Post-orthodontic Pharyngeal Airway Changes Following First Premolar Extraction and Incisor Retraction in Bimaxillary Protrusion Patients–A Retrospective Study
Objectives: The goals of orthodontic treatment are not only limited to correcting malocclusion and facial appearance but also extend to achieving normal function of the stomatognathic system and airway patency. This study aimed to investigate postorthodontic pharyngeal airway changes after the extraction of the four first premolars with subsequent retraction of the incisor teeth in patients with bimaxillary protrusion.
Materials and methods: Pre- and post-treatment cephalometric radiographs of adult patients (age range 18-30 years) who underwent orthodontic therapy for class I bimaxillary protrusion from April to July 2018 were obtained. Fixed orthodontic therapy following first premolar extraction was the absolute inclusion criteria. Cephalometric measurements of dental (upper and lower incisor retraction and retroclination) and pharyngeal airway (tongue length and height, soft palate height, superior, middle and inferior airway spaces, vertical airway length) variables were identified. Collected data was analyzed with SPSS® software. Paired t-test, Pearson’s correlation and linear regression analysis were done with statistical significance set at 95% (p-value<0.05).
Results: A total of 46 patients (16 male and 30 female) were included in the study. Statistically significant difference was evident in the mean values of pre- and post-treatment pharyngeal airway variables like soft palate thickness (0.35 mm, p<0.001), superior airway space (0.69 mm, p<0.001), and middle airway space (0.66 mm, p<0.001). Based on linear regression, retroclination of the lower incisors by 1° could predict a 0.736 mm increase in tongue length, up to 12% of times. Similarly, a 0.043 mm decrease in middle airway space could be predicted up to 17% of times following lower incisor retraction by 1 mm.
Conclusion: First premolar extraction and orthodontic retraction of incisor teeth results in significant reduction of soft palate thickness and superior and middle airway spaces. Comprehensive pre- and post-orthodontic evaluation of the soft palate, tongue and pharynx should be mandated to avoid pharyngeal airway compromise.