Bond Strength of Microwaveable Acrylic Resin as Denture Repair Material

Objectives: 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 material either following the dental flasking procedure or not. The aim of this study was to evaluate the shear bond strength of two microwaveable acrylic resins, Acron MC (GC Corp., Japan) & Justi (Justi Products, div. American Tooth Industries, USA), compared to an auto-polymerizing acrylic resin, ProBase Cold (Ivoclar Vivadent, Liechtenstein), using the non-flasking procedure. Methods: Sixty cylindrical specimens were made using a heat-cured acrylic resin, Vertex Rapid Simplified (Vertex-Dental B.V., Netherlands), simulating the denture base. Repair acrylic resin was poured on the specimen's surface using a cylindrical rubber mould of 8,5mm internal diameter. Twenty specimens for each repair material were made. Ten specimens from each group were stored in water for 24h forming the control group, while the rest ten specimens from each group were subjected to a thermocycling procedure (5-55ºC for 1000cycles). Shear bond strength was measured on a tensometer and mode of bond failure was examined under a stereomicroscope. T-test and Wilcoxon tests were performed to identify putative statistical differences. Results: Shear bond values of Justi were statistically significant inferior to ProBase Cold (P<0,001 for both the control and thermocycling groups) and Acron MC (P=0,004 and P<0,001 for the control and thermocycling groups respectively) repair materials. ProBase Cold and Acron MC acrylic resins exhibited similar values of shear bond strength for both the control and thermocycling groups. Conclusion: Unlike Justi, Acron MC microwaveable acrylic resin exhibited repair bond strength similar to the ProBase Cold auto-polymerizing acrylic resin independently of thermocyling stress.