The Influence of Salivary Contamination During Light Curing on Degree of Conversion and Color Stability of Two Composite Resins Publisher

Summary: Early saliva contamination can drastically lower the polymerization efficiency of dental composites. Could optimal curing techniques help restore it? Study shows promise! #DentalResearch #Polymerization

Rohaninasab M ; Falahat S ; Tayebi G ; Manouchehri F ; Mahounak FS
Source: Journal of Oral Biology and Craniofacial Research Published:2026

Abstract

Background: Adequate polymerization of composite resin restorations is critical for their mechanical performance and long-term clinical success. Salivary contamination during light curing can interfere with polymerization and may influence color stability. Objective: This in vitro study examined how artificial saliva contamination at specific intervals during light curing affects the DC (degree of conversion) and short-term color change or ΔE (Delta E) of two composite resins—Gradia Direct (microhybrid) and N-Ceram Bulk Fill (nanohybrid). Methods: One hundred eighty disk specimens (n = 90 per composite) were allocated into nine experimental groups differing in contamination timing and curing duration. DC was determined by FTIR-ATR (Fourier-Transform Infrared- Attenuated Total Reflectance) spectroscopy immediately after curing and following 24-h incubation at 37 °C. Color change (ΔE) was measured with a spectrophotometer using the CIE (International Commission on Illumination) Lab∗ system. Statistical analysis employed one- and two-way ANOVA (Analysis of Variance) with Tukey's post hoc test (α = 0.05). Results: Early contamination (within the first 5–10 s) produced a significant reduction in DC for both materials (p < 0.001), with N-Ceram showing the greatest loss. Gradia achieved higher DC across most conditions. Post-cure incubation improved DC in all groups, most notably in N-Ceram. All ΔE values remained below the perceptibility threshold of 3.3, with no significant differences among groups (p > 0.05). Conclusion: Saliva exposure early in light curing markedly reduces polymerization efficiency, although extended curing and post-cure polymerization can partially restore DC. Short-term color stability appears unaffected. Strict field isolation and optimized curing protocols are essential to maximize clinical performance. © 2025 The Authors. Published by Elsevier B.V. on behalf of Craniofacial Research Foundation. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/