Effects of Collagen Cross-Linking Agents on Dentin-Composite Interface Strength and Morphology

This in vitro study evaluated the effect of collagen crosslinking agents (grape seed extract, riboflavin, and chitosan nanoparticles with UVA light) on hybrid layer thickness, resin tag length, and shear bond strength (SBS) of a fifth-generation adhesive resin to caries-affected dentin of primary molars. Seventy-five carious human primary molars were selected, exhibiting lesions that reached the middle third of the dentin, according to the International Caries Detection and Assessment System (ICDAS) criteria 5. Infected dentin was removed. The crowns were shortened in height up to CAD, and etching was performed, followed by division of the samples into five groups (n = 15 each). Group 1: No collagen crosslinking (CCL) agent; Group 2:6.5% Grape Seed Extract (GSE); Group 3:0.1% riboflavin (RF)-UVA; Group 4:0.2% chitosan nanoparticles (CHNPs)-UVA; and Group 5: chlorhexidine (CHX). Composite restorations were built using a fifth-generation etch-and-rinse (ER) adhesive, followed by artificial aging. Scanning electron microscopy (SEM) was used to determine the resin tag length (RTL) and hybrid layer (HL) thickness. The SBS and failure modes were assessed using a universal testing machine and a stereomicroscope. One-way ANOVA and post-hoc Tukey tests were used to evaluate the means across all tested groups (p < 0.05). Group 4-CHNPs-UVA demonstrated the highest RTL (20.03 ± 3.54 μm) and thickest HL (5.65 ± 0.42 μm). Group 1 (No CCL agent) displayed the shortest RTL (7.11 ± 1.05 μm) and thinnest HL (1.23 ± 0.11 μm). The CHNPs-UVA pretreated samples showed maximum bond strength (10.31 ± 0.23 MPa). Group 1 (No CCL agent) tested samples presented minimum bond integrity (6.18 ± 0.33 MPa). Within the limitations of this in vitro study, CHNPs-UVA appears promising as a biomodification strategy for CAD in primary molars and warrants further long-term in vivo investigations before clinical recommendations can be made.