OPG knockout mouse teeth display reduced alveolar bone mass and hypermineralization in enamel and dentin

Recent studies showed that local injection or upregulation of OPG gene would result in early temporal retardation of tooth development. It was assumed that this retardation might cause defective tooth mineralization and pulp formation as the long-term effects. However, since those OPG treatments were transient, any possible long-term effects of OPG addition could not be assessed previously. In the present study, a high-resolution microCT was used to evaluate the long-term effect of OPG gene deprivation on the mineralization and morphology of mouse tooth. Our results showed that the mineralization of alveolar bone in OPG(-/-) mouse tooth was decreased while those of enamel and dentin were increased, compared with the wild-type (WT) group. The labial and lingual dentin thicknesses of OPG(-/-) group were significantly higher and with larger area in enamel and dentin than those of WT group. The size of pulp chamber was also substantially decreased in OPG(-/-) mouse incisor. Different responses in mineralization and morphogenesis to OPG gene deprivation were found between bone and tooth. These effects may be independent of the early odontogenesis, and further studies are warranted to investigate the molecular mechanism of the effect of OPG gene expression on bone formation and later tooth development.