To identify the clinical, socioeconomic, dietary, and hygienic predictors of the increasing Decayed, Missing, and Filled Teeth (DMFT) index, in a cohort of school children in Loja, Granada, Spain, during a three-year period (1994-1997).A retrospective cohort study was conducted in 812 students to measure the DMFT index, using the methods recommended by the World Health Organization. Statistical analysis was conducted using logistic regression models.During the study period, the DMFT index increased from 1.86 to 4.5 for the study cohort as a whole, and from 3.71 to 4.47 among twelve-year olds. The DMFT at mid-period was associated to an increase in the final DMFT. The relative risk for attending school no. 3 was 0.69 (95% CI 0.60-0.8) vs. school no. 4, and 0.78 (95% CI 0.67-0.90) vs. school no. 5.The final model showed that the DMFT at mid-period was a risk factor for an increase in the DMFT index and that attending school number 3 was a protective factor.