward the hydroxyapatite-packed socket].

Tipping movement in orthodontic therapy, which is often performed even in the absence of the adjacent tooth, is represented by the movement following tooth extraction. Such tipping movement in the absence of the adjacent tooth depends not only upon the magnitude of orthodontic force as classified into Stoner 4D, but also upon the condition of the extracted wounds. To evaluate the clinical applicability of HAp-packing used in combination with tipping movement, histopathological investigation was performed in the periodontal tissue with tipping movement toward the adjacent to HAp-packed socket. HAp packing into the extracted wound cavity produced no significant changes in quantitative tipping movement compared with non-HAp packing. HAp packing into the extracted wound cavity, followed by tipping movement, produced compressed sides not only for the moved tooth but also for the anchor tooth. Resorption and disappearance of alveolar septum were observed on the compressed sides of both these teeth for all experimental sides. HAp in an amount enough to meet the narrowing of the extracted wound cavity, associated with tipping movement was discharged from the suture surface. In the same region, fibrous connective tissue lay between the dental root and the HAp mass, which were not adjacent to each other. The fibrous connective tissue presented temporal bone regeneration so as to surround the tooth. Apart from the moving distance, the tissue change showed no essential difference either for a weak force or for a strong force. The above results revealed the usefulness of HAp packing into the extracted wound cavity for tipping movement of the adjacent tooth in the direction of the wound cavity and immediate move ability after extraction.

Durapatite↗
PubMed1978

beta-Hydroxybutyrate dehydrogenase activity in human and kitten odontoclasts and kitten osteoclasts.

beta-Hydroxybutyrate dehydrogenase activity was studied in whole cell preparations of human and kitten odontoclasts and kitten osteoclasts. Strong histochemical reactions occurred within 2--10 min in all three giant cell types. The possible significance of the high levels of beta-hydroxybutyrate dehydrogenase activity in the metabolism of odontoclasts and osteoclasts is discussed.

Animals↗