Sequential Software Processing of Micro-CT Dental-images for Optimized 3D-FE Analysis

Objectives: The aim was to optimize 3D-FE tooth/restoration model geometries based on X-ray computed tomographic (µCT) 3D images of molar teeth. This development is part of a project studying the stress-distribution within restored teeth after polymerisation-shrinkage and under mechanical loading.

Methods: An intact mandibular molar was scanned using a high resolution micro-CT instrument (1072, Skyscan, Belgium) in which 960 horizontal slices were obtained. Forty-five non-adjacent bitmap slices were then optimally selected for model-creation. Enamel/dentin boundaries were clarified pixel-by-pixel, for each slice, using image control-system software (ScanIP, Simpleware, UK), generating a 'SFH project'. These were imported into ScanFE reconstruction software to create shell-elements 'SFE project', which were then exported as STL (triangulated 2D-stereolithography) files (Simpleware). The STL files were imported into a FE software package (Patran, MSC Software) and the elements were re-meshed. From these elements, surfaces were created and exported to another FE software (Hypermesh, Altair Hyperworks) to build the tooth cavities using ‘cutting planes'. Finally, the volumetric mesh (tetra-mesh) was created and the model was imported back to the Patran FE software to apply the boundary-conditions, material-properties and initiate post-processing (using Patran and Marc, MSC Software). To demonstrate the use of the resulting model, this was applied to the particular case of a Class I restoration subjected to distributed loading.

Results: The stress-patterns generated in the composite material were truly 3D, which suggested the potential of the model for future simulations. Stress concentrations were found at the surface where the load was applied and in the vicinity of the tooth-composite interface due to its complex geometry.

Conclusion: The described procedure is a successful method able to produce a highly detailed 3D finite element model of restored molar teeth with any cavity configuration and combination of restorative materials.