Influence of Surface Treatment on the Color Stability and Microhardness of Two Nanohybrid Enamel Shade Resin Composites: An In-Vitro Study.

Background: Oxygen-inhibited layer (OIL) is formed due to inadequate polymerization of resin composite (RC), which compromises its physical and mechanical properties.

Aim: This study focuses on analyzing the impact of different OIL control surface treatments on the color stability and microhardness of enamel shade RC.

Methods: Discs (n = 240) were prepared out of two different types of nanohybrid enamel shade RCs, G-aenial A'CHORD (group AC) and Beautifil II Enamel (group BT). After allotting 60 samples each for the two experiments on color stability using spectrophotometer and surface microhardness using Vickers microhardness tester, they were further divided into four subgroups of 15 each based on the OIL control surface treatments: glycerin (G), mylar strip (M), finishing and polishing (FP), and no treatment (NT).

Results: Group AC showed the least ∆E (color difference) values in subgroup M with statistical significance (one-way ANOVA; P = 0.001). However, group BT showed lesser ∆E in subgroups M and G (one-way ANOVA; P = 0.001). Between groups, AC showed significantly lower ∆ E and a higher mean hardness value (HV) than BT. The subgroup FP of both groups exhibited relatively high values (Tukey post-hoc; P = 0.001). The subgroup M showed the least ∆ E, and the subgroup FP showed the highest HV in both groups.

Conclusion: G-aenial A'CHORD showed relatively superior color stability and microhardness than that of Beautifil II Enamel. Finishing and polishing improved the microhardness of both the enamel shade RCs.