A simple and useful method for evaluating biocompatibility of titanium alloy with heterotopic bone induced by demineralized bone matrix (DBM) pellet in mice

Abstract

Titanium (Ti) and Ti alloys are widely used for dental materials. Recently, an aluminium and vanadium free titanium alloy, Ti-29Nb-13Ta-4.6Zr alloy, was developed. In the present study, we used the demineralized bone matrix (DBM) pellet for evaluating biocompatibility of Ti, Ti-6A1-4V alloy (the most widely used alloy) and Ti-29Nb-13Ta-4.6Zr alloy. The DBM pellet made of mouse long bones was implanted on the dorsal muscle of mice under ether anesthesia. After the DBM pellet had been implanted for 4 weeks, the expression of mRNA for osteoblastic and osteoclastic phenotypes and mineralization were observed, suggesting that the DBM could heterotopically induce bone. The DBM pellet combined with a disk of Ti, Ti-6A1-4V alloy and Ti-29Nb-13Ta-4.6Zr alloy was implanted in the mouse in the same way. Four weeks after the implantation, the calcium contents accumulated in the DBM pellet with Ti, Ti-6A1-4V alloy and Ti-29Nb-13Ta-4.6Zr alloy were 36.6±8.0 p g, 50.4± 13.3 p g and 75.6± 16.9 p g, respectively. A significant difference was observed between Ti and Ti-29Nb-13Ta-4.6Zr alloy (p<0.05). This result seemed to suggest the increase of the mineralization in DBM-induced heterotopic bone by Ti-29Nb-13Ta-4.6Zr alloy, because Ti particles showed no toxicities in mouse osteoblastic cells, in mouse bone marrow cells, and in isolated rabbit osteoclasts. These findings suggested that Ti-29Nb-13Ta-4.6Zr alloy might be a higher biocompatible material with bone tissue, and showed that the heterotopic bone induced by the DBM pellet in mice could be a simple and useful method for evaluating biocompatibility of titanium alloys.