Influence of carbamide peroxide on the flexural strength of tooth-colored restorative materials: an in vitro study at different environmental temperatures

The current study investigated the influence of carbamide peroxide on the flexural strength of tooth-colored restorative materials at two environmental temperatures. Seven restorative materials were used, including four resin composites (Filtek Z350, Filtek Z250, Synergy Flow and Filtek P60), a polyacid-modified composite (Dyract AP), a conventional glass-ionomer cement (Ketac Molar Easymix) and a ceramic (Vitablocs Mark II). For each type of material, 80 bar-shaped specimens were fabricated and divided into four groups (n = 20): bleaching group at 25 degrees C, control group at 25 degrees C, bleaching group at 37 degrees C and control group at 37 degrees C. The specimens in the bleaching groups were treated with 10% carbamide peroxide gel for eight hours/day, while the control specimens in their respective groups were stored in deionized water. After 14-day treatment, the flexural strength of the specimens was determined using a universal testing machine. All the results were analyzed with ANOVA and the Tukey's post-hoc test. The data were also submitted to Weibull distribution. The flexural strength and its Weibull distribution of polyacid-modified composite and glass-ionomer cement were more seriously affected by bleaching agents than the resin composite and ceramic, especially at the higher environmental temperature.