Primary tooth emergence in Polish children: timing, sequence and the relation between morphological and dental maturity in males and females.

The purpose of the present study was an assessment of differences between boys and girls in the process of emergence of primary teeth. This paper also provides updated data on the timing and sequence of primary tooth emergence in Polish children. The research were conducted in the years 2004-2008, and covered 865 children (437 boys and 428 girls) aged 3 to 36 months from all nursery and randomly selected "Healthy Child Clinics" in Lodz (central Poland). The first and last primary tooth emerged, on average: in boys at 6.24 months and 24.75 months respectively; in girls at 7.07 months and 24.21 months respectively. All incisors and the first upper molars erupted significantly earlier in boys. Typical order of teeth emergence--central incisor, lateral incisor, first molar, canine, second molar--was observed in 86.36% of boys and in 89.47% of girls. The interdependence between the morphological and the dental criterion of biological maturity during the completion of primary teeth was very strong in both sexes (stronger in boys). The regression equations for the estimation of the number of erupted primary teeth based on child's chronological age, body height and body mass were proposed separately for boys and for girls.