Long-Term Clinical Outcomes and Risk Indicator Analyses of Narrow-Diameter Implants in the Posterior Jaw: A Retrospective Cohort Study of 10 to 27 Years.

OBJECTIVES: To assess the long-term clinical outcomes and patient satisfaction with narrow-diameter implants (NDIs) in the posterior jaws and to identify the risk indicators for NDI failure. MATERIALS AND METHODS: This retrospective study reviewed 479 patients with 666 NDIs (diameter </= 3.5 mm) -supported fixed prostheses in posterior jaws, with a minimum 10-year follow-up. Implant survival, success, complications, demographics, and implantation characteristics were collected. Risk indicators for posterior NDI failure were analyzed using multilevel Cox regression analyses with mixed effects. Patient satisfaction and oral health impact profile (OHIP) were surveyed in a random 10% sample. RESULTS: Over a mean follow-up of 14.0 +/- 3.6 years, implant survival was 95.9% at the implant level and 94.6% at the patient level. Success rates were 93.5% at the implant level and 91.6% at the patient level. Multilevel Cox regression analysis identified an implant length of 10 mm or less (p = 0.001) and the use of single crowns (p = 0.005) as significant risk indicators for posterior NDI failure. Patients showed high satisfaction (4.54/5) with posterior NDIs, and the mean OHIP score of 1.15 reflected an acceptable level of oral health. CONCLUSION: NDIs in the posterior jaws demonstrated robust long-term success and high patient satisfaction. An implant length of 10 mm or less and the use of single crowns are potential risk indicators for posterior NDI failure. TRIAL REGISTRATION: Chinese Clinical Trial Registry: ChiCTR2200062337 on 2022/08/02.