Effect of Successive In-office and At-home Bleaching Protocols on the Surface Properties of CAD/CAM Materials.

Although the effects of in-office and at-home bleaching on the surface properties of CAD/CAM monolithic materials have been extensively explored, their combined effect has not yet been investigated. This study evaluated the effects of different bleaching modalities, including a combination of in-office and at-home beaching in up to three sessions on the roughness, microhardness, and surface topography of five CAD/CAM materials. Disks of a resin nanoceramic (Lava Ultimate, Solventum, St. Paul, MN, USA), a polymer-infiltrated ceramic network (Vita Enamic, Vita Zahnfabrik, Bad Säckingen, Germany), a leucite-reinforced glass-ceramic (IPS Empress CAD, Ivoclar Vivadent, Schaan, Liechtenstein), a lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent), and a zirconia-reinforced lithium silicate glass-ceramic (Vita Suprinity, Vita Zahnfabrik) were subjected to: 1) in-office bleaching with 35% hydrogen peroxide (Whiteness HP Blue, FGM Dental Group, Joinville, Santa Catarina, Brazil) (35% HP), 2) at-home bleaching with 10% carbamide peroxide (Opalescence PF, Ultradent, South Jordan, UT, USA) (10% CP), and 3) a combined protocol of in-office bleaching followed by at-home bleaching. Roughness arithmetical mean height (Sa) (n=12/group), microhardness (n=10/group), and topography (n=2/group) were evaluated before treatment and after the first, second, and third sessions. Data were submitted to mixed repeated measures analysis of variance (ANOVA) (α=0.05). Except for Lava Ultimate and Vita Suprinity, which showed progressive topographic alterations, 35% HP did not affect roughness, microhardness, or topography of any of the materials; 10% CP and the combined protocol caused topographic alterations in all materials. The 10% CP increased roughness of Vita Enamic (from the second session), IPS Empress CAD (from the first session), and IPS e.max CAD and Vita Suprinity (in the third session), and decreased microhardness of IPS Empress CAD (in the third session) and IPS e.max CAD (from the second session). The combined protocol increased roughness (from the second session) and decreased microhardness (in the third session) with IPS Empress CAD. The 35% HP affected the topography of Lava Ultimate and Vita Suprinity and was the safest bleaching protocol for the other materials, regardless of number of sessions. The 10% CP affected both roughness and microhardness of the materials most adversely and, together with the combined protocol, caused topographic changes to all materials.