Low-dose doxycycline inhibits bone resorption associated with apical periodontitis

Aim To test the effect of low‐dose doxycycline on bone resorption associated with apical periodontitis. Methodology Apical periodontitis was induced by occlusal pulp exposure in the mandibular first molars of 36 rats. Animals were divided into three groups of 12: group A received doxycycline in drinking water at a dose of 5.85 mg day−1; group B received a dose of 1.48 mg day−1 (one‐quarter of the original dose); and group C received no medicament and served as the control. A bioassay determined the doxycycline serum levels. After 21 days, the mandibles were removed, radiographed and the radiographs scanned to generate digital images. These images were analysed morphometrically and the total area of the periapical bone resorption of the mesial and distal roots of each tooth was determined and used to compare the groups. Statistical analysis was completed using anova with repeated measures. Results The mean doxycycline serum level in group A was 0.22(±0.03) μg mL−1 and in group B below the detection level of the assay (