## 1 Introduction  
The field of biomaterials and nanotechnology has experienced a notable expansion in recent years, with notable advances in the efficacy and possibilities of dental procedures [1; 2; 3]. The nanoscale of materials allows them to exhibit properties not present in their larger counterparts [4; 5; 6; 7]. The term \"nanotechnology\" is defined as the utilisation of a multitude of natural or synthetic materials that has at least one dimension (height, width, or length) that is smaller than 100 nanometres [8; 9]. The practical application of nanomaterials is evident in numerous scientific and clinical disciplines and is highly demanded in medicine [10; 11; 12]. [PERSON] et al. [13] and [PERSON] et al. [14] studies confirm the increasing role of nanoparticles in medicine, mainly due to their, e.g., unique size, solubility, chemical reactivity increasing role of nanoparticles in medicine, mainly due to their unique size, solubility, chemical reactivity, and high surface area. One of the many principal challenges currently facing researchers in modern dental treatment is the development of materials that are able to withstand the harsh conditions of the oral cavity environment while being able to sustain their function and remain biocompatible [15; 16]. The capacity to effectively replace, repair, and enhance bone tissue with a synthetic form of nanosized hydroxyapatite or fluorapatite is currently under intense investigation in the context of tissue engineering due to their high biocompatibility [17; 18; 19]. The introduction of a nanoparticle-based biomaterial for clinical use in the augmentation of defects in the alveolar bone necessitates comprehensive research and interdisciplinary scientific work [13; 20]. Several scientific works confirm the numerous benefits of the clinical deployment of nanomaterials when their dimensions are aligned with the precise range of 10 to 100 nm. Materials with diameters exceeding 100 nm have been observed to induce embolism and undergo phagocytosis when introduced within the body [21]. Conversely, materials with diameters below 10 nm have been shown to elicit lethal reactions in the body due to their elevated surface reactivity and enhanced surface density beyond the limits of the human body's capacity to withstand [22]. Furthermore, materials of a size below 10 nm can be more readily excreted by the kidneys [23]. Features like high surface-to-volume ratio [24], the similarity of nanobiomaterials to body ligands and proteins [25] or enhanced osteoblast adhesion [26] should allow nanosized apatites to be effective materials for enhancing bone regeneration. Bone regeneration is a complex process, comprising a specific and orchestrated sequence of biological events [22]. At the particle level, nHAp exerts a significant influence on bioactivity, thereby increasing the surface area of the material through enhanced ion exchange [27; 28]. nFAp, on the other hand, has better crystalline properties and is less acid-soluble [29]. In nFAp, the F\({}^{-}\) ion replaces the OH\({}^{-}\) ion, thus forming a solid bond with the NH group [30; 31; 32]. In enamel, the presence of nFAp inhibits demineralisation by lowering the critical pH for enamel solubility [33; 34]. The particle size of nHAp and the presence of fluorine affect their ability to bond with the cell membrane and penetrate into the cell [35]. The objective of this research is to conduct a series of in vitro studies to evaluate the microbiological properties of the nanosized version of apatite materials, including hydroxyapatite (HAp) consisting of the chemical formula Ca\({}_{10}\)(PO\({}_{4}\))\({}_{6}\)(OH)\({}_{2}\) and fluorapatite (FAp) with the chemical formula Ca\({}_{10}\)(PO\({}_{4}\))\({}_{6}\)F\({}_{2}\). Common oral microorganisms were selected, including _Candida albicans_, _Lactobacillus rhamnus_, and _Streptococcus mutans_. The antimicrobial influence of nanosized biomaterials, including nHAp and nFAp, has been corroborated in previous studies [36; 37; 38; 39].