Detection of lead in human teeth by exposure to aqueous sulfide solutions

A recent study has shown that the presence of lead (Pb) as well as other base metals in esthetic restorative materials, especially dental cements, is detectable by color shifts induced by exposure of hardened specimens to a 0.1% (w/v) aqueous solution of sodium sulfide, Na2S. The present study was initiated to determine the applicability of this simple exposure test to the detection of Pb in human teeth. Extracted whole teeth as well as sectioned, thin specimens were exposed first to either a 0.01% or a 0.001% (w/v) aqueous solution of lead nitrate, Pb (NO3)2, at 37 degrees C for 24 h. After rinsing with distilled H2O and a subsequent 24 h exposure to the 0.1% Na2S solution at 37 degrees C, the tooth specimens were examined visually and by a dental color analyzer for color changes. The latter color measurements were evaluated by the Lab system of Hunter, and the color difference, delta E, was determined. Neither control specimens exposed to distilled H2O only or to 0.1% Na2S only exhibited any significant change in appearance after 24 h of storage at 37 degrees C. However, specimens exposed first to the Pb (NO3)2 solutions showed discernible delta E values after exposure to the Na2S solution. Delta E was greatest for specimens exposed to the more concentrated Pb (NO3)2 solution. Most of the discoloration in both thin and intact tooth specimens was confined to the outermost layers of the tooth structure. For the intact specimens, the greatest degree of discoloration occurred in the cementum, the most permeable part of the tooth structure.