Effect of food-simulating liquids on the mechanical properties of provisional restorative materials

Objectives The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the mechanical properties of provisional restorative materials. Methods Four provisional restorative materials were selected: (1) Dentalon Plus (DP), (2) Protemp II (PII), (3) Systemp C&B (SCB) and (4) Integrity (INTG). The specimens were fabricated in customized molds and each type was randomly divided into five groups (n = 10). The test groups were conditioned for 7 days at 37 °C as follows: water, 0.02N citric acid, heptane and 75% ethanol in aqueous solution. Specimens in the control group were stored at room temperature in air. After conditioning, the flexural strength (FS) values were assessed using a universal testing machine (5 mm/min crosshead speed) and the fractured specimens were used for the determination of the Knoop hardness number (KHN) using a digital micro-hardness tester (100 gf/15 s). Kruskal–Wallis and Mann–Whitney U-tests were used for statistical analysis. Results In ethanol and heptane solutions, DP specimens were totally degraded, thus, FS/KHN for DP could not be measured. For all materials, the FS/KHN values were significantly lower than their control groups after conditioning in ethanol. After heptane conditioning, the decrease in FS for SCB and KHN for PII were statistically significant. After citric acid conditioning, KHN for PII and INTG were significantly higher than the controls and the decrease in FS for SCB and INTG were statistically significant. Significance The mechanical properties of provisional restorative materials are strongly influenced by food-simulating liquids.