Removal of intracanal smear layer by doxycycline: SEM analysis

The aim of this study was to verify the efficacy of doxycycline used alone or in association with sodium hypochlorite on smear layer removal. The canals of extracted human teeth were instrumented using a stepback technique. At the end of preparation, they were irrigated with doxycycline (Group 1), ethylenediaminetetraacetic acid + sodium hypochlorite (Group 2), doxycycline + sodium hypochlorite (Group 3) and water (Group 4). The dentinal wall of the cervical, middle and apical thirds was graded according to the amount of remaining debris and smear layer. The results were analysed using the Kruskal–Wallis test (P < 0.05). In Groups 2 and 4, the dentine was completely free and covered with smear layer, respectively. The results from the cervical and middle thirds of Group 3 were worse than those in Groups 1 and 2 (P < 0.05). In relation to apical third, there were differences (P < 0.05) between all groups with best results for Group 2. Doxycycline was effective in removing smear layer from cervical and middle thirds. The use of doxycycline + sodium hypochlorite was partially effective in the cervical and middle thirds, but ineffective in the apical third.