This retrospective study evaluated the long-term clinical success of combination therapy using resin-modified glass ionomer (RMGI) with flap surgery in treating subgingival radicular defects. The study population consisted of 142 patients with 188 radicular defects. Clinical parameters (pocket depth, recession, clinical attachment level [CAL], and bleeding on probing) were evaluated. Statistically significant CAL gain was observed from baseline to follow-up in successful cases (4.3 ± 0.1 mm to 4.1 ± 0.1 mm, respectively; P .01). RMGI with flap surgery demonstrated an overall success rate of 86.7% (77.7% with open flap debridement and 94.4% with coronally advanced flap with or without connective tissue graft), with favorable and stable clinical results over a mean period of 4.2 years (longest follow-up, 13 years).