Introduction: This study aimed to develop a deep learning-based method for interpreting magnetic resonance imaging (MRI) scans of temporomandibular joint (TMJ) anterior disc displacement (ADD) and to formulate an automated diagnostic system for clinical practice.Methods: The deep learning models were utilized to identify regions of interest (ROI), segment TMJ structures including the articular disc, condyle, glenoid fossa, and articular tubercle, and classify TMJ ADD. The models employed Grad-CAM heatmaps and segmentation annotation diagrams for visual diagnostic predictions and were deployed for clinical application. We constructed four deep-learning models based on the ResNet101_vd framework utilizing an MRI dataset of 618 TMJ cases collected from two hospitals (Hospitals SS and SG) and a dataset of 840 TMJ MRI scans from October 2022 to July 2023. The training and validation datasets included 700 images from Hospital SS, which were used to develop the models. Model performance was assessed using 140 images from Hospital SS (internal validity test) and 140 images from Hospital SG (external validity test). The first model identified the ROI, the second automated the segmentation of anatomical components, and the third and fourth models performed classification tasks based on segmentation and non-segmentation approaches. MRI images were classified into four categories: normal (closed mouth), ADD (closed mouth), normal (open mouth), and ADD (open mouth). Combined findings from open and closed-mouth positions provided conclusive diagnoses. Data augmentation techniques were used to prevent overfitting and enhance model robustness. The models were assessed using performance metrics such as precision, recall, mean average precision (mAP), F1-score, Matthews Correlation Coefficient (MCC), and confusion matrix analysis.Results: Despite lower performance with Hospital SG’s data than Hospital SS’s, both achieved satisfactory results. Classification models demonstrated high precision rates above 92%, with the segmentation-based model outperforming the non-segmentation model in overall and category-specific metrics.Discussion: In summary, our deep learning models exhibited high accuracy in detecting TMJ ADD and provided interpretable, visualized predictive results. These models can be integrated with clinical examinations to enhance diagnostic precision.

Magnetic resonance imaging (MRI) has proven excellent performance in dental imaging, especially for temporomandibular joint (TMJ), teeth, and periodontal apparatus. However, the high price and strict installation environment of the conventional high-field MRI has prevented its widespread use in dental clinics or developing regions. The introduction of low-cost and portable MRI scanners will help increase the easy accessibility of MRI examination and reduce the patients’ waiting time. This work introduces a low-cost portable 50 mT MRI scanner for dental imaging. First, the overall structure including permanent magnets, gradient coils, and radio-frequency (RF) coils is introduced. The cooling system is removed because the static field is maintained by the permanent magnets. The system stands 90 cm wide, 110 cm high and weighs 600 kg, which makes it possible to install in an average-sized room. Then, the design processes of specialized RF receiving coils for TMJ, teeth are illustrated. In order to improve patient comfort, an intraoral wireless coil for boosting the signal-to-noise ratio (SNR) inside the oral cavity is proposed. Furthermore, the T1-weighted images of TMJ and teeth are given to show the dental imaging performance of the proposed device.