Purpose: To estimate dental caries prevalence and severity among all 12- and 13-year-old schoolchildren enrolled in a public school in 2005 and to establish comparisons with the results of studies previously conducted in the same school in 1971, 1997 and 2002. Methods: A cross-sectional study involving 190 children was carried out. A single calibrated examiner collected the clinical data according to the World Health Organization (1997) criteria. Results: The response rate was 90.0%. Between 1971 and 2005, the observed reduction in caries prevalence was 58.2%, whereas the mean DMFT Index declined from 9.2 to 0.8, which corresponds to a reduction of 91.3%. The significant caries index (SiC) reduced from 3.4 (CI 95% 3.0-3.8) in 2002 to 2.2 (Cl 95% 1.8-2.5) in 2005. Conclusion: This study indicates an actual decline in dental caries prevalence and severity among the schoolchildren during the studied period, even though different diagnostic criteria were used. Keywords: caries, DMFT Index, oral health, significant caries index (SiC)