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Biomedical subjects

K Tamareselvy

Publications and source records attributed to K Tamareselvy.

3 recordsLinked to original sources

Responses of oral epithelial cells to dental resin components.

The light-polymerized resins used in dentistry and their various constituents have been shown to produce significant levels of cytotoxicity, depending upon the material and the cell type exposed to it. These responses include altered cell growth and macromolecule synthesis. The current study examined the effects of several resin components on growth and lipid metabolism of oral epithelial cells. Resin discs were fabricated from triethyleneglycol dimethacrylate (TEGDMA) as received from the manufacturer and after removal of the stabilizer methyl ether hydroquinone (MEHQ). Some discs also contained the initiators benzoyl peroxide (BPO) and camphoroquinone (CQ), and/or an activator, dimethylaminoethyl methacrylate (DMAEMA). After polymerization, the ability of components to elute from the discs and alter cell growth and lipid synthesis were assayed by a colorimetric method and thin layer chromatography respectively. Purified TEGDMA had little effect on the cells' growth or lipid metabolism, while TEGDMA containing MEHQ did inhibit growth as well as total polar lipid synthesis. Eluates from discs containing DMAEMA inhibited cell growth as well as decreasing polar lipid formation. However, this same material produced increased synthesis of diglycerides and cholesterol esters. Eluates from BPO-containing discs, as well as those with CQ, with or without DMAEMA resulted in increased levels of diglycerides. These results demonstrate that even after polymerization, components used in dental resins may elute into the immediate environment and alter various cell metabolic processes.

Animals↗

Resin cure determination by polymerization shrinkage.

OBJECTIVES: This study was designed to develop a methodology that would measure the monomer conversion of dental restorative resins without the use of an infrared spectrometer. METHODS: Specimens were prepared from heat-cured TEGDMA/MMA copolymers consisting of 0, 20, 40, 50, 80, and 100 mol% TEGDMA. The pre- and post-cure volumes of bar-shaped specimens (45 X 7 X 1 mm) and thin films were measured. The cure of the thin specimens was determined using changes in resin volume as well as by an infrared spectroscopic method. The cure of thin specimens of a commercially available unfilled bonding resin was also determined using the shrinkage method and by conventional infrared spectroscopic methods. RESULTS: There was no difference (p=0.0617) between cure values of the commercial resin using either conventional IR methods or the shrinkage methods. For each copolymer combination of thin films, there was also no significant difference in the extent of cure between the IR method used and the shrinkage method presented (lowest p-value 9.29). The cure of TEGDMA/MMA copolymer bar specimens demonstrated a decreasing trend of cure with increasing proportion of TEGDMA, and had cure values which were similar to others reported in the literature. SIGNIFICANCE: The evidence from this study demonstrated that the specimen volume method can be used to determine the extent of resin cure of thin film or bulk resin specimens. This method represents an easily performed procedure that can be used by all investigators without expensive equipment.

Bisphenol A-Glycidyl Methacrylate↗

Dynamic mechanical analysis of two crosslinked copolymer systems.

OBJECTIVES: This research investigated the dynamic mechanical properties of two model dental restorative copolymers to elucidate the influence of pendent group length and addition of crosslinking agent. METHODS: Two different monomethacrylate resins [(methyl methacrylate (MMA) or 2-ethoxyethylmethacrylate (EEM)] were added to various molar fractions (0, 5, 10, 20, 40, 60, 80 and 100%) of a difunctional monomer [triethylene glycol dimethacrylate (TEGDMA)], resulting in two different copolymer systems (TMMA and TEEM). Bar-shaped specimens were heat-cured and tested for their dynamic mechanical properties at a fixed frequency (1Hz): flexural storage modulus and loss factor. Transition temperatures associated with peaks were determined using tan delta, phase angle and loss factor. The properties of one specimen were also examined using a range of applied frequencies. RESULTS: Below the Tg, all resin systems had similar storage moduli. An increase in pendent group length lowered transition temperatures and demonstrated greater influence on temperature changes than did a change in crosslinker content. With increasing crosslinker, the transition temperatures increased. The values ascribed to transition temperatures were dependent upon the analysis method used: tan delta gave highest values, followed by phase angle, with loss factor values the lowest. Storage and loss moduli values and their ratio increased with increasing frequency of applied signal. Loss factor analysis provided the most elucidation of sub-Tg transitions. SIGNIFICANCE: Restorative polymers with specific desired physical and mechanical properties can be achieved by both judicious selection of monomer structure as well as by the controlled addition of the crosslinking agent.

Analysis of Variance↗