Development and design of a modular robot for testing cracked tooth crown restorations

Purpose Tooth cracks are subtle fractures that may damage teeth, pulp and periodontal tissue, seriously affecting oral health. Traditional evaluation relies on dentist observation and patient feedback, which is subjective and cannot reflect real crown performance. This study aims to develop a modular, cable-driven performance testing robot for crown restorations, enabling standardized in vitro evaluation and providing more reliable data for treatment outcomes. The proposed system adopts a modular cable-driven 6-spherical-prismatic-spherical (SPS) design with detachable occlusal and actuator modules, enabling flexible configuration and rapid sample replacement for various dental restoration testing tasks. Design/methodology/approach The robot design uses a 6-SPS parallel mechanism combined with a cable-driven linear actuator system to replicate mandibular motion. A removable and replaceable occlusion model accounts for individual variation. Kinematic inverse solutions and coordinate transformations were applied to describe mandibular motion, while MATLAB numerical methods solved the reachable workspace. Findings Results show the robot met expected motion requirements and successfully performed standardized in vitro testing of crown samples. The system provides objective and repeatable data to evaluate crown performance, supporting accurate treatment assessment. Originality/value This study is the first to integrate a modular 6-SPS architecture, cable-driven actuation and a detachable occlusal model into a unified dental testing robot. It enables individualized, objective and quantitative evaluation of crown restorations beyond traditional subjective clinical assessment. By combining modular design and cable-driven actuation, the proposed robot provides a novel, reconfigurable platform for standardized in-vitro testing and enhances the reliability and reproducibility of crown restoration evaluation.