REDUCTION OF ARCH LENGTH AND ITS EFFECTS ON AIRWAY DIMENSIONS IN ADULT PATIENTS: A SYSTEMATIC REVIEW

Abstract

Objectives: The aim of this systematic review was to collect and review literature that used cone beam computer tomography (CBCT) imaging to study changes in the upper airway of adults who have undergone orthodontic treatment which retracted incisors. Methods: Pubmed, Mbase, Dentistry and Oral Science Source, and Web of Science databases were searched for relevant articles in English which met the inclusion criteria. Included articles had adult subjects orthodontically treated to retract incisors with pre- and post- treatment CBCT images. Excluded studies were case studies, opinion pieces, studies with adolescent subjects under 18 years old, or subjects with medical conditions or respiratory diseases. Studies were appraised using Joanna Briggs Institute appraisal index for cohort studies. Data collected included the sample size, age, treatment type, changes in airway volume, minimum cross-sectional area, and incisor retraction. Outcomes were analyzed using Forest Plots. Results: Of the 1,314 studies found through search, 3 retrospective cohort studies were included. These studies represented 229 total participant, 154 extraction and 75 non-extraction. All studies found no significance between incisor retraction and airway dimensions between extraction and non-extraction groups. However, within the extraction group, one study found an increase in oropharyngeal volume, while another found a significant inverse correlation of maxillary distalization and airway volume. One study found significant posterior position of hyoid in the extraction group. The studies had moderate risk of bias. Conclusion: Included studies have varying results on airway dimensions and volume that are small, and risk of bias cannot be ignored. The latest evidence for changes in arch length and incisor position on the airway with 3D imaging is weak. There is evidence that airway dimensions change in an adaptive manner to compensate for arch length and incisor position changes, which explains lack of significant changes in airway volume.