Maximum opening of the mouth by mouth prop during dental procedures increases the risk of upper airway constriction

Abstract

From a retrospective evaluation of data on accidents and deaths during dental procedures, it has been shown that several patients who refused dental treatment died of asphyxia during dental procedures. We speculated that forcible maximum opening of the mouth by using a mouth prop triggers this asphyxia by affecting the upper airway. Therefore, we assessed the morphological changes of the upper airway following maximal opening of the mouth. In 13 healthy adult volunteers, the sagittal diameter of the upper airway on lateral cephalogram was measured between the two conditions; closed mouth and maximally open mouth. The dyspnea in each state was evaluated by a visual analog scale. In one subject, a computed tomograph (CT) was taken to assess the three-dimensional changes in the upper airway. A significant difference was detected in the mean sagittal diameter of the upper airway following use of the prop (closed mouth: 18.5 +/- 3.8 mm, maximally open mouth: 10.4 +/- 3.0 mm). All subjects indicated upper airway constriction and significant dyspnea when their mouth was maximally open. Although a CT scan indicated upper airway constriction when the mouth was maximally open, muscular compensation was admitted. Our results further indicate that the maximal opening of the mouth narrows the upper airway diameter and leads to dyspnea. The use of a prop for the patient who has communication problems or poor neuromuscular function can lead to asphyxia. When the prop is used for patient refusal in dentistry, the respiratory condition should be monitored strictly, and it should be kept in mind that the "sniffing position" is effective for avoiding upper airway constriction. Practitioners should therefore consider applying not only systematic desensitization, but also general anesthesia to the patient who refuses treatment, because the safety of general anesthesia has advanced, and general anesthesia may be safer than the use of a prop and restraints.

Keywords: asphyxia; dental procedure; maximum opening of the mouth; mouth prop; risk management; upper airway constriction.

Figures

Figure 1

Measurement points in the upper airway on the lateral cephalogram. Three intervals in the sagittal diameter of upper airway at; A) Uvular tip. B) Midpoint between the 2nd and 3rd cervical vertebra as a tongue base. C) Epiglottic vallecula.

Figure 2

Individual cephalograms for each patient. All subjects indicated upper airway constriction by maximum opening of the mouth.

Figure 3

Decreases in the sagittal upper airway diameter induced by maximum opening of the mouth.

Figure 4

Changes in the upper airway formation induced by maximum opening of the mouth.

Figure 5

Changes of dyspnea and SpO2 induced by maximum opening of the mouth. Abbreviations: SD, standard deviation; SpO2, percutaneous arterial oxygen saturation; VAS, visual analog scale.

Figure 6

Correlation between the constriction rate (%) in the mean upper airway diameter and BMI (kg/m2), maximum opening of the mouth (mm), or VAS (mm). Abbreviations: BMI, body mass index; CI, confidence interval; PI, probability interval; VAS, visual analog scale.

Figure 7

Difference in the airway between the closed mouth and the maximally open mouth. This X-ray computed tomograph (CT) also indicated that the upper airway became narrower when the mouth is maximally open.