Mandibular advancement impairs swallowing ability more than head extension but less than mouth opening in the supine position

Abstract

Mandibular advancement in the supine position may influence swallowing during dental treatment under intravenous sedation. This study investigated the influence of mandibular advancement in the supine position on swallowing ability, compared with head extension and mouth opening. The water swallowing test was performed in 13 healthy, awake, supine, adult subjects under four head and mandibular positions. An electromyogram of the suprahyoid muscles was recorded; the duration and peak amplitude were examined. A greater volume of water remained in the mouth during mouth opening and mandibular advancement relative to the neutral position; the volume in the mandibular advancement position was larger and smaller than that in the head extension position and during mouth opening, respectively. The duration of the electromyogram in the head extension position was longer than that in the mandibular advancement position, without differences in the amplitude. Thus, swallowing ability in the supine position was more impaired with mandibular advancement, relative to neutral and head extension positions, but less than that observed with mouth opening. Although unconfirmed by electromyogram, our findings suggest that head extension might improve airway patency by reducing the impairment of swallowing ability compared with mandibular advancement.

Figure 1

The four head and mandibular positions. (A) Neutral position: the ala-tragus line is perpendicular to the floor and the operating table. (B) Head extension position: 20-degree head extension from the neutral position. (C) Mouth-open position: 30 mm of interincisal distance in the neutral head position. (D) Mandibular advancement position: maximum mandibular advancement using a custom-made mandibular advancement appliance in the neutral head position.

Figure 2

Mandibular advancement appliance. The maxillary and mandibular dental casts were made after the alginate impressions were obtained. The dental arches of both jaws were fabricated by placing a 1-mm thermoforming polyethylene plate on the dental cast using a full pressure dental thermoforming machine. The maxillary and mandibular components were joined by autopolymer resin with the maximum mandibular protrusion tolerated without discomfort or pain.

Figure 3

Representative electroencephalogram of suprahyoid muscles (SH EMG) and piezoelectric sensor trajectory. The duration of SH EMG activity was determined using SH EMG, integrated SH EMG, the trajectory of the piezoelectric sensor, and a video-movie. The piezoelectric sensor was used to determine the duration, defined as the time between the first negative deflection and the return to the pre-swallowing level in the trajectory. Peak amplitude was determined as the maximum absolute value of the amplitude of SH EMG. A supplementary video was also used to determine the duration.