This study was conducted to investigate the principal factors involved in the discoloration of 12 Wt% Au-Ag-Pt alloy. Luminance of cast clasps, oral conditions, the presence cariogenic microbes such as Streptococcus mutans and Lactobacillus in saliva, Candida on the tongue and the amount of volatile sulfur compounds (VSC: H2S and CH3SH) produced by the tongue coating were evaluated in 70 subjects (VSC: 45 subjects). The surfaces of cast clasps were observed using an electron probe X-ray microanalyzer and changes in the surface were evaluated in relation to the degree of discoloration.
The results were as follows:
1. The Mann-Whitney U-test revealed statistically significant differences (p<0.05) between the production of CH3SH and VSC (CH3SH+H2S) and luminance.
2. Examinations of the cross section of markedly discolored casts revealed a very rough surface. A distinct peak of S was also indicated by linear analysis.
The results demonstrated that among the many different factors such as oral conditions and oral flora, the production of CH3SH was the most significantly related to the discoloration of 12 Wt% Au-Ag-Pt alloy. The potential for discoloration tended to be higher in subjects who had a high production of CH3SH.
