title: [Study on the effect of different impression methods on the marginal fit of all-ceramic crowns].
abstract: OBJECTIVE
  To investigate the effect of three different impression methods on the marginal fit of all-ceramic crowns. The three methods include scanning silicone rubber impression, cast models, and direct optical impression.
  
  
  METHODS
  The polymethyl methacrylate (PMMA) material of a mandibular first molar in standard model was prepared with 16 models duplicated. The all-ceramic crowns were prepared using three different impression methods. Accurate impressions were made using silicone rubber, and the cast models were obtained. The PMMA models, silicone rubber impressions, and cast models were scanned, and digital models of three groups were obtained to produce 48 zirconia all-ceramic crowns with computer aided design/computer aided manufacture. The marginal fit of these groups was measured by silicone rubber gap impression. Statistical analysis was performed with SPSS 17.0 software.
  
  
  RESULTS
  The marginal fit of direct optical impression groups, silicone rubber impression groups, cast model groups was (69.18±9.47), (81.04±10.88), (84.42±9.96) µm. A significant difference was observed in the marginal fit of the direct optical impression groups and the other groups (P<0.05). No statistically significant difference was observed in the marginal fit of the silicone rubber impression groups and the cast model groups (P>0.05).
  
  
  CONCLUSIONS
  All marginal measurement sites are clinically acceptable by the three different impression scanning methods. The silicone rubber impression scanning method can be used for all-ceramic restorations.
authors.forename: Lilin
authors.initials: L
authors.lastname: Zhan
authors.forename: Liwei
authors.initials: L
authors.lastname: Zeng
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.forename: Lan
authors.initials: L
authors.lastname: Liao
authors.forename: Shiyue
authors.initials: S
authors.lastname: Li
authors.forename: Renying
authors.initials: R
authors.lastname: Liu
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide