Dynamic Pillow

(TMJ Research)

Faculty Advisor: Dr. Mark S. Baldwin @ UCI Informatics

Medical Advisor: Dr. Steve Kupferman (USA) @Los Angeles Center for Oral and Maxillofacial Surgery; Dr. Alexander Waldman (USA) @Waldman Orthondontics; Dr. Dongmei H. (China) @ SHJT Hospital, Oral and Maxillofacial; Dr. Tsurugi (Japan) @Tsurugi Clinic Tokyo

Sponsored by UCI UROP (Undergraduate Research Opportunities Program)

Individual Research Project

I conducted research on the correlation between different sleeping positions and TMD. I prototyped four iterations of experimental devices to discover the correlation. I'm currently developing a dynamic pillow mechanism that reads the pressure signal from the patient’s head and uses a programmable air system to adjust shapes and place the patient’s
head in the safest range of angles.

Background

I have been living with TMD for over a decade and have undergone three surgeries as part of my treatment journey.

Even though many specialists doubt that there the relationship between jaw pressure and head positions during sleep are correlated, it was barely studied. Because the research process is too tricky.

Questions

What’s the safe range of sleep head positions that could alleviate TMD?
How might we assist people to adjust sleep head positions to that safe range?

Temporomandibular disorders (TMD) are disorders temporomandibular joints, the jaw muscles, and the nerves associated with chronic facial pain. Symptoms include pain in the jaw joint, Pain that spreads to the face or neck. Limited movement or locking of the jaw. Painful clicking, popping in the jaw joint when opening or closing the mouth. Ringing in the ears, hearing loss, dizziness. TMD affects up to 15 to 20% of adult patients, more common in women.

Problems

Expert & Patients Interviews

“I usually wake up sleeping on my right side. My jaw usually clicks in the morning when I wake up."

“The effect of head positions during sleep are under-explored. If you are conducting research on it, keep me in loop”

“I don’t know. I have never read research on that. It’s hard to measure”

Dr. Steven B. Kupferman

Dr. Alexander Waldman

Emily He (Patient)

Personal Background

TMD: A disease that locks mouth

General Facial Pressure Distribution in Sleep

Hypothesized: More sleep pressure on the jaw leads to thinner powder residue there compared to other facial areas.

Tested hypothesis on individuals with and without TMD.
Applied UV powder before sleep; observed residue after waking.
Three out of five subjects showed notably thinner jaw powder.
Observation done under regular and UV light.

Initial Exploration

Electromyography (EMG), as noted by Szyszka-Sommerfeld et al. (2020), effectively measures the electrical activity of masticatory muscles, like the masseter, in both TMD patients and those without TMD. EMG's ability to detect differences in masseter muscle activity across these groups suggests it as a viable alternative for monitoring myoelectric activity, which reflects muscle response to pressure, in a sleep environment. [2]

Literature Research

The stiffness of the headband and sensor covers made the device uncomfortable and affected the accuracy of myoelectric readings. This experience highlighted the need for a balance between secure sensor placement and gentle contact with the face to avoid additional pressure on the masseter muscles.

Portable Device: Monitor Myoelectric Signals

Informed by my observations in Iteration 1, I included two myoelectric sensors to monitor changes in myoelectric activity during different head positions in sleep.

Inspired by headphones, I designed a wearable device with an elastic band linking two sensor covers, each containing a myoelectric sensor.

Testing

Iteration 1:

Designed screw holes on the cover for adjustable angles; Designed an elastic band holder for adjustable length

Myoelectric Sensors

Part B

To support potential future mass testing, I designed a portable testing box to organize the boards.

Part A

Reflection

Overview

3D Modeling

To make the sensor covers more flexible, and improve data accuracy. I modified my prototype and looked for more flexible materials as the sensor covers. Tested Sensor Covers with Acrylic, Rubber, and Ecoflex for Stiffness Variability.

Upon evaluation of each material, I determined that the sensor cover made of Ecoflex had the highest level of flexibility. I used medical tape for secure skin attachment during sleep to minimize data loss.

Testing

Sleep positions were not strictly confined to the side, back, or stomach. Considering integrating an IMU that could quantify and measure the various angles and positions of the head into the prototype could provide a more comprehensive understanding of head movements and their impact on myoelectric signal readings.

Reflection

Iteration 2

Flexible sensor covers for accurate reading

3D Modeling

To solve the problem I encountered in iteration 3, Dr. Baldwin suggested using a head wrap. I found a head wrap that I used after my TMJ surgery and decided to integrate all sensors within the structure of the face wrap itself. To precisely measure the correlation between sleep positions and jaw pressure, We’re using IMU (Inertial Measurement Unit) to monitor the head- neck angle, Myoelectric Sensors to monitor changes in muscle electrical activity, and Pressure Sensors to measure the direct pressure exerted on the skin's surface.

Participants will be guided to sleep in different positions throughout the study. During this period, we will record their head orientation across three axes (x, y, z), the myoelectric activity within the masseter muscles, and the pressure exerted on the stress surface. The gathered data will then be organized into a confusion matrix for detailed analysis, which will be analyzed using Python.

Iteration 3

Pressure Sensor with 16 units

Pressure Sensor kit

IMU + Myoelectric Sensors

3D printed an IMU sensor holder, using elastic band to adjust position

Inertial Measurement Unit

Head band that integrate all sensors within the structure

Wrapped sensors in head band

Myoelectric sensors after wrapped in silicone cover

Myoelectric Sensor, IMU & Pressure Sensor integration

Testing

Step 1: Attached myoelectric sensors and an IMU to the participants.

Step 2: Wrapped the sensors securely with a headband.

Step 3: Positioned a pressure sensor to interface precisely between the participant's jaw area and the pillow surface.

Step 4: Collected data while participants slept in a variety of positions.

Preliminary tests were conducted on 5 individuals with TMD and 6 healthy individuals, aged 19 to 25, in various free sleep positions.

Testing Steps

Conducted tests on 11 participants

Organized the 25 factors — including the pressures of 16 units, AVG_F(g), MAX_F(g), EMG1, EMG2, AVG_EMG, MAX_EMG, Roll, Pitch, and Yaw - into a correlation matrix.