Methods: In this experimental study of enamel specimens, 45 freshly extracted human third molar were prepared and divided in to three groups of white strips, paint on, and toothpaste. Each material was used according to the manufacturers (Crest and Rapidwhite) instructions. Vickers microhardness test was performed for all groups. Data were analyzed by repeated measure ANOVA and LSD test.
Results: Microhardness values of white strips, paint on, and tooth paste groups before and after bleaching treatment were 305.60±51.70 and 289.20±54.24/286.53±62.10&276.13±61.75/256.60±39.77&253.06±38.62, respectively. One-way ANOVA showed significant differences among three OTC groups (P<0.001). There was also significant difference among the value of enamel microhardness before and after the bleaching in each group (P<0.001).
Conclusions: Whitening OTC products affect enamel microhardness. White strips and paint on decreased the microhardness more than whitening toothpaste. Consumers should be aware of these OTC products side effects and use them conservatively.