[Three-dimensional finite element analysis of the protective performance of two types of mouthguards]

Objective: To investigate the biomechanical characteristics of thermoformed mouthguards and three-dimensional (3D)-printed mouthguards through the 3D finite element method (FEM), and to provide a theoretical basis for the selection of mouthguards in clinical and sports scenarios. Methods: A healthy male student volunteer aged 24 years was recruited in the Xi'an Physical Education University in January 2024, and the volunteer signed a written informed consent form. Both types of mouthguards were custom-made individually: the thermoformed mouthguard was fabricated using a traditional vacuum thermoforming process, and the 3D-printed mouthguard was fabricated using a stereolithography 3D printing process. The volunteer wore the two types of mouthguards respectively, and after confirming that the mouthguards fit well and the occlusion was stable, CT scanning of the maxilla and mandible was performed with a spiral CT scanner. 3D finite element models containing the teeth, jaw bones, temporomandibular joint (TMJ) articular disc and the corresponding mouthguards were established based on the acquired CT tomographic scan data. A constant load of 800 N perpendicular to the coronal plane of the human body with a duration of 0.15 s was applied to the lateral region corresponding to the anterior tooth area of the two mouthguard models to simulate the mechanical state of the anterior tooth area under impact in boxing. The magnitude and distribution law of stress on the teeth, jaw bones and TMJ articular disc under the protection of the two mouthguards during impact were compared and analyzed. Results: There were significant differences in the biomechanical performance of the 3D finite element models corresponding to the two types of mouthguards when the load was applied to the lateral region corresponding to the anterior tooth area of the mouthguards. Under the protection of the thermoformed mouthguard, stress concentration was observed in the maxillomandibular-dental hard tissue complex, the cervical region of the mandibular anterior teeth, as well as the condylar side and glenoid fossa side of the TMJ articular disc. The peak von Mises stress of the maxillary anterior teeth was 75.382 MPa, and obvious stress accumulation was detected on the condylar side and glenoid fossa side of the articular disc, with the peak stress values of 0.531 MPa and 0.476 MPa respectively. Under the protection of the 3D-printed mouthguard, the stress was uniformly dispersed in the maxillomandibular-dental hard tissue complex and the mesial and distal sides of the articular disc. The peak von Mises stress of the maxillary anterior teeth was 73.262 MPa, no obvious stress concentration was found on the glenoid fossa side of the articular disc, and the stress on the condylar side was evenly distributed in the mesial and distal regions of the articular disc. Conclusions: The 3D-printed mouthguard has better protective performance, which can effectively avoid stress concentration in the mandibular anterior tooth area and realize uniform stress distribution in the mesial and distal regions of the condylar side of the articular disc. The two types of mouthguards have similar protective performance on the maxillary anterior teeth, while the 3D-printed mouthguard has more advantages in the comprehensive biomechanical protective performance for the entire stomatognathic system.