Pharyngeal airway dimensions: a cephalometric, growth-study-based analysis of physiological variations in children aged 6-17.

OBJECTIVE: The aim was to assess pharyngeal airway dimensions and physiological changes based on lateral cephalometric radiographs from healthy untreated children aged 6-17 years. MATERIALS/METHODS: The sample consisted of 880 lateral cephalograms (412 females and 468 males) of the Zurich Craniofacial Growth Study. Statistical analyses on cephalometric measurements of airway dimensions (distances 'p': shortest distance between soft palate and posterior pharyngeal wall and 't': shortest distance between tongue and posterior pharyngeal wall) and craniofacial parameters were performed. To disclose differences between different age groups, a Kruskal-Wallis test was applied. The influence of gender on 'p' and 't' was analysed by a Mann-Whitney U-test for each age group separately. The Spearman correlation was computed in order to investigate associations between craniofacial parameters. Variables associated with 'p' and 't' were chosen for multiple regression model investigation. RESULTS: The results demonstrated high interindividual variations. A slight influence of age on 'p' (P = 0.034) could be attested (+1.03 mm) but not on 't' (P = 0.208). With the exception of the 9-year age group, no significant differences between the genders were found. Correlation analysis revealed several statistically significant correlations between 't' or 'p' and antero-posterior cephalometric variables. All correlation coefficients were, however, very low and the adjusted coefficient of determination also revealed the regression model to be very weak. CONCLUSIONS: The high interindividual variations of 'p' and 't' render the use of reference values problematic. Contrary to other craniofacial structures, neither age-related changes nor sexual dimorphism were found for 'p' and 't'. Any associations to antero-posterior cephalometric characteristics seem low.

Dentofacial and upper airway characteristics of mild and severe class II division 1 subjects.

The aim of this retrospective, cross-sectional study was to assess whether mild and severe Class II division 1 subjects have craniofacial and upper airway characteristics, which relate to the severity of Class II as judged by overjet or ANB angle. The sample consisted of pre-treatment lateral cephalograms and dental casts of 131 males and 115 females (mean age 10.4 ± 1.6). Inclusion criteria were: healthy Caucasian subjects, at least ¾ Class II first molar relationship on both sides and overjet ≥ 4 mm. The cephalograms were traced and digitized. Distances and angular values were computed. Mild and severe Class II was defined by overjet (<10 mm/≥ 10 mm) or by ANB angle (<7 degrees/≥7 degrees). Statistics were performed with two-sample t-test and Pearson's correlation analysis. In the two overjet groups, significant differences were mainly found for incisor inclination while the two ANB groups differed significantly in SNA, WITS, Go-Pg, SpaSpp/MGo, SN/MGo, and Ar-Gn. The shortest airway distance between the soft palate and the posterior pharyngeal wall was significantly correlated to the NS/Ar angle. Statistical analysis revealed several significant correlations. Patients with a large overjet or ANB angle differed significantly from patients with a small overjet or ANB angle mainly in their incisor inclination. In the present sample, the overjet and to some extent also the ANB angle is determined by soft tissue or individual tooth position rather than by skeletal background. In retrognathic patients, a tendency towards smaller airway dimensions was found. However, statistical analysis did not reveal a strong connection between upper airway and dentoskeletal parameters, but a large interindividual variation.

Long-term changes in pharyngeal airway dimensions following activator-headgear and fixed appliance treatment.

The aim of this study was to evaluate changes in the pharyngeal airway in growing children and adolescents and to compare these with a group of children who received activator-headgear Class II treatment. The sample consisted of 64 children (32 males and 32 females), 32 had a combined activator-headgear appliance for at least 9 months (study group) followed by fixed appliance therapy in most patients, while the other half received only minor orthodontic treatment (control group). Lateral cephalograms before treatment (T1, mean age 10.4 years), at the end of active treatment (T2, mean age 14.5 years), and at the long-term follow-up (T3, mean age 22.1 years) were traced and digitized. To reveal the influence of somatic growth, body height measurements were also taken into consideration. A two-sample t-test was applied in order to determine differences between the groups. At T1, the study group had a smaller pharynx length (P = 0.030) and a greater ANB angle (P < 0.001) than the controls. The pharyngeal area and the smallest distance between the tongue and the posterior pharyngeal wall also tended to be smaller in the study group. During treatment (T1-T2), significant growth differences between the two groups were present: the study group had a greater reduction in ANB (P < 0.001) and showed a greater increase in pharyngeal area (P = 0.007), pharyngeal length (P < 0.001) and the smallest distance between the tongue and the posterior pharyngeal wall (P = 0.038). At T2, the values for the study group were similar to those of the control group and remained stable throughout the post-treatment interval (T2-T3). Activator-headgear therapy has the potential to increase pharyngeal airway dimensions, such as the smallest distance between the tongue and the posterior pharyngeal wall or the pharyngeal area. Importantly, this increase seems to be maintained long term, up to 22 years on average in the present study. This benefit may result in a reduced risk of developing long-term impaired respiratory function.