Microtensile bond strength to dentin and enamel of self-etch vs. etch-and-rinse modes of universal adhesives.

PURPOSE: To compare the immediate microtensile bond strengths (µTBSs) of four mild self-etch universal adhesives applied to dentin and enamel with self-etch and etch-and-rinse techniques. METHODS: Flat middle dentin surfaces from 104 human teeth and two enamel fragments from another 104 human teeth were randomly distributed into eight groups according to the various adhesive systems used: Scotchbond Universal (SBU) [etch-and-rinse mode vs. self-etch mode]; Optibond XTR (OPT) [ etch-and-rinse mode vs. self-etch mode]; Clearfil Universal Bond Quick (CL) [ etch-and-rinse mode vs. self-etch mode]; and Adhese Universal (ADH) [etch-and-rinse mode vs. self-etch mode]. After 24 hours of water storage, the bonded sticks were tested for µTBS. The differences in the pre-test failure and fracture-failure modes were tested by a two-way ANOVA and GEE model analysis. Bond-strength data were analyzed with a two-way ANOVA and mixed-model analysis. RESULTS: : For dentin, the mean µTBS was statistically different among the four adhesives, but not different between the self-etch and etch-and-rinse modes. For enamel, the mean µTBS was statistically different among the four adhesives, as was the application mode. GEE model analysis revealed a statistically significant adhesive failure rate proportion among the four types of adhesives for both enamel and dentin. CLINICAL SIGNIFICANCE: Etching enamel prior to the application of a universal adhesive can be recommended as an approach to enhance bond strength.