Prevalence of a posterior crossbite and sucking habits in Brazilian children aged 18-59 months.

This cross-sectional study aimed to assess the prevalence of posterior crossbites and non-nutritive sucking habits in 2750 Brazilian children aged from 18 to 59 months. The data were collected by 123 previously trained dental students and recorded on a response card according to the model developed by the Forsyth Institute, Boston, Maryland, USA, for optical reading. Information concerning sucking habits and family income was obtained during an interview with a parent or guardian. A clinical examination was also undertaken. Statistical analysis included chi-square and Fisher's exact tests. A posterior crossbite was observed as early as 18 months of age. The prevalence of a posterior crossbite was 10.4 per cent and was associated with age (P = 0.00) and with sucking habits (P = 0.01). The prevalence of sucking habits was 43.5 per cent. A posterior crossbite was not associated with socio-economic status (P = 0.38). While sucking habits were common among the age group studied (43.5 per cent), only a small percentage exhibited a posterior crossbite. These results suggest that further investigations into other aetiological factors, in particular genetics and respiratory problems, are necessary to provide more evidence that could clarify this issue.