Effect of leaching residual methyl methacrylate concentrations on in vitro cytotoxicity of heat polymerized denture base acrylic resin processed with different polymerization cycles

OBJECTIVES: Residual methyl methacrylate (MMA) may leach from the acrylic resin denture bases and have adverse effects on the oral mucosa. This in vitro study evaluated and correlated the effect of the leaching residual MMA concentrations ([MMA]r) on in vitro cytotoxicity of L-929 fibroblasts. MATERIAL AND METHODS: A total of 144 heat-polymerized acrylic resin specimens were fabricated using 4 different polymerization cycles: (1) at 74ºC for 9 h, (2) at 74ºC for 9 h and terminal boiling (at 100ºC) for 30 min, (3) at 74ºC for 9 h and terminal boiling for 3 h, (4) at 74ºC for 30 min and terminal boiling for 30 min. Specimens were eluted in a complete cell culture medium at 37ºC for 1, 2, 5 and 7 days. [MMA]r in eluates was measured using high-performance liquid chromatography. In vitro cytotoxicity of eluates on L-929 fibroblasts was evaluated by means of cell proliferation using a tetrazolium salt XTT (sodium 3´-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) assay. Differences in [MMA]r of eluates and cell proliferation values between polymerization cycles were statistically analyzed by Kruskal-Wallis, Friedman and Dunn's multiple comparison tests. The correlation between [MMA]r of eluates and cell proliferation was analyzed by Pearson's correlation test (p<0.05). RESULTS: [MMA]r was significantly (p<0.001) higher in eluates of specimens polymerized with cycle without terminal boiling after elution of 1 and 2 days. Cell proliferation values for all cycles were significantly (p<0.01) lower in eluates of 1 day than those of 2 days. The correlation between [MMA]r and cell proliferation values was negative after all elution periods, showing significance (p<0.05) for elution of 1 and 2 days. MMA continued to leach from acrylic resin throughout 7 days and leaching concentrations markedly reduced after elution of 1 and 2 days. CONCLUSION: Due to reduction of leaching residual MMA concentrations, use of terminal boiling in the polymerization process for at least 30 min and water storage of the heat-polymerized denture bases for at least 1 to 2 days before denture delivery is clinically recommended for minimizing the residual MMA and possible cytotoxic effects.

[Determination of residual monomer content in Acropars samples by Fourrier Transform Infrared method]

Acrylic resins possess many desirable properties, but it is possible that the denture bases contain residual monomer, which may cause some side effects such as hypersensitivity of oral tissues and altered characteristics of acrylic resin. The purpose of this study was to measure the residual monomer in heat cure Acropars[R] acrylic resin and comparison of these results with ISO standard. This study was an experimental research which was performed according to ISO 1567 standard. At first, five solutions of MMA monomer in MIBT, as the solvent, were produced with concentrations of 0.1, 0.2, 0.3, 0.4 and 0.5 weight percents for which Fourier Transform Infrared [FTIR] spectra were obtained. The calibration curves were then prepared based on these five known samples. As unknown samples, four disks of Acropars acrylic resin with diameter of 50 mm and thickness of 3 mm were provided and were dissolved in MIBT. After the swelling of samples and therefore the releasing of monomer in the solvent, the solutions were characterized by FTIR analysis. Concentration of monomer in solution was assessed by calibration curves. Data were statistically analyzed using t-student test [alpha=0.05]. The average level of residual monomer in Acropars samples was 0.428 weight percent. The level of residual monomer in Acropars samples met the requirements of ISO standard. The difference between the mean concentration of Acropars residual monomer and ISO standard was positively significant [p<0.05]

Oral lesions in relation to prosthetics. A review.

The oral mucosa is not designed to provide a foundation for denture base and is called upon to function in a new environment. Although dentures are fabricated for the purpose of improving health and well being of the patient, they may occasionally become injurious to oral tissues. Dentures are worn because of their essential role in appearance, in speech and mastication far outweighs their potential for damage. A thorough knowledge of the histologic features of the structures that support dentures is necessary for proper denture service. Various pathologic lesions that can occur following use of dentures are reviewed in this article.

Assessment of candida albicans growth level on different acrylic denture base materials, vacuum and non vacuum mixed

Candida species and microbial plaque on the tissue fitting surface of a maxillary complete denture and the palatal mucosa are the chief etiologic agent in the development and maintenance of denture stomatitis [Santarpia et al., 1988]. Denture stomatitis is a multifactorial condition associated with the wearing of a removable prosthesis. Predisposing factors include trauma [Bastiaan, 1976], candida infection [Budtz-Jorgensen and Bertram, 1970] [Renner et al., 1979] bacterial infection [Van Reenen, 1973] [Budtz-Jorgensen et al., 1983] and denture wearing habits [Etting, 1975] Candida albicans organism is part of the normal oral flora of healthy dentate adults [Young et al., 1951] as well as edentulous persons [Budtz-Jorgensen et al., 1975]. The change of candida albicans from commensalism to a pathogen in denture wearers is most probably due to alteration in the oral environment of the host rather than the alteration of the yeast itself [Young et al., 1951]The chief method of prevention and treatment of denture stomatitis is aimed at the : Ielimination of yeast and bacterial species from the denture tissue-fitting surface and denture supporting mucosa by means of an effective denture and oral hygiene cleansing regimen[Augsbruger and Elahi 1982] [Palenikand Miller, 1984]. However, a completely effective denture hygiene program for the treatment of denture stomatitis has not yet been developed [Santarpia et al., 1988]. This study was conducted to determine the level of candida albicans growth on: 1- Heat polymerized resin and auto polymerized resin bases non vacuum mixed 2-Heat polymerized resin and autopolymerized resin bases vacuum mixed 3- Trial VLC resin base