Fatigue resistance of ultrathin CAD/CAM complete crowns with a simplified cementation process.

Abstract

STATEMENT OF PROBLEM:

Traditional tooth preparation for complete crowns requires a substantial amount of hard tissue reduction. This is in contrast with the principles of minimally invasive dentistry. An ultrathin complete crown preparation is proposed instead.

PURPOSE:

The purpose of this in vitro study was to assess the fatigue resistance and failure mode of computer-aided design and computer-aided manufacturing (CAD/CAM) ultrathin complete molar crowns placed with self-adhesive cement. Different restorative materials (resin nanoceramic [RNC], feldspathic ceramic [FEL], and lithium disilicate [LD]) were compared.

MATERIAL AND METHODS:

Forty-five extracted molars with a standardized crown preparation were restored with the Cerec 3 CAD/CAM system using FEL, LD, or RNC (n=15). FEL and LD restorations were etched with hydrofluoric acid and silanated. RNC restorations and all preparations were treated with airborne-particle abrasion. All restorations (thickness=0.7 mm) were cemented with RelyX Unicem II Automix cement and submitted to cyclic isometric loading, beginning with a load of 200 N (5000 cycles) and followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30 000 cycles each. The specimens were loaded until failure or for a maximum of 185 000 cycles. The failure mode was categorized as "catastrophic," "possibly reparable," or "reparable." The groups were compared using life table survival analysis (log rank test at α=.05). Previously published data from the same authors about traditional complete crowns (thickness 1.5 mm) using the same experimental design were included for comparison.

RESULTS:

All specimens survived the fatigue test until the 600 N step. RNC, LD, and FEL failed at an average load of 1014 N (1 survival), 1123 N (2 survivals), and 987 N (no survivals), and no difference in survival rate was found. No catastrophic failures were reported after the fatigue test. Comparison with previously published data showed that 1.5-mm thick complete crowns demonstrated higher survival rates than the ultrathin restorations, independent of the material.

CONCLUSIONS:

The fatigue resistance of ultrathin complete molar crowns (placed with a simplified cementation process) made of RNC, LD, and FEL was not significantly different. All materials survived the normal range of masticatory forces. All failures were re-restorable. Regular crowns of 1.5 to 2.0 mm thickness may present higher survival rates than ultrathin ones.

• Authors: Pascal Magne, Adriana O Carvalho, Greciana Bruzi, Marcelo Giannini
• Journal: The Journal of prosthetic dentistry (J Prosthet Dent) Vol. 114 Issue 4 Pg. 574-9 (Oct 2015) ISSN: 1097-6841 [Electronic] United States
• PMID: 26119017 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Chemical References

• Composite Resins
• Dental Cements
• Dental Materials

Topics

• Cementation (methods)
• Ceramics
• Composite Resins (chemistry)
• Computer-Aided Design
• Crowns
• Dental Bonding
• Dental Cements (chemistry)
• Dental Materials (chemistry)
• Dental Prosthesis Design
• Dental Restoration Failure
• Humans
• Materials Testing
• Surface Properties