79 FUNDAMENTAL RESEARCH Volume 34, Number 1, 2021 Correspondence to: Dr Sven Mühlemann University of Zurich, Center of Dental Medicine, Clinic of Reconstructive Dentistry Plattenstrasse 1, CH-8032 Zurich, Switzerland Fax: +41 44 634 34 54 Email: sven.muehlemann @zzm.uzh.ch Submitted March 24, 2020; accepted July 1, 2020. ©2021 by Quintessence Publishing Co Inc. Purpose: To measure the effect of simulated aging on stained resin-ceramic CAD/CAM materials regarding the durability of color and gloss. Materials and Methods: Test specimens (n = 15 per material) were prepared out of CAD/CAM ingots from two resin nanoceramics (Lava Ultimate [LVU], Cerasmart [CER]) and a polymer- infltrated ceramic (ENA, VITA Enamic) stained with the manufacturer’s recommended staining kit using photopolymerization. Control specimens were made of feldspathic ceramic (VITA Mark II [VM2]) and stained by means of ceramic fring. Negative control specimens (n = 15) (no staining) were prepared for each group. Color and gloss measurements were performed before and after each aging cycle by means of mechanical abrasion with a toothbrush. Groups were compared using Kruskal-Wallis test and paired post hoc Conover test. Changes within a group were calculated using Wilcoxon signed-rank test (α = .05). Results: The color difference (∆E) was statistically signifcant for all stained CAD/CAM materials after simulated aging: CER (P < .001, 95% CI: 2.96 to 3.69), LVU (P = .004, 95% CI: 1.09 to 1.46), ENA (P = .004, 95% CI: 0.20 to 0.42), and VM2 (P < .001, 95% CI: 0.29 to 1.08). Aging resulted in a statistically signifcant increase in gloss in the LVU group (P < 0.001, 95% CI: 13.78 to 17.29), whereas in the ENA (P < .001, 95% CI: 7.83 to 12.72), CER (P < .001, 95% CI: 2.69 to 8.44), and VM2 (P = .014, 95% CI: 0.22 to 1.87) groups, a signifcant decrease in gloss was noted. Conclusion: Color and gloss of stained resin-ceramic CAD/CAM materials changed signifcantly after aging by means of toothbrush abrasion in vitro. Int J Prosthodont 2021;34:79–87. doi: 10.11607/ijp.7019 Change in Color and Gloss Parameters of Stained Monolithic Resin-Ceramic CAD/CAM Materials After Simulated Aging: An In Vitro Study Sven Mühlemann, PD Dr Med Dent Sofia Stromeyer, Med Dent Alexis Ioannidis, Dr Med Dent Clinic of Reconstructive Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland. Thomas Attin, Prof Dr Med Dent Clinic of Conservative and Preventive Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland. Christoph HF Hämmerle, Prof Dr Mutlu Özcan, Prof Dr, PhD Clinic of Reconstructive Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland. T he esthetic success of an indirect restoration represents a signifcant challenge in reconstructive dentistry, as the color and surface quality of a restoration should ideally match the optical properties of the neighboring dentition. Today, a variety of reconstructive materials are available depending on the amount of tooth substance that needs to be replaced and the design of the restoration. 1 Traditionally, all-ceramic restorations are designed with a combination of two lay- ers of ceramic material, including a core material and a veneer layer. The core and ceramic veneer materials are available in a wide range of colors and different grades of translucencies, infuencing the esthetic outcome of a restoration. 2,3 Dental techni- cians face a challenge when selecting the correct material to achieve an optimal color match of the restoration with the natural tooth. 4–6 Additionally, it is a time-consuming fabrication process. CAD/CAM technologies have increased time effciency for the processing of ceramic materials. 7,8 At the same time, this technology has enabled the chairside fabrication of indirect monolithic restorations. These monochromatic ceramic or resin-ceramic restorations, © 2021 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART M AY BE REPRODUCED OR TRANSM ITTED IN ANY FORM WITHOUT WRITTEN PERM ISSION FROM THE PUBLISHER.