Magnetic resonance imaging-guided disc-condyle relationship adjustment via articulation: a technical note and case series

A digital technique to adjust the disc-condyle relationship based on CBCT-MRI fused 3D images

A digital workflow that can adjust the disc-condyle relationship rapidly and precisely is described. Cone beam computed tomography (CBCT), magnetic resonance imaging (MRI), and an intraoral scan at maximal intercuspal position are superimposed depending on the anatomic structure, and the disc-condyle relationship is adjusted on the fused display of the articular disc and condyle in the CBCT-MRI 3-dimensional spatial environment. An occlusal device is then directly designed and fabricated on the achieved maxillomandibular position, and the occlusal device is finely adjusted intraorally to improve function as needed. This technique can also be seamlessly integrated into the virtual environment to allow clinicians and dental laboratory technicians to design prostheses or treatment planning devices in a fully digital workflow.

A proposed novel digital condylar position adjustment technique to help restore a normal disc-condyle relationship

Objectives

To demonstrate a novel digital technique that enables real-time visualisation of occlusal transfer and adjustment of condyle position, to (1) improve the repeatability of occlusal transfer and the accuracy of condyle position adjustment and (2) be clinically effective in helping to restore the disc-condyle relationship.

Materials and methods

Three participants were included in the study and underwent facebow transfers using two different methods. The digital method used patient-related three-dimensional imaging data matched with digital dental casts for occlusal transfer. The conventional method used anatomical facebows. The condylar position was adjusted based on occlusal transfer results. The results were evaluated and compared in three dimensions. In addition, clinical application data from 36 patients were analysed before and after condylar position adjustment. Statistical significance was set at p < 0.05.

Results

Differences in the spatial positions of the three anatomical structures reproduced by both methods were statistically significant (p = 0.000). After adjusting the rotation of the condylar position, the positional deviation of the condylar point along the X- and Z-axes was significantly lower in the digital group (p < 0.05). After adjustment for translation (X and Z), the positional deviation showed no difference along the X- and Z-axes (p > 0.05) but a significant difference along the Y-axis (p < 0.001).

Conclusion

A novel digital technique for occlusal transfer and condylar position adjustment was presented. This technique simplifies clinical practice, improves the accuracy of results, and can help restore a normal disc-condyle relationship.

Effect of the application of digital technology-assisted optimization in the process of adjusting jaw position

OBJECTIVES

The aim of this study was to demonstrate a novel jaw position adjustment technique derived from digital twins and evaluate the application effect of digital technology-assisted optimization in the process of adjusting jaw position on patients with temporomandibular disorders (TMD).

METHODS

A total of 74 patients with TMD who attended the Department of Temporomandibular Joint, West China Hospital of Stomatology, Si-chuan University, between June 2022 and May 2023 were selected. The patient's initial computed tomography (CT) and bilateral temporomandibular joint data obtained by magnetic resonance imaging (MRI) were collected. The 148 joints were divided into the normal disc-condyle relationship (N) group, disc displacement with reduction (DDWR) group, and disc displacement without reduction (DDWoR) group. Assisted by digital technology, the patient's CT data were reconstructed, and a personalized reference plane was established to adjust the jaw position. A three-point bite guiding splint was designed by the adjusted occlusal space and then fabricated by 3D printing technology. It was worn by the patients and then reviewed by MRI. Before and after the adjustment of jaw position, the amount and direction of condyle and disc displacement and the angle between condyle and disc were measured as the evaluation indexes of the effect of the adjustment. The correlation with condylar displacement was evaluated.

RESULTS

In the N group, the disc moved backward and downward along the X and Z axes by (-0.60±0.62) and (0.51±0.71) mm, respectively. In the DDWR group, the disc moved backward and upward along the X and Z axes by (-1.33±1.38) and (-0.09±1.31) mm, respectively. In the DDWoR group, the disc moved forward and downward along the X and Z axes by (0.49±1.76) and (1.35±1.76) mm, respectively. The angle between the condyle and the disc decreased after adjustment of the jaw position in all three groups. All patients showed improvement in symptoms after adjustment.

CONCLUSIONS

Digital technology-assisted jaw position adjustment can simplify the process, reduce the sensitivity of the technique, and improve patients' disc-condyle structure and symptoms. Therefore, its application in the treatment of patients with TMD is of great clinical significance.

Introducing a novice-friendly classification system for magnetic resonance imaging of the temporomandibular joint disc morphology

OBJECTIVE

To introduce a new classification, aiming to correspond TMJ disc configuration with diagnosis, meanwhile reduce difficulty and subjectivity in TMJ MRI evaluation and training of TMD diagnosis for dental students.

METHODS

90 patients sought for TMD treatment were enrolled in the study, whose MRIs were used to establish the new classification. A total of 180 discs were evaluated using MRI for position (normal, DDWR or DDWoR) and classified by morphology according to previous (Murakami's classification) and new classification respectively. 60 discs were selected and judged by two groups (2 TMJ specialists and 30 dental students) to assess the reliability and validity of the new classification. Questionnaires were acquired for all observers to assess the attitude toward two classification systems. Descriptive statistics, Spearman's rank correlation coefficient, and intraclass correlation coefficient were performed. P < 0.05 was considered statistically significant.

RESULTS

In the new classification, Class 1 disc was significantly correlated with DDWR and Class 3 disc was significantly correlated with DDWoR. Interobserver reliability/consistency for observers between TMJ specialists was 0.867 when Murakami's classification was applied and 0.948 when the new classification was applied. Interobserver ICC value for dental students was 0.656 when using Murakami's classification, and 0.831 when using the new classification. The difference in attitude toward different classification systems was statistically significant.

CONCLUSION

A new classification of TMJ disc configuration is presented. The correlation between disc morphology and position revealed helps diagnosis and management. The new classification improves TMJ MRI interpreting accuracy and provides a better learning and using experience.