title: Evaluation of fracture resistance in aqueous environment of four restorative systems for posterior applications. Part 1.
abstract: OBJECTIVE
  The goals of this study were to: (1) establish a range of the performance of four restorative systems for posterior single-tooth crowns under single load to fracture submerged in an aqueous environment, (2) identify restorative system(s) of interest to be examined in the second study phase under sliding contact step-stress fatigue as full-contour anatomically appropriate single posterior tooth restoration(s), (3) establish a range for loading/testing for phase 2.
  
  
  METHODS
  Forty specimens (n = 10/group) of 2 mm uniform thickness were tested. Group 1: monolithic lithium disilicate IPS e.max Press; group 2: IPS e.max ZirPress, 0.8 mm zirconia core with 1.2 mm pressed veneering porcelain; group 3: IPS e.max ZirPress, 0.4 mm zirconia core with 1.6 mm pressed veneering porcelain; group 4: IPS InLine PoM. Specimens were bonded to a block of polycast acrylic resin on a 30° sloped surface with resin cement. Specimens were axially single loaded to failure while submerged under water.
  
  
  RESULTS
  There was a statistically significant difference (p < 0.001) in failure load among the four restorative systems. Lithium disilicate showed a mean failure load similar to mean maximum posterior bite forces (743.1 ± 114.3 N). IPS e.max Zirpress with a 0.4 mm zirconia core exhibited the lowest mean failure load (371.4 ± 123.0 N).
  
  
  CONCLUSIONS
  Fracture resistance of monolithic lithium disilicate in an aqueous environment is promising and requires second phase testing to evaluate the potential of various thicknesses appropriate for posterior single tooth applications. Doubling the IPS e.max Zirpress zirconia core from 0.4 mm to 0.8 mm increased the fracture resistance of this restorative system threefold.
authors.affiliation: Division of Prosthetic and Esthetic Dentistry, Department of Dental Specialties, Mayo Clinic, Rochester, MN 55905, USA. dhima.matilda@mayo.edu
authors.forename: Matilda
authors.initials: M
authors.lastname: Dhima
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Assad
authors.forename: John E
authors.initials: JE
authors.lastname: Volz
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Berglund
authors.forename: Alan B
authors.initials: AB
authors.lastname: Carr
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Salinas
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003442:Crowns; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014867:Water / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D003764:Dental Materials; C508050:IPS e.max Press; C528569:Rely-X; D019279:Resin Cements; C493120:lithia disilicate; D014867:Water; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide