Criteria for the various diagnostic systems were as follows: For caries, a five-graded diagnostic system was used,where enamel lesions were characterised as grades 1 or 2, and dentine lesions as grades 3, 4, or 5. Secondary caries, filled and extracted (due to caries only) teeth and the care index (a fraction with filled teeth as numerator and d3-5mft count as denominator). For dental erosion, a four graded diagnostic system was applied on buccal and palatal surfaces of the primary maxillary anterior teeth (53-63) and the occlusal surfaces of all primary molars. Erosion grade 3 was considered severe and grade 4 very severe. A modified DDE index was selected for DDE registration in which demarcated opacities were coded 1, diffuse opacities 2, demarcated and diffuse opacities 3, hypoplasia 4, hypoplasia and opacities 5, post-eruptive breakdown of enamel 6, and atypical fillings 7. Finally, for dental plaque and gingival bleeding, the PI and GBI were reported around the marker teeth 55, 51, 65, 75, 71, and 85. The presence of plaque in the four amelo-gingival areas was assessed with a dental probe and absence of debris was recorded as score 0 and presence as score 1. Gingival bleeding was recorded by probing cautiously using a WHO periodontal probe with a 0.5-mm ball tip on six surfaces; mesio-buccal, in the middle of the buccal surface, disto-buccal, mesio-lingual, in the middle of the lingual surface and, disto-lingual. If bleeding occurred within 10 seconds in at least one of the places, the tooth was scored 1 (bleeding), otherwise the tooth was scored 0.