Low-Profile Electromagnetic Field Sensors in the Measurement and Modelling of Three-Dimensional Jaw Kinematics and Occlusal Loading

Muscle and joint mechanics during maximum force biting following total temporomandibular joint replacement surgery

Total temporomandibular joint replacement (TMJR) surgery is the established treatment for severe temporomandibular joint disorders. While TMJR surgery is known to increase mouth-opening capacity, reduce pain and improve quality of life, little is known about post-surgical jaw function during activities of daily living such as biting and chewing. The aim of this study was to use subject-specific 3D bite force measurements to evaluate the magnitude and direction of joint loading in unilateral total TMJR patients and compare these data to those in healthy control subjects. An optoelectronic tracking system was used to measure jaw kinematics while biting a rubber sample for 5 unilateral total TMJR patients and 8 controls. Finite element simulations driven by the measured kinematics were employed to calculate the resultant bite force generated when compressing the rubber between teeth during biting tasks. Subject-specific musculoskeletal models were subsequently used to calculate muscle and TMJ loading. Unilateral total TMJR patients generated a bite force of 249.6 ± 24.4 N and 164.2 ± 62.3 N when biting on the contralateral and ipsilateral molars, respectively. In contrast, controls generated a bite force of 317.1 ± 206.6 N. Unilateral total TMJR patients biting on the contralateral molars had a significantly higher lateral TMJ force direction (median difference: 63.6°, p = 0.028) and a significantly lower ratio of working TMJ force to bite force (median difference: 0.17, p = 0.049) than controls. Results of this study may guide TMJ prosthesis design and evaluation of dental implants.

Investigation of the accuracy of dynamic condylar position: A model study

OBJECTIVES

To evaluate dynamic condylar positions by integrating mandibular movement recording data and cone-beam computed tomography (CBCT) and to investigate its accuracy via dynamic model experiments.

METHODS

A polyvinyl chloride skull model was utilized. A robot arm was used to operate the mandible to perform mouth opening, closing, protrusion, and lateral movements. A recording device, worn on the skull, was used to record the dynamic process and an optical position tracking (OPT) system was used to simultaneously trace the movements. A self-developed software module was used to evaluate the dynamic condylar position by integrating the dynamic tracing data and a virtual skull model derived from CBCT images. Errors were defined as differences between the dynamic coordinates of six landmarks around the condylar area derived from the software module (test) and OPT system (gold standard).

RESULTS

The condylar position errors were 0.76 ± 0.31, 0.55 ± 0.15, and 0.68 ± 0.23 mm for mouth opening, bilateral, and protrusion movements, respectively. Furthermore, the errors for small, moderate, and large mouth opening movements were 0.62 ± 0.19, 0.69 ± 0.29, and 0.94 ± 0.31 mm, respectively. The errors for all movements, except for large mouth opening, were significantly less than 1 mm (P < 0.05). The error was not different from 1 mm in the large mouth opening movement (P > 0.05).

CONCLUSIONS

Our developed method of achieving dynamic condylar position by integrating mandibular movement recording data and CBCT images is clinically reliable.

CLINICAL SIGNIFICANCE

This study proved the reliability of evaluating dynamic condylar position using a commercial dynamic recording instrument and CBCT images.

Utilizing additively manufactured custom devices to record mandibular motion by using optical jaw tracking systems: A dental technique

A technique is described for fabricating additively manufactured custom holder devices to assist optical jaw tracking systems. Most jaw tracking systems provide standardized holders attached to the trackers. The technique described aims to provide a more efficient custom holder design that improves marker retention and mandibular motion recording, decreases the incidence of the procedure complications such as tracker decementation or displacement, and increases the efficiency of the intervention by reducing the positioning time of the trackers in the patient's mouth during the clinical appointment.

The effect of periapical bone defects on stress distribution in teeth with periapical periodontitis: a finite element analysis

BACKGROUND

Apical periodontitis directly affects the stress state of the affected tooth owing to the destruction of the periapical bone. Understanding the mechanical of periapical bone defects/tooth is clinically meaningful. In this study, we evaluate the effect of periapical bone defects on the stress distribution in teeth with periapical periodontitis using finite element analysis.

METHODS

Finite element models of normal mandibular second premolars and those with periapical bone defects (spherical defects with diameters of 5, 10, 15, and 20 mm) were created using a digital model design software. The edges of the mandible were fixed and the masticatory cycle was simplified as oblique loading (a 400 N force loaded obliquely at 45° to the long axis of the tooth body) to simulate the tooth stress state in occlusion and analyze the von Mises stress distribution and tooth displacement distribution in each model.

RESULTS

Overall analysis of the models: Compared to that in the normal model, the maximum von Mises stresses in all the different periapical bone defect size models were slightly lower. In contrast, the maximum tooth displacement in the periapical bone defect model increased as the size of the periapical bone defect increased (2.11-120.1% of increase). Internal analysis of tooth: As the size of the periapical bone defect increased, the maximum von Mises stress in the coronal cervix of the tooth gradually increased (2.23-37.22% of increase). while the von Mises stress in the root apical region of the tooth showed a decreasing trend (41.48-99.70% of decrease). The maximum tooth displacement in all parts of the tooth showed an increasing trend as the size of the periapical bone defect increased.

CONCLUSIONS

The presence of periapical bone defects was found to significantly affect the biomechanical response of the tooth, the effects of which became more pronounced as the size of the bone defect increased.

Performance of Oral Cavity Sensors: A Systematic Review

Technological advancements are enabling new applications within biomedical engineering. As a connection point between the outer environment and the human system, the oral cavity offers unique opportunities for sensing technologies. This paper systematically reviews the performance of measurement systems tested in the human oral cavity. Performance was defined by metrics related to accuracy and agreement estimation. A comprehensive search identifying human studies that reported on the accuracy or agreement of intraoral sensors found 85 research papers. Most of the literature (62%) was in dentistry, followed by neurology (21%), and physical medicine and rehabilitation (12%). The remaining papers were on internal medicine, obstetrics, and aerospace medicine. Most of the studies applied force or pressure sensors (32%), while optical and image sensors were applied most widely across fields. The main challenges for future adoption include the lack of large human trials, the maturity of emerging technologies (e.g., biochemical sensors), and the absence of standardization of evaluation in specific fields. New research should aim to employ robust performance metrics to evaluate their systems and incorporate real-world evidence as part of the evaluation process. Oral cavity sensors offer the potential for applications in healthcare and wellbeing, but for many technologies, more research is needed.