and 2 other(s)
Background: Digital three-dimensional planning of dental implant treatment has proven its benefits to the implantation procedure. Hereby, 3D datasets of CBCT scans are able to be superimposed to optically obtained data of the oral situation in order to reproduce and consider the soft tissue situation during the planning process. The quality of this procedure is depending to the used scan datasets and their immanent failure. 416 Aim: This study aimed to compare the accuracy of the superimposition of CBCT images with digital intraoral scanning datasets on the one hand and the accuracy of the superimposition with digitally scanned gypsum models on the other hand. Subsequently, a recommendation for the digital workflow should be given. 270 Materials and methods: A highly precise polymethacrylate model of an upper jaw with full dentition was scanned with a CBCT unit (3D eXam, Kavo dental GmbH, Biberach, Germany) for the digital superimposition with digital intraoral scanning data and lab-side scanning data. In this context, the same polymethacrylate model was also scanned with a TRIOS (3Shape A/S, Kopenhagen, Denmark) digital intraoral scanner first and with the D640 model scanner (lab-side model scanning unit, 3Shape A/S) in a second step. Each of these two procedures was performed ten times to ensure statistically relevant results. Afterwards, all datasets were converted into STL-files. Files obtained with TRIOS were assigned to group 1 and files obtained with D640 model scanner to group 2. Each scan of both groups was superimposed to the CBCT dataset throughout two different ways of local fitting (local-best-fit). Firstly, every scan was superimposed to the CBCT image using the virtual structures of the teeth. Secondly, the hard palate was used to define the relation. Three-dimensional deviations of every image pair were calculated for every locus over the teeth. Statistical analysis was done via IBM® SPSS Statistics. Results: This study clearly showed that the scanning procedure which is used to reproduce the oral hard and soft tissue situation leads to different deviations in the superimposition with a CBCT dataset. Using a digital intraoral scanning unit, mean deviation was limited to 0.075mm. The lab-side scanning revealed a mean deviation of 0.129mm. By comparing these two ways of local-best-fit strategies, the relation over the teeth showed a mean deviation of 0.039 mm and the relation over the hard palate revealed a mean deviation of 0.165mm. The combination of these two examined parameters lead to the lowest mean deviation for the TRIOS scan datasets superimposed to the CBCT scan by using the local-best-fit over the teeth with 0.022mm and the highest for the lab-side scan superimposed by the relation of the hard palate with 0.203mm. All differences between groups and local-best-fit relations and combinations were statistically significant. Conclusion and clinical implications: The present data implicate a huge impact of the scanning method of the oral hard and soft tissue on the accuracy of digital superimposition to corresponding CBCT images. As immanent failure has to be reduced in clinical processes such as digital implant planning, the superimposition of a CBCT dataset with digital intraoral scanning datasets can be recommended regarding this worklflow by using a local-best-fit relation over the virtual structure of the teeth
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