Metrotomography from Carl Zeiss has simplified qualification of new implantology methods for tooth replacement. New implantology procedures for dental prosthetics should be applied quickly with precision. The question of how accurately can implants be inserted was examined by the chair for production metrology and quality management at the machine tool lab (WZL) of the RWTH Aachen and the Clinic for Dental Prosthetics at the University Hospital as a part of an interdisciplinary project. They used a METROTOM computer tomograph from Carl Zeiss for the project.
It is important to quickly insert and precisely position in the jaw bone, the implants which are needed to anchor the dental prosthetics. The computer-enhanced planning of the insertion incorporates the current bone situation and the fictional position of the implant. On this basis, a stereo lithography process is used to create a perfectly aligned template that ensures the precision of the boreholes in the jaw bones.
During the study, the deviations between a model manufactured using the borehole template and the real moulds of the implant situation in the patient’s mouth were measured to verify the accuracy of the procedure.
A METROTOM 1500 computer tomography from Carl Zeiss was used at the WZL for the measurements. It enables determination of geometric features of the implants within a short time. The relative positions to a defined intersection plane and the angular orientations of the implants to each other are relevant to ensure the accuracy of the fit of the subsequent prosthetic.
Cylindrical metal spacing sleeves are screwed into the model at the corresponding positions in order to capture the orientation of the implants. This provides a sufficient number of probing points. As each implant is unique, the single measurement plans must be manually generated. Due to the different orientation of the spacing sleeves, capturing the positions of the implants using contact measurements is time consuming. Furthermore, there is a risk of shaft probing and thus damage to the stylus.
The model and moulds can be examined with the measurements provided by the METROTOM 1500 computer tomography using x-rays. They are then available as virtual 3D models. In addition to visualisation and segmenting possibilities, a volume model can also be used to measure the required geometric features.
CALYPSO measuring software from Carl Zeiss is used for the evaluation. CALYPSO measuring software takes the point cloud generated by METROTOM 1500 computer tomography and creates a surface model. Although each dataset is unique, a measurement including the generation of the required basic coordinate system can be completed quickly. The results are documented as an arranged measurement log, which is then used as a reference for the subsequent comparison with the mould models of the inserted implants.