Abstract
Class II malocclusion may be caused by the maxillary protrusion or the mandibular retrusion. One treatment method is to use a headgear, which might affect the dimensions of the patient's airway. The aim of this study was to assess the effect of a headgear on the airway dimensions in class II malocclusion patients. A digital search and a manual search were conducted for English-language articles published from January 2000 to December 2018 about human clinical trials, including the usage of a cervical headgear in class II malocclusion patients who had measurable changes in the airway and/or jaw size. The synthesis methods of the study consisted of data concerning the study design, the type of treatment device, the patient's age at the start, the sample size, the treatment duration, the type of radiography, and the results of treatment; this data was extracted and compared. The quality of the selected articles was assessed. All of the studies had a high risk of bias, providing low-quality evidence of the effectiveness of the headgear therapy on the airway dimensions. The conclusions of the articles differed from each other and there were different mechanisms of changes in the jaw or airway dimensions. Therefore, further studies are required to find the clearest results showing the effect of a cervical headgear in class II malocclusion.
Highlights
Airway volume is decreased in Class II patients[8] and the diminished upper airway plays an important role in oxygen saturation[9] and in the development of obstructive sleep apnea (OSA), which is known as a sleep respiratory disorder.[10,11]
All selected studies were judged to have a high risk of bias (Table 2), providing low-quality evidence on the effectiveness of headgear therapy on airway dimensions
Considering the discrepancies in the literature, it can be concluded that the dimensions of different parts of the upper airway – such as sagittal dimension, vertical length and retropalatal width – demonstrated various responses to headgear treatment and that individual differences in normal growth play an important role in the response to treatment
Summary
Two major treatment options are available for Class II growing patients: functional appliances, which stimulate mandibular growth,[14] and headgear treatment, which inhibits maxillary growth.[15]. Cervical headgear (CHG) with an expanded inner bow is commonly used for restricting maxillary forward growth and for arch expansion,[16,17] and is typically designed for nighttime usage. The distal movement of the maxilla caused by such headgear seems to have an adverse effect on the size of the upper airway.[18] it has been shown in some studies that CHG facilitates mandibular growth, which may lead to improved airway size.[18,19,20] Some studies have shown that using CHG while sleeping decreases the size of the upper airway and may contribute to the occurrence of sleep apnea in patients with a history of OSA.[19,21]
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