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.