The effect of coping/veneer thickness on the fracture toughness and residual stress of implant supported, cement retained zirconia and metal-ceramic crowns

Christopher S Millen, Robert L Reuben, Richard J Ibbetson

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

OBJECTIVES: The aim of the work was to assess the influence of coping and veneer thickness on the fracture resistance of porcelain-metal and porcelain-zirconia crowns in a clinically representative model.

METHODS: A total of 30 zirconia and 30 precious metal copings were fabricated. There were 10 copings in each group of 0.5mm, 1mm and 1.5mm thickness. Each group of 10 was further divided into two groups with a total thickness of three and four millimeters inclusive of veneering ceramic. The specimens were cemented to a titanium abutment with zinc oxide cement and tested using a microindenter. Crack length, hardness and spalling (chipping) were recorded using an optical microscope from which fracture toughness was calculated.

RESULTS: Kruskal-Wallis tests and simple linear regression analysis were used to analyze the results, revealing a significant difference between zirconia (ZrCC) and metal (MCC) specimens for crack length. 0.5mm coping thicknesses and MCC specimens showed the highest fracture toughness values. Simple linear regression analysis showed a limited effect of the overall thickness or veneer thickness on crack length and hardness; however coping thickness showed a positive correlation with both. Spalling was higher in zirconia specimens. Residual stresses were higher for ZrCC specimens and showed a positive correlation with crack length. The ratio of veneer to coping thickness was negatively correlated with residual stress.

SIGNIFICANCE: Residual stresses due to thermal mismatch between the coping and the veneering ceramic should be kept to a minimum. The ZrCC specimens were found to have lower apparent fracture toughness than MCC specimens. Thermal mismatch caused a larger drop in apparent fracture toughness than the inherent differences in the materials used.

Original languageEnglish
Pages (from-to)e250-e258
Number of pages9
JournalDental Materials
Volume28
Issue number10
Early online date18 Jul 2012
DOIs
Publication statusPublished - Oct 2012

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Veneers
Cermets
Ceramics
Crowns
Zirconia
Fracture toughness
Residual stresses
Cements
Metals
Dental Porcelain
Hardness
Cracks
Spalling
Porcelain
Linear Models
Linear regression
Regression analysis
Hot Temperature
Regression Analysis
Zinc Oxide

Keywords

  • Crowns
  • Dental Porcelain
  • Dental Prosthesis, Implant-Supported
  • Dental Restoration Failure
  • Dental Stress Analysis
  • Dental Veneers
  • Linear Models
  • Materials Testing
  • Metal Ceramic Alloys
  • Thermal Conductivity
  • Zirconium
  • Journal Article

Cite this

The effect of coping/veneer thickness on the fracture toughness and residual stress of implant supported, cement retained zirconia and metal-ceramic crowns. / Millen, Christopher S; Reuben, Robert L; Ibbetson, Richard J.

In: Dental Materials, Vol. 28, No. 10, 10.2012, p. e250-e258.

Research output: Contribution to journalArticle

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abstract = "OBJECTIVES: The aim of the work was to assess the influence of coping and veneer thickness on the fracture resistance of porcelain-metal and porcelain-zirconia crowns in a clinically representative model.METHODS: A total of 30 zirconia and 30 precious metal copings were fabricated. There were 10 copings in each group of 0.5mm, 1mm and 1.5mm thickness. Each group of 10 was further divided into two groups with a total thickness of three and four millimeters inclusive of veneering ceramic. The specimens were cemented to a titanium abutment with zinc oxide cement and tested using a microindenter. Crack length, hardness and spalling (chipping) were recorded using an optical microscope from which fracture toughness was calculated.RESULTS: Kruskal-Wallis tests and simple linear regression analysis were used to analyze the results, revealing a significant difference between zirconia (ZrCC) and metal (MCC) specimens for crack length. 0.5mm coping thicknesses and MCC specimens showed the highest fracture toughness values. Simple linear regression analysis showed a limited effect of the overall thickness or veneer thickness on crack length and hardness; however coping thickness showed a positive correlation with both. Spalling was higher in zirconia specimens. Residual stresses were higher for ZrCC specimens and showed a positive correlation with crack length. The ratio of veneer to coping thickness was negatively correlated with residual stress.SIGNIFICANCE: Residual stresses due to thermal mismatch between the coping and the veneering ceramic should be kept to a minimum. The ZrCC specimens were found to have lower apparent fracture toughness than MCC specimens. Thermal mismatch caused a larger drop in apparent fracture toughness than the inherent differences in the materials used.",
keywords = "Crowns, Dental Porcelain, Dental Prosthesis, Implant-Supported, Dental Restoration Failure, Dental Stress Analysis, Dental Veneers, Linear Models, Materials Testing, Metal Ceramic Alloys, Thermal Conductivity, Zirconium, Journal Article",
author = "Millen, {Christopher S} and Reuben, {Robert L} and Ibbetson, {Richard J}",
note = "Acknowledgement Support: Zirconia materials for this article were supplied courtesy of 3M ESPE.",
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T1 - The effect of coping/veneer thickness on the fracture toughness and residual stress of implant supported, cement retained zirconia and metal-ceramic crowns

