Carbonate apatite increases gene expression of osterix and bone morphogenetic protein 2 in the alveolar ridge after socket grafting.

PURPOSE

After tooth extraction, preservation of the alveolar ridge by socket grafting attenuates bone resorption. Runt-related transcription factor 2 (RUNX2) and SP7/Osterix (OSX) are transcription factors playing an important role in osteoblast differentiation. The purpose of this study was to evaluate the effects of carbonate apatite (COAp) on osteoblast-related gene and protein expression after socket grafting.

METHODS

Alveolar bone and new bone after COAp grafting were collected at the time of implant placement. Levels of mRNA for RUNX2, SP7/OSX, bone morphogenetic protein 2 (BMP2), BMP7 and platelet derived growth factor B were determined by real-time PCR. Immunostaining was performed using antibodies against RUNX2, SP7/OSX, vimentin and cytokeratin. To evaluate bone resorption rates, cone-beam CT (CBCT) imaging was performed after socket grafting and before implant placement.

RESULTS

CBCT imaging showed that the average degree of bone resorption at the COAp graft site was 7.15 ± 3.79%. At the graft sites, levels of SP7/OSX and BMP2 mRNA were significantly increased. Replacement of COAp with osteoid was evident histologically, and in the osteoid osteoblast-like cells were stained for SP7/OSX and vimentin.

CONCLUSION

These results show that gene expression of both SP7/OSX and BMP2 can be induced by COAp, suggesting that increased expression of SP7/OSX and vimentin may be involved in the BMP pathway.