Introduction: Computer-Aided-Design (CAD) and Computer-Aided-Manufacturing (CAM) of dental prostheses can save time and effort for dental technicians thus reducing cost of manufacture. Laser-Sintering (LS) and Milling (M) CAD/CAM fabrication routes are currently available for alloy frameworks. However, inaccuracies arising from the transition of virtual model to actual fabricated component may partly negate the benefits that these methods offer.
Objectives: - To introduce a novel method utilizing micro-computed tomography (micro-CT) that examines the CAD to CAM transition introduced inaccuracies.
- To compare volume between LS and M fabricated copings.
- To compare accuracy of LS and M copings to the original CAD design.
Methods: An aluminium model of a prepared lower premolar tooth for a metal-ceramic crown was made. A virtual cobalt chrome coping was then designed (InciseCAD, Renishaw, UK) and saved as stereolithography (STL) format. Two groups of five copings were then fabricated via LS (AM125, Renishaw, UK) and M (Cybaman Replicator, Cybaman-Tech, UK) methods of CAD/CAM. All copings were then scanned and saved as STL format with micro-CT (Nanotom-X) to produce three-dimensional digital models. Actual/Nominal comparisons were then performed utilizing multiple modelling/inspection software. Colored deviation maps and volume differences were computed and statistically analyzed.
Results: Volume of LS copings differentiated significantly (p<0.01) to M copings with mean of 52.99(1.93) mm3 and 62.62(0.75) mm3 respectively. Volume of CAD design (56.96 mm3) was significantly different (p<0.01) to volume of LS and M copings. Mean deviations of LS and M copings were different significantly (p<0.05) to CAD design. Colored distance mapping show contrast in surface roughness of LS and M copings.
Conclusion: The CAD design differentiated statistically from the actual fabricated component. Results may negate time, labor and cost saving benefits of CAD/CAM, however the findings may facilitate improvements. Presented method also holds promise as a non-destructive method for manufacture accuracy testing.