Faculty Collaboration Database

Effect of CNC-milling on the marginal and internal fit of dental ceramics: a pilot study. Dent Mater 2013 Aug;29(8):851-8

Date

06/08/2013

Pubmed ID

23743092

DOI

10.1016/j.dental.2013.04.018

Scopus ID

2-s2.0-84880736310 (requires institutional sign-in at Scopus site)   36 Citations

Abstract

OBJECTIVES: Machined restorations have been investigated for their preciseness before, while detailed information on the milling-step itself are lacking. Therefore, the aim of this laboratory study was to quantify the effect of a novel milling-procedure on the marginal and internal fit of ceramic restorations.

METHODS: An acrylic model of a lower left first molar was prepared to receive a ceramic partial crown and was duplicated by one step dual viscosity impressions. Gypsum casts were formed and laser-scanned to realize virtual datasets, before restorations were designed, exported (PRE) and machined from lithium disilicate blanks. Crowns were digitized by a structure-light-scanner to obtain post-milling-data (POST). PRE and POST were virtually superimposed on the reference tooth and subjected to computer-aided-inspection. Visual fit-discrepancies were displayed with colors, while root mean square deviations (RMSD) and degrees of similarity (DS) were computed and analysed by t-tests for paired samples (n=5, α=0.05).

RESULTS: The milling procedure resulted in a small increase of the marginal and internal fit discrepancies (RMSD mean: 3μm and 6μm, respectively). RMSD differences were not statistically significant (p=0.495 and p=0.160 for marginal and internal fit, respectively). These results were supported by the DS data.

SIGNIFICANCE: The products of digital dental workflows are prone to imprecisions. However, the present findings suggest that differences between computer-aided designed and actually milled restorations are small, especially when compared to typical fit discrepancies observed clinically. Imprecisions introduced by digital design or production processes are small.

Author List

Schaefer O, Kuepper H, Thompson GA, Cachovan G, Hefti AF, Guentsch A

Authors

Arndt Geuntsch in the CTSI department at Medical College of Wisconsin - CTSI
Arthur Hefti DDS,PhD Associate Dean - Research & Graduate Studies in the Dentistry department at Marquette University

MESH terms used to index this publication - Major topics in bold

Calcium Sulfate
Ceramics
Computer-Aided Design
Crowns
Dental Impression Technique
Dental Marginal Adaptation
Dental Materials
Dental Porcelain
Humans
Image Processing, Computer-Assisted
Imaging, Three-Dimensional
Molar
Pilot Projects
Surface Properties
Tooth Preparation, Prosthodontic
User-Computer Interface