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To the Editor: In his Editorial on neurotoxic risk of mercury in dental amalgam, Dr Needleman¹ comments on the results of 2 randomized controlled trials in the same issue of JAMA.^2-3 The findings in the trials of no effect of exposure to mercury-containing amalgam on neurobehavioral and neuropsychological outcomes after 5 to 7 years are reassuring. Although we agree with Needleman's general comments on the limitations of these studies, there are 2 issues that may assist health care professionals in counseling patients and guide future research considerations.

First, the evidence cited regarding susceptibility of a coproporphyrin oxidase genotype in the US population⁴ does not appear to be robust. This study used a cross-sectional method with no controls, and there was no consideration of other conditions and confounding factors that could explain what the authors themselves describe as "exploratory findings."

Second, even though Needleman suggests that a small IQ decline . . . [Full Text of this Article]

Frederick Fung, MD, MS
Fred.fung@sharp.com
University of California
San Diego

F. Lee Cantrell, PharmD
California Poison Control System, San Diego Division
San Diego

Richard F. Clark, MD
University of California
San Diego