title: Mechanical performance of implant-supported posterior crowns.
abstract: BACKGROUND
  The fracture of implant-supported restorations, especially of the veneering layer, is a common problem in dentistry. Monolithic ceramic or resin restorations might help solve this problem.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to obtain additional insight into the risk of fracture of implant-supported restorations.
  
  
  METHODS
  Identical crowns (n=10) of 10 different ceramic and composite resin materials were cemented on conventional abutments on implant replicas embedded in polymethyl methacrylate blocks. The specimens were subjected to compressive load in a universal testing machine to record initial load to failure (ILF). Additionally, the flexural strength (FS), compressive strength (CS), and elastic modulus (E) of the investigated materials were determined. These results were used in a finite element analysis model of a composite resin and a lithium disilicate crown.
  
  
  RESULTS
  Anatomic contour zirconia (Lava Plus) crowns had the highest ILF (6065 N), followed by lithium disilicate (IPS e.max) (2788 N) and the composite resin materials (Protemp 4, Majesty Flow, Telio CAD, Estenia C&B, Lava Ultimate, VITA Enamic) (2386 to 1935 N). Veneered zirconia (Lava) crowns showed the lowest ILF (1477 N). The highest FS, CS, and E were found for Lava Plus and IPS e.max. No direct relationship was found between ILF and the FS, CS, or E. The finite element analysis showed stresses that did not exceed the FS or CS of IPS e.max. The surface roughness of these crowns might have caused initial failure at relatively low stresses.
  
  
  CONCLUSIONS
  In this laboratory study, monolithic implant-supported crowns showed a higher ILF than conventional veneered ceramic crowns. Monolithic ceramic restorations might perform better than composite resin crowns.
authors.affiliation: Doctoral student and Clinical Instructor, Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands. Electronic address: p.d.kok@acta.nl.
authors.forename: Paul
authors.initials: P
authors.lastname: de Kok
authors.affiliation: Associate Professor, Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Kleverlaan
authors.affiliation: Assistant Professor, Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Niek
authors.initials: N
authors.lastname: de Jager
authors.affiliation: Assistant Professor, Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Ruud
authors.initials: R
authors.lastname: Kuijs
authors.affiliation: Faculty Dean and Full Professor, Department of Dental Material Sciences, Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Feilzer
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D019245:Compressive Strength; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C493120:lithia disilicate; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium