Bond Strength of Denture Teeth to Heat-Cured, CAD/CAM and 3D Printed Denture Acrylics

Purpose To establish the fracture toughness (K-1C) and flexural bond strength of commercially available denture teeth to heat cured, CAD/CAM and 3D printed denture-based resins (DBRs). Materials and Methods Three types of DBRs (Heat cure, CAD-milled and 3D printed) and four different types of commercial denture teeth (Unfilled PMMA, double cross-linked PMMA, PMMA with nanofillers and 3D printed resin teeth) were investigated. DBR and epoxy embedded denture teeth (n = 30 per group) specimen beams (25 x 4 x 3 mm) were fabricated. The testing ends of all the specimens were surface treated, bonded and processed according to manufacturer's instructions. Twenty specimens were thermal cycled to simulate the effects of 6 and 12 months intraorally. A 4-point bend test, using the chevron-notched beam method was done and K-1C (MPa center dot m(1/2)) and flexure bond strength (MPa) were calculated. All specimens were analysed for the mode of failure under the light microscope and selected specimens under scanning electron microscope. Results were statistically analysed using ANOVA (SPSS Ver 24). Results The mean K-1C was the highest for the teeth bonded to the heat-cured DBR group (1.09 +/- 0.24), followed by CAD/CAM (0.43 +/- 0.05) and 3D printed groups (0.17 +/- 0.01). Differences were statistically significant (p < 0.01). Within each group, aging showed statistically significantly lower values but no statistical significance between the mean K-1C and flexural bond strength (p = 0.36). The dominant mode of failure was cohesive in the CAD/CAM groups and adhesive in the heat-cured and 3D printed groups. Conclusion Teeth bonded to heat-cured DBRs produced the highest K-1C.The bond strength decreased significantly with aging. Teeth bonded to CAD/CAM and 3D printed DBRs showed significantly lower bond strength, with no significant influence of aging.