Effects of Mandibular Advancement Device (MAD) on Airway Dimensions Assessed With Cone-Beam Computed Tomography
Section snippets
Overview of OSA
Sleep apnea is defined as a decrease in respiration, yielding hypoxia and hypercapnia during sleep. It can be caused by many factors, including those of either neurologic origin or physical blockage of the airway. This study focused on the latter, more common, OSA. OSA physically limits the amount of air that a person can inhale during sleep. It occurs in 4% of men and 2% of women. Many authors agree that polysomnographic data are needed for definitive diagnosis of OSA; however, there are
Continuous Positive Airway Pressure (CPAP)
The general aim of all treatment modalities in sleep-breathing disorders is to facilitate breathing and thereby reduce the risk of increased morbidity. Because there can be many causes of OSA, there are also several different treatment types. They all focus on preventing collapse of the lumen of the pharynx during sleep. The gold standard for initial treatment is home use of a device called CPAP18 because it seems to be somewhat of a “cure-all” OSA treatment. No matter where the obstruction in
Cephalometrics in OSA Imaging
The imaging of the upper airway space has traditionally been accomplished with the use of lateral cephalometric radiography (Fig 4). An advantage of this type of imaging is that it is widely used and readily available. It also uses a relatively low radiation dosage. However, images taken from a lateral viewpoint give only 2D information. This information is valuable because the AP dimension is that which is most likely to be changed with mandibular protrusion. It is not an ideal imaging
Radiation Dosage
A main advantage of using CBCT to image the oropharynx is the relatively low dosage of radiation. Several studies have been done to determine the exact radiation dosage to different parts of the body of different types of radiography.36, 37, 38 It has been found that the general dosage of CBCT dosimetry is up to 50 times less than spiral CT. CBCT uses only minimal radiation, equal to 7 panoramic exposures, or approximately 3.5 days of background exposure. This is a huge reduction from spiral
Methods
Twenty-six patients diagnosed with OSA who had been previously treated with mandibular advancement device (MAD) therapy by a general dental practitioner with advanced training in the diagnosis and treatment of OSA patients (J.M.) were recruited for the study following guidelines designated by the intuitional review board of the University of Louisville. There were 17 men and 9 women in this study group. Each subject underwent polysomnography to diagnose their OSA, defined as an AHI greater than
Cephalometric Measurements
The lateral cephalogram simulated image allowed the measurement of classic cephalometric measurements with the Dolphin Program. A custom cephalometric analysis was created for the purpose of this study. The measurements were tested by measuring the same image on another cephalometric analysis package, RMO Joe (Rocky Mountain Orthodontics, Inc., Denver, CO), and found to be the same.
Two series of cephalometric measurements were made. The first series described the anatomy of the subject on the
Results
The linear regression showed that there were 6 dependent, or “outcome,” variables measured on the volumetric scan that were found to be predictable by independent variables. These outcome variables were Volume of the oropharynx, largest cross-sectional area (LgCa), the cross-sectional area at C2 (C2Ca), the lateral linear dimension of the cross section at C2 (L-C2Ca), the AP linear dimension of the cross section at C2 (AP-C2Ca), and the ratio of these 2 linear dimensions (L:AP-C2Ca). One
Discussion
This study was the first to show a sample of OSA patients successfully treated with a removable MAD in 3D imaging. The authors of previous work with MAD and 3D imaging46, 50 used subjects who only snored or had untreated OSA patients with conventional CT, and MRI.
This was also the first study to use CBCT volumetric imaging of OSA patients. Previous 2D studies were limited to cephalometrics, whereas previous CT and MRI studies were limited to cross-sectional area and linear measurements. These
Conclusion
Lateral airway dimensions of the cross-section at C2, total volume, and cross-sectional area gained in the oropharynx can be predicted from the amount of mandibular forward movement. The saddle angle was a predictor of the linear anterior-posterior dimension, while the facial axis predicted the ellipticality of the airway at C2. With the placement of a MAD appliance, the smallest airway cross-section may move to an unpredictable position, superiorly or inferiorly along the length of the
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2020, American Journal of Orthodontics and Dentofacial OrthopedicsCitation Excerpt :Although our results showed that the annual OPA change (Fig 7) approximated the growth velocity of the MnL (Fig 10), functional appliances may still benefit patients with Class II skeletal malocclusions despite the commonly accepted notion that functional appliances do not “grow mandibles.” The mechanism behind this increase in the airway is not entirely well-known, but it has been suggested that patency of the oropharynx was attributed to a forward repositioning of the tongue and soft palate with the mandibular advancement.34-36 Nejaim et al37 found a significant correlation between the pharyngeal space volume and the mandible and hyoid bone measurements, including but not limited to the anteroposterior distance of the mandible and hyoid bone.
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2019, International OrthodonticsCitation Excerpt :Regarding the mean values of UAWV for OSA subjects, the findings in the 3D studies are disparate depending on the boundaries used to define upper airway or the methods used to measure the volume [10]. The results are often discussed in terms of cross-sectional areas and/or length of the upper airway [28,31,32] as well as treatment effects on airway volume after use of oral appliances or maxillo-mandibular advancement surgery [12,33,34]. In this investigation, the significant differences between the means of volumetric variables in both groups were found for UAWV and post-hyoid volume, where UAWV was found to be significantly smaller and post-hyoid volume significantly bigger in the OSA group.
The present study is currently under IRB approval at the University of Louisville as of April 20, 2006. It has undergone 2 annual reviews and is not due for another annual review until April 21, 2009. Risk to the subjects is from radiation exposure using a FDA/CDRH approved device. The short and long-term risks of somatic and genetic damage at the level used in this study are considered negligible.