Toothbrushing’s Effect on the Color of Extrinsically Stained Monolithic Zirconia

Objectives: Full contour zirconia restorations are opaque white with minimal translucency. External staining is often used to match the natural teeth. The aim of this study is to test the effect of toothbrushing on extrinsically stained monolithic zirconia and to evaluate the protective potential of glazing.
Methods: Two brands of monolithic zirconia were used in this study: Vita InCeram YZ and Sirona inCoris TZI. Zirconia blocks were sectioned into tiles (15.5mm × 19mm × 4mm) and stained with: A. Vita Akzent spray stain/glaze; or B. Zirlux Full Characterization and Staining kit (Zirlux FC). Glaze was applied to 50% of stained specimens. A mechanical toothbrushing simulator replicated abrasion by toothbrushing with dentifrice using Colgate Extra-Clean toothbrush and Sensodyne Extra-Whitening toothpaste. Specimens were exposed to 20,000, 40,000, and 60,000 brushing cycles, representing 2, 4, and 6 years of toothbrushing. Results were calculated from reflective color measurements by spectrophotometer (Color i5, GergtagMacbeth) before and after brushing.
Results: Shown in figures below.
Conclusions: Glazing can be essential to protect stained monolithic zirconia exposed to toothbrushing. Color change caused by brushing of unglazed zirconia restorations may be clinically relevant. Glazing seems to increase the longevity of the external stains. Although ΔE is significant, the color changes is beyond visual perception and crowns may last 20 years or more with discoloration becoming more visible.