Bond preservation in caries-affected dentin restored with acrylamide-based adhesives

Abstract

Objectives: Multi-acrylamides have been shown to enhance the bond stability of the adhesive interface in sound dentin (SD). This study aimed to evaluate the performance of triacrylamides as primers for improving bonding efficacy in caries-affected dentin (CAD).

Materials and methods: Caries was induced in dentin using a 5-day microcosm biofilm model, and demineralization was characterized by ATR/FTIR spectroscopy. Primers were formulated with glycerol dimethacrylate (50 %) combined with secondary (TAAEA) or tertiary (TMAAEA) triacrylamides, HEMA (control), or dopamine methacrylamide (Dopa) with HEMA or TMAAEA, in a solvent mixture (ethanol/water, 70/30, 40 vol%). CAD and SD were treated with a three-step etch-and-rinse adhesive, restored with resin composite, and sectioned (1 mm²) for microtensile bond strength (μTBS, n = 6) testing after 24 h and six months of water storage at 37 °C. Collagen degradation (hydroxyproline assay, n = 5), in situ zymography (n = 2), and monomer viscosity (n = 3) were also evaluated. Data were analyzed using ANOVA and Tukey's post hoc test (α=0.05).

Results: In SD, all acrylamides and the control exhibited stable or increased μTBS after six months (>50 MPa). For CAD, bond strengths were comparable to SD, except for HEMA, which consistently showed lower μTBS (<40 MPa). CAD demonstrated reduced mineral content, elevated hydroxyproline release, and greater collagen degradation (p < 0.001). Acrylamides indirectly protected collagen by mitigating enzymatic activity and exhibited higher viscosity than HEMA.

Significance: Multi-acrylamides effectively preserve the structural integrity of collagen and sustain bond strength in both sound and caries-affected dentin, contributing to the longevity and performance of adhesive restorations.

Keywords: Acrylamides; Adhesives; Caries -affected dentin; Collagen.