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Bond strength and quality of the hybrid layer of one-step self-etch adhesives applied with agitation on dentin

Abstract:

Objectives: This study evaluated the effect of the application mode on the microtensile resindentin bond strength (μTBS) and silver nitrate uptake (SNU) of three one-step self-etch adhesives systems (Clearfil S3 Bond [S3], Xeno III [XE] and Adper Prompt L-Pop [AD]). Materials and Methods: The occlusal enamel of 30 caries-free extracted molars was removed with a slow-speed diamond saw under copious water-cooling in order to expose a flat dentin surface. The adhesives were applied passively or with agitation. After light-curing (600 mW/cm2 for 10 seconds), composite buildups were constructed incrementally and the specimens were stored in water (37°C/24 hours). The specimens were longitudinally sectioned in the "x" and "y" direction to obtain bonded sticks (0.8 mm2) to be tested immediately in tension at 0.5 mm/minute. For SNU, two bonded sticks from each tooth were coated with nail varnish, placed in silver nitrate and polished down with SiC paper. The μTBS and SNU data were submitted to two-way ANOVA and Tukey's test (a=0.05). Results: Regarding the μTBS, only the main factor mode of application was statistically significant (p=0.01). All adhesives showed higher uTBS when applied with agitation. Regarding SNU, only the main factor adhesive was statistically significant (p=0.001). A higher amount of silver nitrate uptake, located in both the hybrid and adhesive layer, occurred for AD, regardless of the mode of application. Conclusions: Application with agitation on the dentin surface is a clinical tool capable of improving the resin-dentin bond strength of one-step self-etch adhesives; however, this clinical approach does not improve the hybrid layer resistance to silver nitrate uptake.