title: Effects of cementation surface modifications on fracture resistance of zirconia.
abstract: OBJECTIVE
  To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia.
  
  
  METHODS
  Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending.
  
  
  RESULTS
  Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength.
  
  
  CONCLUSIONS
  While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia.
authors: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA.
authors: Ramanathan
authors: R
authors: Srikanth
authors: Engineering Ceramics Department, Jozef Stefan Institute, Jamova 39, SI 1000 Ljubljana, Slovenia.
authors: Tomaz
authors: T
authors: Kosmac
authors: Post-graduation Program in Dentistry, Dental School, University of Passo Fundo, Passo Fundo, RS, Brazil.
authors: Alvaro
authors: A
authors: Della Bona
authors: School of Engineering and Physical Sciences, James Cook University, Townsville, Qld 4811, Australia.
authors: Ling
authors: L
authors: Yin
authors: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY 10010, USA. Electronic address: yz21@nyu.edu.
authors: Yu
authors: Y
authors: Zhang
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D002484:Cementation; D002516:Ceramics / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D008422:Materials Testing; D013499:Surface Properties; D013718:Tensile Strength; D015040:Zirconium / Q000737:chemistry*
chemical_list: C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide
keywords: Alumina coating; Ceramic restorative materials; Flexural strength; Graded zirconia; Indentation flexural load; Surface modification; Zirconia