Comparison of experienced and inexperienced operators on bond strengths of total-etch and self-etch bonding systems.

Purpose: to compare a two-step etch-and-rinse adhesive system and a one-step self-etch adhesive system in order to evaluate the influence of clinical experience on dentin bond strength. Methods: Twenty-four human molars were sectioned to obtain two 1 mm-thick slabs of mid-coronal dentin. Both surfaces of one of the two slabs that were obtained from each tooth were treated with a two-step etch-and-rinse adhesive (OptiBond Solo Plus), while both surfaces of the other slab were treated with a one-step self-etch adhesive (OptiBond All-In-One). Twenty-four undergraduate, second-year students applied the adhesive on one of the two surfaces of each slab (Student group), while twelve dentists with experience in adhesive restorative dentistry (Expert group) applied the same adhesive on the other surface of the slab. Nine conical frustum-shaped resin composite (Premise Flowable) build-ups, whose smaller base was bonded to the dentin surface, were constructed on both surfaces of each dentin slab using a custom made device. After thermo-cycling, specimens were subjected to micro shear bond strength test. Data were analyzed by a multilevel statistical model. Results: The interaction term Experience x Adhesive resulted statistically significant (p<0.0001). The bond strength (MPa) resulting from the self-etch adhesive was similar in the Student (27.8 ± 9.0) and in the Expert group (26.5 ± 7.0). The etch-and-rinse adhesive bond strength within the Student group (23.6 ± 10.4) was lower than that within the Expert group (28.1 ± 8.9). Clinical significance While the etch-and-rinse adhesive used in this study showed to be experience-sensitive, the self-etch one proved to be less experience-sensitive in obtaining a reliable bond strength with dentin.