Does the duration of fixed orthodontic treatment affect caries activity among adolescents and young adults?

This cross-sectional study assessed the relationship between fixed orthodontic treatment duration and caries activity. Two hundred and sixty 10-to 30-year-olds were divided into 4 groups (n = 65): No fixed orthodontic appliances (G0), orthodontic treatment for 1 year (G1), 2 years (G2), or 3 years (G3). Orthodontic treatment duration was significantly associated with active caries: Prevalence was 1.5% for G0, 27.7% for G1, and 72.3% for G2 and G3; the median number of lesions was 0 for G0 and G1 and 2 for G2 and G3. No differences were observed between G2 and G3. The longer the duration of orthodontic treatment, the higher the prevalence/extent of active caries lesions.