  Citation: Porojan, L.; Vasiliu, R.D.; Porojan, S.D. Masking Abilities of Dental Cad/Cam Resin Composite Materials Related to Substrate and Luting Material. Polymers 2022, 14, 364. https://doi.org/10.3390/ polym14030364 Academic Editor: Evangelia Vouvoudi Received: 21 December 2021 Accepted: 15 January 2022 Published: 18 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). polymers Article Masking Abilities of Dental Cad/Cam Resin Composite Materials Related to Substrate and Luting Material Liliana Porojan 1 , Roxana Diana Vasiliu 1, * and Sorin Daniel Porojan 2 1 Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, “Victor Babes , ” University of Medicine and Pharmacy Timis , oara, Eftimie Murgu Sq. no. 2, 300041 Timis , oara, Romania; sliliana@umft.ro 2 Department of Oral Rehabilitation (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, “Victor Babes , ” University of Medicine and Pharmacy Timis , oara, Eftimie Murgu Sq. no. 2, 300041 Timis , oara, Romania; porojan.sorin@umft.ro * Correspondence: roxana.vasiliu@umft.ro Abstract: An outstanding treatment challenge related to aesthetic monolithic materials is to mask discolored substrates in aesthetic areas. The purpose of the study is to evaluate the substrate masking ability of different resin composite materials and the influence of their association with luting agents and substrates. Five types of 2M2 HT (high translucency) resin composite materials were selected: Vita Enamic [E] and four types of nanoparticle-filled composites Lava Ultimate [L], Cerasmart [C], Shofu HC [S], and Hyramic [H]. Resin composite Vita VM LC with different shades was used for the substrates: 2M2, 3M2, and CP2. Variolink Esthetic Try-inpastes neutral, light+, and warm+ colors were chosen to simulate the luting agent color. Optical parameters (TP (translucency), CR (contrast ratio), and OP (opalesce)) and color differences ΔE (chromatic difference) were calculated. Statistical analyses were performed to evaluate the comparisons between the groups and establish correlations. TP average values for all materials were in the range of 21.49–24.53. OP average values were in the rage of 6.31–7.85. OP is moderate positive correlated to TP and CR is negative and strong correlated to TP. Related to materials, average color changes decrease as following: E > H > C > L > S. Referring to the tryin material, warm colors induce marked color changes of the restoration. The differences of the color changes determined by all studied substrates are significant. For the final aesthetic aspect of the restoration, it is essential to consider the underlying dental structure, luting agent, and restoration material as a whole unit. The masking ability of the investigated resin matrix ceramic materials materials shows differences, the best behavior demonstrated Shofu HC and Lava Ultimate. Marked color changes are related to high chroma substrates. For substrates with a darker color, the association with warm try-in pastes lead to marked color changes, but with neutral and light try-in pastes at most perceivable. Keywords: resin-composite; masking ability; luting material; substrate 1. Introduction Due to the fact that patients’ requirements for aesthetic dental restorations are in- creasing, different material options have to be considered. Taking into account the fact that the trends towards monolithic restorations are more and more obvious, several types of materials have been developed for these purposes. Besides established ceramics and composite, the new generation of materials, resin matrix ceramic materials materials, a compound of the previous, was introduced as an alternative [1]. The physical properties of these materials are very close to those of natural teeth. Resin matrix ceramic materials materials are less brittle, less rigid, than ceramics, however are easy to repair. The fracture toughness, elastic modulus, hardness lie between ceramics and composites. They cause less abrasion of natural teeth than ceramic materials and the wear is lower than those of composites [2–7]. Due to these properties, these materials are Polymers 2022, 14, 364. https://doi.org/10.3390/polym14030364 https://www.mdpi.com/journal/polymers