Urinary levels of nickel and chromium associated with dental restoration by nickel–chromium based alloys

This paper aims to investigate if the dental restoration of nickel–chromium based alloy (Ni–Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni–Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of <1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of <1, 1 to <3 and 3 to <6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni–Cr alloy restoration need to be investigated. Dental fillings made of nickel—chromium-based alloys appear to increase the levels of these toxic metals excreted in recipients’ urine. A team led by Qing-wu Jiang of Fudan University in Shanghai, China, compared the urinary concentrations of nickel and chromium in 795 people who had metal dental fillings with 198 people who had no such fillings. Nickel concentrations were significantly higher in people who had received the fillings within the past month compared with controls. Elevated chromium levels were detectably higher in people who had received fillings within the past six months. Urinary concentrations of both metals were also greater in people with more than one nickel–chromium alloy fillings. The authors call for follow-up work to investigate the potential health outcomes of having these metals leaching into the body’s circulation system following dental restoration.