There are several treatment modalities for Class II division 1 malocclusion, but there are only few studies exploring the treatment effect upon pharyngeal airway. The study aimed to compare the effects of extraction versus non-extraction mechanics on pharyngeal airway after treatment of Class II division 1 malocclusion.
The 60 Class II division 1 growing patients (whose mean age was 11.81 ± 0.79 years) were divided into Group I four first premolar extraction and Group II non-extraction with Class II traction. Skeletal development was evaluated from cervical vertebral maturation stages. Dento-skeleton and pharyngeal airway dimension were analyzed from consecutive lateral cephalograms before and after treatments. Significant differences within and between groups of the studied variables were evaluated by Paired-samples T test and Independent-Samples T test (p < 0.05), respectively.
Before treatment, the extraction group exhibited lower skeletal maturation, less retrognathic mandible, more protrusive incisors, wider oropharyngeal and hypopharyngeal airway, shorter soft palate and more anterior position of the tongue. Both treatments produced significant backward rotation of the mandible and retroclination of the upper incisors, downward and forward movement of hyoid bone. Significant increase of the nasopharyngeal and hypopharyngeal dimensions, soft palate length and thickness, tongue length and forward movement of the tongue were only found in the non-extraction group. Forward movement of the bony chin had significant correlations (p < 0.05) with the increase of hypopharyngeal dimensions, forward movement of the tongue and hyoid bone.
Treatment of Class II division 1 malocclusion in growing patients by either extraction or non-extraction mechanics did not produce significant adverse effect on pharyngeal airway dimension. Non-extraction treatment with Class II traction tended to have a positive effect on the pharyngeal airway.