title: Effects of build direction on the mechanical properties of 3D-printed complete coverage interim dental restorations.
abstract: BACKGROUND
  The application of 3-dimensional printing technology is emerging in dentistry and is being increasingly used to fabricate dental restorations. To date, scientific evidence is lacking regarding the effect of different factors on the mechanical properties of the printed restorations with the additive manufacturing technique.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the effect of build direction (layer orientation) on the mechanical properties of a novel 3-dimensionally (3D)-printed dental restorative material.
  
  
  METHODS
  Based on the printing direction, 2 groups were tested. In the first group (n=20), the specimens were vertically printed with the layers oriented perpendicular to the load direction. In the second group (n=20), the specimens were horizontally printed with the layers oriented parallel to the load direction. All specimens were fabricated using the DW028D 3D-printer. The specimens were loaded with a universal testing machine at a crosshead speed of 1 mm/min with a 10-kN load cell. The test was performed at room temperature (22°C) under dry testing conditions. The compressive strength was calculated for both groups, and the results were compared using the unpaired t test (α=.05).
  
  
  RESULTS
  The mean ±SD compressive strength for the vertically printed specimens was 297 MPa (±34) compared with 257 MPa (±41) for the horizontally printed specimens (P=.002).
  
  
  CONCLUSIONS
  Within the limitations of this study, the layer orientation was found to influence the compressive strength of the material. Vertically printed specimens with the layers oriented perpendicular to load direction have improved mechanical properties more than horizontally printed specimens with the layers oriented parallel to load direction.
authors.affiliation: Doctoral student, Department of Oral Implantology and Prosthetic Dentistry, Academic Centrum for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije University, Amsterdam, The Netherlands. Electronic address: nawalmurshed@gmail.com.
authors.forename: Nawal
authors.initials: N
authors.lastname: Alharbi
authors.affiliation: Researcher, Department of Oral Implantology and Prosthetic Dentistry, Academic Centrum for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije University, Amsterdam, The Netherlands; and Lecturer, Department of Removable Prosthodontics, Faculty of Dentistry, Cairo university, Cairo, Egypt.
authors.forename: Reham
authors.initials: R
authors.lastname: Osman
authors.affiliation: Professor, Department of Oral Implantology and Prosthetic Dentistry, Academic Centrum for Dentistry Amsterdam (ACTA) University of Amsterdam and Vrije University, Amsterdam, The Netherlands.
authors.forename: Daniel
authors.initials: D
authors.lastname: Wismeijer
mesh_terms: D003188:Composite Resins / Q000627:therapeutic use; D019245:Compressive Strength; D003761:Dental Impression Technique; D003764:Dental Materials; D003794:Dental Restoration, Temporary / Q000379:methods*; D003799:Dental Stress Analysis; D006801:Humans; D066330:Printing, Three-Dimensional
chemical_list: D003188:Composite Resins; D003764:Dental Materials