الفهرس 
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Abstract
This study was carried out to assess the fracture resistance of interim crowns which were fabricated by 3D printing technique compared to CAD/CAM in different oral media.
According to the sample size calculation, 40-crown-shaped samples were divided into two groups (n=20); group I was manufactured by CAD/CAM, and group II was manufactured by 3D printing technology. Each group was subdivided into four subgroups (n=5). According to the immersion solution, subgroup (A) Artificial saliva, subgroup (B) Tea, subgroup (c) Carbonated orange juice, and subgroup(D) the control (non-immersion).
Typodont model of maxillary 1” molar was prepared according to the
Following criteria: 2 mm occlusal reduction, 1.5 mm overall axial reductions.
The prepared model was scanned using an extra-oral scanner. Duplication of master die through using Silicone duplicating material.
Interim crowns were designed using 3Shape software. STL file was Produced and sent to both milling machine and printer. Crowns were milled using the IDC shape milling machine from TelioCAD temp Disc made of PMMA. The other interim crowns were printed using the Rapid Shape 3D printer using Nextdent C&B PMMA resin material.
The interim crowns were cemented on their corresponding epoxy resin dies. Using automix dual-cure self-adhesive resin cement, using cementation loading device for applying uniform load during setting of the cemented interim crowns on epoxy resin dies. All samples then were immersed in the different oral media (artificial saliva, ready-made carbonated orange juice, and tea) for 7 days.
Finally all samples were subjected to fracture resistance testing under a compressive load at the center to their long axis using computer controlled Universal testing machine with a load cell of 5 newton (N) and at a crosshead Speed lmm/min. Data was recorded, tabulated and statistically analyzed.
The following results were obtained:
The results of the fracture resistance testing for the samples. In control media, there is no statically significance difference between 3d printing and cad cam techniques. While (mean ±SD) of fracture resistance was higher in the CAD CAM technique (1262.8±580.68) compared to the 3D printing technique (817.98±78.48).
There was a statistically significant difference when comparing the 3D printed technique in different media; highest fracture resistance was in control media (817.98±78.48) then was in tea media (547.74±124.18) then was in saliva media (545.7±154.16) while the lowest fracture resistance was in orange media (500.31±102.9). When comparing CAD-CAM techniques in different media, there was no statistically significant difference between different media, when the highest one was control media(1262.8± 580.68) then was in tea media(1012.39±250.58) followed by orange media (941.38±233.43) while the lowest one was saliva media(833.65±227.48).
Regarding the total mean of resistance fracture in all media, (Means±SD) of the 3D printing technique was (594.9 ± 163.1) compared to (1012.56±363.97) for the CAD CAM technique. The CAD CAM technique had significantly higher (Means±SD) than the 3D printing technique at P=0.001.