Biomechanical rationale for a single implant-retained mandibular overdenture: an in vitro study.

OBJECTIVES This study aimed to examine the biomechanical rationale of a single implant-retained overdenture (SIO) system using an in vitro model. MATERIAL AND METHODS Laboratory implant analogs (3.75 x 13 mm) were embedded into the midline and canine regions on both sides of the mandibular phantom model with artificial mucosa. Magnetic attachments (flat, FM; dome, DM) and a ball attachment (Ball) were mounted to the abutment where lateral forces were measured with four miniature strain gauges attached to the surface. A 50 N static load was applied at five different sites of the occlusal surface of the simulated denture base using each counterpart of the attachments. Strain data were compared between SIO and two implant-retained configurations (TIO) with three attachments. Three-dimensional (3D) denture base displacements were also measured. Statistical analysis was performed by multiple comparisons using a post hoc test (P<0.05). RESULTS Statistically significantly smaller lateral forces to abutments were obtained in SIO than in TIO with the Ball with the molar load, while there were no statistical differences between SIO and TIO with FM. There were no statistical differences in 3D denture base movements between SIO and TIO in the midline and molar regions, while there were larger movements in SIO than in TIO with FM. CONCLUSION Within the limitations of our in vitro study, we suggested that single-implant overdentures with dome-type magnet or ball attachments had biomechanical effects similar to two-implant overdentures in terms of lateral forces to the abutment and denture base movements under molar functional loads.