Effects of the upper respiratory tract cross-section on the vertical and sagittal dimension and the facial axis according to Ricketts

This study assesses the effects of the upper respiratory tract width at the level of the adenoid in patients with a normal and abnormal breathing route on basic parameters of the morphology of the facial skeleton.

Aim
Comparison of skeletal parameters determining vertical (SNL/ML, NL/ML, NL/ML), sagittal (SNA, SNB) dimensions and type of facial rotation (the angle of the facial axis according to Ricketts) in the study and control groups and determination of the threshold value (a cut-off point) of width according to Holmberg, at which there is a deviation from the average values of basic parameters of morphology of the facial skeleton.

Material and methods
The study included 221 patients treated at an orthodontic clinic in Kielce. Based on the medical history taken, clinical examination and subjective evaluation of the upper respiratory tract width according to Holmberg 112 patients were enrolled into the study group and 109 patients into the control group. The width of the upper respiratory tract was measured using the modified Holmberg method and parameters assessing the vertical (SNL/ML, NL/ML) and sagittal (SNA, SNB) dimensions, as well as the anterior angle of the Ricketts’ axis were measured using the analysis of lateral teleroentgenograms of the head.

Results
All compared skeletal parameters indicated significant statistical differences between the study and control group. These differences were: Ricketts’ angle 6.5°, SNL/ML 8.5°, NL/ML 9.7°, SNA 2.4°, SNB 1.4°.

Conclusions
The width of the upper respiratory tract at the level of the adenoid significantly affects values of skeletal parameters evaluating the vertical (SNL/ML, NL/ML) and sagittal (SNA, SNB) dimensions and the type of rotation of the facial axis. There is a correlation between a gradual decrease in the airway dimension according to Holmberg and an increase in the vertical dimension (SNL/ML, NL/ML) and anterior angle of the Ricketts’ facial axis (posterior rotation of the mandible) and a decrease in the sagittal dimension (SNA, SNB).