Evaluation of shear bond strength of microwaveable acrylic resins in denture repair: a comparative study

Acrylic denture base fracture is a common mode of failure. Heat-cured, auto-polymerized, visible light-cured, and microwaveable acrylic resins have been used as repair materials. The aim of this study was to evaluate the shear bond strength of two microwaveable resins (Acron MC and Justi) and one auto-polymerizing acrylic resin (ProBase Cold) as denture repair materials as opposed to a heat-cured one using the non-flasking procedure after thermocycling and photoaging.

Ninety cylindrical specimens were made using the Vertex Rapid Simplified heat-cured acrylic resin. Each repair acrylic resin was poured on the specimen's surface using a cylindrical rubber mold with an internal diameter of 8.5 mm. Thirty specimens for each repair material were made. The control group consisted of 10 specimens from each group which were stored in water for 24 h at 37 degrees C; another 10 specimens from each group were subjected to a thermocycling procedure (5-55 degrees C for 1,000 cycles), while the remaining 10 specimens were subjected to a photoaging procedure. Shear bond strength was measured on a universal testing machine and mode of bond failure was examined under a stereomicroscope. Two-way ANOVA and the Bonferroni post hoc test were performed to identify statistical differences at alpha = 0.05.

Justi's shear bond values were significantly inferior to those of ProBase Cold (p <0.05) and Acron MC (p <0.05). ProBase Cold and Acron MC acrylic resins exhibited similar values (p >0.05) of shear bond strength. Thermocycling and photoaging did not affect the shear bond values of any of the materials under investigation (p >0.05).

ProBase Cold and Acron MC exhibited similar shear bond values. Justi repair material exhibited inferior bond strength compared with that of ProBase Cold and Acron MC. Aging procedures did not affect the bonding properties of any of the repair materials.