Bone resorption in apical periodontitis enhanced by cigarette smoke inhalation: histometric, immunohistochemical and microtomographic analysis in rats

INTRODUCTION:This study evaluates the effects of cigarette smoke inhalation (CSI) on apical periodontitis (AP) induced in rats by histometric, immunohistochemical, and microtomographic analysis. METHODS:A total of 32 male Wistar rats were divided into four experimental groups (n=8): C (control), CSI, AP and CSI+AP. Rats in the CSI and CSI+AP groups inhaled cigarette smoke by remaining inside a smoking chamber for 8 minutes, three times a day for 50 days. After 20 days of smoke inhalation, rats in the AP and CSI+AP groups had the pulp of their first right lower molar exposed to induce apical periodontitis. Blood was collected on day 50 to evaluate nicotine and serum cotinine levels. The animals' mandibles were removed for histological processing to evaluate bone resorption by histometric, immunohistochemical (RANKL/OPG) and microtomographic analysis. Student's t-test was applied. RESULTS:Histometric analysis showed a larger area of bone resorption (p<0.05) and microtomographic analysis found greater resorption volume (p<0.001) for the CSI+AP group compared with the AP group. The CSI+AP group presented a high RANKL immunostaining pattern compared with the AP group (p<0.001). CONCLUSIONS:Cigarette smoke inhalation increased bone resorption caused by apical periodontitis.