Different Palatal Coverage designs as a Determinant of Stress Distribution on Locator attachment Maxillary implant Overdenture

Abstract

This in vitro study aimed to evaluate the strain distribution around two and four implants supporting maxillary implant overdentures retained by Locator attachments with different palatal coverage designs (full versus partial). Four identical acrylic models simulating completely edentulous maxillary arches were fabricated and covered with a polyvinyl siloxane layer to mimic the oral mucosa over the residual ridge. The models were divided into two main groups according to the number of implants (two or four), and each group was further subdivided based on palatal design (full or partial palatal coverage).

Locator abutments were connected to the implants using the manufacturer’s driver, and the overdenture frameworks were subsequently constructed. Four strain gauges were bonded to each implant fixture using strain gauge adhesive to record peri-implant microstrain values. A digital loading device (LLOYD Instruments) was used to apply controlled compressive loads, and the resulting strain values around the implants were measured for each configuration.

Statistical analysis revealed a significant difference between two-implant overdentures with full palatal coverage (30.64 ± 17.47 µε) and those with partial palatal coverage (49.72 ± 23.17 µε), with higher strain values observed in the partial coverage design. In contrast, although four-implant overdentures with partial palatal coverage (8.77 ± 4.54 µε) demonstrated higher mean strain values than those with full palatal coverage (5.51 ± 3.83 µε), the difference was not statistically significant.

Within the limitations of this in vitro study, full palatal coverage reduced peri-implant strain compared with partial palatal coverage in two-implant-supported maxillary overdentures. For four-implant-supported overdentures, full palatal coverage also showed lower strain values; however, the difference was not statistically significant.