Multi-acrylamides improve bond stability through collagen reinforcement under physiological conditions

Lincoln Borges; Matthew Logan; Samuel Weber; Steven Lewis; Clark Fang; Lourenço Correr-Sobrinho; Carmem Pfeifer

doi:10.1016/j.dental.2024.05.002

Multi-acrylamides improve bond stability through collagen reinforcement under physiological conditions

Dent Mater. 2024 May 9:S0109-5641(24)00103-9. doi: 10.1016/j.dental.2024.05.002. Online ahead of print.

Authors

Lincoln Borges¹, Matthew Logan², Samuel Weber², Steven Lewis², Clark Fang², Lourenço Correr-Sobrinho¹, Carmem Pfeifer³

Affiliations

¹ Oregon Health & Science University, Portland, OR, USA; Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil.
² Oregon Health & Science University, Portland, OR, USA.
³ Oregon Health & Science University, Portland, OR, USA. Electronic address: pfeiferc@ohsu.edu.

PMID: 38729779
DOI: 10.1016/j.dental.2024.05.002

Abstract

Objectives: Acrylamides were shown to significantly improve bonding stability in adhesive restorations, but the reinforcement mechanism has not been fully elucidated. We tested the hypothesis that hydrogen bonding reinforcement of the collagen network (with secondary or tertiary acrylamides), as well as degree of crosslinking of the polymer network (with di- or tri-functional acrylamides), can be two of the factors at play.

Methods: Two-step total etch adhesives comprising UDMA (60 wt%) and 40 wt% of: TAAEA, TMAAEA (secondary, tertiary tri-acrylamides), BAAP, DEBAAP (secondary, tertiary di-acrylamides) or HEMA (mono-methacrylate - control) were formulated. Simulated composite restorations (n = 5) were tested after cyclic mechanical and biological (S. mutans biofilm) challenges. Gap formation before and after aging was assessed with SEM imaging. Micro-tensile bond strength (μTBS, n = 6) was assessed after seven-day incubation in water or S. mutans-containing culture medium. Collagen reinforcement was assessed with hydroxyproline assay (n = 10) and rheology (n = 3). Data were analyzed with one-way/two-way ANOVA/Tukey's test (alpha=5%).

Results: Gap formation increased and bond strength decreased for all monomers after biofilm incubation (p < 0.001). Except for DEBAAP, secondary and tertiary di/tri-acrylamides showed lower occlusal gap width values, but no significant differences overall gap length compared to HEMA. μTBS increased for tri-acrylamides compared with HEMA. Samples treated with multi-acrylamides had lower concentration of hydroxyproline (by-product of collagen degradation) (p < 0.001), except for DEBAAP, which showed values close to HEMA (p > 0.05). Dentin shear modulus increased for all acrylamides after 72 h, especially TMAAEA.

Significance: In general, multi-acrylamides promote collagen reinforcement, leading to reduced gap formation, and stabilize the bond strength under physiological conditions.

Keywords: Acrylamides; Adhesives; Biofilms; Collagen; Polymers.