Clinically relevant approach to failure testing of all-ceramic restorations,☆☆

Presented at the 80th annual meeting of the Academy of Prosthodontics, Colorado Springs, Colo., May 1998.
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Abstract

Statement of problem. 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. Purpose. 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. (J Prosthet Dent 1999;81:652-61.)

Section snippets

Ceramics supported by dentin

Elementary beam theory cannot be used to examine a cemented crown or to predict its clinical behavior. Homogeneous all-ceramic restorations consist of a layer of ceramic (approximately 1.0 to 2.0 mm thick) atop a layer of cement (approximately 30 to 120 μm thick) supported by a thickness of dentin (Fig. 1).

. Cemented all-ceramic restorations comprise tri-material structures in which ceramic is fully supported by and often bonded to dentin. High tensile stresses develop directly below loaded area

Clinical contact stresses

Loaded restorations and teeth develop features that have come to be called “wear facets.” Clinicians recognize that wear facets are usually not point contacts, but have dimensions of approximately 0.5 to 3.0 mm in diameter. Unfortunately, the sizes and size distributions of wear facets does not appear to have been documented in the literature, except for anthropologic studies of aboriginal populations38, 39 and hominid remains.40, 41 However, the size of this contact area along with the loads

Producing the appropriate crack system

The use of large balls (>40 mm in diameter) to load all-ceramic prostheses is unrealistic for laboratory experimentation. However, large radii can be machined onto the ends of steel pistons to create contact stresses and contact areas within the target range calculated previously, based on clinical observations and measurements. Flat pistons should be avoided because they can become edge-loading as the ceramic deforms slightly beneath the piston. Another benefit to large radii is that contact

CONCLUSIONS

Significant differences were found between the failure behavior created during traditional load-to-failure tests and that observed to have occurred during clinical failure of all-ceramic restorations. Traditional loading conditions created contact stresses that favor the formation of median-lateral crack systems, Hertzian cone cracks, and localized crushing damage: None of which are reported to cause the bulk failure of clinical all-ceramic restorations. Thus, it appears that traditional

References (62)

  • JA De Boever et al.

    Functional occlusal forces: an investigation by telemetry

    J Prosthet Dent

    (1978)
  • KC Julien et al.

    Normal masticatory performance in young adults and children

    Arch Oral Biol

    (1996)
  • CW Fairhurst et al.

    Dynamic fatigue of feldspathic porcelain

    Dent Mater

    (1993)
  • KA Malament et al.

    Survival of Dicor glass-ceramic dental restorations over 14 years: part I. Survival of Dicor complete coverage restorations and effect of internal surface acid etching, tooth position, gender and age

    J Prosthet Dent

    (1999)
  • JY Thompson et al.

    Microscopic and energy dispersive x-ray analysis of surface adaptation of dental cements to dental ceramic surfaces

    J Prosthet Dent

    (1998)
  • TB Smith et al.

    In vitro fracture behavior of ceramic and metal-ceramic restorations

    J Prosthodont

    (1994)
  • DD Carrier et al.

    In-Ceram failure behavior and core-veneer interface quality as influenced by residual infiltration glass

    J Prosthodont

    (1995)
  • M Yoshinari et al.

    Fracture strength of all-ceramic crowns

    Int J Prosthodont

    (1994)
  • FJ Burke et al.

    Fracture resistance of teeth restored with dentin-bonded crowns

    Quintessence Int

    (1994)
  • JT McCormick et al.

    Effect of luting media on the compressive strengths of two types of all-ceramic crown

    Quintessence Int

    (1993)
  • P Passi et al.

    Resistance to fracture of ceramic jacket crowns

    Quintessence Int

    (1992)
  • SS Scherrer et al.

    The fracture resistance of all-ceramic crowns on supporting structures with different elastic moduli

    Int J Prosthodont

    (1993)
  • JR Kelly et al.

    fracture surface analysis of dental ceramics: clinically failed restorations

    Int J Prosthodont

    (1990)
  • JY Thompson et al.

    Fracture surface characterization of clinically failed all-ceramic crowns

    J Dent Res

    (1994)
  • D Lundgren et al.

    Occlusal force patterns during chewing and biting in dentitions restored with fixed bridges of cross-arch extension. I. Bilateral end abutments

    J Oral Rehabil

    (1986)
  • DJ Anderson et al.

    Masticatory stresses in normal and modified occlusion

    J Dent Res

    (1958)
  • C. Hagberg

    Electromyography and bite force studies of muscular function and dysfunction in masticatory muscles

    Swed Dent J Suppl

    (1986)
  • RM Mansour et al.

    In vivo occlusal forces and moments: I. Forces measured in terminal hinge position and associated moments

    J Dent Res

    (1975)
  • E Hellsing et al.

    Changes in maximum bite force related to extension of the head

    Eur J Orthod

    (1990)
  • E Helkimo et al.

    Bite force and state of dentition

    Acta Odontol Scand

    (1977)
  • C Hagberg et al.

    Regression analysis of electromyographic activity of masticatory muscles versus bite force

    Scand J Dent Res

    (1985)
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    Reprint requests to: Dr J. Robert Kelly, Dental and Medical Materials Group, National Institute of Standards and Technology, 100 Bureau Dr, Mail Stop 8545, Gaithersburg, Md 20899-8545,Fax: (301)963-9143,E-MAIL: [email protected]

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