Evaluating the Depth of Cure under Chemical and Dual Cure Modes in Novel Biosustainable Dual Cure Flowable Composites Reinforced with Rice Husk Nanohybrid Silica

Abstract

Dual-cure composites are designed to achieve increased depth of cure through the synergistic action of both chemical and light-activated initiator systems. Due to these enhanced curing properties, they are widely used as core buildup and luting agents. The present study aimed to evaluate and compare the depth of cure of newly formulated dual-cure flowable composites prepared with varying ratios of base and diluent monomers. The evaluation was conducted under two curing conditions: light curing (dual-curing mode) and without light curing (chemical curing mode). The newly formulated dual-cure flowable composites incorporated nanohybrid silica derived from rice husk as the filler material. The experimental groups consisted of two formulations with bisphenol A-glycidyl methacrylate (Bis-GMA) to triethylene glycol dimethacrylate (TEGDMA) ratios of 50:50 and 30:70, two groups with urethane dimethacrylate (UDMA) to TEGDMA ratios of 50:50 and 30:70, and one group combining Bis-GMA, UDMA, and TEGDMA in a 25:25:50 ratio. Paracore Slow was utilized as the control material. Depth of cure was assessed employing the ISO 4049 scraping method. Statistical analysis of the results was performed using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test for multiple comparisons. All formulations containing urethane dimethacrylate (UDMA) exhibited higher mean depth of cure values. The group with a UDMA to TEGDMA ratio of 30:70 demonstrated the greatest depth of cure among all tested groups. Moreover, every group exceeded the minimum depth of cure threshold established by ISO standards. Notably, depth of cure measurements were consistently higher under chemical curing conditions across all groups. In conclusion, the enhanced depth of cure observed in the novel DCFCs supports their potential application as sustainable dental restorative materials, contingent upon further comprehensive evaluation.