Impact of craniofacial skeletal characteristics on temporomandibular joint's articular disc position in temporomandibular disorders

Abstract

This retrospective study aims to: (1) determine whether craniofacial skeletal characteristics differ based on the type of temporomandibular joint (TMJ) disc displacement (DD); and (2) identify cephalometric variables that correlate with and predict articular disc position. A total of 294 joints corresponding to 147 female patients, aged 18 to 41 years, were included. Based on the criteria of DC/TMD and subsequently magnetic resonance imaging (MRI) findings, the joints were categorized into three groups: 1) bilateral normal disc position (BN), 2) disc displacement with reduction (DDR), and 3) disc displacement without reduction (DDWR). The lateral cephalograms were assessed, and twelve landmarks were marked on each radiograph, from which fifteen variables were derived. Cone beam computed tomography (CBCT) images were evaluated for joint spaces, glenoid fossa characteristics, and condylar inclination. One-way ANOVA and post-hoc Tukey tests were used to compare variables across groups. Bivariate Pearson correlation analysis was conducted to assess relationships between glenoid fossa characteristics, disc position, condylar position, and skeletal morphology. Multiple linear regression (MLR) was applied to determine cephalometric predictors of disc position. Significant differences were observed in joint spaces, condylar inclination, and fossa morphology across the three groups. ANB, FMA, y-axis, gonial angle, and ramus height showed significant correlations with disc position. MLR demonstrated that FMA, ramus height, and articular angle were the strongest predictors of DD, particularly in DDWR, with an explanatory power of 55% (R² = 0.55, p < 0.001). Craniofacial morphology plays a key role in the pathophysiology of DD. Patients with a steeper mandibular plane (higher FMA) and reduced ramus height were more prone to DDWR. These findings highlight the importance of cephalometric evaluation in assessing TMD and predicting disc position.

Keywords: Cone beam computed tomography; Craniofacial morphology; Disc displacement; Internal derangement; Magnetic resonance imaging; Temporomandibular disorders; Temporomandibular joint.

Fig. 1

Measurement of disc position distance in relation to the long axis of the condyle. (A,B) Long axis of the condyle; (C,D) Distance from the posterior border of the disc (D) to the intersection point (C) of the condylar long axis and the external condylar contour.

Fig. 2

MRI assessment of TMJ disc position: (A) Normal disc position, closed mouth; (B) Normal disc position, open mouth; (C) Disc displacement with reduction (DDR), closed mouth; (D) DDR, open mouth; (E) Disc displacement without reduction (DDWR), closed mouth; (F) DDWR, open mouth.

Fig. 3

Cephalometric landmarks used in this study: 1, Sella (S); 2, Nasion (N); 3, Porion (Po); 4, Orbitale (Or); 5, Point A (A); 6, Point B (B); 7, Pogonion (Pog); 8, Menton (Me); 9, Gonion (Go); 10, Articulare (Ar); 11, Anterior nasal spine (ANS); 12, Posterior nasal spine (PNS).

Fig. 4

Linear cephalometric measurements used in this study: 1, Anterior cranial base length (S-N); 2, Posterior cranial base length (S-Ar); 3, Ramus height (Ar-Go); 4, Total posterior facial height (S-Go); 5, Total anterior facial height (N-Me).

Fig. 5

Angular cephalometric measurements used in this study: 1, SNA; 2, SNB; 3, Articular angle (S-Ar-Go); 4, FH to mandibular plane angle (FMA); 5, Gonial angle (Ar-Go-Me); 6, Facial convexity; 7, Facial angle; 8, ANB; 9, Y-axis.

Fig. 6

CBCT measurements: (A) Head orientation. (B) Sagittal spaces: AS, anterior space; PS, posterior space; SS, superior space. (C) Glenoid fossa: AEH, anterior eminence height; AEI, anterior eminence inclination; HF, height of the fossa; WF, width of the fossa. (D) Condylar inclination: ACI, anterior condylar inclination; PCI, posterior condylar inclination. The figure was produced using Dolphin Imaging software (Version 11.9, Dolphin Imaging, Chatsworth, CA, USA; https://www.dolphinimaging.com/).

Fig. 7

Shows the line fit plot of actual and predicted disc positions in the DDWR group, generated using multiple linear regression.

Fig. 8

Shows the line fit plot of actual and predicted disc positions in the BN group, generated using multiple linear regression.

Fig. 9

Shows sagittal CBCT views of the condyle position with the disc in (A) BN, (B) DDR, and (C) DDWR positions.