Effect of orthodontic force associated with cigarette smoke inhalation in healthy and diseased periodontium. A histometric and immunohistochemistry analysis in rats

Background: The aim of the present study is to evaluate the effect of orthodontic forces in healthy or diseased periodontium of rats submitted/not submitted to cigarette smoke inhalation. Material and methods: Fifty-six male Wistar rats were allocated into two groups of conditions: smoking and non-smoking. Each group was divided into the following subgroups: control (C), orthodontic tooth movement (OTM), ligature-induced periodontitis (P) and P+OTM (POTM), with n = 14 each. Periodontitis was induced in the lower first molar by cotton ligature, and a 4 mm closed stainless steel spring was used for orthodontic movement. Animals were exposed to the smoke of 10 cigarettes for 8 minutes, 3 times a day for 60 days before P induction and OTM. Evaluation parameters were macroscopic analysis of dental movement, bone loss and bone density. In addition, the receptor activator of nuclear factor-kappaB (RANK) immunostaining and RANK ligand/osteoprotegerin ratio in the furcation region were assessed. Results: There was no statistically significant difference between groups, ie, smoking and non-smoking conditions (P =.338). Bone loss intragroup analysis between the P and POTM groups was not significant in smoking (P = 1) and non-smoking (P =.5) conditions; both were different from OTM and C in each condition. Regarding bone density, POTM and P were significant to C (P <.05). The POTM group was significant to the P and C (P =.001) regarding dental movement. The RANK ligand/osteoprotegerin ratio in the non-smoking condition was higher in P and POTM compared to C and OTM and to P and POTM in the smoking condition. RANK immunostaining was significant in the smoking condition for the P and POTM groups (P <.05). Conclusion: Within the limitations of the present study, it was concluded that cigarette smoke inhalation had no influence on the evaluated groups, even with the presence of low levels of nicotine, carbon monoxide and tar. The POTM groups did not present greater bone loss compared to P groups, thus periodontal disease is essential for bone loss.