Purpose: To investigate the effect of different etching products used prior to the application of universal self-etching adhesive on dentin bonding. Materials and Methods: The etching products Multi Etchant (ME), Enamel Conditioner (EC), and K-etchant GEL (KE) were used as pre-treatments prior to the application of the one-bottle self-etching adhesive Adhese Universal (AU). Ground human dentin surfaces were randomly divided into four treatment groups: 1. control (CT; AU without con-ditioner); 2. ME; 3. EC; 4. KE. Microtensile bond strength (µTBS) tests with a thermocycling challenge (0-TC or 10,000-TC) were carried out and the morphological attributes of the adhesive-dentin interface were observed after an acid-base challenge using SEM to observe the acid-base resistant zone (ABRZ). Results: The KE group had a statistically significantly lower µTBS than did the ME and EC groups at 0-TC, and than the CT, ME, and EC groups at 10,000-TC (p 0.05). An ABRZ was observed in all groups but had partially disappeared in KE. A funnel-shaped area of erosion was also observed at the junction of the dentin and bonding layer in the CT, ME, and EC groups, while the hybrid layer was thicker in the KE group with no evidence of erosion. Conclusion: The application of ME or EC did not reduce the microtensile bond strength and resulted in ABRZ formation, while the ABRZ was partially reduced in the KE group. Schlagwörter: dentin, selective enamel-etch, acid-base resistant zone, microtensile bond strength test, thermal cycling test