Effect of mastication load on retention force of custom-made LOCATOR abutments manufactured for angled implants: An in vitro study.

Abstract

Custom-made angled LOCATOR abutments have been used to compensate for the angulation of implants placed to support removable prostheses; however, their retention forces and the impact of mastication loading on retention have yet to be well addressed. The purpose of this in vitro study was to evaluate the retention force of custom-made LOCATOR abutments for implants placed at 0-, 15-, and 30-degree angulations with prefabricated abutments and to investigate the effect of mastication load on retention. Implant analogs were placed at the first molars of 40 maxillary typodonts, and 40 LOCATOR abutments were fabricated. Twenty implant analogs were placed at 0 degrees, 10 of which received prefabricated LOCATOR abutments and 10 of which received custom abutments. The remaining 20 implant analogs were placed at 15- and 30-degree angulations (n=10), and custom LOCATOR abutments were fabricated on them. A denture analog was digitally designed and manufactured from polymethyl methacrylate (PMMA) billets. Metal housings were then picked up using PMMA. The specimens were subjected to 2 rounds of 120 000 cycles of mastication loading. Retention force was assessed before and after each round of mastication loading using a universal testing machine. The wear of nylon inserts before and after mastication loading was accessed with a digital stereomicroscope. A 2-way ANOVA followed by the Tukey HSD test was used to determine the impacts of LOCATOR abutment type and times of mastication loading on the retention forces of the denture base (α=.05). No significant difference in retention forces was found between prefabricated LOCATOR and custom abutments (placed at 0-, 15-, and 30-degree angulations) regardless of mastication loading (P>.05). The retentive force values of all groups increased significantly after the first round of mastication loading and decreased significantly to the initial level after the second round of mastication loading (P<.05). Mastication loading impacted the retention force of both prefabricated and custom LOCATOR abutments; however, no significant difference in retention forces was found among various types of abutments.