Objective To explore whether the dental restoration of nickel-chromium（Ni-Cr） based alloys will lead to extra excretions of urinary Ni and Cr. Methods Urinary Ni and Cr were repeatedly measured in 33 patients before and 2 months after the dental restoration of Ni-Cr alloys. The associations between alloy restoration and urinary Ni or Cr were analyzed by paired t test and general linear model of repeated measures. Results A slightly higher urinary Ni was found in patients after 2 month of the alloy restoration, but the difference was not statistically significant （before: 46.4 μg·mol-1 crea; after: 67.6 μg·mol-1 crea; P=0.063）. This difference was only in female subjects（before: 44.8 μg·mol-1 crea; after: 73.7 μg·mol-1 crea; P=0.068）. A significant higher urinary Cr was found in patients after 2 month of the alloy restoration（before: 57.0 μg·mol-1 crea; after: 99.4 μg·mol-1 crea; P=0.024）. This significant difference was only in female subjects（before: 59.8 μg·mol-1 crea; after: 124.4 μg·mol-1 crea; P=0.023）. General linear models of repeated measurements showed that urinary excretions of Ni and Cr were associated with the number of restoration and the area of metal basis uncovered with porcelain. Conclusion Dental restoration of Ni-Cr alloy might lead to the enhanced excretions of urinary Ni and Cr.
