TMJ Research
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.
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
Background
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?
TMD: A disease that locks mouth
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.
Expert & Patients Interviews
“The effect of head positions during sleep are under-explored. If you are conducting research on it, keep me in loop”
Dr. Steven B. Kupferman
“I don’t know. I have never read research on that. It’s hard to measure”
Dr. Alexander Waldman
“I usually wake up sleeping on my right side. My jaw usually clicks in the morning when I wake up."
Emily He (Patient)
Problems
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.
Initial Exploration
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.
Literature Research
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]
Iteration 1
Testing
The stiffness of the headband and sensor covers made the device uncomfortable and affected the accuracy of myoelectric readings.
Reflection
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.
Designed screw holes on the cover for adjustable angles; Designed an elastic band holder for adjustable length. To support potential future mass testing, I designed a portable testing box to organize the boards.
Iteration 2
Testing & Reflection
Flexible sensor covers for accurate reading
To make the sensor covers more flexible, and improve data accuracy. I modified the 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.
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.
Myoelectric Sensor, IMU & Pressure Sensor integration
To address limitations from Iteration 3, I integrated the sensing system into a soft head wrap structure inspired by a post-surgery TMJ face wrap. The prototype uses an IMU to track head-neck orientation, myoelectric sensors to monitor masseter muscle activity, and pressure sensors to measure direct contact pressure across key facial stress points. I guided participants through different sleep positions while recording head orientation across the X, Y, and Z axes, muscle activity, and localized pressure data. The collected signals were then organized and analyzed in Python to evaluate patterns between sleep posture and jaw pressure.
Testing
Conducted tests on 11 participants
Preliminary tests were conducted on 5 individuals with TMD and 6 healthy individuals, aged 19 to 25, in various free sleep positions.
Testing Steps
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.
Data Analysis
I 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.
Analyze 25 factors in correlation matrix; Preliminary Tests showed a ±41-degree safe angle range
Future Potential Application: Dynamic Pillow
Shape Testing & Sensor integration:
I made three different shapes of neck pillows using Ecoflex. Upon personally testing them, I found the first prototype to be the most comfortable. Attached one pressure sensor to the inner side of each unit.
Mechanism
I programmed 4 units with pressure sensors, labeled A1 to A4. The system is designed to activate an air pump for either A1 or A4 when the ratio of A1 to A2 or A4 to A3 exceeds the cos41 (a parameter I aim to refine with further research). This activation causes the air pump to inflate, gently adjusting the user's head position.
收集数据的过程