Effects of cyclosporin A on dental alveolar bone: A histomorphometric study in rats

Background: We have previously reported cyclosporin A (CA)-induced osteopen ia around the dental alveoli of the mandibular incisors of rats. The drug-i nduced tooth displacement and the regional anatomical complexity around the mandibular incisors might complicate the local effects of CA. Therefore, t he purpose of this study was to evaluate the dental alveolar bone histomorp hology around maxillary secondary molars in CA-treated rats and to further elucidate the effects of CA on the dental alveolus. Methods: Twenty Sprague-Dawley rats were assigned to a CA and a control gro up. Animals in the CA group received CA (15 mg/kg) daily and the control ra ts received only mineral oil. At the end of weeks 2 and 4, five animals in each group were sacrificed. Dental alveoli around the maxillary second mola r region were frontally sectioned and stained with toluidine blue by undeca lcified histological processing. Ten serial tissue sections, 80 mum apart, were selected for histometric evaluation. Bone volume, bone-specific surfac e, and osteoid formation were measured at buccal, apical, and palatal locat ions in dental alveolus. Results: Overall bone mass in dental alveolus decreased more in the CA grou p than in the control group at both observation intervals. All histometric measurements, except the bone-specific surface, were significantly affected by the alveolar location (palatal, apical, and buccal) and CA therapy (P = 0.004 and <0.001, 0.001 and <0.001, 0.004 and <0.001 for drug therapy and location of the dental alveolus in bone volume, marrow volume, and the rati o of bone surface to volume, respectively). Decreased bone volume, but incr eased marrow volume, were noted in the CA group compared to the control gro up. Although the alveolar bone surface area did not differ between the CA g roup and the control group, greater alveolar surface-to-volume ratio was no ted in the CA group. For osteoid, more decreased volume, seam width, and fr actional formation surface were observed in the CA group compared to the co ntrol group (P <0.001, <0.001, and = 0.046 in osteoid volume, seam width vo lume, and formation surface, respectively). Conclusions: Because the bone mass and the osteoid formation in the dental alveolus around the maxillary molar region showed a decrease after CA expos ure, we conclude that this drug has inhibitory effects on the dental alveol i.