Kinematics of mandibular advancement devices (MADs): Why do some MADs move the lower jaw backward during mouth opening?

Mandibular advancement devices (MADs) are widely used treatments for obstructive sleep apnea. MADs function by advancing the lower jaw to open the upper airway. To increase patient comfort, most patients allow the mouth to be opened. However, not all systems maintain the lower jaw in a forward position during mouth opening, which results in the production of a retrusion that favors the collapse of the upper airway. Furthermore, the kinematic behavior of the mechanism formed by the mandible-device assembly depends on jaw morphology. This means that, during mouth opening, some devices cause lower jaw protrusion in some patients, but cause its retraction in others. In this study, we report the behavior of well-known devices currently on the market. To do so, we developed a kinematic model of the lower jaw device assembly. This model was validated for all devices analyzed using a high-resolution camera system. Our results show that some of the devices analyzed here did not produce the correct behavior during patient mouth opening.

Graphic abstract