On treatment outcomes of immediately loaded conventional diameter and mini-implant retained overdentures in the edentulous mandible

Abstract

Background: Little is known on the differences between conventional diameter and mini-implants immediately loaded with overdentures in the edentulous mandible. Objectives: To compare the biological-, prosthetic-, patient-based- and economic treatment outcomes using two immediately loaded conventional or mini-implants for mandibular overdentures. Materials and Methods: Edentulous patients receiving either conventional (4.1mm) or mini-implants (2.9 mm or less), based on available bone width were analyzed. All implants were immediately loaded with mandibular overdentures installed using Locator abutments. Biological, prosthetic, oral health related quality of life and denture satisfaction using OHIP-14, DSQ and GOHAI questionnaires, respectively, were assessed within a one-year follow-up. Finally, an economic cost comparison analysis was carried out between the two groups after collecting initial and long-term cost data. Results: A total of 50 patients (25 receiving conventional implants – 12 females, mean age of 65.3±7.3 years; and 25 receiving mini-implants 11 females, mean age of 66.8 ±8.1 years) were analyzed. Peak insertion torque (p=0.001) and bone loss (p=0.02), as well as change in plaque (p=0.02) and bleeding (p=0.04) indices at 12 months differed significantly between groups. Furthermore, linear regression revealed that height of Locator as risk factor for bone loss (p=0.038). Adjusted Odds Ratio (AOR) analysis showed a significant association between abutment loosening and overdenture fracture (AOR=12.00, 95% CI = 1.11-129.45; p=0.041). Prosthetic maintenance requirements, OHIP-14, DSQ and GOHAI results for overdentures on both implant diameter groups were comparable. Finally, the initial cost of the conventional group was significantly higher than the mini-implant group. Conclusions: The present findings suggest that two mini-implants are significantly more susceptible to bone loss after immediate loading, for which height of Locator might be considered a risk factor. Implant diameter does not affect number of prosthetic maintenance and complications, and that abutment loosening is a risk factor for overdenture fractures, regardless of the implant diameter used. Quality of Life outcomes were similar for both groups. A Cost minimization analysis showed that mini-implant overdentures may be a more attractive treatment option from an economic point of view.