Changes in the sagittal pharyngeal airway dimension following levelling and alignment in class II division 2...

This study aimed to evaluate changes in the sagittal pharyngeal airway dimensions (SPAD) and the related mandibular position following maxillary levelling and alignment in late adolescent Class II division 2 (Class II/2) patients.

Thirty Class II/2 patients (mean age 14.07 ± 1.21 years) were included. Pre-treatment orthodontic records were acquired, including panoramic and lateral cephalometric x-rays (T0), photographs, and study models, followed by the onset of levelling and alignment in the upper arch. Lateral cephalometric x-rays and photographs were repeated six months later at the termination of this stage (T1), and measurements were performed in comparison to T0. SPAD was assessed at the nasopharyngeal, oropharyngeal, and laryngopharyngeal levels. Mandibular position was evaluated using the Ba-Ar distance, while sagittal and vertical skeletal relationships were assessed using SNA°, SNB°, ANB°, and FMA°. Upper incisor inclination was accounted for using the U1-FH° measurement.

Alignment of the maxillary arch in Class II/2 patients elicited a significant SPAD increase at the nasopharyngeal and the oropharyngeal levels (p < 0.001), with a non-significant change evoked at the laryngopharyngeal level (p = 0.42). Antero-posteriorly, a significant increase in the SNAº, SNBº, together with a significant decrease in the ANBº angle have been documented at T1. A significant increase in the Ba-Ar has been noted at T1 in contrast to T0, in addition to a significant reduction in the vertical dimension (FMAº). Dentally, a significant increase in the U1-FHº has been documented following the implemented treatment stage (p < 0.001).

Results of this study may suggest that maxillary levelling and alignment in Class II/2 patients during the decelerating growth phase is associated with augmentation of the nasopharyngeal and oropharyngeal airways. These changes coincide with the significant labial tipping of the maxillary incisors and subsequent functional mandibular advancement, which collectively improve the intermaxillary relationship and reduce the vertical skeletal dimension. While natural growth cannot be entirely excluded, the rapid change suggests that these improvements are closely linked to the functional mandibular response.

Maxillary alignment in Class II division 2 cases may enhance upper airway patency by triggering a forward functional mandibular response, highlighting a potential link between orthodontic correction and upper airway patency. Name of the Registry: ClinicalTrials.gov Trial Registration Number: NCT06602518 Date of Registration: 19/09/2024 "Retrospectively registered". URL: https://clinicaltrials.gov/study/NCT06602518?cond=nct06602518&rank=1.