Surface Analysis of Conditioned Dentin and Resin–Dentin Bond Strength

Purpose : To evaluate the effect of different dentin conditioning procedures for resin bonding on dentin surface properties (i.e., wettability, roughness and nano-hardness). Methods: Polished human dentin surfaces were obtained and treated with: (1) 35% phosphoric acid (15 s); (2) 0.1 M ethylenediaminetetreaacetic acid (EDTA) (pH 7.4) (60 s); (3) 35% phosphoric acid (15 s) followed by 3% potassium oxalate gel (120 s). Contact angles were measured with water, to assess the surface wettability and were done by axisymetric drop shape analysis; the average roughness (Ra) was measured using a contact profilometer and an atomic force microscope; and the nano-hardness was assessed using a Berkovich diamond tip mounted in a Hysitron triboscope nanoindenter. The conditioned surfaces were bonded with an etch and rinse adhesive system (Single Bond) and bond strength was assessed using a microtensile bond strength test. Data were examined by analysis of variance and Student–Newman–Keuls multiple comparison tests (p < 0.05). Results: All the tested surface treatments resulted in a decrease of the water contact angle. The dentin surface conditioned with phosphoric acid or phosphoric acid plus oxalate resulted in a significant increased in roughness and a decrease in nano-hardness. Ethylenediaminetetraacetic acid (EDTA) induced no significant changes in either the dentin surface roughness or the nano-hardness values. The three tested conditioned systems all showed similar bond strengths. Conclusions: Conditioning the dentin with EDTA improved the dentin wettability as a result of chemical surface modifications without altering the dentin nano-hardness. The EDTA-conditioned dentin surface may be suitable for resin bonding. The application of potassium oxalate after phosphoric acid etching did not alter the surface properties of the phosphoric acid etched dentin.