Purpose: This study aims to evaluate the impact of varying exposure to dental amalgam on urinary mercury levels in children by measuring the number of amalgam-filled teeth and the variance of mercury concentration in urine over a period of 2 years.
Methods: A total of 317(male 158, female 159) elementary school children(1st~4th graders) attending 2 schools in urban regions participated in this study. At 6-month intervals, 4 oral examinations were conducted to check any variance in the conditions of dental caries and the status of dental fillings. Also, urine tests were conducted followed by a questionnaire survey. To elucidate the factors potentially affecting the mercury concentration in urine, t-test, ANOVA, chi-square test and a mixed model were used for the analysis.
Results : Regarding the status of dental fillings in line with examination time periods, deciduous teeth had more amalgam-filled surfaces than those filled with resin, whereas permanent teeth had more resin-filled surfaces than those filled with amalgam. A significant relevance was found between the exposure to dental amalgam and urinary mercury levels. Specifically, subjects whose teeth surfaces had been filled with dental amalgam showed higher urinary mercury levels than those who had no dental amalgam fillings. The more the amalgam-filled teeth surfaces, the higher the urinary mercury levels. Factors affecting the urinary mercury levels included gender, mother''s education levels, frequency of tooth brushing and fish intake. Based on the analysis using the mixed model, the increase in the number of teeth surfaces filled with amalgam was found to be the factor affecting the increase in urinary mercury levels.
Conclusion: The urinary mercury levels were found to be highly associated with the exposure to dental amalgam. The more the teeth surfaces filled with amalgam, the higher the urinary mercury levels. Hence, even a trace of dental amalgam fillings can liberate mercury, affecting the variance in the urinary mercury levels. These findings suggest that some criteria or measures should be developed to minimize the exposure to dental amalgam. Moreover, relevant further studies are warranted.