One failure mode of all-ceramic crown restorations is radial cracking at the cementation surface, from occlusally-induced flexure of the stiffer crown layer on the softer dentin underlayer. We hypothesize that such failure may be substantially mitigated by an appropriate grading of elastic modulus through the crown thickness. In this study, graded structures were fabricated by infiltrating glass into zirconia plates, with resulting diminished modulus in the outer surfaces. The plates were then bonded to a polymeric base and subjected to flexure by contact loading until fracture. Comparison of infiltrated specimens with non- infiltrated controls showed a significant increase in the fracture loads, by nearly a factor of 2. Finite element analysis revealed the cause of increase in the load-bearing capacity to be diminished tensile stresses within the lower-modulus graded zone. The results confirm that suitably graded structures can be highly beneficial in the design of next-generation all-ceramic crowns and bridges.
Citation: Journal of Dental Research
Pub Type: Journals
dental crowns and bridges, fracture, glass zirconia layers, modulus gradient, load-bearing capacity