In situ evaluation of color stability and hardness' decrease of resin-based composites.

Objective: To determine the color stability (CS) and hardness' decrease (HD) of two commercial resin-based composites (RBCs), after in situ staining conditions (SC).

Methods: Six disc-shaped specimens (6 × 2 mm) of two RBCs-Filtek Z350 XT (FZX) and IPS Empress Direct (IED)-were randomly distributed into palatal devices. Eight volunteers (aged 20-30 years) participated in this study. The in situ SC consisted of 400 mL consumption (2 × 200 mL/day) of water, orange juice, cola soda, and coffee and 140 mL consumption of red wine, 10 days each. CS was obtained by CIELAB color difference (ΔE*) and HD (in %) by the Knoop method (50 g for 15 s), after curing (baseline) and after the in situ SC. Data were statistically analyzed at α = 0.05 significance level.

Results: For both RBCs, the coffee (5.7 ± 0.5 for FZX; 5.9 ± 1.3 for IED) and red wine (6.1 ± 1.1 for FZX; 6.2 ± 1.6 for IED) groups showed the highest ΔE* while water the lowest (1.6 ± 0.6 for FZX; 1.8 ± 0.2 for IED). The highest HD was induced by red wine group for FZX (40.7 ± 5.4) and by cola soda for IED (40.6 ± 3.2) while the water groups (8.3 ± 1.7 for FZX; 7.8 ± 2.1 for IED) presented the lowest values for both RBCs.

Conclusion: Both RBCs were affected by the in situ SC, but no significant differences for CS and HD were observed between them. Red wine and coffee showed higher discoloration potential.

Clinical Significance: This in situ study suggests that color stability and hardness' decrease of resin-based composites were dependent on the type of consumed beverage and materials' composition. Patients with esthetic direct restorations should be aware of the degradative potential of them.