Introduction: In oral microflora, microorganisms that pile in the form of biofilm cannot be avoided. The bacterium most associated with plaque formation is Streptococcus mutans, which is commonly present in the oral cavity. Bacterial adhesion and biofilm formation are affected by various environmental factors and physico-chemical properties of bacterial and material surfaces. In dental prosthetics, zirconium oxide ceramics is increasingly used as a dental substitute, as it has excellent mechanical and aesthetic properties and is biocompatible. Purpose: The aim of this study is to evaluate how different composition and different surface treatment affect Streptococcus mutans adhesion and biofilm formation. We will examine how certain physical properties such as streaming potential, surface roughness and hydrophobicity of the material surface influence the degree of adhesion of Streptococcus mutans. Methods: We prepared samples of four granules used for production of dental crowns, inlays and onlays. Zirconium oxide ceramics with different content of additives were compared, namely 3 mol% Y2O3 (TZ- 3YB-E), 4 mol% Y2O3 (Zpex 4), 5,2 mol% Y2O3 (Zpex Smile) and 0,05 mol% Al2O3 (TZ-PX-242A). We continued the preparation of the discs by sintering them. Half of the sintered discs were also sanded. This was followed by complete characterization for the analysis of physical properties such as surface roughness, zeta surface potential and hydrophobicity/contact angle. We prepared a pure culture of Streptococcus mutans in the microbiological laboratory and investigated the adhesion of this bacterium on discs of various compositions and treatments. In the dental laboratory we made monolithic ZrO2 ceramic dental veneers on teeth 11, 12, 21 and 22 with CAD-CAM technology. Results: The highest roughness was measured on sanded surfaces. In the case of zirconium oxide stabilized with yttrium oxide, it is observed that the surface roughness decreases with increasing proportion of yttrium oxide. The least negative charge was measured on the surface of Zpex4 p (-22 mV ± 12 mV) and the most negative in zirconium oxide stabilized with 3mol % Y2O3 (TZ- 3YB-E) as (-56 mV ± 3 mV). Sanded surfaces are less negatively charged than only sintered, except in the composition TZ-PX-242A (ZrO2 + 0,05 mol% Al2O3). The lowest contact angle (62,6°) was measured on sanded Zpex4 surface and the highest (87,8°) on as sintered Zpex-smile. Surfaces that were only sintered had higher contact angle than those that were sanded, except for zirconium oxide stabilized with 3 mol% Y2O3 (TZ- 3YB-E). The highest absorbance was measured at the Zpex-Smile p surface (0,36 ± 0,04) and the lowest on the Zpex-Smile as (0,09 ± 0,00). Three of the four materials we measured there was higher absorbance in sanded surfaces than in those that are only sintered. Discussion and conclusion: The factor, that most affected the bacterial adhesion is surface roughness. We also confirmed that a more negative streaming potential means lower degree of adhesion of Streptococcus mutans. Due to unclear results, it is not possible to determine exactly to what extent hydrophobicity affects bacterial adhesion.
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