AU - Millen, Christopher S

AU - Reuben, Robert L

AU - Ibbetson, Richard J

N1 - Acknowledgement Support: Zirconia materials for this article were supplied courtesy of 3M ESPE.

PY - 2012/10

Y1 - 2012/10

N2 - OBJECTIVES: The aim of the work was to assess the influence of coping and veneer thickness on the fracture resistance of porcelain-metal and porcelain-zirconia crowns in a clinically representative model.METHODS: A total of 30 zirconia and 30 precious metal copings were fabricated. There were 10 copings in each group of 0.5mm, 1mm and 1.5mm thickness. Each group of 10 was further divided into two groups with a total thickness of three and four millimeters inclusive of veneering ceramic. The specimens were cemented to a titanium abutment with zinc oxide cement and tested using a microindenter. Crack length, hardness and spalling (chipping) were recorded using an optical microscope from which fracture toughness was calculated.RESULTS: Kruskal-Wallis tests and simple linear regression analysis were used to analyze the results, revealing a significant difference between zirconia (ZrCC) and metal (MCC) specimens for crack length. 0.5mm coping thicknesses and MCC specimens showed the highest fracture toughness values. Simple linear regression analysis showed a limited effect of the overall thickness or veneer thickness on crack length and hardness; however coping thickness showed a positive correlation with both. Spalling was higher in zirconia specimens. Residual stresses were higher for ZrCC specimens and showed a positive correlation with crack length. The ratio of veneer to coping thickness was negatively correlated with residual stress.SIGNIFICANCE: Residual stresses due to thermal mismatch between the coping and the veneering ceramic should be kept to a minimum. The ZrCC specimens were found to have lower apparent fracture toughness than MCC specimens. Thermal mismatch caused a larger drop in apparent fracture toughness than the inherent differences in the materials used.

AB - OBJECTIVES: The aim of the work was to assess the influence of coping and veneer thickness on the fracture resistance of porcelain-metal and porcelain-zirconia crowns in a clinically representative model.METHODS: A total of 30 zirconia and 30 precious metal copings were fabricated. There were 10 copings in each group of 0.5mm, 1mm and 1.5mm thickness. Each group of 10 was further divided into two groups with a total thickness of three and four millimeters inclusive of veneering ceramic. The specimens were cemented to a titanium abutment with zinc oxide cement and tested using a microindenter. Crack length, hardness and spalling (chipping) were recorded using an optical microscope from which fracture toughness was calculated.RESULTS: Kruskal-Wallis tests and simple linear regression analysis were used to analyze the results, revealing a significant difference between zirconia (ZrCC) and metal (MCC) specimens for crack length. 0.5mm coping thicknesses and MCC specimens showed the highest fracture toughness values. Simple linear regression analysis showed a limited effect of the overall thickness or veneer thickness on crack length and hardness; however coping thickness showed a positive correlation with both. Spalling was higher in zirconia specimens. Residual stresses were higher for ZrCC specimens and showed a positive correlation with crack length. The ratio of veneer to coping thickness was negatively correlated with residual stress.SIGNIFICANCE: Residual stresses due to thermal mismatch between the coping and the veneering ceramic should be kept to a minimum. The ZrCC specimens were found to have lower apparent fracture toughness than MCC specimens. Thermal mismatch caused a larger drop in apparent fracture toughness than the inherent differences in the materials used.

KW - Crowns

KW - Dental Porcelain

KW - Dental Prosthesis, Implant-Supported

KW - Dental Restoration Failure

KW - Dental Stress Analysis

KW - Dental Veneers

KW - Linear Models

KW - Materials Testing

KW - Metal Ceramic Alloys

KW - Thermal Conductivity

KW - Zirconium

KW - Journal Article

U2 - 10.1016/j.dental.2012.06.008

DO - 10.1016/j.dental.2012.06.008

M3 - Article

VL - 28

SP - e250-e258

JO - Dental Materials

JF - Dental Materials

SN - 0109-5641

IS - 10

ER -