Abstract
BACKGROUND: During endodontic treatment, exposure of coronal dentin to various endodontic chemical substances (ECS) impacts its structural integrity, thereby affecting therapy's success. This study employs preendodontic dentin hybridization (PEDH) to shield the coronal dentin from ECS. AIM: This study evaluates the influence of chemicals used during endodontic therapy on coronal dentin microhardness and resin-dentin microshear bond strength (µSBS) and the protective effect of PEDH. METHODOLOGY: Eighty square-shaped coronal dentin specimens were divided into four groups according to the time of chemical exposure: Control: No exposure to ECS. Late Dentin Hybridization (LDH): Exposed to ECS followed by dentin hybridization (DH); PEDH: DH followed by ECS; Ultrasonic LDH (ULDH): ECS followed by Ultrasonic repreparation then DH. Ten samples in each group were restored with composite and subjected to shear stresses under a Universal testing machine. The remaining 10 samples were tested for microhardness using a Vickers micro indenter. STATISTICAL ANALYSIS: Data were analyzed with one-way analysis of variance and Tukey's test. RESULTS: LDH causes a significant reduction in bond strength compared to all groups. The PEDH group exhibits µSBS and microhardness values close to the control group. ULDH group showed increased bond strength values compared to the LDH group, but exhibited a significant reduction in microhardness values compared to all experimental groups. CONCLUSION: Chemical exposure deteriorates properties of coronal dentin, thereby reducing µSBS and microhardness, whereas PEDH acts as a shield on coronal dentin, which effectively preserves its properties, producing outcomes close to untreated controls without the need for ultrasonic repreparation.