Preparation and evaluation of a ternary thiol-yne-dimethacrylate dental resin composite exhibiting low stress and high mechanical performance.

OBJECTIVES

This study aimed to comparatively evaluate whether the incorporation of multifunctional thiol‑ene or thiol‑yne resin systems into conventional dimethacrylate‑based DRCs offers greater advantages in achieving both low polymerization shrinkage stress and high mechanical strength. The first hypothesis was that increasing the thiol‑ene and thiol‑yne content would promote the interaction between dimethacrylates and the thiol‑ene or thiol‑yne reaction pathways, thereby reducing polymerization shrinkage stress while maintaining adequate mechanical properties. The second hypothesis was that dimethacrylate‑based DRCs incorporating thiol‑yne components would exhibit superior overall mechanical properties compared to those containing thiol‑ene components.

METHODS

Polymerization kinetics and methacrylate double bond conversion were quantified using Fourier-transform infrared spectroscopy (FTIR). Dynamic mechanical analysis (DMA) was used to determine dynamic mechanical properties. The mechanical properties of the cured DRCs were comprehensively assessed through three-point bending tests, compression tests, diametral tensile tests, Vickers microhardness, and fracture toughness tests. Shrinkage stress during DRC curing was monitored in real-time using a universal testing machine's stress sensor. Finally, the biocompatibility of the DRCs was verified using the CCK8 assay.

RESULTS

The results indicated that incorporating thiol-ene or thiol-yne mixtures as resin components into conventional dimethacrylate resins synergistically combined the excellent mechanical properties of dimethacrylates with the reduced shrinkage stress advantage of thiol-ene/yne systems via improved polymerization kinetics through step-growth polymerization. Among these systems, ternary thiol-yne-dimethacrylate DRCs outperformed ternary thiol-ene-dimethacrylate DRCs in terms of mechanical properties due to a more highly crosslinked network formed by the thiol-yne components. At high thiol-yne content, ternary thiol-yne-dimethacrylate DRCs exhibited a 50.3-75.3% reduction in shrinkage stress compared to conventional dimethacrylate DRCs, while maintaining adequate mechanical properties. Additionally, the flexural strength of the DRCs improved by 22.5-37.1%.

SIGNIFICANCE: The ternary thiol-yne-dimethacrylate DRCs developed in this study hold the potential to significantly reduce polymerization shrinkage stress, enhance mechanical strength and other fundamental properties of DRCs, leading to superior dental restorative materials.