Influence of Pb Contaminated Water on Optical Properties of Composites

Chitre, Swati Dinesh, Jasmine Yousif, Nayan Suryavanshi, Alexa Rihana-Abdallah, and Rafael Rocha Pacheco

The aim of this study was to evaluate the influence of lead (Pb) contaminated water at different concentrations on optical properties of restorative materials. For this study, solutions were formulated by diluting a lead stock solution, varying at 4 different concentrations: 0.03ppm, 1ppm, 2ppm and 10ppm. The pH of the water samples was adjusted to either 7 or 8. Two restorative materials were evaluated: [C] resin composite (Premise, A2 shade, Kerr, USA) and [G] resin-modified glass ionomer (Fuji II LC, A2 shade, GC, Japan). Samples were prepared by using a PVS (Imprint 4, 3M ESPE) mold with internal dimensions of 6mm diameter x 2 mm thickness. Materials were inserted into molds and light-cured according to manufacturer’s instructions. Surface roughness and thickness were standardized by using SiC abrasive papers (#320, #600, #800 and #1200) under water refrigeration. All samples were stored at 100% humidity, at 37oC, for 24h. In order to assess L*a*b* parameters, samples were evaluated by using a spectrophotometer (VITA Easyshade® Compact, VITA), using two different backgrounds (~0% [BB] or ~100% [WB] reflection). Radiopacity was assessed by radiographic analysis associated to aluminum-standard (step-wedge). Samples (n=5) were then randomly assigned to each of the 18 groups, stored for 1 and 7 days, and re-evaluated. Data was subjected to statistical analysis at a pre-set alpha of 0.05. L*, a* and b* values for C where statistically different for BB and WB. After 1 day of storage, a reduction on b* and a* parameters was observed for all groups exposed to lead, higher when exposed to lower pH and higher lead concentrations. After 7 days, a reduction for L*, a* and b* parameters was observed for G while an increase was observed for C. Different concentrations of lead in water altered optical properties of restorative dental materials.