title: Scanning accuracy and precision in 4 intraoral scanners: an in vitro comparison based on 3-dimensional analysis.
abstract: BACKGROUND
  Intraoral scanners may use proprietary acquisition and manufacturing processes. However, limited information is available regarding their accuracy, their precision, and the influence that refraction or coating may have on their output.
  
  
  OBJECTIVE
  The purpose of the study was to evaluate the scanning accuracy and precision of 4 intraoral scanners and to assess the influence of different test materials and coating thicknesses.
  
  
  METHODS
  Models were fabricated in 3 materials (polymethyl methacrylate [Telio CAD], titanium, and zirconia) and reference scanned with an industrial optical scanner. The models were scanned with intraoral scanners (3M Lava COS, Cerec AC/Bluecam, E4D, and iTero). A thick layer of coating was applied and scanned (3M Lava COS). Further evaluation on a gypsum cast was undertaken for the E4D system. Data were evaluated by using 3-dimensional analysis with "3D compare" software commands (3D compare analysis) regarding standard, mean, and maximum deviations, with subsequent statistical analysis.
  
  
  RESULTS
  The 3M Lava COS, Cerec AC/Bluecam, and iTero generally displayed similar results regarding deviations. Maximum deviations, however, increased by several factors for the noncoating scanners (iTero and E4D). Statistical significance was found regarding material properties for noncoating scanners (P<.05). iTero displayed consistent material-specific, localized errors on the translucent material (Telio CAD). E4D showed the largest deviations. Scans of the gypsum cast displayed specific localized areas with greater deviations. Excessive coating was nonsignificant.
  
  
  CONCLUSIONS
  Significant differences were found between the coating and noncoating scanners, and specific scanning errors for the system with parallel confocal microscopy were found for certain model materials. Specific areas of sizable deviations for the system with laser triangulation technology can be explained by the scanner design and noncoating technology. Excessive coating had no negative effect.
authors.affiliation: Former Resident, Associate Researcher, Department of Dental Medicine, Karolinska Institute, Huddinge, Sweden. Electronic address: robert@nedelcu.se.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Nedelcu
authors.affiliation: Quality Specialist, Nobel Biocare AB, Hägersten, Sweden.
authors.forename: Anna S K
authors.initials: AS
authors.lastname: Persson
mesh_terms: D000497:Alloys; D002133:Calcium Sulfate / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D017076:Computer-Aided Design / Q000592:standards / Q000706:statistics & numerical data*; D003722:Dental Alloys / Q000737:chemistry; D003734:Dental Casting Investment / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation*; D003764:Dental Materials / Q000737:chemistry; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000706:statistics & numerical data*; D007834:Lasers; D018613:Microscopy, Confocal; D055096:Optical Devices / Q000592:standards / Q000706:statistics & numerical data; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012031:Refractometry; D015203:Reproducibility of Results; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; C031462:titanium alloy (TiAl6V4); C009495:titanium dioxide; D019904:Polymethyl Methacrylate; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide; D002133:Calcium Sulfate