The objective of this study was to assess the anticaries efficacy of a toothpaste containing 3% sodium trimetaphosphate (TMP; test) relative to a toothpaste containing no caries-preventive agent (control). The study was designed as a 3-year double-blind caries incidence study involving about 2,500 subjects aged 11 years at baseline. After a clinical examination, subjects were stratified by sex, presence of supragingival calculus and caries status and randomly assigned to either the control or the test group. Clinical examinations then took place at annual intervals. At baseline and at the final examination bite-wing radiographs were taken of subjects not radiographed within the previous 6 months. The change in caries between baseline and the 3-year examination was calculated as DMFS increments. The result showed a statistically significant difference of 8% between the test and control groups (p