117 - Comparison of Discoloration in Universal Shade and Conventional Resin-based Composites

M Maesako; M Fujitani; A Tsujimoto

doi:10.1016/j.dental.2025.01.130

Purpose / Aim: To sustain the color in universal shade resin-based composites, it is necessary to preserve a designed structure within the composites without any deterioration. Degradation of the resin matrix and failure of the bond between matrix and filler may both disrupt this designed structure. Thus, these composites need resin matrices that are resistant to degradation and a tight bond between the matrix and the filler to avoid discoloration. These properties would also be expected to lead to high mechanical properties. However, it has been reported that the mechanical properties of universal shade resin-based composites are similar or inferior to conventional resin-based composites. This might suggest that universal shade resin-based composites are more vulnerable to discoloration. The purpose of this study is to compare the degree of discoloration of conventional and structurally colored resin-based composites. Materials & Methods: The resin-based composite used in this study were a conventional resin-based composite, Clearfil AP-X (Kuraray Noritake Dental, Tokyo, Japan, AP-X), and a universal shade resin-based composite, Omnichroma (Tokuyama Dental, Tokyo, Japan, OC). Blocks (10 mm x 20 mm x 4 mm) of each composite were prepared. One surface (10 mm × 20 mm) of each block was mirror polished and immersed in a black tea solution prepared at 37°C for 7 days. The color of the polished surface before and after immersion was measured using a dental spectrophotometer (Rayplicker Handy, Borea, Limoges, France), and the color difference in ΔE*ab was calculated. Subsequently, an alkali acceleration test was conducted to reproduce aging degradation, and the degree of discoloration of the alkaline-degraded surface before and after immersion in tea solution was measured. Finally, the degraded layer was removed by repolishing and the degree of discoloration of the refurbished surface before and after immersion in tea solution was measured. The color difference for each composite under the three conditions was examined by two-way ANOVA (α = 0.05). Results: The two-way ANOVA revealed that material and condition were significant factor on discoloration. There were significant differences in ΔE*ab between AP-X and OC and the values of OC were significantly higher than those of AP-X under all conditions (p<0.001). ΔE*ab of AP-X and OC in alkaline-degraded condition showed significantly higher than those of mirror-polished and refurbishing conditions (p<0.001). Conclusions: These results suggest that the structural and compositional differences between conventional and universal shade resin-based composites have a systematic influence on vulnerability to discoloration.

117 - Comparison of Discoloration in Universal Shade and Conventional Resin-based Composites

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