The effect of simulated toothbrushing with regular and whitening dentifrices on the colour stability of high translucency zirconia.

BACKGROUND: High translucency zirconia (HTZ) restorations are increasingly used for aesthetic dental applications due to their superior optical properties. However, colour stability under routine oral hygiene procedures, especially toothbrushing with regular or whitening dentifrices, remains a clinical concern. This study evaluated the effect of simulated toothbrushing on the colour stability (ΔE) of two different HTZ materials. METHODS: Sixty unglazed and unpolished HTZ samples (10 mm × 2 mm) were fabricated using Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) technology and divided into two groups based on translucency (HTZ-A: 5.8-9.7 wt% yttria and HTZ-B: 4.4-5.5 wt% yttria; n = 30 each). Each group was subdivided into three subgroups (n = 10) according to the treatment: artificial saliva (control), regular dentifrice and whitening dentifrice. Baseline colour measurements were recorded using a reflectance spectrophotometer. Specimens underwent simulated toothbrushing or storage in artificial saliva for 520 min, simulating approximately 17 years of brushing. Colour differences (ΔE) were calculated using the CIELAB system. Data were analysed using one-way Analysis of Variance (ANOVA), Tukey's post-hoc test and independent t-tests. RESULTS: Artificial saliva caused minimal colour change in both zirconia groups (ΔE = 1.677 for HTZA, 1.802 for HTZB). Regular dentifrice induced significant ΔE values (HTZ-A: 8.722, HTZ-B: 8.346), while whitening dentifrice caused a significantly highest colour change for HTZ-B (HTZ-A: 6.348, HTZ-B: 11.062). Pairwise comparison revealed significant differences among all subgroups (p < 0.05). Intergroup analysis showed a significant difference between HTZ-A and HTZ-B only in the whitening dentifrice subgroup (p = 0.0001). CONCLUSION: Simulated toothbrushing significantly affects the colour stability of HTZ restorations. Whitening dentifrices produced the greatest colour change in highly translucent zirconia. Material composition and dentifrice selection should be considered to maintain long-term aesthetics of zirconia restorations.