Evaluating Temporomandibular Disorder symptoms and patterns through

jaw motion tracking technology

Ariana Motamedi, Armin Jamshidi, Tariq Alsahafi BDS MS, Jane K. Rydin, Wendy A. Clark DDS MS

Adams School of Dentistry, University of North Carolina at Chapel Hill

OBJECTIVES

This study aimed to assess the accuracy of jaw motion

tracking (JMTK) technology in measuring maximum

opening (MO) and lateral excursion (LE) movements, and

to evaluate its reliability in detecting disc displacements.

INTRODUCTION

Understanding movements of the condyle is essential to

clinical practices of dentistry as deviations in condylar

trajectories can lead to Temporomandibular disorder (TMD)

symptoms including jaw pain.1 Healthy condylar movement

involves a fixed and stable trajectory, making it crucial to

understand and track in clinical settings, particularly in

complex rehabilitations.2 A definitive TMD diagnosis often

requires adjunctive diagnostic imaging including magnetic

resonance imaging (MRI) of the TMJ. However, the addition

of JMTK devices may aid in the early detection of disc

displacements.3 Previous methods of mandibular tracking included using

kinematic facebows and infrared cameras to track the

opening and closing patterns of the mandible and condyles.4-5

These studies showed that while healthy subjects displayed

the expected condylar trajectories, those with TMJ clicking

had deflections in their condylar paths at the point of the

click. Other studies conducted on current JMTK devices,

including Modjaw, showed how this technology can be used

alongside clinical examinations to increase the accuracy of

diagnosis and treatment.6-8

METHODS & MATERIALS

Twenty-one participants were recruited to participate in this study (UNC IRB 24-0296). Inclusion criteria included those with or

without TMJ pain and symptoms. A licensed Prosthodontist (WAC) performed a clinical exam on each participant. Measurements

for MO, deviations during MO, and LE movements were noted during the examination using a ROM scale ruler (Great Lakes

Orthodontics, Ltd).

Maxillary and mandibular scans of each participant were captured using an intraoral scanner (Trios 4, 3Shape) and imported into

the Modjaw (Tech In Motion; MedTech). Participants were then asked to perform MO and LE recorded movements. The

following measurements were compared between the Modjaw data and clinical exam: MO, deviations during MO, and LE. These

values were statistically analyzed using a Bland-Altman analysis and interclass correlation coefficient (ICC). The presence of disc

displacement during MO and LE motions was also compared between digital and clinical data. This categorical data was evaluated

using Cohen's Kappa, Phi Correlation, and McNemar test.

RESULTS

The measurements of MO, deviations on MO, and LE

showed statistically significant difference between digital

and clinical methods (p<.01). The Modjaw underestimated

the MO, with a mean difference of –8.66 mm, but recorded

greater deviations compared to the clinical method. This

value was not within the clinical range of acceptability. The

ICC values indicated poor reliability for MO and LE, but

moderate reliability for deviations during MO. Deviations

during MO also showed a strong and significant correlation

from the Pearson's r analysis (Table 1).

There was substantial agreement and strong association

between the Modjaw and clinical data when detecting disc

displacement during MO. This data was statistically

significant, and McNemar's test determined no significant

disagreement between the two methods (Table 2).

 

CONCLUSIONS

The Modjaw demonstrated improved detection of disc

displacements during MO, and accurate measurement

recordings of LE and deviations during MO. While Modjaw

can identify objective measurements and condylar

deviations, it does not substitute for a clinical examination.

However, by detecting significant and subtle deviations in

the jaw or condylar trajectories, Modjaw can aid in the early

detection of TMD symptoms and disc displacements.