Effect of Alveolar Bone Mass on Mechanical Stress in Calcium-sufficient and -deficient Rats

It is clinically important to check whether sufficient supporting bone mass is maintained in subjects with a low calcium diet. In this study, alveolar and femoral bone mass were measured after tooth movement in calcium-sufficient and -deficient rats, and the correlation between mechanical stress and bone mass was examined using the serum level and histological observation. Seventy rats were divided into 2 groups : normal (NDG) and low calcium diet (LCG) groups. After feeding for 28 days, the distance of tooth movement and the alveolar and femoral bone mass were observed on days 1, 3, 5 and 7 after fitting the appliance. Tooth movement distance was large in LCG. Alveolar bone mass in NDG and LCG showed a different tendency than tooth movement ; the former was increased and the latter was decreased. Body weight decreased from the start of the experiment until day 3 in both groups, and increased gradually thereafter. Femoral bone mass in NDG slightly decreased and then recovered at day 7, but such a result was not observed in LCG. These results suggest that the tooth was able to move when an orthodontic force was applied in rats, even in cases of low alveolar bone mass, although various physical influences were present.