Effect of artificial aging on colour stability and surface analysis of filtek Z350XT and omnichroma

Millions of people consume coffee daily, subjecting dental restorations to staining and physico-chemical degradation. Dental composite resins are especially susceptible to acidic or staining nature of coffee which compromises long-term aesthetics and durability. Objectives: To elucidate the comparative effect of coffee between thermocycling and static immersion, as artificial aging methods on dental composite resins. Then, to compare color changes (∆E00) between Filtek Z350XT and Omnichroma following thermocycling within coffee solution. Next, to evaluate and compare the subsurface properties and surface microhardness of Filtek Z350XT and Omnichroma after immersion in coffee staining solution using SEM-EDS analysis and Vicker’s hardness test, respectively. Methods: Phase 1: 40 discs (1mm thick x 10mm diameter) of Filtek Z350XT were prepared and divided into 2 groups: thermocycling and static immersion, with 2 immersion solutions (n=10) – coffee (TC: Thermocycled Coffee, SC: Static Coffee) and distilled water (TDW: Thermocycled Distilled Water, SDW: Static Distilled Water). Color measurements were obtained using a spectrophotometer at 20 time points and analyzed. Phase 2: 20 new discs were prepared from Filtek Z350XT (n=10) and Omnichroma (n=10). The specimens were subjected to 10,000 cycles in coffee and color changes were studied. Phase 3: Filtek Z350XT and Omnichroma were evaluated for post-staining surface morphology and mechanical properties. Results: Pearson Correlation Analysis showed no significant association between ∆E00 and standardized Surface Roughness. Phase 1: Repeated Measure Anova revealed significant differences across all groups (p<0.001). Post hoc Tukey’s test indicated significantly higher color changes between (TC) and (SC), (TC) and (TDW), as well as (TC) and (SDW). However, no significant differences were observed between SDW and TDW (p>0.001). Phase 2: An independent t-test demonstrated a significant difference in ∆E00 values between Filtek Z350XT and Omnichroma (p<0.001), with Omnichroma exhibiting significantly higher ∆E00. Phase 3: SEM and EDS analyses revealed significant changes in the surface morphology and elemental composition of the composites after thermocycled in coffee solution. Regardless of materials investigated, Wilcoxon Signed Rank Test showed no significant differences in median Vicker’s Hardness Number (VHN) before and after immersion. Conversely, the Mann- Whitney Test indicated a significant difference (p=0.05) between the groups, with Filtek Z350XT exhibiting a higher median VHN (195) compared to Omnichroma (114.4). Conclusions: Coffee significantly influenced the staining of dental composite resins. Thermocycling causes pronounced color changes when compared to static immersion, with Omnichroma elucidating a higher ∆E00. Filtek Z350XT exhibited superior colour and surface stability despite changes observed after thermocycling.