Halloysite nanotube incorporation into adhesive systems-effect on bond strength to human dentin

Objectives This study aimed to evaluate the effect of HalloysiteA (R) aluminosilicate clay nanotube (HNT) incorporation into a two-step etch-and-rinse (ER) and a one-step self-etch (SE) adhesive on human dentin shear bond strength (SBS). Materials and methods Ten groups (n = 12) were prepared according to the adhesive system (i.e., ER or SE) and amount of HNT incorporated (5-20 %, w/v), as follows: commercial control (i.e., the adhesive was used as purchased, 0 % HNT); experimental control (i.e., the adhesive was processed through mixing/stirring and sonication similarly to the HNT-incorporated experimental groups, but without HNT); and 5, 10, and 20 % HNT. SBS testing was performed after 24 h of storage in deionized water at 37 A degrees C. Failure modes were examined using a stereomicroscope (x40). Scanning electron microscopy (SEM) of the resin-dentin interface of selected specimens was carried out. Results Two-way ANOVA revealed that incorporation of HNT up to 20 % (w/v) in ER and up to 10 % (w/v) in SE demonstrated an increased SBS compared to their experimental controls. Compared to the commercial control, SBS of HNT-modified dentin adhesives was not significantly different for ER adhesives (p > 0.05) but was significantly higher with 5 % HNT in the SE adhesive (p < 0.05). Failure modes were predominantly adhesive and mixed failures. SEM micrographs of resin-dentin interfaces for ER-commercial control and ER-10 % showed a similar morphology. A thicker adhesive layer and the presence of agglomerated HNT on the resin tags were seen in ER-10 %. An increased number of short resin tags in SE-5 % compared with SE-commercial control were observed. Conclusions HNT addition up to 20 % in ER and up to 10 % in SE showed increased SBS to dentin compared with the experimental control.