الفهرس 
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Abstract
The recent evolution of digital dentistry along with the newly introduced three-dimensionally (3D) produced models in fixed prosthodontics are widely used nowadays.
Aim of study: to assess marginal and internal fit of CAD/CAM zirconia crowns constructed by stone dies versus 3D printed dies.
Materials and methods: This study was performed as a clinical trial and in vitro. For the clinical study; A maxillary molar tooth was prepared to receive monolithic zirconia crown. Twelve Stone model were poured in type IV dental stone using polyether impression material to be the control group (I) (n=12). A digital Intra-oral scanning system was utilized to scan the prepared tooth, and the images were transformed into standard tessellation language (STL) files. Three different 3D printer were utilized to produce group (II). Subgroup (II-A) Stereolethography (SLA) using Formlab 2 3D printer, subgroup (II-B) Low force Stereolethography (LFS) using Formlab 3 3D printer and subgroup (II-C) Digital Light Processing (DLP) using Asiga 3D printer each (n=36). The four models were scanned by the lab scanner, followed by fabrication monolithic zirconia crowns and for each group then marginal and internal fit on the master die were analyzed statistically (p≤0.05) using the silicone replica technique (SRT).
For the invitro study; A typodont maxillary molar tooth was prepared to receive monolithic zirconia crown. Twelve Stone model were poured in type IV dental stone using polyether impression material to be the control group (I) (n=12). A digital Intra-oral scanning system was utilized to scan the prepared tooth, and the images were transformed into standard tessellation language (STL) files. Three different 3D printer were utilized to produce group (II). Subgroup (II-A) Stereolethography (SLA) using Formlab 2 3D printer, subgroup (II-B) Low force Stereolethography (LFS) using Formlab 3 3D printer and subgroup (II-C) Digital Light Processing (DLP) using Asiga 3D printer each (n=36). The four models were scanned by the lab scanner, followed by fabrication monolithic zirconia crowns and for each group then marginal and internal fit on the master die were analyzed statistically (p≤0.05) using the silicone replica technique (SRT) and Cone beam computed tomography (CBCT).
Results: Stone models and DLP 3D printer exhibited lower mean marginal and internal fit values than SLA and LFS with statistically insignificant difference between studied groups.
Conclusions: No significant difference was evident for all groups. Although DLP 3D printer had superior marginal and internal fit than SLA 3D Printer but within an acceptable clinical range and therefore can possibly be utilized in a digital workflow to construct fixed dental prostheses.
Keywords: 3D printing, Marginal and internal fit discrepancy, Monolithic zirconia, Silicon replica technique.