Methods The research was conducted in 110 children aged 10–12 years. The presence and degree of malocclusions were estimated in a subgroup of children with oral breathing and in a subgroup with nasal breathing. Mann–Whitney U-test and χ² test were used for the statistical evaluation of differences between compared subgroups.

Results Oral respiration was reported in 40 children and nasal respiration was reported in 70 children. Malocclusion was noted in 71.8% of children, including: distocclusion 32.7%, crossbite 10.0%, vertical overlap 9.1%, openbite 6.4%, supraocclusion 3.6%, meriocclusion 0.9% and linguocclusion 0.9%. An improper way of breathing was connected with distocclusion. Distocclusion was found statistically more frequently (p<0.05) in children with oral respiration (37.5%) than in children with nasal respiration (28.5%). Parents of children with oral respiration and distocclusion more often reported in interview inflammation of the upper respiratory tract and the third tonsil has often been observed and tension of the orbicular muscle of the mouth was lower in comparison with children with nasal respiration and proper occlusion. The period of breast-feeding in children with malocclusion was shorter (6.5 months) than in children with proper occlusion (9.1 months) (p<0.05) but childhood habits (thumb sucking and nail biting) and remaining infant type of swallowing were reported more frequently (p<0.05).

Conclusion Oral respiration was connected with the presence of distocclusion and openbite coexisting with hypotension of the orbicular muscle of the mouth and remaining infant type of swallowing in children examined in adolescence.