Abstract This study aimed to assess the discriminant validity of the Caries Assessment Spectrum and Treatment (CAST) at different thresholds, compared with the Decayed, Missing, and Filled Teeth Index (dmf) instrument, to discriminate caries risk factors. A cross-sectional study was conducted including children aged 2-5 years from preschools in Southern Brazil. Parents answered a questionnaire, and children were clinically examined using the CAST instrument and, in the following weeks, using the dmf index.

Two caries thresholds were adopted for CAST:

caries in dentin (CAST4-7/CAST2,4-8) and enamel caries (CAST3-7/CAST2-8). Poisson regression was used in the analysis (p < 0.05). A total of 200 children were included. The prevalence of caries was 47.0% with dmf, 42.5% with CAST4-7, and 77.5% with CAST3-7. When the outcome was caries prevalence, CAST4-7 discriminated between sexes, household crowding, and dental pain, and CAST3-7 discriminated age and family income, while the dmf was associated with dental pain. When experience of caries was the outcome, all the criteria discriminated between sexes, age, family income, household overcrowding, visible dental plaque, and dental pain, while dmf and CAST2-8 also discriminated maternal schooling. The CAST discriminated caries risk factors similar to the dmf index when caries experience was the outcome. When prevalence was considered, CAST was able to discriminate for more individual characteristics than dmf.