Marginal Bone Response Around Immediate- and Delayed-Loading Implants Supporting a Locator-Retained Mandibular Overdenture: A Randomized Controlled Study

Purpose: Implant-supported mandibular overdentures (OVDs) have been proposed as the gold standard for the treatment of edentulous mandibles. There is limited evidence on the clinical outcomes of immediate loading of two unsplinted implants supporting a mandibular OVD. The purpose of this randomized controlled trial was to evaluate the performance of two unsplinted implants supporting a Locator-retained mandibular OVD over 12 months loaded immediately or after a delay. Materials and Methods: Each patient received two implants 4.0 mm in diameter and 8 to 15 mm long. Locator-retained mandibular OVDs were connected to the implants either immediately (IL) or 3 months postsurgery (DL). The primary response variable was radiographic bone loss (RBL) at 6 and 12 months postsurgery. Implant length, insertion torque, implant failure, prevalence of maintenance visits, and prosthetic complications were also recorded. Results: Thirty participants ( 15 in the IL and 15 in the DL groups) were evaluated at 12 months. The implant cumulative survival rates were 100% and 93% for DL and IL, respectively. The mean RBL from baseline to 1 year was 0.54 (+/- 0.5) mm and 0.25 (+/- 0.5) mm for DL and IL, respectively. A statistically significant difference was observed at 12 months, with less RBL in the IL group. Insertion torque and implant length were not correlated with RBL. Also, no difference in frequency of maintenance visits and prosthetic complications was reported between the groups. Conclusion: Immediate loading of two unsplinted implants supporting a Locator-retained mandibular OVD seems to be a suitable treatment option. Significantly less RBL was observed after 1 year of loading around IL implants than around DL implants. Furthermore, neither implant length nor insertion torque seemed to affect RBL 1 year after surgical placement.