## 1 Introduction  
Related to the high demand of patients for biomimetic dental restorative materials, ceramics and composites come into question. Longevity is an essential aspect when restoring natural teeth structures and it is important that the physical properties of the restorative materials overlap the tooth structures [1; 2; 3]. The rapid development of CAD/CAM technologies provided accurate, repeatable and high-quality dental restorations using a variety of materials. CAD/CAM systems represent an outstanding advancement, offering practitioners the chance to achieve improved dental restorations [4; 5]. During the last decade, a new category of dental esthetic materials has been researched, called resin matrix ceramics or hybrid ceramics. These materials consist of an organic matrix with a high content of ceramic particles. These materials are included in the classification of dental ceramics, after the American Dental Association Code on Dental Procedures and Nomenclature (version 2013), which defines the term porcelain/ceramic as \"pressed, fired, polished, or milled materials containing predominantly inorganic refractory compounds--including porcelains, glasses, ceramics, and glass-ceramics\". The former version of the ADA code did not include materials with resin matrix in the category of ceramic materials [6; 7; 8; 9]. The physical properties related to resin matrix ceramics lie very close to those of natural teeth, and between ceramics and composites. The milling time in the CAM unit is shorter compared to other ceramic materials, leading to a longer lifetime of the milling burs. The polymer structure of the material could also prevent crack propagation through the ceramic phase. Well-known resin composites wear out; they lose their surface gloss and color stability overtime more easily compared to ceramic materials [2; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20]. As surface processing methods of these materials, conventional polishing and glazing for high gloss and gloss stability are designated. Glaze materials are used to seal the surfaces and to obtain smoother and glossy surfaces. This has a great impact in decreasing surface asymmetries, increasing wear resistance, and improving the resistance to staining [21; 22]. The surface roughness of a material is important for esthetics and long-term success, but there is a need for more studies related to the effectiveness of glazes on CAD/CAM resin matrix ceramic materials. Ensuring success in esthetic restorations is a difficult process, because of the optical complexity of tooth structures. To obtain success, basic principles in optical characterization, such as mimicking of the opalescence and translucence of natural teeth, must be taken into consideration [23; 24; 25]. Due to the hydrophilic characteristics of resin-based materials, studies demonstrated the relation with their optical properties. Resin-based materials are known for their esthetic appearance, strength, and accessibility, but lack the strength and optical stability of ceramic materials. Thus, resin matrix ceramics were introduced in order to combine the benefits of ceramics and composites. They may limit the absorption of water compared to resin-based materials, and thus preserve optical properties. Information regarding the properties of resin matrix ceramic materials after a prolonged usage period is limited [18]. The Vickers hardness test is important because it is a predictor of surface wear [26]. Thermocycling is one of the widely used aging methods to investigate restorative materials and there are different in vitro aging protocols. Thermocycling represents the oral environments better than isothermal storage conditions. Temperatures of 5-55 \({}^{\circ}\)C are considered the limits for the real situation in the oral cavity. A total of 10,000 cycles were selected for the study, which represent one year of clinical service and are generally used for in vitro studies [27; 28]. Dental restorations are exposed to dynamic temperature changes in the oral cavity.