Caries Rate of Children Participating in a Clinical Trial

A randomized clinical trial designed to assess the safety of low-level mercury exposure from amalgam restorations was concluded recently. The “Study of the Health Effects of Dental Amalgams in Children” started in 1997 as a cooperative agreement between the University of Washington (Seattle) the University of Lisbon, and the National Institute of Dental and Craniofacial Research. A total of 507 children, aged 8 to 11 at the beginning of the study, received full dental treatment in accordance with US and Portuguese standards of care, for a period of 7 years. Half of the children had their posterior teeth restored with amalgam only, and the other half with composite only. Anterior teeth were treated with composite in both groups. This study provided a good opportunity to assess caries rates using standardized diagnostic criteria. Objectives: To compare the new and secondary caries rates of permanent teeth in the two treatment groups. Methods: Participants were seen annually for oral examinations and bite-wing radiographs, at which time complete dental charting was performed, and new treatment needs were noted. Annual rates of new and secondary carious surfaces (events/surface.years), for anterior and posterior teeth, were calculated and compared between groups. Results: New caries rates were 0.0064 (amalgam group) and 0.0081 (composite group), and secondary caries rates were 0.0068 (amalgam) and 0.0220 (composite). The annual caries rates were higher in the composite group in all instances, but statistically significant differences were found only for new caries in anterior teeth and total teeth; and for secondary caries in posterior teeth and total teeth. Conclusion: These results confirm previous findings that secondary caries risk is higher in posterior composite restorations when compared with amalgam restorations. Secondary caries risk in a restored tooth surface was generally higher than new caries risk in an unrestored surface. (Grant 1U01DE11894-01)