Effect of enamel regions and prisms orientation on the microshear bond strength of a multimode and a two-step self-etch adhesives applied with different adhesion protocols

Abstract

Multi-mode adhesives (MMA) with different adhesion protocols are postulated to improve bonding to enamel. Thus, this study compared the microshear bond strength (μSBS) of (MMA) and self-etch adhesive (SEA) to different regions and prism orientations of enamel. Materials and methodsThirty premolars were assigned for preparing 160 specimens for μSBS. Specimens were equally divided (n = 80) according to the enamel region evaluated: cuspal, and mid coronal enamel. Each group was divided into two subgroups according to the direction of tooth sectioning: axial, or tangential. Each subgroup was divided into two classes according to the applied adhesive system; either MMA or SEA. Finally; each class was divided into two subclasses (n = 10) according to the adhesion protocol utilized; self-etch adhesion protocol or with etch-and-rinse (pre-etching) adhesion protocol. Nano-filled flowable composite was used to prepare μSBS specimens. μSBS was measured using universal testing machine at a cross head speed of 0.5 mm/min until failure. Statistical analysis was carried out using four-way ANOVA test. ResultsDifferent enamel regions had no statistically significant effect at P-value 0.491. Direction of sectioning had a statistically significant effect at P-value <0.001. Adhesive systems had a statistically significant effect at P-value <0.001. Adhesion protocols had a statistically significant effect at P-value 0.001. ConclusionPre-etching of enamel before the application of the MMA improves the resin-enamel μSBS, while there was no advantage of the pre-etching step with the SEA. The μSBS of the tested adhesive systems were influenced by the direction of enamel prisms. The μSBS of the tested adhesive systems were not influenced by the enamel regions tested.