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Evaluation of the airway, soft tissue, and hyoid bone position changes following premolar-extraction orthodontic treatment in Class I malocclusion
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Parnian Tadayonnezhad   , Mehdi Rafiei * , Azadeh Torkzadeh , Ali Tabrizi |
| Department of Orthodontics, Faculty of Dentistry, Isf.c, Islamic Azad University, Isfahan, Iran |
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Abstract: (13 Views) |
Background: Extracting premolars can influence changes in the soft tissue profile, airway, and position of the hyoid bone. The soft tissue profile plays a significant role in the patient's appearance and treatment satisfaction, while the airway affects breathing patterns. This study aimed to investigate these changes before and after treatment involving the extraction of the four first premolars.
Materials and Methods: This retrospective analytical study analyzed pre-and-post treatment lateral cephalograms of 27 Class I patients aged 18 to 30, referred to Isfahan Islamic Azad University. Each patient received fixed orthodontic treatment that included the extraction of all four first premolars. The cephalograms were captured in natural head position with the same distance between the x ray source and the patient, and also between the patient and the film, and manually traced. Toassesssoft tissue profile, E-line, UL-E line, LL-E line, U1-L1, FCA, ILA, MLA, and HNB were evaluated. For airway and the hyoid bone position, S-H, H-RGN, VAL, U-MPW, TB-TPPW, and V-LPW were assessed. Data were analyzed by Paired t-test and Pearson correlation coefficients (α= 0.05).
Results: The values of LL-E line (p=0.006), UL-E line (p=0.001), and the HNB angle (p=0.049) significantly decreased after treatment. Other soft tissue variables showed no significant differences(p>0.05). The airway variables did not show significant differences; however, S-H, which relates to the hyoid bone, showed a significant decrease (p=0.038).
Conclusion: Treatment of Class I patients with first premolar extraction did not change the airway but resulted in hyoid bone being positioned more superiorly. This treatment also retracted both lips and reduced facial convexity.
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Type of Study: Research |
Subject:
Oral Medicine
Received: 2025/09/16 | Accepted: 2025/09/11 | Published: 2025/09/11
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