# Prevalence of articular disc displacement among Thai TMD patients: a retrospective study on the association with demographic and clinical characteristics

## TL;DR

This study found that disc displacement in the jaw is more common in younger, female Thai patients with certain oral habits.

## Contribution

The study identifies demographic and behavioral factors associated with disc displacement in Thai TMD patients.

## Key findings

- Disc displacement was diagnosed in 54.5% of patients and was more common in younger individuals and females.
- Behaviors like resting the chin on the hand and prior orthodontic treatment were linked to disc displacement.
- Functional occlusal contact patterns were associated with an increased likelihood of disc displacement.

## Abstract

Background: Disc displacement (DD) is among the most prevalent
intra-articular temporomandibular disorders. Identifying associated factors can
support early diagnosis and management. The objective of this study was to
evaluate the relationship between disc conditions and patient demographics and
clinical characteristics. Methods: This retrospective study analyzed 770
patient records collected from 2021 to 2025 using data extracted from the
hospital’s digital system. Variables included demographic information, behavioral
habits, occlusal characteristics, clinical findings, and temporomandibular joint
(TMJ) diagnoses. Statistical analyses were performed using descriptive
statistics, chi-square tests, independent t-tests, one-way analysis of
variance, and binary logistic regression, with significance set at p <
0.05. Results: DD was diagnosed with 420 patients (54.5%). DD patients
were significantly younger (mean 39.0 years, p < 0.001), predominantly
in the 21–40 age group (p = 0.002), and more often female (72.0%,
p < 0.001). Behavioral habits such as resting the chin on the hand
(p < 0.001) and previous orthodontic treatment (p = 0.010)
were more prevalent in the DD group. Occlusal characteristics, including overjet,
overbite, midline deviation, and occlusal scheme, showed no significant
association with DD. However, DD patients exhibited reduced posterior and total
static articulation (p < 0.05), as well as decreased working contacts
and increased non-working contacts during the right excursion. The distribution
of TMJ clicking and disc diagnoses was comparable between the left and right
sides. More advanced subtypes of DD were linked to younger age, female sex,
reduced mouth opening capacity, and greater mandibular deviation.
Conclusions: DD was associated with demographic and behavioral factors,
particularly younger age, female sex, and certain oral habits. Functional
occlusal contacts were also found to be associated with an increased likelihood
of DD. Comprehensive assessment is essential for diagnosis and management.