Prevalence of malocclusion among mouth breathing children: do expectations meet reality?

The aim of this study was to report epidemiological data on the prevalence of malocclusion among a group of children, consecutively admitted at a referral mouth breathing otorhinolaryngological (ENT) center. We assessed the association between the severity of the obstruction by adenoids/tonsils hyperplasia or the presence of allergic rhinitis and the prevalence of class II malocclusion, anterior open bite and posterior crossbite.

Cross-sectional, descriptive study, carried out at an Outpatient Clinic for Mouth-Breathers. Dental inter-arch relationship and nasal obstructive variables were diagnosed and the appropriate cross-tabulations were done.

Four hundred and one patients were included. Mean age was 6 years and 6 months (S.D.: 2 years and 7 months), ranging from 2 to 12 years. All subjects were evaluated by otorhinolaryngologists to confirm mouth breathing. Adenoid/tonsil obstruction was detected in 71.8% of this sample, regardless of the presence of rhinitis. Allergic rhinitis alone was found in 18.7% of the children. Non-obstructive mouth breathing was diagnosed in 9.5% of this sample. Posterior crossbite was detected in almost 30% of the children during primary and mixed dentitions and 48% in permanent dentition. During mixed and permanent dentitions, anterior open bite and class II malocclusion were highly prevalent. More than 50% of the mouth breathing children carried a normal inter-arch relationship in the sagital, transversal and vertical planes. Univariate analysis showed no significant association between the type of the obstruction (adenoids/tonsils obstructive hyperplasia or the presence of allergic rhinitis) and malocclusions (class II, anterior open bite and posterior crossbite).

The prevalence of posterior crossbite is higher in mouth breathing children than in the general population. During mixed and permanent dentitions, anterior open bite and class II malocclusion were more likely to be present in mouth breathers. Although more children showed these malocclusions, most mouth breathing children evaluated in this study did not match the expected "mouth breathing dental stereotype". In this population of mouth breathing children, the obstructive size of adenoids or tonsils and the presence of rhinitis were not risk factors to the development of class II malocclusion, anterior open bite or posterior crossbite.