Experimental evaluation of polymer construction materials: effects of acrylic resin and a fiberglass-based composite upon cytokine production

Abstract

Polymethyl methacrylate-based acrylic resin is commonly used in current dental practice as an underlying material for fabrication of overdenture restorations. To increase service life of laminar overdentures, we have developed a technique to fabricate a novel combined base for a full overdenture using a fiberglass-based composite. It makes sense to evaluate probable hazards of inflammatory process which could be activated when using structural polymer materials and composites in dental practice. Our study aimed for assessment of changes in production of key cytokines (interferon-y and interleukin-4) by ex vivo incubated human mononuclear leukocytes in the presence of acrylic resin and fiberglass-based composite.The experiments dealt with peripheral venous blood leukocytes obtained from 13 apparently healthy male volunteers (mean age = 24 years). The leukocytes were isolated from heparinized blood by gradient centrifugation. The cells were cultured in plastic round-bottom 96-well plates, in moist atmosphere with 5% CO2 at 37 °C for 72 h. Following the incubation, the culture supernates were collected and frozen for further determination of cytokine concentration using ELISA reagent kits for interferon-y and interleukin-4 measurement (Vector-Best, Russia). The samples of two structural materials were tested in the bioassays: the specimens of acrylic resin, Ftorax were compression-moulded by hot polymerization in prefabricated casts; the specimens of a composite, Trinia, were computer-milled. Glass specimens of similar shape and size were used as references. The statistical analysis used a software package, Statistica 7.0. Significance of the differences was evaluated using the Student's test and the Mann-Whitney test. When testing the statistical hypotheses, the significance level (p) was taken to be 0.05.Significant decrease of IFNγ production was revealed in presence of Trinia than in the samples with glass and with the acrylic specimens, whereas cell viability counts did not differ from the blank values. There was no statistical differences in IL-4 production between the samples with the polymer materials and the glass. When estimating individual stimulation indexes, the materials used in this research were found to showed a pronounced stimulatory effect with peripheral blood lymphocytes from only one volunteer. These findings indicate that Trinia triggers anti-inflammatory activity of leukocytes, whereas IFNγ production level is somewhat decreased, and IL-4 production remains unchanged.Thus, the research assessed the method for personalized evaluation of reactivity of prosthodontic structural polymer materials. Absence of increase in lymphocytic production of key cytokines can be regarded as a hopeful sign which indicates that inflammatory process is not activated when Trinia is used in overdenture bases.