الفهرس 
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Abstract
This study aimed to compare the accuracy of two methods of digitization of dental models (the direct intraoral scanning and the indirect desktop scanning). Ten partially edentulous patients with unilateral bounded edentulous space (Kennedy class III), were selected from the out-patient clinic of Prosthodontics Department, Faculty of Dentistry, Ain Shams University. Each patient received impressions using two techniques:
A. group I: Conventional impression using medium body addition silicon to be scanned by the desktop scanner.
B. group II: Digital impression was done using intraoral scanner (Medit i700).
A metallic transfer aid was manufactured to fix the resin blocks in each subject consistently in the same predefined spatial relation and distance from each other. The shape of the transfer aid was based on an average sized lower dental arch, the distance between central fossae of lower second molars of the two sides was around 50 mm ±2mm and between central fossae of lower first premolar was around 36 mm ±2mm. The four blocks formed the corners of a symmetrical trapezoid. The transfer aid was cut out of a aluminum blank using a laser cutting machine and the resin blocks were constructed from composite resin in the four cubic- recesses of the transfer aid. For group I a conventional impression with a medium body polyether impression material 3M™ Monophase impression material was taken in a custom made acrylic special tray, this procedure was followed by pouring of the cast using type IV stone, then the cast was scanned using a InEos X5 desktop scanner which uses Digital light stripe projection and the scans were exported in STL format. For group II, a scan of the full lower dental arch was taken with intra-oral scanner for each of the ten patients by Medit i700. All the scans were exported to a standard STL-format for further processing.
The RPD design was carried out using 3 shape partial denture module, the denture base was designed as a metallic denture base. Claps assembly was properly chosen and designed (Aker clasp). Double Aker clap was drawn on the other side of the arch on lower second premolar and second molar. A lingual bar was chosen to connect the framework components. A 3d printed cobalt chromium metallic removable partial denture using Vulcantech metal 3d printer VM120.
Try in of the metallic partial denture frameworks were performed, teeth setting, and denture processing were done. Occlusal adjustments were performed for all patients.
All digital models scan files were imported into and analyzed using digital inspection software, Geomagic Control X by 3D Systems for three-dimensional point clouds comparison. Data was collected, tabulated, and statistically analysed.
The results of this study showed that there was no statistical significance difference in the linear measurements between the desktop scanning group and the IO scanning group.
Regarding the difference in calculated surface area of the reference block, there was no statistical significance difference between both group
Within the limitation of this study, it could be concluded that:
- Data acquisition techniques either direct (using intra oral scanner) or indirect (using desktop scanner) are reliable imaging techniques with no statistical significant difference between them for the construction of partial denture frameworks in Kennedy class III cases.
• The accuracy assessment study can be applied on free end saddle cases
• The accuracy of multiple intraoral scanners can be compared.