Cyclosporin-induced gingival overgrowth at the newly formed edentulous ridge in rats: A morphological and histometric evaluation

Background: Since cyclosporin A (CsA)-induced overgrowth seldom occurs at s ites distant from teeth, the periodontal ligament has been considered signi ficant. The aim of this study was to examine overgrowth occurrence at the e dentulous ridge-the sites without the ligament-after CsA therapy in rats. Methods: After extracting all right maxillary molars, 16 Sprague-Dawley rat s underwent a 2-week healing period. The animals were separated into CsA an d control groups. CsA rats received 15 mg/kg of CsA by gastric feeding for 4 weeks, while the control group received only mineral oil. At the end of s tudy, all animals were sacrificed and stone models were immediately obtaine d by rubber-based impressions. The edentulous ridge morphology, including t he bucco-lingual width and the vertical height, was measured on the models. For histometry, 10 sections were selected from the edentulous ridge of eac h animal after undecalcified tissue preparation. The soft tissue areas of t he edentulous ridge and the trabecular bone morphology of the dental alveol us were measured. Results: CsA therapy produced a significant increase of the ridge width and height, measured from the stone models, when compared to the control group . Under histometry, CsA resulted in a significant increase of the epitheliu m, connective tissue, and total soft tissue areas. The measured trabecular bone volume was affected by both examining factors: the drug therapy and th e location of the dental alveolus. CsA therapy produced a significant loss of bone volume but a significant increase of the bone-specific surface area . Although the mean osteoid volume was similar between CsA and control grou ps, a significant decrease of the fractional formation surface in the CsA g roup was revealed. Conclusions: An enlarged edentulous ridge and an altered dental alveolar bo ne morphology were observed in CsA-treated animals at the end of the study; therefore, we suggest that CsA may induce not only a soft tissue overgrowt h but also an alveolar bone alteration at the edentulous ridge. The hypothe sis that tooth or periodontal ligament is an essential component for the ov ergrowth development is questioned.