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Microshear bond strength and interfacial morphology of etch-and-rinse and self-etch adhesive systems to superficial and deep dentin.

OBJECTIVE
To compare microshear bond strength (uSBS) of two pairs of etch-and-rinse and self-etch adhesives to superficial and deep dentin.


METHOD AND MATERIALS
Occlusal surfaces of 40 sound extracted noncarious human molars were ground to obtain flat dentin surfaces (20 superficial and 20 deep dentin). Twenty-four teeth were used for uSBS test and 16 for scanning electron microscopic examination. Each dentin group was randomly assigned into four groups, according to the adhesive system tested. An etch-and-rinse and a self-etch adhesive from the same manufacturer were utilized: Scotchbond-MultiPurpose and Adper-Scotchbond SE and XP Bond and Xeno IV. CeramX was used for composite microcylinder construction (0.9 mm in diameter and 0.7 mm in height). Five composite microcylinders were constructed on each dentin surface (n = 15 per group). A Lloyd universal testing machine was used to test uSBS at a crosshead speed of 0.5 mm/min. Fractographic analysis of the failure site was performed using a stereomicroscope and measured by image-analysis software. Data were statistically analyzed using ANOVA and Duncan tests.


RESULTS
In superficial dentin, Xeno IV showed significantly the highest uSBS, while in deep dentin, XP Bond showed the highest uSBS. The lowest uSBS values in both dentin depths were recorded for Adper-Scotchbond SE. Etch-and-rinse systems bonded better to deep than to superficial dentin, while self-etching systems showed similar performance at both dentin depths.


CONCLUSION
Bond strength to dentin is both adhesive- and substrate-dependent. Contemporary adhesive systems may produce variable bonding results to superficial and deep dentin due to variations in their composition rather than their bonding approach or application technique.