Porcelain veneered alumina crown restorations often fail from bulk fracture resulting from radial cracks that initiate at the cementation surface with repeated flexure of the stiffer crown layers on the soft dentin support. We hypothesize that bulk fracture may be substantially mitigated by grading the elastic modulus at the crown surfaces. In this study, graded structures were fabricated by infiltrating glass into dense alumina plates, resulting in a diminished modulus at the surface layers. The plates were then bonded to polycarbonate substrates and subjected to fatigue loading in water. Tests were terminated when fracture occurred at the cementation tensile surface or at the fatigue endurance limit (1 million cycles). Infiltrated specimens showed a significant increase in fatigue fracture loads over non-infiltrated controls. Our results indicate that controlled elastic gradients at the surface could be highly beneficial in the design of fracture resistant alumina crowns.
Citation: Journal of Dental Research
Pub Type: Journals
Alumina crowns, aluminaglass layers, modulus gradient, fatigue loading, bulk fracture