Effect of core design and veneering technique on damage and reliability of Y-TZP-supported crowns.

Abstract

OBJECTIVES:

To evaluate the effect of framework design modification and veneering techniques in fatigue reliability and failure modes of veneered Yttria-Stabilized Tetragonal Zirconia Polycrystals (Y-TZP) crowns.

METHODS:

A CAD-based mandibular molar crown preparation served as a master die. Y-TZP crown cores (VITA-In-Ceram-YZ, Vita-Zahnfabrik, Bad Säckingen, Germany) in conventional (0.5mm uniform thickness) or anatomically designed fashion (cusp support) were porcelain veneered with either hand-layer (VM9) or pressed (PM9) techniques. Crowns (n=84) were cemented on 30 days aged dentin-like composite dies with resin cement. Crowns were subjected to single load to fracture (n=3 each group) and mouth-motion step-stress fatigue (n=18) by sliding a WC indenter (r=3.18 mm) 0.7 mm buccally on the inner incline surface of the mesio-lingual cusp. Stress-level curves (use level probability lognormal) and reliability (with 2-sided 90% confidence bounds, CB) for completion of a mission of 50.000 cycles at 200 N load were calculated. Fractographic analyses were performed under light-polarized and scanning electron microscopes.

RESULTS:

Higher reliability for hand-layer veneered conventional core (0.99, CB 0.98-1) was found compared to its counterpart press-veneered (0.50 CB 0.33-65). Framework design modification significantly increased reliability for both veneering techniques (PM9 [0.98 CB 0.87-0.99], VM9 [1.00 CB 0.99-1]) and resulted in reduced veneer porcelain fracture sizes. Main fracture mode observed was veneer porcelain chipping, regardless of framework design and veneering technique.

SIGNIFICANCE:

Hand-layer porcelain veneered on conventional core designs presented higher reliability than press-veneered with similar core designs. Anatomic core design modification significantly increased the reliability and resulted in reduced chip size of either veneering techniques.

• Authors: Petra C Guess, Estevam A Bonfante, Nelson R F A Silva, Paulo G Coelho, Van P Thompson
• Journal: Dental materials : official publication of the Academy of Dental Materials (Dent Mater) Vol. 29 Issue 3 Pg. 307-16 (Mar 2013) ISSN: 1879-0097 [Electronic] England
• PMID: 23228337 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Chemical References

• yttria stabilized tetragonal zirconia
• Yttrium
• Zirconium

Topics

• Computer-Aided Design
• Crowns
• Dental Prosthesis Design (methods)
• Dental Restoration Failure
• Dental Veneers
• Materials Testing
• Microscopy, Electron, Scanning
• Yttrium (chemistry)
• Zirconium (chemistry)