Abstract
The study models of 100 Grade Seven students were used to compare the Dental Aesthetic Index (DAI), the Dental Health Component (DHC) and the Aesthetic Component (AC) of the Index of Orthodontic Treatment Need (IOTN), and the Danish Ministry of Health (DMH) screening system. The basis for comparison was the agreed subjective assessment of two orthodontists for each subject. Disagreements between the subjective assessment and each screening method were further analysed in an attempt to identify the specific occlusal traits responsible for the disagreement. The DAi under-estimated treatment need in cases with displaced canine teeth, incisor crowding or rotations and increased overbite. The DAi over-estimated treatment need in cases with increased overjet in otherwise well-aligned arches. The DMH guidelines over-estimated treatment need in cases with increased overjet and crowded arches. The DHC was found to be over-sensitive in cases with increased overjet and contact point displacements greater than 2 mm. The AC under-estimated treatment need in cases with excessive overjet and buccally displaced canines, and over-estimated treatment need in cases with spaced arches and deep overbite.