Abstract: PURPOSE: To develop a training program for lip muscle function in children with mouth breathing and craniofacial deformities, and to preliminarily verify its impact on craniofacial morphology and function. METHODS: Through a literature review, this study organized the current application status, core elements, and existing issues of orofacial myofunctional therapy(OMT) in children with mouth breathing and facial deformities, both domestically and internationally. Based on this, semi-structured interviews were conducted with 9 family members of children and 10 medical staff from a tertiary hospital, combined with qualitative interviews and the Delphi method, inviting 14 experts for two rounds of Delphi consultations to optimize and validate the consensus on the program. Results: Qualitative interviews found that all parents of the affected children focused on the improvement of facial aesthetics and respiratory function, while 90% of healthcare professionals emphasized personalized training. Delphi consultation showed that the expert authority coefficient was 0.87 and the Kendall harmony coefficient was 0.73(P<0.01). The final plan included four modules: lip muscle strength training, lip muscle coordination training, respiratory pattern adjustment, and correction of daily habits. Preliminary experimental results indicated that after 12 weeks of training, the children's static lip closure pressure increased by 81%(P<0.001), dynamic lip endurance improved by 143%(P<0.001), and the frequency of mouth opening during the day decreased by 27% (P<0.001). CONCLUSIONS: The training program developed in this study can effectively improve the lip muscle function and breathing patterns of children with mouth breathing. It has positive implications for early intervention of craniofacial morphology, providing a standardized intervention framework for clinical practice.

Key words: Mouth breathing children, Maxillofacial deformities, Lip muscle function training program, Delphi method