Doxycycline prevents root resorption and alveolar bone loss in rats after periodontal surgery.

The effect of systemic doxycycline administration on frequency of root resorption cavities and extent of bone loss following periodontal surgery was studied in albino rats. Thirty Wistar rats with healthy gingiva were divided into four groups. Six untreated animals (Group 1) served as controls. Gingivectomy (Group 2, six rats), mucoperiosteal flap operation (Group 3, eight rats), and mucoperiosteal flap operation with doxycycline added to the drinking water (Group 4, 10 rats) were performed on the palatal aspect of maxillary left molars. After a healing period of 3 wk, the rats were killed by an overdose of sodium pentothal, and specimens of first molars were prepared for light microscopy. Root resorption was absent in normal and gingivectomized animals (Groups 1 and 2). Resorption cavities occurred in all flap-operated animals (Group 3) and in one of 10 doxycycline-treated animals (Group 4). The distance from cementoenamel junction to alveolar bone crest remained unchanged in gingivectomized (Group 2) and doxycycline-treated animals (Group 4), as compared with control specimens. In flap-operated animals (Group 3), the crestal bone level was located more apically than in doxycycline-treated rats (Group 4). This study has shown that root resorption and bone loss were associated with flap operations involving exposure of periodontal ligament and bone. Systemic doxycycline prevented both root resorption and bone loss.