The effect of bleaching on the optical and physical properties of externally stained monolithic zirconia

Abstract

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 Â 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.

The Effect of Home and In-Office Bleaching on Microhardness and Color of Different CAD/CAM Ceramic Materials

“…Concerning ceramic materials, the effects of bleaching on surface roughness, color, and microhardness are not consistent among studies and appear to be dependent on the type of ceramic material, the method of surface treatment (whether autoglazed, overglazed, or polished), and the concentration and application time of the bleaching agent [ 7 ]. Monolithic glazed zirconia was recently investigated and showed no significant changes in surface roughness and color, but demonstrated a significant reduction in microhardness after HP in-office bleaching [ 8 ].…”

Clinical outcomes of tooth-supported monolithic zirconia vs. porcelain-veneered zirconia fixed dental prosthesis, with an additional focus on the cement type: a systematic review and meta-analysis

“…Monolithic zirconia restorations were defined as those with the same chemical and physical properties throughout its thickness [ 9 ]. These are dental prostheses with a bulk of zirconia fabricated by computer-aided design and computer-aided manufacturing (CAD/CAM) and painted with external stains [ 4 ].…”

“…There are today two main categories of dental prostheses made of Y-TZP: monolithic zirconia (MZ), in which the bulk of the restorations is made of zirconia and external stains are painted in order to better copy the natural colors of teeth, and porcelain-veneered zirconia (PVZ), in which a framework of zirconia is fabricated, upon which veneering porcelain is applied [ 4 ]. Prostheses made of MZ are stronger, but present a compromised aesthetic aspect, while PVZ prostheses, with a core of Y-TZP and an outer layer of ceramic (also called as bilayer structure), better resemble natural teeth, although are vulnerable to chipping and delamination [ 2 ].…”