الفهرس 
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Abstract
Aim: To compare the efficiency of oblique and horizontal build orientations on the fracture resistance of full coverage provisional restoration fabricated by 3d printer.
Materials and methods:Typedont die of maxillary first molar was prepared for full coverage crowns. After tooth preparation, typodont was duplicated into thirty-two epoxy dies using a silicon base. The epoxy dieswere randomly divided into two equal groups.Epoxy dies were scanned by an extraoral scanner digitally. Then Exocad software was used for the restoration design. Thirty-two crowns, divided into two groups and each group included 16 crowns, were put on a platform in the 3D printer software and rotated according to each build direction, 120° and 180° directions. The post cured is a LED light design for post-curing. Using A cementation loading device to cement all provisional crowns on their corresponding resin dies. Then, both groups were divided into three sub-groups,six samples nonaged, five samples were subjected to thermal cycle (1250 cycles, 5-55˚C), and five samples mechanical cycles (37,000cycles,50N). a USB digital microscope was used to assess the surface topography for samples in both groups. The specimens were loaded to failure in newton (N) using universal testing machine. Fractured samples were examined using a digital microscope with 35x magnification power to determine the failure mode pattern.
Result:oblique group recorded statistically significant (p=0.044 < 0.05) higher mean value; (2122.16 N) than horizontal group subgroup; (1820.18 N) for non-aged groups.Regarding the effect of building direction on fracture load (vertical > horizontal),
Regarding the effect of aging, non-aged > thermally aged > thermo-mechanical aged).The difference between groups regarding failure mode analysis was statistically non-significant.
Conclusion:oblique printed specimens have greater fracture resistance after aging than horizontally printed specimens. For 3D printing, an orientation of 120° is better.
Keywords: 3D printing, build direction, Aging ,Additive manufacturing, Fracture resistance, Provisional restoration.