Hyperosmotic Stimulus Down-regulates 1alpha, 25-dihydroxyvitamin D(3)-induced Osteoclastogenesis by Suppressing the RANKL Expression in a Co-culture System.

The hyperosmotic stimulus is regarded as a mechanical factor for bone remodeling. However, whether the hyperosmotic stimulus affects 1alpha, 25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3))-induced osteoclastogenesis is not clear. In the present study, the effect of the hyperosmotic stimulus on 1alpha,25(OH)(2)D(3)-induced osteoclastogenesis was investigated in an osteoblast-preosteoclast co-culture system. Serial doses of sucrose were applied as a mechanical force. These hyperosmotic stimuli significantly evoked a reduced number of 1alpha,25(OH)(2)D(3)-induced tartrate-resistant acid phosphatase-positive multinucleated cells and 1alpha,25(OH)(2)D(3)-induced bone-resorbing pit area in a co-culture system. In osteoblastic cells, receptor activator of nuclear factor kappaB ligand (RANKL) and Runx2 expressions were down-regulated in response to 1alpha,25(OH)(2)D(3). Knockdown of Runx2 inhibited 1alpha,25(OH)(2)D(3)-induced RANKL expression in osteoblastic cells. Finally, the hyperosmotic stimulus induced the overexpression of TonEBP in osteoblastic cells. These results suggest that hyperosmolarity leads to the down-regulation of 1alpha,25(OH)(2)D(3)-induced osteoclastogenesis, suppressing Runx2 and RANKL expression due to the TonEBP overexpression in osteoblastic cells.

Effects of calcium phosphate ceramic bone graft materials on permanent teeth eruption in beagles.

OBJECTIVE: The aim of this study was to evaluate the use of calcium phosphate ceramic (CPC) materials as a potential alternative to autogenous secondary alveolar bone grafting in cleft lip and palate patients who are in mixed dentition. SAMPLE: Four 12-week-old beagles and one 15-week-old beagle were used as subjects. INTERVENTIONS: In each experimental beagle, the third and fourth deciduous premolars were extracted. The sockets were filled with four different CPC materials and sutured. MAIN OUTCOME MEASURES The beagles were fed a soft diet for the following 8 weeks and then sacrificed for clinical, radiological, histological, transmission electron microscope (TEM), and infrared (IR) absorption analysis. RESULTS: All four experimental graft materials allowed normal development and eruption of permanent premolars. In histological sections, small particles of biphasic calcium phosphate (BCP) and carbonate apatite (CO(3)-AP) were resorbed, and large particulate forms served as bone frames in cortical bones. Polymer coated with carbonate apatite (Poly/CO(3)-AP) did not cause inflammation but was pushed away to the soft tissue by erupting teeth. Alginate coated with carbonate apatite (alginate/CO(3)-AP) caused a severe inflammatory reaction to the point of destroying a part of the dental follicle and cortical bone. In TEM, resorption activity by phagocytic cells was observed only in CO(3)-AP. Direct bonding of CO(3)-AP to the bone was observed as the electron-dense interface between bone and CO(3)-AP. CONCLUSION: BCP and CO(3)-AP proved to be suitable as alveolar bone graft materials in areas where tooth eruption occurs. Of the four materials tested, CO(3)-AP produced the best results.