Physicomechanical Properties of a Technical Polyethylene Glycol-Silica-Based Hydrogel as an Alternative Low Shrinkage Dental Polymer Composite

Abstract

Dental composite resins are widely used in restorative dentistry; however, polymerization shrinkage leads to marginal gaps and reduced bond strength. An expandable hydrogel monomer can reduce shrinkage, but it may lack sufficient mechanical strength when used alone. This study developed a low-shrinkage dental composite by incorporating an expandable hydrogel monomer to counteract volumetric shrinkage after curing, aiming to maintain strong bonding to tooth structure. Polyethylene glycol 400 (PEG 400) was chemically modified with acryloyl chloride to produce diacrylated polyethylene glycol 400 (DAPEG 400) expandable hydrogels, which was formulated with silica filler loadings by weight. Statistical analysis involved the Shapiro–Wilk test and one-way ANOVA. A synthesized expandable monomer with good polymerization shrinkage properties and the incorporation of silica filler significantly enhanced the mechanical properties compared to pure cured DAPEG 400, with flexural and compressive strengths reaching 10.27 MPa (standard deviation (SD) = 0.96) and 441.42 MPa (SD = 2.80), respectively. The composite also demonstrated improved dimensional stability, showing 475.32 μg/mm3 (SD = 22.76) reduction in water absorption and 33.37% (SD = 2.26) decrease in volumetric swelling. Most notably, the optimal formulation containing 60% filler exhibited minimal polymerization shrinkage as low as 1.58% (SD = 0.24). The hydrogel’s water absorption and expansion after curing offset polymerization contraction, while silica filler regulates expansion to prevent cracking.