*Svyatoslav Rozhko1, 2, Roman Kutsyk1, 2
The influence of base resin of removable dentures on the planktonic growth of individual representatives of oral microflora
1Department of Dentistry of the Institute of Postgraduate Education, Ivano-Frankivsk National Medical University, Ukraine
2Department of Microbiology, Ivano-Frankivsk National Medical University, Ukraine
Introduction. Microbiological researches of the role of denture base materials in violation of the oral cavity micro ecology were conducted.
Aim. 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.
Material and methods. 7 types of denture base materials and their influence on the planktonic growth of microorganisms have been studied.
Results. The planktonic growth of the S. oralis strain was suppressed by all base materials: SYNMA (by 35.5%), Bre.Flex (by 27.5%) and Protacryl-M (by 25.7%), in the smallest – Nylon (by 5.4%), Villacryl (by 9.5%).
Conclusions. Through experimental research, we have proved the direct involvement of basic resin materials in changes in the oral cavity micro ecology and the process of occurrence of prosthetic stomatitis.
Key words: denture base resin, microorganisms, planktonic growth
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 4-7th 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.
Material and methods
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.
Tab. 1. Characteristics of materials, which were used in the research
|Brand name||Chemical composotion||Manufacturer (producer)||The type of polimerization|
|Polian IC||Polymethyl methacrylate||Bredent, Germany||Heat polimerization|
|Bre.Flex||polyamide/nylon||Bredent, Germany||Heat polimerization|
|Nylon||Polyamide|| ||Heat polimerization|
|Protacryl-M||Fluorine-containing acrylic copolimer, methacrylate||AT ”?????”, Ukraine||Cold polimarization|
|Villacryl||Polymethyl methacrylate|| ||Heat polimerization|
|Biocryl||Polymethyl methacrylate||SHEU-DENTAL, Germany||Pressing|
|SYNMA||Fluorine-containing copolimer, mixture of acrylic monomers and oligomers.||AT ”?????”, Ukraine||Heat polimerization|
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).
The test sample was placed in the tube of 2.0 ml of Brain Heart Broth (HiMedia Laboratories Pvt. Ltd., India) with the addition of 1% glucose, pre-freshly seeded test-strains of microorganisms in the ultimate concentration of 1 104 ?U?/ml. The crops where cultivated for 24 hours at a temperature of 37°C with constant agitation on the MR-1 shaker (SIA BIOSAN, Latvia) at a stirring frequency of 20 times/min. After cultivation, we selected 5 servings of 200 μl planktonic culture per well polystyrene tablet. The optical density of the culture (OD) was determined using a multi-mode photometer for the micro-tablet Synergy™ HTX S1LFTA (BioTek Instruments, Inc., USA) with wavelength 495 nm using Gen5™ Data Analysis Software. Control growth of crops was evaluated under similar culture conditions in test tubes with nutrient plastic samples. Based on the results of the experiment for each sample tested of the base material was calculated by the integral index of inhibition of growth of microorganisms:
The results were processed by method of variational statistics.
Conducted experimental researches have demonstrated that the tested samples of materials exhibit ability to inhibit the planktonic growth of microbial cultures. Growth intensity of most microbial crops in the presence of comparison material (glass) wasn’t significantly different from the control values. A credible decline of planktonic growth in the glass presence has been registered only in Staphylococcus epidermidis (by 31.5%, p < 0.01), Streptococcus oralis (by 23.7%, p < 0.05).
The most practical interest is the study of the effect of polymer materials on growth properties of resident representatives of oral microflora – α-hemolytic streptococci (fig. 1).
Fig. 1. The impact of base resin materials on the planktonic growth of oral streptococci cultures
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