The effect of mouth breathing on respiratory function and maxillofacial development in children

Objectives: The present study examines the effect mouth breathing on respiratory function and maxillofacial development of children in dental age III A. Methods: The subjects included 6 dental age III A children with ordinary state nasal breathing and 6 children with nasal disorders, and consequently demonstrated ordinary state mouth breathing. Pneumogram was obtained with a respiratory converter. The respiratory cycle, respiratory rate, tidal volume at rest and during gum chewing were analyzed. The maxillofacial development of these children was measured by the following parameters on lateral head X-rays: SNA angle, SNB angle, ANB angle and SN-Mp angle. Also, U1-SN angle and IMPA were measured to analyze tooth shape. These items were compared between nasal breathing and mouth breathing subjects in order to examine the effect of nasal obstruction on the interrelationship between respiration and maxillofacial development. Statistical analyses were carried out using a Studentfs t-test. Results: The following results were obtained from the comparison of children with ordinary state nasal breathing (nasal breathing group) and those with ordinary state mouth breathing (mouth breathing group): 1. The respiratory cycle and tidal volume tended to be lower in mouth breathing group at rest. 2. The respiratory cycle tended to be lower and tidal volume tended to be higher among mouth breathing group during gum chewing. 3. Significantly decreased SNB angle (p<0.001), significantly increased ANB angle (p<0.05), decreased SNA angle, and increased SN-Mp angle in mouth breathing group. However, there were no remarkable differences in U1-SN angle and IMPA. Conclusions: The present results indicate that mouth breathing children tend to show reduced respiratory functions at rest and during mastication. In mouth breathing children, underdevelopment of maxilla and increase of mandibular height were clarified. Thus, the mouth breathing affects the front-to-back and vertical growth of the jaw.