Development of a Wrench-Based System for Occlusal Force Analysis: A Biomechanical Approach to Evaluating Dental Occlusion

Background The forces of the jaw muscles are transmitted to the dentition and the temporomandibular joints (TMJs). Imbalances in the force distribution can lead to occlusal trauma, excessive tooth wear, or TMJ osteoarthritis, making the assessment of bite force (BF) distribution clinically significant. Existing thin-film BF measurement devices capture the magnitudes of a system of BFs distributed at multiple occlusal contacts (OCs), but fail to capture their directional components, limiting their clinical utility. This study aimed to develop a method for representing BF systems as a wrench, a simplified force-couple model, using digital dentistry tools, and to evaluate its reliability in terms of inter-examiner reproducibility Methods A semi-automated system was developed to integrate thin-film BF measurement data with digital models of maxillary and mandibular dental arches. BF systems were represented as wrenches with six parameters: resultant force magnitude, wrench axis location, orientation, and pitch. Ten young adult participants (5 women, 5 men; mean age: 20.1 ± 2.9 years) were recruited. BF measurements were performed on all participants using the developed system. Two independent operators manually assigned BFs to the identified OCs, and the reliability of these assignments was evaluated between the examiners. Intraclass correlation coefficients (ICCs) for wrench parameters were calculated to assess the consistency of biomechanical outcomes using appropriate statistical tests, with significance set at p < .05. Results The proposed system allowed substantial automation; manual steps were limited to segmenting the IR model for each mandibular tooth and assigning BFs to identified OCs. For the BFs assigned to the identified OCs, inter-examiner agreement was evaluated, yielding an 87% match rate. Furthermore, the impact on wrench parameters was assessed using intraclass correlation coefficients (ICCs), which ranged from 0.93 to 0.99, indicating high reliability. Conclusions The developed system efficiently integrates BF measurements and three-dimensional OC analysis, providing a practical method for clinical evaluation of the BF systems. In addition, the system provides consistent outcomes in biomechanical analysis across different operators.