Effect of Different Surface Treatments and Thermocycling on Bond Strength of a Silicone-based Denture Liner to a Denture Base Resin

The aim of this study is to evaluate the effects of three different surface treatments and thermocycling on the tensile strength of a silicone lining material to denture resin. A total of 96 cube-shaped specimens were fabricated using heat-cured polymethyl methacrylate (PMMA) denture base resin. Three millimeters of the material was cut from the midsection. The specimens were divided into four groups. The bonding surfaces of the specimens in each group received one of the following surface treatments: no surface treatment (control group), airborne particle abrasion with 110 pirn alumina particles (air abrasion group), Er:yttrium aluminum garnet laser irradiation (laser group), and air abrasion + laser. After the lining materials were processed between the two PMMA blocks, each group was divided into two subgroups (n = 12), either stored in distilled water at 37°C for 24 hours or thermocycled between 5 and 55°C for 5,000 cycles. The specimens were tested in tensile and shear strength in a universal testing machine. Data were analyzed with two-way analysis of variance and Tamhane's post hoc tests (α = 0.05). The mode of failure was determined, and one specimen in each group was examined by scanning electron microscopy. Surface-treated groups demonstrated significantly higher tensile strengths compared to the control group (p < 0.001). Nonetheless, no significant differences were found between surface-treated groups (p > 0.05). The tensile strength was significantly different between thermocycled and water-stored specimens (p = 0.021). Altering the surface of the acrylic denture base resin with air abrasion, laser, and air abrasion + laser increased the tensile strength. Thermocycling resulted in decrease in bond strength of silicone-based liner to surface-treated acrylic resin. Pretreatment of denture base resins before applying the soft liner materials improves the bond strength. However, thermocycling results in decrease in bond strength of soft denture liner to surface-treated acrylic resin.