## 1 Introduction  
CAD/CAM, which stands for computer-aided design and computer-aided manufacturing is a technique gaining significant popularity in many fields, among which is modern reconstructive dentistry. On the market, there is a wide variety of materials, sold as prefabricated blocks, that may be milled and used in the temporary or definitive reconstruction of hard tissues in patients' oral cavities. In general, materials for CAD/CAM can be divided into major groups, such as metal, polymer, ceramic, or composite materials [1]. Materials are constantly evaluated and enhanced to meet the high demands of modern dentistry. Among the favourable characteristics of dental materials for indirect restorations, we may list mechanical resistance, durability and functionality similar to natural tissues, as well as good aesthetics and biocompatibility [2; 3]. To critically evaluate a biomaterial, many aspects should be appraised considering the material's purpose. Its marketing claims must be considered, and in vitro and animal tests should be performed [4]. In our paper, we focused on several crucial aspects of the in vitro evaluation of a new material. One of them is biocompatibility, defined as \"the ability of a material to elicit an appropriate biological response in a given application\" [5]. This is especially important when the material remains in contact with patients' tissues for a long time, such as in reconstructive dentistry [4]. Materials whose purpose involves contact with human cells should be validated according to standards such as EN ISO 10993-5 (Biological evaluation of medical devices--Part 5: Tests for in vitro cytotoxicity) [6]. Cytotoxicity was evaluated considering the cell morphological changes described in this standard, according to which a material can be regarded as cytotoxic when it presents at a second or higher grade in the set scale. CAD/CAM restorations frequently come into contact not only with hard tissues of the tooth such as the enamel or dentin but also with soft gingival connective tissue, in which its major population is fibroblasts [7]. Testing the adhesion of fibroblast cells to a material allows a prediction of its potential interaction with a tissue. Dental caries is regarded as a complex transmissible disease affecting biofilm development [8]. The risk for caries includes many factors--physical, biological, environmental, behavioural and lifestyle-related--among which we can distinguish levels of colonization of the oral cavity by angiogenic bacteria [9]. In the human oral microbiota, over 700 different species of bacteria coexist [10]. Both natural tissues and restorative and prosthetic materials in the oral cavity are covered by an acquired pellicle followed by bacterial colonization. Bacteria tend to bind to the pellicle in the course of the first 4 h after cleaning the teeth. Both Gram-positive (_Streptococcus mutans_, _S. salivarius_, _S. motis_ and _Lactobacillus_ spp.) and Gram-negative (_Actinobacillus_ spp., _Campylobacter_ spp., _Fusobacterium nucleatum_ and _Porphyomonas gingiralis_) bacteria colonize the oral cavity [11]. The multispecies biofilm of the oral cavity is the main factor in the development of tooth decay, periodontitis, peri-implantits and stomatitis [12; 13; 14; 15; 16]. Due to the formation of biofilms on biomaterials, especially in marginal gaps, secondary caries may develop [14; 17]. Restorative material are desired to be precise and stable in their form to reduce the risk of microleakage or of aforementioned marginal gaps and secondary caries as a result [18]. Modern restorative materials should play a role in the limitation of the level of attachment of microorganisms inside the oral cavity. A number of studies have noticed that the colonization of materials by their biofilm depends on different factors, such as free energy or hydrophilic/hydrophobic properties [19; 20]. To evaluate the hydrophilic/hydrophobic character of the tested materials, the water contact angle was measured and taken into interpretation.