title: Plastic damage induced fracture behaviors of dental ceramic layer structures subjected to monotonic load.
abstract: OBJECTIVE
  The aim of this study was to compare failure modes and fracture strength of ceramic structures using a combination of experimental and numerical methods.
  
  
  METHODS
  Twelve specimens with flat layer structures were fabricated from two types of ceramic systems (IPS e.max ceram/e.max press-CP and Vita VM9/Lava zirconia-VZ) and subjected to monotonic load to fracture with a tungsten carbide sphere. Digital image correlation (DIC) and fractography technology were used to analyze fracture behaviors of specimens. Numerical simulation was also applied to analyze the stress distribution in these two types of dental ceramics.
  
  
  RESULTS
  Quasi-plastic damage occurred beneath the indenter in porcelain in all cases. In general, the fracture strength of VZ specimens was greater than that of CP specimens. The crack initiation loads of VZ and CP were determined as 958 ± 50 N and 724 ± 36 N, respectively. Cracks were induced by plastic damage and were subsequently driven by tensile stress at the elastic/plastic boundary and extended downward toward to the veneer/core interface from the observation of DIC at the specimen surface. Cracks penetrated into e.max press core, which led to a serious bulk fracture in CP crowns, while in VZ specimens, cracks were deflected and extended along the porcelain/zirconia core interface without penetration into the zirconia core. The rupture loads for VZ and CP ceramics were determined as 1150 ± 170 N and 857 ± 66 N, respectively.
  
  
  CONCLUSIONS
  Quasi-plastic deformation (damage) is responsible for crack initiation within porcelain in both types of crowns. Due to the intrinsic mechanical properties, the fracture behaviors of these two types of ceramics are different. The zirconia core with high strength and high elastic modulus has better resistance to fracture than the e.max core.
authors.affiliation: The Tenth People's Hospital of Tongji University, Shanghai, PR China.
authors.forename: Raorao
authors.initials: R
authors.lastname: Wang
authors.forename: Chenglin
authors.initials: C
authors.lastname: Lu
authors.forename: Dwayne
authors.initials: D
authors.lastname: Arola
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Zhang
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003198:Computer Simulation; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D003801:Dental Veneers; D055119:Elastic Modulus; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D017680:Potassium Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D017973:Tungsten Compounds / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; C508050:IPS e.max Press; D017680:Potassium Compounds; D017973:Tungsten Compounds; C493120:lithia disilicate; C499362:yttria stabilized tetragonal zirconia; C002802:tungsten carbide; D003776:Dental Porcelain; C016447:feldspar; D015019:Yttrium; D015040:Zirconium
keywords: DIC; ceramic crowns; crack; fracture; monotonic load