Developing and Validating an Intelligent Mouth-Opening Training Device: A New Solution for Restricted Mouth Opening

Abstract

Restricted mouth opening (trismus) is one of the most common complications following head and neck cancer treatment. Early initiation of mouth-opening exercises is crucial for preventing or minimizing trismus. Current methods for these exercises predominantly involve finger exercises and traditional mouth-opening training devices. Our research group successfully designed an intelligent mouth-opening training device (IMOTD) that addresses the limitations of traditional home training methods, including the inability to quantify mouth-opening exercises, a lack of guided training resulting in temporomandibular joint injuries, and poor training continuity leading to poor training effect. For this device, an interactive remote guidance mode is introduced to address these concerns. The device was designed with a focus on the safety and effectiveness of medical devices. The accuracy of the training data was verified through piezoelectric sensor calibration. Through mechanical analysis, the stress points of the structure were identified, and finite element analysis of the connecting rod and the occlusal plate connection structure was conducted to ensure the safety of the device. The findings support the effectiveness of the intelligent device in rehabilitation through preclinical experiments when compared with conventional mouth-opening training methods. This intelligent device facilitates the quantification and visualization of mouth-opening training indicators, ensuring both the comfort and safety of the training process. Additionally, it enables remote supervision and guidance for patient training, thereby enhancing patient compliance and ultimately ensuring the effectiveness of mouth-opening exercises.

Keywords: mouth-opening exercise; quantification of exercises; remote guidance; the intelligent mouth-opening training device; trismus.

Figure 1

(a) The location of the infrared sensor shown in the red square in the figure can accurately sense the change in mouth opening; (b) the location of the piezoelectric sensor shown in the yellow square in the figure; and (c) a photo demonstrating clinical usage of the IMOTD.

Figure 2

(a) Schematics of the four-bar linkage concept, where $\overrightarrow{\mathrm{C}\mathrm{B}}$ represents the handle of the mouth-opening device and $\overrightarrow{\mathrm{O}\mathrm{A}}$ represents the lower jaw of patients; (b) a pattern diagram of the IMOTD, where yellow box highlighting the stop holes on the metal beam and red box highlighting occlusal plates.

Figure 3

(a) Display screen: N is the cycles of mouth-opening exercises, L is the mouth-opening degree, and F is resistance forces; (b) WeChat applet patient side: training plan, mouth opening, force, dietary advice, and training effect diagram. (c) The above illustration shows an example displaying the exercise data for 21 days. The pink line represents the resistant forces, the green line represents the average distraction distance, and the light blue line represents the duration of mouth opening (the horizontal axis is the number of exercising days). Bracket A illustrates a terrible compliance, while peak B demonstrates the good practice.

Figure 4

The force measurement process of the doctor’s finger with an FSR thin-film pressure sensor.

Figure 5

(a) The occlusal plate is designed to be inserted into the slider. (b) The slider is designed to be inserted into the occlusal plate.

Figure 6

(a) The IMOTD used by patients 1, 2, and 3; (b) the finger training method used by patient 4; (c) the wedge occlusal pad used by patient 4; and (d) the traditional mouth-opening device used by patient 5.

Figure 7

Maximum resistant forces were measured using both the IMOTD and the commercial pressure sensor (FSR thin-film pressure sensor).

Figure 8

Mises stress distribution under a 280 N compression (the stop nail and metal pins are hidden): (a) coupler bar; (b) pinhole; and (c) stop holes.

Figure 9

Patient 1 exercising records (triangle dots represent the mouth-opening extent and circle dots represent the resistant force).

Figure 10

MIO trends of five patients against the treatment timeline (patients 2 and 3 are still in training).