Determines the effect of acidic food and drinks on surface hardness of enamel, dentin and tooth-colored filling materials. Fifty specimens of enamel, dentin from human premolar teeth and tooth-colored filling materials : hybrid resin composite (Filtek Z250), microfilled resin composite (Filtek A110), conventional glass ionomer cement (Fuji IX), resin modified glass ionomer cement (Fuji II LC) and polyacid modified resin composite (Dyract AP) were prepared. Each specimen was subjected to Vickers microhardness measurements to obtain a baseline value, which was averaged from 6 indentations. The specimens were allocated into 5 groups, and soaked in selected food and drinks : Coca cola, yogurt, orange juice, sport drink and Tom Yum. The artificial salivary soaking process consisted 10 cycles of 5 sec immersion in food or drinks alternated with 5 sec immersion in artificial saliva. Microhardness measurements were performed again. Microhardness values before and after soaking in each food or drink were analyzed using paired t-test and one-way ANOVA at 0.05 level of significance. The result showed that soaking in Coca cola significantly reduced surface hardness of enamel, dentin, microfilled resin composite and resin modified glass ionomer cement (p-value<0.05). Orange juice and sport drink significantly reduced surface hardness of enamel (p-value<0.05). Yogurt and Tom Yum did not reduce surface hardness.
