Purpose: The purpose of this study was to investigate the reaction products formed by application of three tooth etchants to hydroxyapatite.
Methods: Tooth etchants with three different compositions, designed for application to teeth before dental adhesive - " K-etchant GEL" (containing phosphoric acid), "Enamel Conditioner" (containing organic acids), and "Multi Etchant" (containing acidic monomer) - were applied to hydroxyapatite plates.
Results: Atomic force microscopy measurements revealed that Multi Etchant formed nano-sized particles on the hydroxyapatite. X-ray diffraction and Fourier transform infrared spectrometer analyses of the powdered hydroxyapatite indicated that Enamel Conditioner produced calcium tartrate whereas K-etchant GEL generated monetite. These results indicated that each etchant reacted with hydroxyapatite in a different way.
Conclusion: Not only differences among the etching ability of etchants, but also differences in the reaction compounds they produce may influence bonding performance in clinical practice.
Keywords: Fourier transform infrared; X-ray diffraction; atomic force microscopy; hydroxyapatite; tooth etchant.