This case report evaluated the long-term effects of osseous resective therapy in the treatment of a patient with moderately advanced periodontal disease. In 1984, the patient underwent initial therapy followed by a periodontal surgical phase consisting of osseous recontouring with an apically positioned flap. After 20 years, in 2003, the patient presented with a traumatic complication. An exploratory surgery revealed a fracture on the roof of the pulp chamber on the maxillary left first molar. The buccal roots were resected, preserving the palatal root, and a reevaluation of the long-term outcome of osseous resective surgery was performed. It is suggested that the positive treatment result is the consequence of the reestablishment of tissue morphology favorable for oral hygiene and plaque control by the patient.