On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.
Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations.
Tel Aviv University, School of Mechanical Engineering, Faculty of Engineering, Tel Aviv, Israel.
Herzl
H
Chai
National Institute of Standards and Technology, Ceramics Division, Gaithersburg, MD 20899, USA.
James J-W
JJ
Lee
New York Center For Specialized Dentistry, 150 East 58th Street, Suite 3200, New York, NY 10155, USA.
Adam J
AJ
Mieleszko
New York Center For Specialized Dentistry, 150 East 58th Street, Suite 3200, New York, NY 10155, USA; Columbia University College of Dental Medicine, Department of Prosthodontics, 622 West 168th Street, New York, NY 10032, USA.
Stephen J
SJ
Chu
New York University College of Dentistry, Department of Biomaterials and Biomimetics, 345 East 24th Street, Room 813C, New York, NY 10010, USA. Electronic address: yz21@nyu.edu.
Yu
Y
Zhang
D003198:Computer Simulation; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000379:methods; D003801:Dental Veneers; D020342:Finite Element Analysis; D006244:Hardness; D008422:Materials Testing; D008956:Models, Chemical; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D015040:Zirconium / Q000737:chemistry*
D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
All-ceramic dental restorations; Delamination; Graded zirconia; Interfacial fracture energy; Porcelain-veneered zirconia