Peri-Implant Strain around Conventional Locator versus Locator R-Tx Attachments in Mandibular Overdentures Before and After Simulated Aging: An In Vitro Study

Abstract

Background and Aim: Unfavorable load transfer in implant-retained overdentures compromises osseointegration and longevity. While the Locator R-Tx aims to improve durability, its biomechanical impact relative to the conventional Locator remains understudied. Therefore, this study compared peri-implant strain between conventional and R-Tx Locator systems in mandibular overdentures before and after simulated functional aging. Materials and Methods: Twelve epoxy resin edentulous mandibular models, each with two implants placed bilaterally in the canine regions, were used. Twelve acrylic resin implant-retained overdentures were fabricated and equally allocated into two groups (n = 6): Group I received conventional Locator attachments, and Group II received Locator R-Tx attachments. Strain gauges measured peri-implant microstrain (µε) at the buccal, lingual, mesial, and distal surfaces under a 98 N vertical load. Measurements were recorded at baseline and after 3,285 insertion–removal cycles, simulating three years of clinical service. Data were statistically analyzed using IBM SPSS Statistics software. Results: The baseline overall mean strain was comparable between Group I (136.38 ± 10.43 µε) and Group II (135.17 ± 6.46 µε; P = 0.406). However, after cycling, Group II exhibited significantly lower strain at the left buccal site (152.33 ± 9.04 µε) compared to Group I (162.00 ± 14.22 µε; P = 0.032). Similarly, the mean strain on the left side was significantly lower in the R-Tx group (147.08 ± 6.71 µε) versus the conventional group (155.50 ± 14.15 µε; P = 0.045). Conclusions: While both systems demonstrated similar initial biomechanical behavior, the Locator R-Tx system exhibited superior stress distribution at specific sites after simulated aging, suggesting enhanced long-term biomechanical stability compared to the conventional design