Yu Zhang1, Zhisong Mai2, Amir Barani3, Mark Bush3, Brian Lawn4. 1. Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA. Electronic address: yz21@nyu.edu. 2. Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA. 3. School of Mechanical and Chemical Engineering, University of Western Australia, Crawley, WA 6009, Australia. 4. Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Abstract
OBJECTIVE: To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. METHODS: Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. RESULTS: Experimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. SIGNIFICANCE: The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity.
OBJECTIVE: To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns. METHODS:Fracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution. RESULTS: Experimental measurements and XFEM predictions were self-consistent within data scatter. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Stages of crack propagation within the crown and support substrate were quantified. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. SIGNIFICANCE: The results confirm that monolithic crowns are able to sustain high bite forces. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity.
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