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. Then randomly divided into two equal groups. Dies were scanned by an extraoral scanner digitally. Then 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 samples were loaded to failure in newton (N) using a universal testing machine. To assess the failure mode pattern, fractured samples were examined using a digital microscope with a magnification of 35x.

Result: Vertical 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: Vertically printed specimens have greater fracture resistance after aging than horizontally printed specimens. For 3D printing, an orientation of 120° is better.