Performance of dental ceramics: challenges for improvements

Abstract

The clinical success of modern dental ceramics depends on an array of factors, ranging from initial physical properties of the material itself, to the fabrication and clinical procedures that inevitably damage these brittle materials, and the oral environment. Understanding the influence of these factors on clinical performance has engaged the dental, ceramics, and engineering communities alike. The objective of this review is to first summarize clinical, experimental, and analytic results reported in the recent literature. Additionally, it seeks to address how this new information adds insight into predictive test procedures and reveals challenges for future improvements.

Figure 1.

Cross-section of mouth-motion uniaxially loaded 0.5-mm-thick Y-TZP core following 110,000 cycles at 325 N with a 1.54-mm-diameter WC indenter in water. A tensile radial fracture from the as-machined and bonded (Panavia-21) intaglio surface intersects with a propagating inner cone crack, deflecting this inner cone. This indicates that the radial crack was present before the inner cone. Note the lack of propagation of the outer cone crack (from the study by Guess et al., 2010).

Figure 2.

Schematic of possible crack evolution in veneered high-modulus core ceramics (alumina or zirconia). Friction-assisted partial cone cracks and surface wear develop beneath the indenter. One partial cone crack propagates toward the veneer core interface. Radial cracking from the intaglio surface of the core can develop. In sliding contact studies, radial cracks develop in nearly all of the alumina core specimens and rarely in less stiff zirconia cores (Santana et al., 2009).

Figure 3.

Mouth-motion step stress fatigued veneered Y-TZP crowns exhibiting typical veneer chipping failure mode. In views A-C, an approximately uniform 1.0-mm core was veneered with 0.5-1.0 mm porcelain, while in views D-F, a 0.5-mm core had a 1.0- to 1.5-mm veneer applied. The anatomic core support resulted in smaller chips which developed at higher loads than for the less supportive thinner core. Note that the veneer-core interface is rarely exposed. These laboratory test results parallel clinical reports.