Anterior space relations and lower incisor alignment in 9-year-old children born in the 1960s and 1980s.

The anterior arch spaces and the effect of early loss of deciduous canines have been studied in 2 different cohorts of 9-year-old children. One group of 119 children was from Norway and consisted of 56 girls and 63 boys, and 1 group of 133 children was from Sweden and consisted of 72 girls and 61 boys. Within these cohorts, half of the children were born in the 1960s and half in the 1980s. The 1960s group has been compared with the 1980s group to look for anterior arch changes occurring during this period of time. The children who had lost a lost deciduous canine at the age of 9 years were also compared with the children with all deciduous canines remaining. Groups were compared with analysis of variance. It was found that children with a lost deciduous canine at the age of 9 years belong to a group with less available arch space and are a crowded group when compared with an earlier study. For the girls, this was also associated with larger teeth. Anterior arch space did not differ between the 1960s and the 1980s groups except for the Swedish boys, where there was less available mandibular arch space in the 1980s group. The irregularity index for the 4 mandibular incisors was increased in the 1980s group compared with the 1960s group. This could indicate a secular trend toward an increased prevalence of malocclusion in the present population.