title: Influence of object translucency on the scanning accuracy of a powder-free intraoral scanner: A laboratory study.
abstract: BACKGROUND
  Limited information is available regarding the influence of object translucency on the scanning accuracy of a powder-free intraoral scanner.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the scanning accuracy of a confocal microscopy principle powder-free intraoral scanner on ceramic copings and to analyze the relationship between scanning accuracy and object translucency.
  
  
  METHODS
  Six slice specimens (12×10 mm) and 6 offset copings (1.00-mm thickness) were made from different translucent homogeneous ceramic blocks (CEREC Blocs, S0-M to S5-M, highest to lowest translucency). The primary sintered zirconia offset coping was produced in the same way as the control. Optical parameters related to the translucency of each slice were measured with a spectrophotometer. Three-dimensional (3D) datasets of the surface morphology of offset copings were obtained by using the intraoral scanner. The same white wax resin bases were used for registration. Quantitative parameters of scanning trueness and precision were measured. One-way ANOVA was used to analyze the values of each parameter among the 6 ceramic blocks. Bivariate correlation was used to analyze the relationships between each parameter of scanning accuracy and translucency (α=.05).
  
  
  RESULTS
  Translucent copings showed a positive 3D bias (S0-M to S5-M: 0.149 ±0.038 mm to 0.068 ±0.020 mm), a narrower collar diameter (Dd=-0.067 mm), larger convergence angle (ΔΦ=2.79 degrees), and larger curvature radius of the internal gingivoaxial corner (Δρ=0.236 mm). The smaller the percentage sum of scattering and absorption, the greater was the occurrence of scanning bias (r=-0.918) and curvature (r=-0.935) decrease.
  
  
  CONCLUSIONS
  Use of the tested powder-free intraoral scanner, higher translucency objects (greater translucency than S1-M/A1C) resulted in lower scanning accuracy and morphological changes. Therefore, more suitable methods of measurement are still required.
authors.affiliation: Graduate student, Graduate Prosthodontics, Center of Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health, Beijing Key Laboratory of Digital Stomatology, Beijing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.affiliation: Professor, Center of Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health, Beijing Key Laboratory of Digital Stomatology, Beijing, China. Electronic address: kqlpj@bjmu.edu.cn.
authors.forename: Peijun
authors.initials: P
authors.lastname: Lyu
authors.affiliation: Professor, Center of Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health, Beijing Key Laboratory of Digital Stomatology, Beijing, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Assistant Professor, Center of Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Research Center of Engineering and Technology for Digital Dentistry of Ministry of Health, Beijing Key Laboratory of Digital Stomatology, Beijing, China.
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Sun
mesh_terms: D002516:Ceramics; D003761:Dental Impression Technique; D017267:Dental Prosthesis Design / Q000379:methods; D006801:Humans; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D015203:Reproducibility of Results; D012117:Resins, Synthetic; D015040:Zirconium
chemical_list: D012117:Resins, Synthetic; D015040:Zirconium; C028541:zirconium oxide