Effects of pH on the microhardness of resin-based restorative materials

This study determined the effect of pH on the microhardness of commonly used resin-based restorative materials which included a resin composite (Esthet-X, Dentsply), a new generation compomer (Dyract Extra, Dentsply) and a giomer (Beautifil, Shofu). Fifty-four specimens (3-mm wide x 3-mm long x 2-mm deep) were made for each material. The specimens were divided into six equal groups and conditioned in the following solutions at 37 degrees C for one week: 0.3% citric acid at pH 2.5, sodium hydroxide-buffered citric acid at pH 3, 4, 5, 6 and 7. After conditioning, the specimens were subjected to hardness testing using a digital microhardness tester (load 500gf; dwell time 15 seconds). Data was analyzed using one-way ANOVA and Scheffe's test at a significance level of 0.05. The effects of pH on the microhardness of resin-based restoratives were material dependent. The compomer and giomer materials were more affected by acids of low pH than the composite material that was evaluated.