Effects of bisphosphonate on alveolar bone resorption during experimental tooth movement in rats: Biochemical & histological observations

Choi, Jin Hugh; Kim, Jong Chul

Abstract

This study was performed to examine the effect of bisphosphonate, an inhibitor of bone resorption, on the formation of osteoclast and bone resorption during experimental tooth movement. Whether bisphosphonate has a cytotoxicity in high dose was also examined. Eighty-seven male Sprague-Dawley rats. Weighing 260-350g, were classified into normal (no appliance + 0.9% NaCl), control (appliance + 0.9% NaCl) and four bisphosphonate-treated( appliance + 0.8mg, 4mg, 20mg, or 100mg/kg) groups. The maxillary left first molar was moved mesially with the tippping movement using 50-70g of force. Bisphosphonate(etidronate disodium)was injected intraperitoneally with a dose of 0.8mg, 4 mg, 20mg, or 100mg/kg simultaneously with the application of the orthodontic force. They were killed at day 1.3 or 7after the application of the orthodontic force. The activities of serum acid phosphatase and lactate dehydrogenase (LDH) were assayed, and osteoclasts and the degree of bone resorption were examined histologically. The results obtained were as follows: 1. Acid phosphatase activities were significantly higher in the appliance groups, both control and bisphosphonate-treated( 4, 20 and 100mg/kg) groups, at days 1and 3 than these in normal. At day 1, bisphosphonate -treated(4, 20mg/kg) groups showed even higher acid phosphatase than control. However, at day 7, no significant difference was noted between the control and bisphosphonate-treated groups. 2. LDH activities in the 4, 20mg/kg bisphosphonate-treated groups were increased during the experimental periods examined, but there were no significant differences in the 0.8, 100mg/kg bisphosphonate-treated groups. 3. There was no bone resorption at day 1, but severe bone resorption was observed at days 3and 7 in the control. Bone resorption was reduced by bisphosphonate-treatment at day 3. Bone resorption observed at day 7 was similar between the control and bisphosphonate-treated groups. 4. Few osteoclasts were observed at the alveolar bone in the control and biosphosphnate-treated groups at day 1. At day 3. numerous osteoclasts were shown in the control, the degree of which was reduced in bisphosphonate-treated groups. These results suggest that the inhibition of the osteoclast formation was not the mechanism of bone resorption by the bisphosphonate-treatment during experimenal tooth movement. There was no distinct cytotoxicity with a high dose of bisphosphonate. And the drug should be administrated repeatedly to maintain the inhibitory effect of bone resorption.