First Randomized Clinical Trial Of Dental Amalgams

JAMA. 2006 Apr 19;295(15):1775-83.
Neuropsychological and renal effects of dental amalgam
in children: a randomized clinical trial.
Bellinger DC, Trachtenberg F, Barregard L, Tavares M,
Cernichiari E, Daniel D, McKinlay S.
Department of Neurology, Children's Hospital Boston,
and Harvard Medical School, Boston, Mass, USA.

CONTEXT: No randomized trials have been published that
address the concern that inhalation of mercury vapor
released by amalgam dental restorations causes adverse
health effects.

OBJECTIVE: To compare the neuropsychological and renal
function of children whose dental caries were restored
using amalgam or mercury-free materials.

DESIGN AND SETTING: The New England Children's Amalgam
Trial was a 2-group randomized safety trial involving
5 community health dental clinics in Boston, Mass, and
1 in Farmington, Me, between September 1997 and March
2005.

PARTICIPANTS AND INTERVENTION: A total of 534 children
aged 6 to 10 years at baseline with no prior amalgam
restorations and 2 or more posterior teeth with caries
were randomly assigned to receive dental restoration of
baseline and incident caries during a 5-year follow-up
period using either amalgam (n=267) or resin composite
(n =267) materials.

MAIN OUTCOME MEASURES: The primary neuropsychological
outcome was 5-year change in full-scale IQ scores.
Secondary outcomes included tests of memory and
visuomotor ability. Renal glomerular function was
measured by creatinine-adjusted albumin in urine.

RESULTS: Children had a mean of 15 tooth surfaces
(median, 14) restored during the 5-year period
(range, 0-55). Assignment to the amalgam group was
associated with a significantly higher mean urinary
mercury level (0.9 vs 0.6 microg/g of creatinine at
year 5, P.001). After adjusting for randomization
stratum and other covariates, no statistically
significant differences were found between children
in the amalgam and composite groups in 5-year change
in full-scale IQ score (3.1 vs 2.1, P = .21). The
difference in treatment group change scores was 1.0
(95% confidence interval, -0.6 to 2.5) full-scale IQ
score point. No statistically significant differences
were found for 4-year change in the general memory
index (8.1 vs 7.2, P = .34), 4-year change in
visuomotor composite (3.8 vs 3.7, P = .93), or year 5
urinary albumin (median, 7.5 vs 7.4 mg/g of creatinine,
P = .61).

CONCLUSIONS: In this study, there were no statistically
significant differences in adverse neuropsychological
or renal effects observed over the 5-year period in
children whose caries were restored using dental amalgam
or composite materials. Although it is possible that
very small IQ effects cannot be ruled out, these
findings suggest that the health effects of amalgam
restorations in children need not be the basis of
treatment decisions when choosing restorative dental
materials.