Outer Shell Thickness Measuring Tool for Structures with Curved Surfaces

Accurate measurement of surface-to-interface thickness in biological structures, such as cortical bone or root dentine, is important for clinical applications in oral radiology and anatomy particularly in endodontics where inadequate remaining dentine may increase the risk of procedural complications such as perforation. Conventional methods typically rely on two-dimensional sections aligned to fixed global axes, which often fail to account for the natural curvature and complex geometry of three-dimensional (3D) biological models. This study proposes a novel automated software tool for high-resolution thickness mapping of small, highly curved structures. Using the Physics.Raycast function within the Unity 3D development platform, the tool implements a five-stage workflow: slice generation, longitudinal centerline establishment, centerline refinement, surface remeshing, and automated thickness computation. Virtual 2D slices are created at the model origin to establish a longitudinal axis, ensuring that subsequent slices remain perpendicular to the local anatomical curvature. Surface reconstruction through linear interpolation corrects segmentation artifacts and artificial holes, producing a cohesive watertight model. Validation using cylindrical and cuboidal computer-generated models representing morphological extremes demonstrated high precision, with measurements accurate to 0.0001 mm on curved surfaces. Although the software currently requires manually annotated inner and outer surfaces in .obj format, it generates robust numerical outputs and color-mapped visualizations of local thickness. Application of this method enables consistent and reproducible assessment of dentine thickness in complex root morphologies. Beyond dental applications, this framework enables reliable and repeatable quantitative analysis of curved hollow structures, including long bones, the cranial vault, and airway walls.