Microtensile dentin and enamel bond strengths of recent self-etching resins

In this study, the microtensile bond strengths of resin composites to dentin and enamel produced by recently introduced self-etching resins were determined. Included were two adhesives with self-etching primers, Clearfil SE (Kuraray) and Peak SE (Ultradent), four self-etching adhesives, OptibondAll-In-One (Kerr), Clearfil S³ (Kuraray), Adper Prompt L-Pop (3M ESPE) and iBond (Heraeus Kulzer) and, as a positive control, PQ1 (Ultradent), an etch-and-rinse adhesive. Each product was evaluated using the same hybrid resin composite, Z250 (3M ESPE). Testing was performed after 48 hours using a "non-trimming" microtensile test at a crosshead speed of 0.6 mm/minute. Sample size was five teeth per group, with the value for each tooth calculated by averaging the bond strengths of seven beams derived from it. Mean values in MPa (SD) for dentin were: Clearfil SE 81.6 (3.5), Peak SE 80.3 (9.9), PQ1 73.4 (4.9), Optibond All-In-One 64.4 (5.9), Clearfil S³ 62.5 (2.2), iBond 51.0 (4.0) and Prompt L-Pop 33.9 (6.4). Mean values in MPa (SD) for enamel were: PQ1 55.6 (2.5), Clearfil SE 54.1 (5.4), Prompt L-Pop 54.0 (5.4), Peak SE 51.8 (1.5), Clearfil S³ 44.3 (5.2), Optibond All-In-One 40.1 (2.1) and iBond 33.8 (3.3). (Values for each substrate with the same letter were not significantly different, one-way ANOVA, Tukey-Kramer Multiple Comparison Test, p<0.05.) Compared to the positive control, PQ1, only adhesives with self-etching primers, Clearfil SE and Peak SE, were as effective in bonding to both enamel and dentin. With the exception of Prompt L-Pop, scanning electron micrographs of the etched enamel surface produced by self-etching products indicated far less surface topography than conventional etching, even for self-etching primer systems producing the same bond strengths as the etch-and-rinse adhesive.