Abstract
The aim of the present study was to evaluate the function of cementum on root resorption resulting from mechanical stress in rats, by means of the rabbit-osteoclast culture in the serum of rabbits on a low calcium diet.
Mechanical stress was created by insertion of an elastic between the first and second maxilary rat molars for two days, and tartrate resistant acid phosphatase (TRAP) positive cells in periodontal tissues were induced and appeared. However, root resorption was not observed with the mechanical stress. Cellular and acellular cementum obtained from rat molars were used for the present examinations and the following results were obtained.
1. Rabbit-osteoclasts were cultured in serum obtained from rabbits on a low calcium-diet on the root. Rabbit-osteoclasts were observed using scanning electron microscopy. As a result, the rabbitosteoclast resorbed acellular cementum on the rat root region with the mechanical stress, but it did not resorb the cellular cementum on the rat apical root region. The same resorption reaction also occurred on the cellular and acellular cementum without applying mechanical stress.
2. To examine the effect of cellular cementum on the culture of osteoclasts on a slice of calf bone in serum obtained from rabbits on a low calcium-diet, minced cellular rat cementum was added to the low calcium serum medium, and the number of osteoclast was inhibited by 70% compared to the control (p<0.01). The effect of inhibition by the cellular cementum on the culture increased with mechanical stress with respect to the rat root. These results suggest that cellular cementum could react with mechanical stress and strengthen the resistance to root resorption.
