Impact of digital impression techniques on the adaption of ceramic partial crowns in vitro

Oliver Schaefer; Mike Decker; Frank Wittstock; Harald Kuepper; Arndt Guentsch

doi:10.1016/j.jdent.2014.01.016

Impact of digital impression techniques on the adaption of ceramic partial crowns in vitro

J Dent. 2014 Jun;42(6):677-83. doi: 10.1016/j.jdent.2014.01.016. Epub 2014 Feb 6.

Authors

Oliver Schaefer¹, Mike Decker², Frank Wittstock², Harald Kuepper², Arndt Guentsch³

Affiliations

¹ Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany. Electronic address: oliver.schaefer@med.uni-jena.de.
² Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany.
³ Policlinic of Prosthetic Dentistry and Material Science, Centre for Dental Medicine, Jena University Hospital, Jena, Germany; School of Dentistry, Marquette University, Milwaukee, WI, USA.

PMID: 24508541
DOI: 10.1016/j.jdent.2014.01.016

Abstract

Objectives: 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.

Clinical significance: 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.

Keywords: CAD/CAM; Digital impressions; Internal fit; Lithium disilicate ceramics; Marginal fit.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Ceramics / chemistry*
Computer-Aided Design*
Crowns*
Dental Impression Materials / chemistry
Dental Impression Technique*
Dental Marginal Adaptation*
Dental Materials / chemistry*
Dental Porcelain / chemistry
Dental Prosthesis Design
Humans
Image Processing, Computer-Assisted / methods
Molar / anatomy & histology
Polyvinyls / chemistry
Siloxanes / chemistry
Surface Properties
Tooth Preparation, Prosthodontic
User-Computer Interface

Substances

Dental Impression Materials
Dental Materials
Polyvinyls
Siloxanes
lithia disilicate
vinyl polysiloxane
Dental Porcelain
Glass ceramics