title: Evaluation of different approaches for using a laser scanner in digitization of dental impressions.
abstract: OBJECTIVE
  This study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner.
  
  
  METHODS
  Ten working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student's t-test (α=0.05), repeated measures ANOVA and two-way ANOVA (α=0.05).
  
  
  RESULTS
  The mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups.
  
  
  CONCLUSIONS
  The mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit (120 µm).
authors.affiliation: Department of Health Science, Graduate School, Korea University, Seoul, Republic of Korea.
authors.forename: Wan-Sun
authors.initials: WS
authors.lastname: Lee
authors.affiliation: Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
authors.forename: Woong-Chul
authors.initials: WC
authors.lastname: Kim
authors.affiliation: Department of Public Health Science, Graduate School & BK21+ Program in Public Health Science, Korea University, Seoul, Republic of Korea.
authors.forename: Hae-Young
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Dental Laboratory, Sinheung University, Uijeongbu, Republic of Korea.
authors.forename: Wook-Tae
authors.initials: WT
authors.lastname: Kim
authors.affiliation: Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, Republic of Korea.
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kim
keywords: Dental CAD/CAM system; Digitization of impression bodies; Internal gap; Marginal gap; Zirconia three-unit FPDs