SUMMARY Little is known about the effects of in-office bleaching on the surface properties and on other aspects of CAD-CAM monolithic materials, especially when successive bleaching sessions are conducted. This study evaluated the effect of up to three successive in-office bleaching sessions on the microhardness, roughness, topography, substance loss, biaxial flexural strength (BFS), and reliability of CAD-CAM monolithic materials. Disks from Lava Ultimate (LU), Vita Enamic (VE), and IPS Empress CAD (EMP) were fabricated and submitted to one, two, and three bleaching sessions. In-office bleaching was performed with 40% hydrogen peroxide and each session consisted of three applications of 20 minutes each. The analyses regarding the aforementioned parameters were assessed before and after the first, second, and third bleaching sessions, except for BFS, which was evaluated at the baseline and after the third session. Weibull modulus was calculated from the BFS data. Bleaching decreased the microhardness of LU and VE from the third and second sessions, respectively, and affected neither the roughness nor the BFS of the three materials. However, in LU, it decreased the reliability and caused topographic changes, which were accentuated by the increase in the number of sessions. In general, LU and EMP showed, respectively, the highest and the lowest substance losses. Successive in-office bleaching sessions with the use of the protocol of the present study should be avoided in LU and VE.

SUMMARY Little is known about the impact of bleaching on the optical properties of computer-aided design and computer-aided manufactured (CAD-CAM) monolithic materials. The aim of the present study was to evaluate the effect of one session of in-office bleaching on stain removal, staining susceptibility, translucency, and whiteness variations of CADCAM monolithic materials. Disks were fabricated from Lava Ultimate (LU), Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS). A spectrophotometer was used to register Commission Internationale de l’Eclairage L*a*b* coordinates. For stain removal, 80 specimens from each material were assessed at baseline (R0) and after immersion in deionized water or coffee for 365 days followed or not by bleaching with 40% hydrogen peroxide (R1). For staining susceptibility, 80 specimens from each material were analyzed at baseline (R0’), and after having been bleached or not and immersed in deionized water or coffee (R1’). Both analyses were calculated as the color difference (ΔE00) between R1-R0 and R1’-R0’, respectively. Differences in translucency (ΔTP00) and whiteness (ΔWID) between R1-R0 and R1’-R0’ were also calculated. Data were analyzed by three-way ANOVA and the Games-Howell post hoc test (α=0.05). Clinical significance was based on 50%:50% perceptibility and acceptability thresholds for ΔE00, ΔTP00 and ΔWID, respectively. Surfaces were analyzed by scanning electron microscopy. Coffee increased ΔE00 in LU, VE, and VS, and decreased their translucency and whiteness, whereas the IPS had only its whiteness affected. Bleaching after immersion in coffee decreased ΔE00 in LU and VE, and increased translucency and whiteness of LU, VE, and VS. No effect was observed on IPS. Bleaching before immersion in coffee decreased translucency of LU, but within the acceptable interval, while VE exhibited lower ΔE00, and became more translucent and less dark. Both VS and IPS were not affected. One session of in-office bleaching benefited optical properties of the previously stained LU, VE, and VS, without increasing their susceptibility to staining or adversely providing clinically unacceptable variations in their translucency and whiteness. All variations exhibited by the IPS were below the perceptible threshold.

SUMMARY The effect of annual at-home bleaching on the color, translucency, and whiteness properties of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials requires investigation. The aim of the present in vitro study was to evaluate the effect of simulated annual at-home bleaching (consisting of daily applications for 10 hours a day for 14 days), for up to 3 years, on susceptibility to staining (ΔE00), translucency (ΔTP00), and whiteness (ΔWID) variations and on topography of CAD-CAM monolithic materials. Disks from the Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), and IPS e.max CAD (EMAX) were allocated as follows: 1) nonbleached or 2) bleached with 10% carbamide peroxide. After reading the CIE L*a*b* coordinates at baseline (R0), specimens were bleached or not and subsequently immersed for a 1-year simulated period in coffee before the next reading (R1). This process was repeated two more times, resulting in R2 and R3. The ΔE00, ΔTP00, and ΔWID between R1, R2, and R3 in relation to R0 were calculated. The surface topography was analyzed by scanning electron microscopy. In general, bleaching increased the staining susceptibility of all materials when compared to the nonbleached groups and that of the LU, VE, and EMAX over the years. Bleaching decreased the translucency of the VE in all years and over the years. When compared to the nonbleached groups, bleaching decreased the whiteness of the LU and EMAX and increased the whiteness of the EMP, while the VE was not affected. In the LU, the whiteness decreased over the years in both treatments, whereas the other materials were not affected with time. All materials showed progressive topographic changes over the years. The simulated annual at-home bleaching with 10% carbamide peroxide adversely affected the topography and the optical and/or colorimetric properties of the evaluated materials.