Experiment 1

Background: Many types of jaw tracking devices have been developed for the analysis of functional jaw movement, but most of them are still not handy.
To improve the handiness of the jaw movement analysis devices, we propose a jaw-tracking prototype by using WB-3 IMU. The IMU was attached to mandible during normal tests without physical restriction to the subjects. The preliminary results of jaw movement analysis during free chewing with three types of food of different shapes and hardness are evaluated. A group of 9 healthy subjects aged from 21 to 36 years old kindly participated in the experiment. Chewing time, chewing frequency, Power Spectrum Density (PSD) of jaw's angular speed and acceleration, mouth opening angle were evaluated.

The results clearly show that the subjects used less chewing time, chewing frequency and energy to eat soft food; higher values were found in the case of hard food; and there was no significant difference in mouth opening angle while eating these three foods.

Objective: Our aim, therefore, is to develop evaluation methodologies to overcome the limitations of the existing devices and improve the handiness of tools for jaw movement analysis by using WB-3 system.

Results: The parameters of chewing time, chewing frequency, power spectrum density of jaw’s angular speed and acceleration, cumulative distribution function of jaw’s acceleration, and mouth opening angle are presented.
The experimental results clearly show that the subjects used less chewing time, less chewing frequency, less acceleration cumulative distribution and energy to eat
soft food; higher values were found in the case of hard food; and there was no significant difference in mouth opening angle while eating these three foods.
Our jaw movement analysis prototype using IMU WB-3 was proved to be a valid and handy method for jaw movement and pattern analysis which may be used clinically as an assistant system for dental therapy.

Experiment 2

Background:Mastication Analysis is sometimes used to diagnose and cure recent years. The purpose of Mastication Analysis is to present objective information to make a diagnosis for jaw's musculoskeletal injury and support the development of a cure. So, the development of the machine, which is used for quantitative measurement and analysis of jaw's motion, is getting more attention in medical scene.

Before now, various machines to follow jaw's motion were developed to analyze jaw's motion. But, they are inconvenient to carry. Then, we made an attempt to follow jaw's motion by WB-4 to improve the portability of jaw's motion analysis machine.

Objective and Method; The purpose is to develop the evaluation methodology of jaw's motion analysis and improve the drawbacks of the existing machine by using WB-4. We use two WB-4 sensors. One is attached under the jaw to measure the jaw's motion; the other is attached to the forehead to measure its motion when chewing (Fig. 2).
The grained gum is used to chewing, which size is 20x12x6.0[mm] Cweight is 1.4[g]. Three patterns of experiments are done;

(1)Chewing gum naturally (2)Chewing gum on right side only (3)Chewing gum on left side only

The experiment order is from (1) to (3). Measurement time is 60[s].Trial number is total 15 times (each experiment type is repeated 5 times).