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Varying accuracy of superimposition of CBCT images with chairside scanning data and labside scanning data
EAO Online Library. MOTEL C. Oct 9, 2018; 232637; P-BR-85
Constantin MOTEL
Constantin MOTEL
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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 depends on the used scan datasets and their immanent failure.This study aimed to compare the accuracy of the superimposition of CBCT images with digital intraoral scanning datasets of a polymethacrylate model on the one hand and with lab-side scan datasets of the same model on the other hand. Subsequently, a recommendation for the workflow should be given.A highly precise polymethacrylate model of an upper jaw with full dentition was scanned with a CBCT unit (3D eXam, Kavo dental GmbH, Germany) for the digital superimposition with digital intraoral scanning data and lab-side scanning data. In this context, the same model was scanned with the TRIOS digital intraoral scanner (3Shape A S, Denmark) first and with the D640 model scanner (lab-side scanning unit, 3Shape A S) second. 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) after conversion into STL-files. In a first step, every scan was superimposed to the CBCT image by using the virtual structures of the teeth. Afterwards, the hard palate was used to define the relation. 3D deviations of every image pair were calculated for every locus over the teeth using ATOS professional software (GOM GmbH, Germany).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 the two ways of local-best-fit strategies, the relation to the teeth showed a mean deviation of 0.039 mm and the relation to 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 in relation to the hard palate with 0.203mm. All differences between groups and local-best-fit relations and combinations were statistically significant (statistical evaluation performed with SPSS Statistics 23).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 to the virtual structure of the teeth.
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