Effect of Age, Gender, Years of Practice, Specialty and Number of Amalgam restorations on Mercury Concentration in Nails of dentists practicing in Tehran

Dental professionals are at risk of being exposed to inorganic mercury, through handling amalgam. The purpose of the present investigation was to evaluate the effect of age, sex, years of practice, specialty and number of amalgam fillings on the concentration of mercury in nails of dentists practicing in Tehran. This analytic-descriptive study, conducted between May 2005 and May 2006, involved a randomly selected sample of 100 dentists and 35 controls in Tehran. All participants were asked to provide a nail sample and complete a questionnaire. Mercury was measured by the LECO AMA 254 Advanced Mercury Analyzer (USA) according to ASTM, standard No. D-6722. The LECO AMA254 is a unique Atomic Absorption Spectrometer (AAS) that is specifically designed to determine total mercury contents in various solids and certain liquids without sample pre-treatment or sample pre-concentration. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U-tests. Mercury content in nails differed significantly among operative dentists: 0.14-27.27 mg/kg; orthodontists: 0.15-14.53 mg/kg; and controls: 0-1.7 mg/kg (p=0.000). Age had a significant effect on mercury concentrations (p=0.01). However, gender (p=0.93), years of practice (p=0.49), number of amalgam fillings (p=0.58) and the studied specialties (p=0.07) did not significantly affect mercury levels. Mercury levels were significantly higher in dentists and correlated with age. High mercury concentrations in some dentists appeared to be related to background exposure from the preparation of amalgam, amalgam residues and spillage of mercury.