One of the main complications that arise during using full or partial dentures is prosthetic stomatitis (common recurrent disease with localization on a mucous membrane of both prosthetic bed and intact areas of gum and vestibular part of oral cavity). Despite the multi-factor etiology, the significant importance in the development of stomatitis belongs to the bacterial and fungal microflora of oral cavity (1, 2). Previously we demonstrated substantial changes of microbiocenosis of the mucous membrane of the prosthetic bed and periodontal area of patients with partial and complete dentures (3, 4), that are deepening due to poor oral hygiene (5), accompanying somatic pathology and adverse effects of environmental conditions.

The presence in the oral cavity of dental and orthodontic constructions prevent the free washing the mucous membrane of the saliva, which provides a constant clearance of microbial cells. In addition, numerous researches confirm the ability of oral microorganisms to adsorb on dental materials to form on their surface-resistant groups – multi-view microfilms. Their composition is quantitatively dominated by α-hemolytic streptococcus (in particular Streptococcus oralis, S. sanguinius, S. gordonii, representatives of the S. mutans-group), Aggregatibacter actinomycetemcomitans, Actinomyces viscosus, A. naeslundii, and also yeast fungi Candida albicans, C. tropicalis, C. dublinensis. There are complex directional interrelations in both synergistic and antagonistic nature between separate species of microbiocenosis that form biofilm on the surface of the mucous membrane of oral cavity, prosthetic bed and dental materials. These include competition for certain nutrient deficiencies and growth factors, level of aero tolerance, sensitivity to compete types of hydrogen peroxide and lactic acid, the ability to withstand the effects of factors of immunity of the body (anti-lysozyme activity, inactivation of complement system factors and SIgA, phagocytosis resistance). Minimal extra external influence changes the relationship between different species, some of which receive additional preference for increased growth. In light of modern ideas about the mechanisms of communication of microbes and their ability to coordinate their behavior by secretion of molecular signals (quorum sensing) after achieving the specific critical cell number the conditionally pathogenic bacteria are becoming quite aggressive to cause the disease – in this case, the involvement of the mucous membrane of oral cavity. In addition, microbial colonization (along with mechanical damage) is an important factor in reducing the durability of dentures (6).

A significant impact on the micro ecology of oral cavity in the area of the prosthetic bed can have residual monomer (metylmetacrylat) and formaldehyde, which continue to be released from resin base (7, 8). They can also cause adverse reaction on the mucous membrane of the prosthetic bed, since are released at concentrations, potentially high enough to detect cytotoxic effect and cause irritation, inflammatory and allergic response to mucous membrane tissues (8). Thus, in the water environment (including oral fluid) is washed off 5-10% of residual monomer, that equivalent ? 2% weight of acrylic resin of most types. Chemical methods have shown that the main part of the residual monomer is released from the base resin for the first 3 days, although this release is also on the 4-7^th days (which was the limit of observation) (7). However, the mutagenic activity of the extract of acrylic dentures were also found in individuals with an average prosthesis use time of 14.3 years (9, 10).

During the analysis of literary sources we haven’t found any researches related to the influence of base resin of dentures and classic acrylic resin methylmetacrylat monomer on growth of microorganisms (although other microbiological aspects, as adhesion of microorganisms and formation of biofilm on the surface of plastics are intensively studying). Okita et al. (11) did not find noticeable antimicrobial activity in 4 acrylic fabric conditioners by classical microbiological methods – disco-diffusion and diffusion in agar.

Therefore, the purpose of research is to study the effect of different polymeric materials on denture bases, on the intensity of planktonic growth of resident and transient representatives of oral cavity microflora in a periodic culture on the basis of registration of its optical density.

To assess the impact on the growth of microorganisms, 7 types of denture base materials samples (for production of bases on complete and partial removable dentures) were used.

The table 1 presents the physicochemical compositions and their methods of polymerization.

The finished base materials samples for the experiment were like 2 mm thick plates and 1 cm² in area. As a control, we used similarly sized glass plates. The research and control samples were placed in sealed cellophane packaging and sterilized X-ray irradiation in a dose of 0.44 mGy during 1,540 s.

The research used strains of conditionally-pathogenic microorganisms that are represent optionally anaerobic transient oral cavity microflora (3-5), as well as α-hemolytic streptococci Streptococcus oralis, S. gordonii, S. Sanguinis as major representatives of resident microflora of this biotype. Microbial culture has been isolated from the oral mucosa (prosthetic bed, gingival pockets) of patients with removable dentures with prosthetic stomatitis and identified on the basis of morphological, cultural properties and biochemical microtests using “STAPHYtest 16”, “STREPTOtest 16” (Lachema, Czech Republic) ?? VITEK 2 YST (bioMerieux, France).