A non-randomized concurrent controlled trial of myofunctional treatment in the mixed dentition children with functional mouth breathing assessed by cephalometric radiographs and study models

Objectives: This study aimed to examine the clinical effects of myofunctional treatment on children with functional mouth breathing by cephalometric radiographs and study models. Methods: A total of 224 children (6–10 years old; 114 males and 110 females; SNA°: 82.24 ± 1.67°; ANB°: 2.79 ± 0.80°, 28° < SN-GoGn° < 37°) formed three groups: MB-M group (mouth breathers with myofunctional treatment,n = 75); MB-N group (mouth breathers with no treatment,n = 70); NB group (nasal breathers with no treatment, n = 79). A blind evaluation of cephalometric radiographs and study models was conducted at T1(pre-study) and T2 (post-study), respectively. Results: Two hundred four children (MB-M:66, MB-N:68, NB:70) completed the present study. At T1, MB-M and MB-N groups, compared to their NB counterpart, had greater anterior lower facial height(P < 0.01) and overjet(P < 0.001) but shorter overbite and maxillary canines width (P < 0.001). At T2, the MB-N group exhibited a higher ANB angle, anterior lower facial height, and overjet, but shorter overbite and maxillary canines width (P < 0.001). From T1 to T2, the anterior lower facial height increased, overbite and the maxillary canines width further decreased in the MB-N group (P < 0.001). However, in the MB-M group, the incisors were retracted, overbite increased (P < 0.001), anterior lower facial height increased insignificantly (P > 0.05), and maxillary canines width increased slightly (P < 0.05). In the NB and MB-M groups, the mandible showed a normal tendency to grow forward, whereas, in the MB-N group, the mandible showed a tendency to grow downward (P < 0.001). Conclusions: Mouth breathers demonstrated increased anterior facial height and overjet but reduced overbite and maxillary arch width, which improved significantly following myofunctional treatment. Trial registration: TCTR: TCTR20220401001. Registered 1^stApril 2022-Retrospectively registered.