Long-term data on dental implant outcomes remain among the most valuable evidence in implantology, and this study provides a rare 15-17-year follow-up of a randomized clinical trial comparing one-piece (STM) and two-piece (BRA) implant systems.

From an original cohort of 60 patients, 39 patients with 95 implants completed the long-term follow-up (STM: 22 patients/45 implants; BRA: 17 patients/50 implants), with a mean follow-up of 16.4 ± 1.1 years. The cumulative implant survival rate was 95.0% overall (STM: 91.8%; BRA: 98.0%).

Marginal bone levels told a nuanced story. At 15-17 years, the one-piece system showed superior marginal bone preservation (0.08 ± 1.15 mm) compared to the two-piece design (1.53 ± 0.81 mm). This difference is clinically meaningful over such a long horizon. However, the one-piece system carried a substantially higher rate of technical complications — 35.4% at implant level versus just 5.8% for two-piece. These included prosthetic complications over the 23 affected implants in the STM group versus only 5 in the BRA group.

Biological complications were also documented: peri-implant mucositis was observed in 49.7% of all implants and peri-implantitis in 13.3%, with higher rates in the STM group. Bleeding on probing was higher in the one-piece group. Esthetic observations included visible crown margins in 62 implants and mucosal shimmering in 54 implants; no implant fractures were reported.

The clinical takeaway is a clear trade-off: one-piece implants preserve bone better but demand more prosthetic maintenance. Two-piece systems offer greater prosthetic reliability with acceptable bone remodeling. These 15+ year data help clinicians make informed design choices based on patient-specific priorities.