Digital radiographic measurement of approximal caries progression in fluoridated and non-fluoridated areas of Rio de Janeiro, Brazil

The effect of fluoridation on approximal caries progression was investigated using serial digitized bitewing images and conventional film images of 290 12-16-year-old schoolchildren who were lifetime residents of either Rio de Janeiro (a fluoridated area) or Mangaratiba and Angra dos Reis (non-fluoridated areas) in the state of Rio de Janeiro, Brazil. One examiner scored a maximum of 28 approximal surfaces of posterior teeth per subject using both methods. The intra-examiner reliability for rating lesion depth with digital images was comparable with that of the conventional bitewing films (namely, intraclass correlation of 0.99 and weighted Kappa scores of 0.82, respectively). Approximal surface D₁S was 3.17±0.25 (s_x) in fluoridated areas and 6.64±0.44 in non-fluoridated areas. After 1 year, the rate of caries progression in approximal surfaces was significantly lower in the fluoridated areas (0.54±0.14) as compared with the non-fluoridated areas (1.41±0.20) using Pitts' scoring system for conventional bitewing radiographs (P>0.001). Similarly, the digital radiographic method was able to detect subtle differences in approximal caries progression in the enamel and the dentin (overall mean: 0.34 mm/year in fluoridated areas vs 0.49 mm/year in non-fluoridated areas, Ps=0.7). Assuming a constant rate over time, these results indicate that lesion progression from the outer half of the enamel into the outer half of the dentin takes approximately 3-4 years in schoolchildren from the fluoridated areas compared to 21/2 years in the non-fluoridated areas.