Effect of glass-ceramic implants on primary calcification in rat tibial bone after injury.

Using histomorphometry and transmission electron microscopy the distribution of extracellular matrix vesicles around bone-bonding and non-bonding glass-ceramic implants in tibial bone healing was studied. Grouping of vesicles was performed according to type, diameter and distance to the calcified front. Most vesicles were 0.06-0.22 microns in diameter in both implants tested. The mean vesicular distance of matrix vesicles to the calcified front was statistically significantly lower in non-bonding material compared with KG Cera. The sequence of vesicle arrangement according to diameter was: 'empty', 'amorphous', 'crystal', 'rupture'. Empty vesicles were the smallest and rupture vesicles the largest. Distances of vesicles to the calcified front showed the same sequence of arrangement, while the rupture type was located nearest to the front. The findings support the widely acknowledged hypothesis on the role of matrix vesicles in mineralization. It was shown that mineralizing tissue around bone-bonding glass-ceramics contains more matrix vesicles, which are distributed further from the front with a lower degree of calcification. The parameters studied could serve as standard criteria for the evaluation of implant materials.