Effect of Home Bleaching Agent on CAD-CAM Materials’ Long-Term Aesthetics

Objectives: To assess the effect of home bleaching agents on surface properties and long-term aesthetic performance of different CAD-CAM materials.
Methods: Four types of CAD-CAM materials were investigated: Polymer Infiltrated Ceramic Network (PICN) (Vita Enamic-VE), resin composite CAD-CAM (Lava™ Ultimate-Lava), glass ceramic (IPS e.max CAD-E-max) and zirconia ceramic (IPS e.max zirCAD-Zir) (n=9). All CAD-CAM blocks were sliced into 1 mm thickness. The sample was polished via a polishing machine under constant water cooling. Three times home bleaching agent (Opalescence^TM PF15%) applications were applied for 6 h in three days, with an interval of 12 h. At 24 h after the 3rd bleaching application, a total of 20,000 thermal cycles were carried out. Surface gloss, microhardness and CIELab values were measured before bleaching, after 1st/2nd/3rd bleaching, 24 h after bleaching and after 10,000/20,000 thermal cycles using a glossmeter, micro-hardness instrument and a digital spectrophotometer, respectively. SEM analysis of specimens before bleaching, at 24 h after bleaching and control-group specimens (only bleached, only thermal cycled and without any treatment) were performed. Data were statistically analysed using One-way ANOVA, independent T-test and Tukey’s post-hoc (p<0.05).
Results: The gloss of the tested materials decreased following home bleaching, albeit VE remained relatively stable. Compared to the control groups, the gloss of the bleached specimens did not greatly change, except for ZirCAD, which had higher gloss values than the control group. Lava and ZirCAD had the lowest and highest VHN results, respectively. After home bleaching, VHN results of VE and Lava significantly decreased, while E-max and ZirCAD showed minor variation. The material-dependent ΔE-TP correlations illustrated that the aesthetic properties of Lava significantly changed after home bleaching and thermal cycles.
Conclusions: Overall, bleaching agents may interact with CAD-CAM materials’ aging. ZirCAD demonstrated the most stable aesthetic properties after simulating home bleaching application and 2-year-aging mimicked by the thermal cycle.