SERUM AND ALVEOLAR BONE PHOSPHATASE CHANGES REFLECT BONE TURNOVER DURING ORTHODONTIC TOOTH MOVEMENT

Acid and alkaline phosphatase changes have been demonstrated histochem ically and biochemically during the early stages of an orthodontic too th movement cycle. However, quantitative data on neither alveolar bone nor serum phosphatase changes over an entire tooth movement cycle hav e been reported. This study examined acid, tartrate-resistant acid (TR AP), and alkaline phosphatase changes in serum and alveolar bone durin g an orthodontic tooth movement cycle in 288 adult male Sprague-Dawley strain rats. The effect of differing initial force magnitudes on phos phatase changes was also examined. Data were obtained from four groups : sham control and three treatment groups (20, 40, and 60 gm activatio ns). Each group (n = 72) was subdivided equally into six sacrifice sub groups (1, 3, 5, 7, 10, and 14 days). Treated animals received a preci sely loaded orthodontic tipping force to the maxillary molars. Phospha tase measures were obtained by colorimetric assays. Analysis of varian ce (ANOVA) procedures were performed to examine for differences within groups across time and among groups at each time point. Data from tre ated animals were combined, adjusted for control values, and examined across time to permit comparisons with previously described histomorph ometric changes. Analysis of variance indicated no differences occurre d in the control group across time. Significant differences in serum v alues occurred across time within the force groups (p < 0.01), and amo ng force and control groups at various times in both sera and bone (p < 0.05). In the pooled treatment data, a peak in serum acid phosphatas e occurred at day 1 and in bone at day 3 (the later mirroring histomor phometric findings) (p < 0.001). A peak in serum and bone alkaline pho sphatase occurred at day 7, with a significant drop at day 10 (the lat ter drop in contrast to elevated osteoblast numbers) (p < 0.001). Both the serum and the bone phosphatase data clearly support previous hist omorphometric observations that bone turnover, characterized by period s of activation, resorption, and formation, occurs during orthodontic tooth movement; serum data suggested differing force magnitudes may al ter the timing of these bone turnover events.