Effect of indenter material on reliability of all-ceramic crowns

Fabio C Lorenzoni; Estevam A Bonfante; Guilherme B Valverde; Paulo G Coelho; Gerson Bonfante; Van P Thompson; Nelson R F A Silva

doi:10.1016/j.jmbbm.2020.103831

Effect of indenter material on reliability of all-ceramic crowns

J Mech Behav Biomed Mater. 2020 Aug:108:103831. doi: 10.1016/j.jmbbm.2020.103831. Epub 2020 Apr 28.

Authors

Fabio C Lorenzoni¹, Estevam A Bonfante², Guilherme B Valverde³, Paulo G Coelho⁴, Gerson Bonfante⁵, Van P Thompson⁶, Nelson R F A Silva⁷

Affiliations

¹ Department of Prosthodontics, Unigran University School of Dentistry, Dourados, MS, Brazil; Lorenzoni Education Institute, Ponta Porã, MS, Brazil.
² Department of Prosthodontics and Periodontology, University of São Paulo Bauru School of Dentistry, Bauru, Brazil. Electronic address: estevam.bonfante@fob.usp.br.
³ Assistant Professor - Advanced Education in Esthetic and Operative Dentistry, Tufts School of Dental Medicine, Boston, MA, USA, Private Practice, Newton Dental.
⁴ Department of Biomaterials, Hansjörg Wyss Department of Plastic Surgery, Mechanical and Aerospace Engineering, New York University, New York City, New York, USA.
⁵ Department of Prosthodontics and Periodontology, University of São Paulo Bauru School of Dentistry, Bauru, Brazil.
⁶ Professor Emeritus King's College London Faculty of Dentistry Department of Tissue Engineering and Biophotonics London, UK.
⁷ Department of Restorative Dentistry, Federal University of Minas Gerais, FO/UFMG, Brazil.

PMID: 32469725
DOI: 10.1016/j.jmbbm.2020.103831

Abstract

Objectives: Controversy exists about whether the elastic modulus (E) mismatch between the loading indenter and ceramic materials influences fatigue testing results. The research hypotheses were that for porcelain veneered Y-TZP crowns 1) A low modulus Steatite indenter (SB) leads to higher fatigue reliability compared to a high modulus tungsten carbide indenter (WC); 2) Different surface damage patterns are expected between low and high modulus indenters after sliding contact fatigue testing. All ceramic crowns will exhibit similar step-stress accelerated life testing (SSALT) contact fatigue reliability (hypothesis 1) and failure characteristics (hypothesis 2) when using high stiffness tungsten carbide (WC, E = 600 GPa) vs. enamel like steatite (SB, E = 90 GPa) indenters.

Methods: Manufacturer (3M Oral Care) prepared Y-TZP-veneered all-ceramic molar crowns were bonded to aged resin composite reproductions of a standard tooth preparation and subjected to mouth-motion SSALT fatigue (n = 18 per indenter type). Failure was defined either as initial inner cone crack (IC), or final fracture (FF) when porcelain fractured (chipping). Selected IC specimens that did not progress to FF were embedded in epoxy resin and sectioned for fractographic analysis.

Results: The distribution of failures across the load and cycle profiles lead to similar calculated Weibull Use Level Probability Plots with overlap of the 2-sided 90% confidence bounds. The calculated reliability for IC and FF was equivalent at a mission of 300 N or 700 N load and 50,000 cycles, although the WC indenter had a trend for lower reliability for IC at 700 N. Both indenters produced similar patterns of wear and cracking on crown surfaces. Fractographic landmarks showed competing failure modes, but sliding contact partial inner cone cracks were the most dominant for both groups.

Significance: The more compliant Steatite indenter had similar veneered crown fatigue reliability and failure modes to those found with use of a high stiffness tungsten carbide indenter (hypotheses 1 and 2 rejected).

Keywords: Biomaterial; Ceramics; Fractography; Indenter; Steatite ceramic; Step-stress fatigue; Tungsten carbide.

Publication types

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

MeSH terms

Ceramics*
Composite Resins
Crowns*
Dental Porcelain
Dental Restoration Failure
Dental Stress Analysis
Materials Testing
Reproducibility of Results

Substances

Composite Resins
Dental Porcelain