Genotoxicity evaluation of locally produced dental porcelain--an in vitro study using the Ames and Comet assays.

The aim of this study was to determine the genotoxicity of a locally produced dental porcelain (Universiti Sains Malaysia, Malaysia) using the Ames and Comet assays. In the Ames assay, four genotypic variants of the Salmonella strains (TA98, TA100, TA1537 and TA1535) carrying mutations in several genes were used. The dental porcelain was incubated with these four strains in five different doses both in the presence and absence of metabolic activation (S9) and the result was assessed based on the number of revertant colonies. Concurrently, appropriate positive controls were used so as to validate the test. The average number of revertant colonies per plate treated with locally produced dental porcelain was less than double as compared to that of negative control. In the Comet assay, L929 (CCL-1 ATCC, USA) mouse fibroblast cells were treated with the dental porcelain in three different concentrations along with concurrent negative and positive controls. The tail moment which was used as a measurement of DNA damage was almost equal to that of the negative control, suggesting that the locally produced dental porcelain did not induce any DNA damage. The results indicated that the locally produced dental porcelain is non-genotoxic under the present test conditions.

Endothelial nitric oxide synthase G894T gene polymorphism and response to skin reactive hyperemia.

Post occlusive skin reactive hyperemia (PORH) is a tool used to assess microcirculation. Endothelial nitric oxide synthase (eNOS) mediates nitric oxide (NO) production; polymorphism of the eNOS gene may affect response to the PORH process. This study aims to determine whether eNOS G894T gene polymorphism affects response to skin PORH. 230 normotensive male and females between 18 and 40 years participated in this cross-sectional study. 170 subjects were of the homozygous GG genotype, whereas 60 were of the GT genotype. Skin PORH was performed by occlusion of the upper arm at 200 mm Hg for 3 min. Skin perfusion and temperature were monitored before, during and after occlusion release using the laser Doppler fluximetry. There were no significant differences between genotypes in their baseline blood pressure, serum cholesterol, BMI and age. Maximum change in perfusion after occlusion release (PORHmax) for the GG and GT genotypes were not significantly different at 50.15+/-1.29 vs. 47.92+/-2.17 AU; ANCOVA, p=0.351. Peak perfusion (PORHpeak) were also not significantly different between the two genotypes (61.23+/-1.36 vs. 57.72+/-2.32 AU; p=0.169). Minimum baseline perfusion were however higher in the GG compared to the GT genotype (10.83+/-0.29 vs. 9.61+/-0.50, p=0.029). We conclude that microvascular reactivity, assessed by change in perfusion after temporary ischemia was not significantly different between the GG and GT genotypes of the eNOS G894T gene. eNOS 894T allele carriers however, have lower baseline perfusion compared to the homozygous G894 allele carrier.