title: Impact of digital impression techniques on the adaption of ceramic partial crowns in vitro.
abstract: OBJECTIVE
  To investigate the effects, digital impression procedures can have on the three-dimensional fit of ceramic partial crowns in vitro.
  
  
  METHODS
  An acrylic model of a mandibular first molar was prepared to receive a partial coverage all-ceramic crown (mesio-occlusal-distal inlay preparation with reduction of all cusps and rounded shoulder finish line of buccal wall). Digital impressions were taken using iTero (ITE), cara TRIOS (TRI), CEREC AC with Bluecam (CBC), and Lava COS (COS) systems, before restorations were designed and machined from lithium disilicate blanks. Both the preparation and the restorations were digitised using an optical reference-scanner. Data were entered into quality inspection software, which superimposed the records (best-fit-algorithm), calculated fit-discrepancies for every pixel, and colour-coded the results to aid visualisation. Furthermore, mean quadratic deviations (RMS) were computed and analysed statistically with a one-way ANOVA. Scheffé's procedure was applied for multiple comparisons (n=5, α=0.05).
  
  
  RESULTS
  Mean marginal (internal) discrepancies were: ITE 90 (92) μm, TRI 128 (106) μm, CBC 146 (84) μm, and COS 109 (93) μm. Differences among impression systems were statistically significant at p<0.001 (p=0.039). Qualitatively, partial crowns were undersized especially around cusp tips or the occluso-approximal isthmus. By contrast, potential high-spots could be detected along the preparation finishline and at central occlusal boxes.
  
  
  CONCLUSIONS
  Marginal and internal fit of milled lithium disilicate partial crowns depended on the employed digital impression technique.
  
  
  CONCLUSIONS
  The investigated digital impression procedures demonstrated significant fit discrepancies. However, all fabricated restorations showed acceptable marginal and internal gap sizes, when considering clinically relevant thresholds reported in the literature.
authors: Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany. Electronic address: oliver.schaefer@med.uni-jena.de.
authors: Oliver
authors: O
authors: Schaefer
authors: Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany.
authors: Mike
authors: M
authors: Decker
authors: Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany.
authors: Frank
authors: F
authors: Wittstock
authors: Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany.
authors: Harald
authors: H
authors: Kuepper
authors: Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany; School of Dentistry, Marquette University, Milwaukee, WI, USA.
authors: Arndt
authors: A
authors: Guentsch
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008963:Molar / Q000033:anatomy & histology; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic; D014584:User-Computer Interface
chemical_list: D003760:Dental Impression Materials; D003764:Dental Materials; D011145:Polyvinyls; D012833:Siloxanes; C493120:lithia disilicate; C034183:vinyl polysiloxane; D003776:Dental Porcelain; C023506:Glass ceramics
keywords: CAD/CAM; Digital impressions; Internal fit; Lithium disilicate ceramics; Marginal fit