The present systematic review and meta-analysis was performed to assess the association between mouth breathing and facial morphological characteristics in children and adolescents. PubMed, Medline, Scopus and Google Scholar databases were searched for cross-sectional case-control studies published between 1 January 1980 and 1 April 2019. Studies comparing cephalometric data of mouth breathers and nasal breathers were included, while studies on adults were excluded. Meta-analysis was performed regarding 11 angular and 4 linear measurements. A total of 19 studies were included in the systematic review and data from 18 studies were extracted for the meta-analysis. The results indicated statistically significant decreases in Sella-Nasion-Point A (SNA) angle [mean difference (MD)=-1.33; 95% CI -2.03 to -0.63; P=0.0002] and Sella-Nasion-Point B (SNB) angle of mouth breathers as compared to nasal breathers (MD=-1.33; 95% CI -2.18 to -0.49; P=0.002). There was no difference in Point A-Nasion-Point B (ANB) angle between the two groups (MD=0.25; 95% CI -0.26 to 0.75; P=0.34). Mouth breathers demonstrated an increased mandibular plane angle, total and lower anterior facial height and decreased posterior facial height. Within the limitations of the study, the results indicated that mouth breathers tended to have a retrognathic maxilla and mandible, vertical growth pattern with high mandibular plane angle, downward and backward rotation of the mandible and an increase in total and lower anterior facial height and decrease in posterior facial height. Further high-quality studies are required to strengthen the evidence on this subject.
