A basic study for estimation of occlusal force using an ear wearable sensor

Abstract

We aim to develop earphone type wearable devices for measuring occlusal force. In this article, we investigated the correlation between occlusal force and the movement of the ear canal as a basic study to estimate the occlusion force. The proposed estimation method uses the least squares method and the weighted average. We developed an experimental device for simultaneously measuring occlusal force and the movement of the ear canal. This device primarily consists of an occlusal force sensor and a wearable ear sensor, and converts analog signals from both sensors into digital signals using an analog‐to‐digital (AD) converter, then records the data as signals associated with measurement time. The experiment involved six subjects, who performed chewing of the occlusal force sensor five times, for 2 seconds. The occlusal force sensor was placed at the right second molar, with the wearable ear sensor placed on the right ear. Through the experiment, the occlusion and the ear canal movement were found to have a strong correlation. The average correlation coefficients consistently exceeded 0.89 for all subjects.

Simultaneous Measurement of Ear Canal Movement, Electromyography of the Masseter Muscle and Occlusal Force for Earphone-Type Occlusal Force Estimation Device Development

“…In our previous research [4,30], a strong correlation was found with regard to the Pearson product-moment correlation coefficient between the ear sensor outputs and the occlusal force for weak occlusal forces of approximately 40 N; we then successfully obtained a regression line using the least squares method. Therefore, we also used single regression analysis to perform the estimations in this study.…”

“…In previous research [4,30], a strong correlation between the ear sensor outputs and the occlusal force for weak occlusal forces of approximately 40 N had been investigated. In this research, we performed experiments with strong occlusal forces exceeding 400 N. Therefore, as shown in Table 1, each absolute average of the correlation coefficient between the ear sensor value and the occlusal force, the correlation coefficient between the ear sensor value and the EMG value, and the correlation coefficient between the EMG value and the occlusal force showed high correlation for all subjects.…”

“…In advance of this study, we conducted an experiment involving five subjects about the correlation between the occlusal force with light chewing on second molar (occlusal force from approximately 0 to 40 N) and the movement of the ear canal measured using the ear sensor [4,30]. Using the results, the strong correlation between the occlusal force and the movement of the ear canal was then investigated.…”

Earable Ω (OMEGA): A Novel Clenching Interface Using Ear Canal Sensing for Human Metacarpophalangeal Joint Control by Functional Electrical Stimulation

“…Earable is an earphone-type wearable device that has a reflective photosensor in the earpiece’s center. It can measure clenching force by sensing ear canal deformation [ 42 , 43 , 44 ]. Earable is shown in Figure 1 .…”

“…Therefore, we propose an earphone-type clenching sensor interface for FES, unlike existing ones that require the placement of sensors around the mouth. We have developed an earphone-type ear canal movement sensor [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ] and showed its application in measuring clenching occlusal force [ 42 , 43 , 44 ]. We use this earphone-type ear canal movement sensor, an earphone-type occlusal measurement device (earable (OMEGA)), for an FES interface to make the mouth free from sensors by measuring the clenching motion in the ear canal.…”