Objective: This study aimed to investigate the effects of bleaching on the color, translucency, surface roughness, and surface hardness of monolithic zirconia with external stainin .
Methods: In this experimental study, 32 specimens of monolithic zirconia (1 × 1 mm; shade A2) were divided into two groups based on random permuted blocks. Overglaze and staining procedures were performed with a yellow stain or a value stain (GC Stain). Baseline color, translucency, roughness, and surface hardness were measured. The specimens were then randomly bleached with hydrogen peroxide (HP) 40% (20 min, twice with a 1-week interval in between) as office bleaching or carbamide peroxide (CP) 20% (4 h per day for 14 days) as home bleaching. Finally, the color, translucency, surface roughness, and surface hardness were measured again.
Results: Bleaching with CP and HP caused a perceptible change in the color of the specimens (ΔE > 2), although this change was within the clinically acceptable range (ΔE < 3.3). HP significantly reduced the surface hardness of the specimens (p = 0.043). Changes in surface roughness of the specimens were neither statistically nor clinically significant (p = 0.19 and p = 0.25 for office and home bleaching, respectively).
Conclusion: The effects of home and office bleaching on the surface characteristics of monolithic zirconia were almost the same. It is not necessary to exchange or even to polish the surfaces of zirconia restorations after exposure to bleaching agents. Further studies are recommended to confirm the color stability of externally stained monolithic zirconia.
Keywords: color stability; externally stained ceramics; monolithic zirconia; surface hardness; surface roughness; translucency.
© 2021 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.