The influence of lead content in water and its effects on properties of tooth substrates

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

Introduction: Heavy metals are present in food, air and water consumed by all living being. There is an assumption that heavy metals and toxicity are inter-related, so they have potential toxic effects even at low exposures. One heavy metal that may be found in water is Lead (Pb), which was a common component of solders, used for plumbing. Water’s corrosive properties can leach out lead ions from aging pipes. Lead is harmful at high concentrations in water, and can only be detected by laboratory analysis. Lead poisoning may cause many health effects in adults and children, also known to have an effect on salivary glands and teeth substrates. Mineralized tissues, such as enamel and dentin, are susceptible to developmental failure, similar to bone.

Objectives: The objective of this study is to evaluate the influence of different lead (Pb) concentrations in water on tooth substrates properties (optical and mechanical).

Materials and Methods: Sound extracted unerupted human third molars will be used for this study. Teeth will be obtained from Oral Surgery Department of University of Detroit Mercy under IRB protocol previously approved. Teeth will be cleaned (using a scalpel), and stored in 0.1% Thymol solution, under refrigeration, prior to use. Roots will be removed with a diamond disc, in low speed handpiece, and crowns will be sectioned in a low-speed saw (IsoMet, Low Speed Saw, Buehler Ltd.) with a high-concentration diamond impregnated blade in two parts, in order to separate buccal/lingual portions. Blocks of 10x10x2mm (1mm of enamel and 1mm of dentin) will be sectioned from these portions and finishing/polishing procedures will be performed using SiC abrasive papers (grits #80, #120, #320, #600, #800 and #1200), under water irrigation, in order to standardize the surface of the samples. Each sample will be stored in different water solutions, according to varying concentrations of ions and pH, at 37oC. Deionized water will be used as control group (n=5). 5 different concentrations of Lead (Pb) will be evaluated (mg/L): 0.000, 0.001, 0.010, 0.100 and 1.000. Samples will be evaluated after 24 hours, 1 week, 1 month and 6 months of exposure. Knoop microhardness, microshear bond strength, white light transmission (spectroradiometer) and shade evaluation (CIE L*a*b* parameters) methodologies will be performed in order to determine the influence of Lead concentration on mechanical properties (such as hardness and bond strength) and optical properties (such as shade and opacity/translucency) prior and after exposure.

Results/Hypothesis: Similar to calcium, lead (Pb) gets accumulated in bones and teeth, and these deposits are permanent. Our study expects to prove that different concentration of lead in water interferes with the tooth substrates, altering its properties (such as shade and hardness). Enamel is a porous tissue that may allow permeability of water containing ions through it, reaching dentin and pulp tissues. The molecular weight of the Lead (Pb) molecules may absorb more light, associated to oxidation processes that may alter the shade of teeth substrates.

Conclusion: Lead (Pb) may have influence on tooth substrates mechanical and physical properties.