This study aimed to examine the longitudinal influence of bonded composite resin cingulum rest seats on abutment tooth periodontal tissues in removable partial dentures (RPDs). Twenty-eight patients with RPDs were enrolled in the study. Thirty-one cingulum rest seats were prepared for an anterior tooth using composite resin and a standardized method for each patient. Periodontal indices such as probing pocket depth (PD), bleeding on probing (BoP), and tooth mobility (TM) were measured at the time of denture insertion (baseline) and at least 3 months postinsertion (up to 8 years). Control data were obtained from the remaining nonprepared anterior teeth on the other side of the arch. None of the bonded resin rest seats failed, but slight abrasion was observed in 3 rest seats. No significant differences were found in terms of PD, BoP, and TM between baseline and postinsertion data for abutments with bonded resin rest seats and controls. It is suggested that bonded composite resin cingulum rest seats can be used longitudinally without damaging the periodontal tissues of abutment teeth.