In nonsurgical endodontic procedures, the healing of apical periodontitis is achieved by treatment provided within the root canal system. The new Apexum procedure is based on advancing the debridement one step further by minimally invasive removal of the inflamed periapical tissues through root canal access, thereby enhancing the healing kinetics of periapical lesions. The Apexum procedure uses 2 sequential rotary devices designed to extend beyond the apex and to mince periapical tissues on rotation in a low-speed handpiece, followed by washing out the minced tissue. This initial animal study was conducted to evaluate the efficacy and potential adverse effects of this procedure. Periapical lesions were induced in the lower premolars in dogs by placement of autologous dental plaque and subsequent radiographic verification. Fifty roots with periapical lesions were then subjected to cleaning, shaping and disinfection of their root canals, using a conventional root canal treatment protocol. Teeth in group 1 were subjected to the new Apexum procedure just before obturation, whereas roots in group 2 were subjected to no additional intervention before obturation. Clinical and radiographic follow-ups were carried out for 6 months. Radiographic healing of the periapical lesions in dogs at 3 and 6 months showed significantly enhanced kinetics in the Apexum-treated group compared with the conventional treatment group, at both time points (p <0.01). No noticeable adverse events occurred in either of the groups. This new procedure might significantly enhance healing kinetics of apical periodontitis compared with conventional nonsurgical endodontic treatment.