Clinical Question: Are amalgam dental restorations containing mercury safe for children?

Setting: Randomized controlled trial (double-blinded)

Study Design: Population-based

Allocation: Concealed

Synopsis: Health risks associated with inhalation of mercury vapor released during amalgam dental restoration are unknown. The investigators identified 534 children, six to 10 years of age, with no known prior or existing amalgam restorations and at least two posterior teeth with dental caries requiring restoration. Eligible children were assigned randomly (concealed allocation) to restoration with standard amalgam containing 50 percent elemental mercury or with a resin composite material (white filling) free of mercury. All persons assessing outcomes remained blinded to treatment group assignment.

Complete outcome data were available for at least 75 percent of enrolled children during the five-year trial, with an equal number of children unavailable in both treatment groups. Full assessment of intelligence, auditory memory, visual-motor integration, attention, and emotional state using previously validated scoring tools occurred at baseline before caries restoration and again at three and five years. Children had a mean of 15 tooth surfaces restored during the five-year period.

Using intention-to-treat analysis, investigators found no statistically significant differences between children in the amalgam group and the composite group in any of the outcomes measured. A nonsignificant increase in IQ was detected in children assigned to the amalgam group. The study was 80 percent powered to detect a three-point difference in IQ scores between the treatment groups. Authors of a similar seven-year randomized trial enrolling 507 children from another setting also reported no significant differences in neurobehavioral assessments between children receiving dental restorative treatment with amalgam and those receiving a resin composite (DeRouen TA, et al. Neurobehavioral effects of dental amalgam in children: a randomized clinical trial. JAMA 2006;295:1784–92). In the second study, children assigned to restoration with resin composite were more likely to require additional restorative treatment.

Bottom Line: Children who receive dental restorative treatment with amalgam do not score significantly better or worse on neurobehavioral and neuropsychological assessments than children who receive resin composite material. Children who receive restoration with resin may be more likely to need additional treatment. Studies evaluating outcomes for longer than five to seven years are needed. (Level of Evidence: 1b–)