ADA Standards in Lead
In 1991, the ADA issued standard specification No. 69 dealing with dental ceramics. At that time, the ADA determined that 300 ppm was a safe, allowable level of lead for dental ceramics. In 1999, that standard was changed, the 300-ppm level abandoned, and a solubility standard for dental ceramics was instituted.
Dr. Robert Kelly, MS, DMSc, is in charge of the Working Group that writes the international standards on dental ceramics and metal ceramic systems and is also involved in the ADA standards committee. Commenting on the current ADA solubility standard, he said:
“The only way lead can be released from the ceramic and get into the bloodstream is if the glass ceramic of the crown dissolves in the mouth. If we take the solubility tests where porcelain crowns are placed into a 4% acetic acid solution, heated to nearly the boiling point of water and held there for 16 hours, the measurable amount of lead released in this harsh test is less than the allowable levels of lead in our drinking water, which by EPA standards is 15 parts per billion (ppb).”
