Surface roughness and shear bond strength of novel polymethylmethacrylate-based materials

The aim was to evaluate the surface roughness (Ra) and shear bond strength (SBS) of novel polymethylmethacrylate (PMMA)-based materials. Thirty rectangular specimens were prepared from three different PMMA-based materials: nanographene-reinforced PMMA, milled PMMA, and self-curing PMMA. All specimens underwent a polishing process and the Ra value was then recorded using a non-contact profilometer. A special plate was then used to bond nanoflowable composite resin to the specimens' surfaces, after which they underwent thermocycling between 5 and 55 °C for 5000 cycles. The SBS was subsequently evaluated at a crosshead speed of 1 mm/min. One-way ANOVA and Tukey's HSD test (α = 0.05) were used for data analysis. The Ra and SBS values differed significantly (p < 0.001). The self-curing PMMA specimens had the highest mean Ra value (1.15 μm), while the G-CAM specimens had a mean Ra value of 0.55 μm and the milled PMMA specimens had a mean Ra value of 0.53 μm. SBS in the milled PMMA group was measured at 51.25 MPa; SBS in the G-CAM and self-curing PMMA specimens was lower than in the milled PMMA specimens (34.36 and 31.22 MPa, respectively). Although nanographene-reinforced PMMA exhibited an acceptable Ra value, its SBS value was lower than that of milled PMMA.