ABSTRACT
STATEMENT OF PROBLEM: How implant alignment impacts stud attachment retention and wear-induced alterations, notably when the attachment exhibits metal-to-metal frictional interlocking, is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the interimplant angulation on retention forces and wear changes before and after 2 years of simulated clinical use of implant overdentures retained by titanium stud overdenture attachments. MATERIAL AND METHODS: The canine regions of 3 identical edentulous mandibular models were used to receive 2 dental implants analogs with TiTach attachments (Dental Evolutions, Inc) at interimplant angulations of 0, 30, and 60 degrees. Six identical overdentures were constructed over each model (n=6). A universal testing machine was used to determine overdenture retention forces at 0, after 1440, and after 2880 insertion and removal cycles to simulate the average insertion and removal cycles in 12 and 24 months. A stereomicroscope, a laser microscope, and a scanning electron microscope were used to evaluate the wear in the attachments. A linear regression model, ANOVA, and the Kruskal-Wallis tests were used to analyze the data (α=.05). RESULTS: All groups demonstrated reduced retention over the study duration (P<.001). The retention forces of the 0- and 30-degree groups were not significantly different after 2880 insertion and removal cycles, but both were significantly higher than those of the 60-degree group (P=.002). Within each group, the wear pattern of the matrix cap was more noticeable than that of the patrix abutment, with increased wear changes as interimplant angulation increased (P<.001). CONCLUSIONS: TiTach attachments could retain overdentures on parallel and divergent implants with a 30-degree angle of interimplant angulation. However, at a 60-degree angle of interimplant angulation, considerable reduction in retention forces and increased wear changes were observed after 2 years of simulated clinical use.
