Enabling X-ray computed tomography measurement of contact surfaces in mono-material assemblies and titanium dental implant systems

Since X-ray computed tomography (CT) can analyse non-accessible features and parts in a non-destructive way, it enables the inspection of the individual components of assemblies in the assembled state. Such unique inspection capability is of great relevance because, even when each part of an assembly meets the specified tolerances, the proper functioning of the assembled system is not guaranteed, as variations can occur during the assembly operations, for instance due to clamping and/or assembly forces. Besides the dimensional evaluation of components in the assembly state, contact surfaces/interfaces and micro-gaps between coupled assembled components are in many cases important to be accurately identified and measured. These evaluations can be more easily conducted on multi-material assemblies in which the materials of the single components are characterized by different densities and characteristics, thus enabling their mutual distinction and segmentation within the CT reconstructed volume. In the case of mono-material assemblies, instead, due to the single X-ray attenuation coefficient to be considered, the three-dimensional model of the assembly resulting after CT reconstruction would appear as a unique and continuous volume in regions where components are in contact, with serious difficulties in evaluating their interface. To overcome this limit, the present research was aimed at developing new CT-based methods to enable a complete evaluation of mono-material assemblies. Such methods were applied to titanium dental implant systems, for which an accurate analysis of contact surfaces and interfaces between the assembled components is crucial to ensure perfect sealing and prevent mechanical failures as well as microbiological leakage and consequent bacteria infiltrations. Finally, the accuracy of the obtained measurement results is evaluated using a reference object made of titanium, featuring different calibrated micro-gaps.