Work

Photoinitiator-dependent effects of N-acetylcysteine incorporation in dental resin-based composites

Year: 2026

Type: article

Abstract: Objectives: To investigate how N-acetylcysteine (NAC) incorporation affects the polymerization behavior, material properties, monomer release, and cellular response of dental resin-based composites (RBCs) formulated with different photoinitiator systems.Methods: Experimental RBCs were formulated using either a camphorquinone/amine (CQ, type II) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO, type I) photoinitiator system. NAC was incorporated at 0, 0.5, or 1 wt%. Degree of conversion (DC), free radical concentration, microhardness, elastic modulus, and flexural strength were evaluated. NAC and monomer release were quantified by UHPLC-MS/MS. Human dental pulp cells (hDPCs) were exposed to composite eluates to assess metabolic activity and reactive oxygen species (ROS) production.Results: NAC incorporation produced markedly different effects depending on the photoinitiator system. In CQ-based composites, NAC reduced free radical concentration, decreased DC, altered mechanical properties, and increased TEGDMA release, particularly at 0.5 wt%. In contrast, TPO-based composites maintained their polymerization efficiency and mechanical performance following NAC incorporation, with a slight increase in DC observed in some formulations. NAC release was dose-dependent, greater in uncured materials, and sufficient to significantly reduce ROS production in most experimental conditions. Despite this antioxidant effect, hDPC metabolic activity remained largely unchanged among cured composites (~80% of control), with only a modest increase observed for CQ-1%NAC. Eluates from uncured materials resulted in substantial cytotoxicity irrespective of NAC concentration.Conclusions: The effects of NAC incorporation were strongly dependent on the photoinitiator system employed. While NAC consistently reduced oxidative stress, this effect did not translate into a substantial improvement in cellular metabolic activity. These findings indicate that ROS scavenging alone is insufficient to overcome monomer-related cytotoxicity and further demonstrates the importance of simultaneously evaluating polymerization behavior, material performance, monomer release, and biological response when developing multifunctional methacrylate-based biomaterials.

Source: Journal of the mechanical behavior of biomedical materials/Journal of mechanical behavior of biomedical materials

DOI: 10.1016/j.jmbbm.2026.107638

Authors: Matthieu Gilli, Lene A. Grutle, S. Bebelman, Silvio Uhlig, Hilde B.M. Kopperud, Julian G. Leprince

Institutions: Cliniques Universitaires Saint-Luc, UCLouvain, Nordic Institute of Dental Materials, University of Geneva

Language: English

Topic: Dental materials and restorations

Subfield: General Dentistry

Field: Dentistry

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,690