Surface Hardness of Acrylic Resins Exposed to Toothbrushing, Chemical Disinfection and Thermocycling

Abstract

The aim of this study is to investigate the effect of the toothbrushing, chemical disinfection and thermocycling treatments on the surface hardness of acrylic resins used for denture bases. The Classico (conventional), Onda Cryl (microwaved) and QC-20 (boiled) thermoactivated acrylic resins were used to prepare specimens. Prior to and after cleaning procedures, the specimens were submitted to a hardness test in an indenter (HMV-2000 Shimadzu), employing a load of 50 gf for 10 s. Three-way ANOVA and Tukey's test (α=0.05) were used to analyze the data. Prior to thermocycling, statistical differences were found among treatments for Onda Cryl, with greater hardness values observed for Efferdent and hypochlorite; lower hardness value was obtained after toothbrushing, and intermediate value was found for the control. Differences were found among resins for the control treatment, with higher value for QC-20 resin, lower value for the Classico, and intermediate value for the Onda Cryl. Following thermocycling, differences were observed among treatments for Onda Cryl, with control specimens presenting higher values, lower value for toothbrushing and intermediate values for Efferdent and hypochlorite. Differences were also found for QC-20, with Efferdent and hypochlorite presenting higher values, lower value for control and intermediate value for toothbrushing. Differences were found among resins for the control treatment, with higher value for Onda Cryl resin, lower value for the QC-20, and intermediate value for the Classico. The QC-20 resin showed higher value for control prior to thermocycling and Onda Cryl after thermocycling. Different effects on the surface hardness of acrylic resins used for denture bases were observed when associating thermocycling with toothbrushing or chemical disinfections.