This case report describes a suspected case of chronic apical periodontitis caused by cementum detachment at the maxillary left lateral incisor. Treatment consisted solely of root surface debridement and curettage of pathological granulation tissue, and no periodontal regenerative therapy was performed. As adjunctive therapy, intraoperative irrigation with ozonated water was carried out, and ozonized glycerin was applied to the lesion site. On postoperative day 2, the clinical findings were as follows: no pain, swelling, or bleeding, with mild erythema; analgesic medication was not required. Inflammatory symptoms were well controlled from the early postoperative period, and additional antibiotic administration was deemed unnecessary. Sutures were removed on postoperative day 7. At the time of suture removal, mild wound dehiscence was observed at part of the incision; however, no bone exposure was noted. Two weeks postoperatively, proliferation of granulation tissue and regeneration of the oral mucosal epithelium were confirmed. At one month postoperatively, the surgical site had almost completely healed, and the incision line had become inconspicuous. Radiographic examination demonstrated a transition from radiolucency to radiopacity at the initial lesion site, indicating a healing tendency of the bone defect. No recurrence of infection was observed during the follow-up period, and a favorable healing course was achieved. These findings suggest that adjunctive therapy using ozonated water and ozonized glycerin may be effective for lesions suspected of chronic granulomatous apical periodontitis.