## 4 Discussion
albicans_ ATCC 90028, respectively, for VM2 and EC. Higher CFU/mL values were observed for fungi, and lower values for bacteria. The surface that was most susceptible to the adhesion of _L. rhamns_ and both strains of _C. albicans_ was VM2 + Cu. _S. mutans_ did not adhere to VM2, VM2 + Cu or EC + Cu--VM2 was denoted with the highest and EC with the second highest WCA values. _L. rhamns_ did not adhere to VS and EC. In their evaluation of CAD/CAM materials, [PERSON] et al. [11] observed that non-polished surfaces exhibited a greater susceptibility to the adhesion of _C. albicans_ ATCC 90028 than polished ones. In accordance with this cited article, the presented study demonstrated that the _C. albicans_ ATCC 90028 strain exhibited a strong adhesion to non-polished surfaces. Furthermore, [PERSON] et al. [48] investigated the impact of polishing methods on surface properties. With the same conclusion as the presented article, the referenced study concluded that the adhesion of _C. albicans_ ATCC 90028 to rough (non-polished) surfaces is higher than to polished ones. [PERSON] et al. evaluated the adhesion of _Streptococcus oralis_ and _C. albicans_ to CAD/CAM dental material surfaces. The authors concluded that the higher the roughness and contact angle are, the more favourable the adhesion to the material surface for both the analyzed microbial strains [49]. During the evaluation of strains _F. mucleatum_, _C. albicans_, _S. oralis_, _V. parvula_ and _P. gingivalis_ in terms of their adhesion to rough surfaces, the same authors [50] assessed the contact angle. Their study concluded that materials exhibiting higher contact angle values and greater hydrophobic properties were likely to exhibit increased microbial adhesion. VM2 before modification with Cu possessed the highest contact angle. Both the strains of _C. albicans_ and _L. rhamns_ exhibited the highest adhesion among all the evaluated materials, which is in line with the referred study. However, no adhesion in _S. mutans_ was observed. Nanoparticles of copper find an application in dentistry as a microorganism-inhibiting component [51]. It has been established that copper is capable of damaging microbial cells thanks to its ability to generate reactive oxygen species and to replace or bind with native cofactors in metalloprotein [52]. Moreover, copper may destroy cell walls and cell membranes and react with proteins and DNA [51]. As summarized in the review by [PERSON] et al., there are studies proving the toxic effect of copper and its compounds on some kinds of human tissues, such as brain, lung or spleen tissue [53]. At the same time, there are studies that prove no or a weak cytotoxic effect of copper-containing materials on human fibroblast-like cells [54] or osteoblasts [55]. The cellular effect of copper-containing nanoparticles may depend on their different aspects, such as size or morphology, as well as on environmental conditions and chemical factors [51]. This fact may explain the slight differences in the cytotoxicity of coated and non-coated materials. In our study, two materials (NP-VM2 + Cu and NP-EC + Cu) showed moderate changes in cell cultures, described as grade 2 according to ISO norms [6]. The other evaluated materials (CD and VS) coated with copper showed no or weak changes in the cell cultures. Furthermore, our studies show that human NHDFs adhere to the surfaces of the evaluated materials, confirming the known properties of CAD/CAM materials.