Monolithic crowns fracture analysis: The effect of material properties, cusp angle and crown thickness

Mahdi Shahmoradi; Boyang Wan; Zhongpu Zhang; Tom Wilson; Michael Swain; Qing Li

doi:10.1016/j.dental.2020.04.022

Monolithic crowns fracture analysis: The effect of material properties, cusp angle and crown thickness

Dent Mater. 2020 Aug;36(8):1038-1051. doi: 10.1016/j.dental.2020.04.022. Epub 2020 Jun 11.

Authors

Mahdi Shahmoradi¹, Boyang Wan², Zhongpu Zhang³, Tom Wilson⁴, Michael Swain⁵, Qing Li⁶

Affiliations

¹ School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: mahdi.shahmoradi@sydney.edu.au.
² School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: bwan9310@uni.sydney.edu.au.
³ School of Engineering, Western Sydney University, Penrith, NSW 2751, Australia. Electronic address: leo.zhang@westernsydney.edu.au.
⁴ School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: twil8481@uni.sydney.edu.au.
⁵ School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: michael.swain@sydney.edu.au.
⁶ School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: qing.li@sydney.edu.au.

PMID: 32534794
DOI: 10.1016/j.dental.2020.04.022

Abstract

Objectives: This study aimed to investigate the collective influence of material properties and design parameters on the fracture behavior of monolithic dental crowns.

Methods: Three-dimensional (3D) models (N=90) with different combinations of design parameters (thickness, cusp angle and occlusal notch geometry) and material type (lithium disilicate, feldspar ceramic, zirconia, hybrid resin ceramic and hybrid polymer-infiltrated ceramic) were developed for the failure analysis using extended finite element method (XFEM) to identify the stress distribution, crack initiation load, fracture surface area and fracture pattern. Analytical formulation, in vitro fracture tests and fractographic analysis of dedicated models were also performed to validate the findings of the XFEM simulation.

Results: For all material types considered, crowns with a sharp occlusal notch design had a significantly lower fracture resistance against occlusal loading. In most of the models, greater crown thickness and cusp angle resulted in a higher crack initiation load. However, the effect of cusp angle was dominant when the angle was in the low range of 50° for which increasing thickness did not enhance the crack initiation load.

Significance: Comparing the critical load of crack initiation for different models with the maximum biting force revealed that for the studied monolithic materials excluding zirconia, a design with a rounded occlusal notch, 70° cusp angle and medium thickness (1.5mm occlusal) is an optimum combination of design parameters in terms of tooth conservation and fracture resistance. Zirconia crowns exhibited sufficient strength for a more conservative design with less thickness (1.05mm occlusal) and sharper cusp angle (60°).

Keywords: Cusp angle; Extended finite element analysis; Material property; Monolithic dental crown; Thickness.

Publication types

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

MeSH terms

Ceramics
Crowns*
Dental Porcelain
Dental Prosthesis Design*
Dental Restoration Failure
Dental Stress Analysis
Materials Testing
Zirconium

Substances

Dental Porcelain
Zirconium