title: Accuracy and mechanical properties of orthodontic models printed 3-dimensionally from calcium sulfate before and after various postprinting treatments.
abstract: BACKGROUND
  Dental models fabricated with 3-dimensional printing technologies are revolutionizing the practice of orthodontics, but they generally comprise polymeric materials that may not be suitable for certain applications, such as soldering appliances. The objective of this study was to investigate the dimensional accuracy and mechanical properties of 3-dimensional printed ceramic-based models before and after various treatments intended to improve their mechanical properties.
  
  
  METHODS
  Thirty identical models were printed 3-dimensionally from a calcium sulfate-based substrate and divided into 3 groups for treatment: high heat (250°C for 30 minutes), low heat (150°C for 30 minutes), and Epsom salt treatment. Each model was scanned before and after treatment with a laser scanner, and dimensional stability was analyzed by digital superimpositions using a best-fit algorithm. The models were weighed before and after treatment to evaluate mass changes. Additionally, 3-dimensional printed cylinders treated as described above and an untreated control group were subjected to compressive mechanical testing (n = 11 per group).
  
  
  RESULTS
  The Epsom salt treatment group had statistically significant increases in both peak compressive stress and modulus of elasticity when compared with the other treatment groups. All treatment groups had statistically significant changes in mass, with the Epsom salt group gaining mass and the 2 heat-treatment groups losing mass. The low-temperature treatment group had a statistically significantly lower mean average for dimensional deviations (0.026 ± 0.010 mm) than did the other treatment groups (0.069 ± 0.006 and 0.059 ± 0.010 mm for high temperature and Epsom salt, respectively).
  
  
  CONCLUSIONS
  Dental models printed 3-dimensionally with calcium sulfate and treated with Epsom salt showed significant improvement in compressive mechanical properties and retained clinically acceptable dimensional stability.
authors.affiliation: Resident, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex.
authors.forename: Austin D
authors.initials: AD
authors.lastname: Ledingham
authors.affiliation: Professor and chair, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex.
authors.forename: Jeryl D
authors.initials: JD
authors.lastname: English
authors.affiliation: Associate professor and graduate program director, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex.
authors.forename: Sercan
authors.initials: S
authors.lastname: Akyalcin
authors.affiliation: Clinical assistant professor, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex.
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Cozad
authors.affiliation: Professor, Department of Restorative Dentistry and Prosthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex.
authors.forename: Joe C
authors.initials: JC
authors.lastname: Ontiveros
authors.affiliation: Assistant professor, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center, Houston, Tex; assistant professor, Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Tex. Electronic address: Fred.K.Kasper@uth.tmc.edu.
authors.forename: F Kurtis
authors.initials: FK
authors.lastname: Kasper
mesh_terms: D002133:Calcium Sulfate / Q000627:therapeutic use; D002516:Ceramics / Q000627:therapeutic use; D019245:Compressive Strength; D004548:Elasticity; D006801:Humans; D003765:Models, Dental / Q000592:standards; D009970:Orthodontics / Q000295:instrumentation / Q000379:methods; D066330:Printing, Three-Dimensional / Q000592:standards*; D015203:Reproducibility of Results; D013314:Stress, Mechanical
chemical_list: D002133:Calcium Sulfate