Effects of hardness and surface pretreatment on the bond strength of a polyvinylsiloxane attachment matrix to denture base resin

Abstract

Polyvinylsiloxane (PVS) matrices are used in implant-supported overdentures; however, detachment from the denture base remains a common complication. This in- vitro study evaluated the effects of matrix hardness and surface pretreatment on the tensile bond strength of a PVS matrix to denture base resin. A total of 144 specimens were prepared using a PVS attachment-matrix system in 3 different Shore A hardness (SH) values (SH25, SH50, and SH65) and 3 acrylic resin surface pretreatment (phosphoric acid etching, monomer application, and combined acid–monomer) and control groups. Specimens were fabricated using a computer numerical control (CNC)–milled brass mold. Bonding surfaces were grit-blasted with 110 μ primer, and subjected to 1000 thermocycles between 5 ◦ C and 55 ◦ m aluminum oxide particles, treated with a manufacturer-recommended C. Tensile bond strength was measured using a universal testing machine, and failure modes were classified as adhesive, cohesive, or mixed. Data were analyzed using two-way ANOVA and Tukey HSD post hoc test ( α = 0.05). Both matrix hardness and surface pretreatment significantly affected bond strength (P < 0.05). The SH50 group demonstrated the highest bond strength, whereas the SH25 group showed the lowest values. Phosphoric acid significantly increased bond strength only for the SH25 group, while monomer application improved bond strength across all hardness groups. In contrast, the combined acid–monomer pretreatment significantly reduced bond strength in all groups. These findings suggest that bond strength is not directly proportional to matrix hardness and suggest an optimal hardness range, highlighting the influence of matrix hardness–surface pretreatment interactions.