title: Clinically relevant approach to failure testing of all-ceramic restorations.
abstract: BACKGROUND
  One common test of single-unit restorations involves applying loads to clinically realistic specimens through spherical indenters, or equivalently, loading curved incisal edges against flat compression platens. As knowledge has become available regarding clinical failure mechanisms and the behavior of in vitro tests, it is possible to constructively question the clinical validity of such failure testing and to move toward developing more relevant test methods.
  
  
  OBJECTIVE
  This article reviewed characteristics of the traditional load-to-failure test, contrasted these with characteristics of clinical failure for all-ceramic restorations, and sought to explain the discrepancies. Literature regarding intraoral conditions was reviewed to develop an understanding of how laboratory testing could be revised. Variables considered to be important in simulating clinical conditions were described, along with their recent laboratory evaluation.
  
  
  CONCLUSIONS
  Traditional fracture tests of single unit all-ceramic prostheses are inappropriate, because they do not create failure mechanisms seen in retrieved clinical specimens. Validated tests are needed to elucidate the role(s) that cement systems, bonding, occlusion, and even metal copings play in the success of fixed prostheses and to make meaningful comparisons possible among novel ceramic and metal substructures. Research over the past 6 years has shown that crack systems mimicking clinical failure can be produced in all-ceramic restorations under appropriate conditions.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, and Naval Dental Research Institute Detachment, Naval Dental School, Bethesda, MD, USA. robert.kelly@nist.gov
authors.forename: J R
authors.initials: JR
authors.lastname: Kelly
mesh_terms: D002484:Cementation; D002516:Ceramics / Q000737:chemistry*; D019245:Compressive Strength; D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003766:Dental Occlusion; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003830:Denture, Partial, Fixed; D005260:Female; D006244:Hardness; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D013314:Stress, Mechanical
chemical_list: D003722:Dental Alloys; D003738:Dental Cements; D003764:Dental Materials