An In Vitro Biocompatibility Study of Conventional and Resin-modified Glass Ionomer Cements
ABSTRACT Purpose: To evaluate the biocompatibility of a glass-ionomer (GIC) and a resin-modified glass-ionomer cement (RM-GIC), cell viability was examined in a model of human gingival fibroblasts using morphological, biochemical, and ionic patterns by means of phase contrast microscopy, lactate dehydrogenase (LDH) release, and quantitative x-ray microanalysis (EPXMA). Materials and Methods: The GIC Ketac-Molar Easymix (3M ESPE) and the RM-GIC Vitrebond (3M ESPE) were compared in human gingival fibroblasts exposed to the cements for 72 h. As controls, fibroblasts cultured with DMEM culture medium (negative control) and with 1% triton × (positive control) were used. Results: Light microscopic findings showed greater morphological alterations in cells exposed to RM-GIC than to GIC. The relative percentage of LDH released from the cells to the supernatant was significantly higher in RMGIC cultures than in the control. Quantitative x-ray microanalysis showed that cultures exposed to RM-GIC were characterized by an increase in intracellular Na and a decrease in intracellular Cl and K. These changes in ion composition were significant compared to control and GIC cultures. Conclusion: The three indicators of cellular biocompatibility after 72 h of exposure showed that RM-GIC led to more marked alterations than GIC in human gingival fibroblasts.
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ABSTRACT: Resin monomers such as HEMA (2-hydroxyethyl methacrylate) can be released from restorative materials and diffuse into the tooth pulp over long periods of time. Although the short-term toxicity of resin monomers has been well documented, little is known about the risk for chronic toxicity resulting from low concentrations of resins. Thus, the hypothesis tested in this study was that sub-lethal concentrations of HEMA alter the functions of macrophages after long-term exposure. Human THP-1 monocyte-macrophages were exposed to concentrations of HEMA between 0 and 1.5 mmol/l for up to 6 weeks. Cellular proliferation was measured by a hemocytometer with trypan-blue dye exclusion. Mitochondrial activity was measured by the MTT assay, and total cellular protein was measured using the bicinchoninic acid assay. Macrophage proliferation was inhibited 40-50% (significant, p < 0.05) by as little as 0.75 mmol/l after 1 week of exposure. Inhibition of proliferation remained constant after 1 week. The total protein per cell increased by as much as 80% (significant, p < 0.05) after 2 weeks and remained elevated through 6 weeks. Mitochondrial activity per cell increased 60-80% (significant, p < 0.05) after 2 weeks, then decreased. However, mitochondrial activity remained significantly elevated above controls through 6 weeks. Findings from the current study indicate that 6-week exposures of monocytes to HEMA alter their proliferation and other activities at concentrations substantially lower than previously reported. This is particularly relevant in light of evidence that such concentrations have been previously shown to come through dentin by diffusion.Dental Materials 05/2000; 16(3):213-7. DOI:10.1016/S0109-5641(00)00011-7 · 4.16 Impact Factor
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ABSTRACT: Although the identification of events that occur during apoptosis is a fundamental goal of apoptotic cell death research, little is know about the precise sequence of changes in total elemental composition during apoptosis. We evaluated total elemental composition (Na, Mg, P, Cl, S, and K) in relation to molecular and morphological features in human U937 cells induced to undergo apoptosis with staurosporine, an intrinsic pathway activator. To evaluate total elemental content we used electron probe X-ray microanalysis to measure simultaneously all elements from single, individual cells. We observed two phases in the changes in elemental composition (mainly Na, Cl and K). The early phase was characterized by a decrease in intracellular K (P<0.001) and Cl (P<0.001) content concomitant with cell shrinkage, and preceded the increase in proteolytic activity associated with the activation of caspase-3. The later phase started with caspase-3 activation, and was characterized by a decrease in the K/Na ratio (P<0.001) as a consequence of a significant decrease in K and increase in Na content. The inversion of intracellular K and Na content was related with the inhibition of Na+/K+ ATPase. This later phase was also characterized by a significant increase (P<0.001) in intracellular Cl with respect to the early phase. In addition, we found a decrease in S content and an increase in the P/S ratio. These distinctive changes coincided with chromatin condensation and DNA fragmentation. Together, these findings support the concept that changes in total elemental composition take place in two phases related with molecular and morphological features during staurosporine-induced apoptosis.APOPTOSIS 12/2005; 10(6):1317-31. DOI:10.1007/s10495-005-2718-x · 3.61 Impact Factor
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ABSTRACT: In vitro exposure to chemical compounds in dental materials may cause cell death by apoptosis, necrosis or a combination of both. The aim of this paper was to evaluate aqueous extracts of freshly cured compomers Freedom (SDI) and F2000 (3M ESPE), and constituents identified in the extracts, GDMA (glycerol dimethacrylate), TEGDMA (triethylene glycol dimethacrylate) and HEMA (2-hydroxyethyl methacrylate) for their ability to induce necrosis and apoptosis in primary rat alveolar macrophages and the J744A1 macrophage cell line. The cells were exposed to either extracts of freshly cured samples of the products or to one of the constituents identified in the extracts. Cytotoxicity and necrosis were assayed by MTT test and fluorescence microscopy, respectively. Apoptosis was assayed by fluorescence microscopy and flow cytometry. Concentration-related apoptosis and necrosis were found in both cell types after exposure to extracts from Freedom and F2000. GDMA appeared to be the most cytotoxic of the tested constituents in the J744A1 cell line as evaluated by the MTT test. TEGDMA was more cytotoxic than HEMA using the MTT test and fluorescence microscopy, whereas HEMA caused a greater accumulation of apoptotic cells seen by fluorescence microscopy and flow cytometry. For various concentrations of HEMA and TEGDMA, the extent of apoptosis appeared inversely related to the cytotoxicity evaluated by the MTT test. As an apoptotic response elicits less inflammatory response in the surrounding tissues than a necrotic process, the role of cell death pattern could be important for the evaluation of the biocompatibility of dental materials.Dental Materials 08/2006; 22(7):630-40. DOI:10.1016/j.dental.2005.05.013 · 4.16 Impact Factor