Oral Appliances See Also Chapter

The evidence assessing the role of oral appliances in the treatment of OSA continues to grow in both quantity and quality with several randomized placebo-controlled and cross-over trials having been completed (151). The efficacy of oral appliances in successfully treating mild-to-moderate OSA (defined as less than or equal to 10 apneas or hypopnea per hour of sleep) is approximately 50% (151). The oral appliances can be broadly divided into two types: devices that reposition the mandible

FIGURE 11 (See color insert.) Volumetric magnetic resonance imaging reconstruction of the upper airway in a normal subject with progressively greater continuous positive airway pressure (CPAP) (0 to 15 cm H2O) settings. Upper airway volume increases significantly in both the retro-palatal (RP) and retroglossal (RG) regions with higher levels of CPAP. Source: From Ref. 26.

FIGURE 11 (See color insert.) Volumetric magnetic resonance imaging reconstruction of the upper airway in a normal subject with progressively greater continuous positive airway pressure (CPAP) (0 to 15 cm H2O) settings. Upper airway volume increases significantly in both the retro-palatal (RP) and retroglossal (RG) regions with higher levels of CPAP. Source: From Ref. 26.

and devices which advance the tongue. In general, their mechanism of action is thought to be related to anterior displacement of the jaw/tongue increasing the cross-sectional diameter of the airway and/or reducing the collapsibility of the upper airway (152). Upright lateral (153,154) and supine cephalometry studies (155-157), CT, and MRI have shown that mandibular repositioning appliances can increase the following: posterior airway space (153,154), airway cross-sectional area (153-157) at multiple levels, pharyngeal size (153,158), and pharyngeal volume (159). However, the specific biomechanical change in airway configuration produced by the oral appliances remains unclear and may be device dependent. Some

FIGURE 12 Axial retropalatal magnetic resonance imaging in a normal subject at two levels of continuous positive airway pressure (CPAP) (0 and 15 cm H2O). Airway area is significantly greater at 15 cm H2O than without CPAP. The airway enlargement with the application of CPAP is predominantly in the lateral dimension. Source: From Ref. 26.

FIGURE 12 Axial retropalatal magnetic resonance imaging in a normal subject at two levels of continuous positive airway pressure (CPAP) (0 and 15 cm H2O). Airway area is significantly greater at 15 cm H2O than without CPAP. The airway enlargement with the application of CPAP is predominantly in the lateral dimension. Source: From Ref. 26.

FIGURE 13 Axial retropalatal magnetic resonance imaging in a normal subject (the same subject as in Fig. 12) with continuous positive airway pressure (CPAP) ranging from 0 to 15 cm H2O. Significant lateral airway enlargement with progressive increase in CPAP results in thinning of the lateral pharyngeal walls but the parapharyngeal fat pads are not displaced. The increase in airway size with greater levels of CPAP is primarily in the lateral dimension; the anterior-posterior dimensions of the airway do not change significantly with CPAP. Source: From Ref. 26.

FIGURE 13 Axial retropalatal magnetic resonance imaging in a normal subject (the same subject as in Fig. 12) with continuous positive airway pressure (CPAP) ranging from 0 to 15 cm H2O. Significant lateral airway enlargement with progressive increase in CPAP results in thinning of the lateral pharyngeal walls but the parapharyngeal fat pads are not displaced. The increase in airway size with greater levels of CPAP is primarily in the lateral dimension; the anterior-posterior dimensions of the airway do not change significantly with CPAP. Source: From Ref. 26.

investigators report increased diameter of the retroglossal region in an anterior-posterior orientation (154,160), while others report greater changes in the retropalatal region (153,161) and lateral dimension (161). Videoendoscopy techniques provide further support to the latter findings, revealing that mandibular repositioning appliances lead to greater changes in the retropalatal region (77,161). Overall, these disparate findings suggest that the effect of oral appliances on airway configuration

FIGURE 14 Mid-sagittal magnetic resonance imaging of a normal subject (the same subject as in Figs. 12 and 13) at two levels of continuous positive airway pressure (CPAP) (0 and 15 cm H2O). There is very little change in airway caliber with the application of CPAP since CPAP does not significantly affect the anterior-posterior structures. Source: From Ref. 26.

FIGURE 14 Mid-sagittal magnetic resonance imaging of a normal subject (the same subject as in Figs. 12 and 13) at two levels of continuous positive airway pressure (CPAP) (0 and 15 cm H2O). There is very little change in airway caliber with the application of CPAP since CPAP does not significantly affect the anterior-posterior structures. Source: From Ref. 26.

is complex. To predict the success of oral appliances, investigators are beginning to use upper airway imaging techniques to access the size and position of the upper airway (77).

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