Material Considerations
March 1, 2012
Volume 3, Issue 3, March 2012
Page(s):
Specifically designed for use with CAD/CAM technology, yttrium-stabilized zirconia is a zirconia-oxide based ceramic. Yttria oxide stabilizes the zirconia oxide at room temperature. In a “chalk-like,” partly sintered state, its approximately 50% porosity enables easy processing.1 Color versatility is provided with the availability of natural and shaded pre-sintered zirconium oxide blocks. After the restoration has been milled into shape, the material is sintered to densify the microstructure.1 The final restoration is sintered to approximately 99.5% theoretical density (TD).1 Once sintered to full density, its hardness and inertness make it an ideal material for dental restorations. Sintered zirconium-oxide blocks boast a fracture toughness of more than twice that of glass-ceramic and a flexural strength of more than 900 MPa.1 IPS e.max ZirCad blocks achieve exceptional accuracy of fit, high fracture resistance, and a fracture toughness that meets the clinical requirements presented by posterior masticatory forces.
Characterized by high mechanical strength and superb esthetic properties, IPS e.max lithium disilicate is ideal for anterior and posterior tooth restorations. Developed with controlled size, shape, and density, and containing approximately 70% by volume needle-like crystals in a glassy matrix, IPS e.max possesses unique structural characteristics that ensure greater strength and durability than conventional ceramics.6,7 Lithium disilicate also demonstrates life-like translucency and superior optical properties due to a relatively lower refractive index.6-9 Pressable lithium disilicate demonstrates a flexural strength of 400 MPa7-9 and is the material of choice when using the wax hot-press technique. While press technology ensures exceptional fit, several translucencies and opacities and different brightness effects provide natural-looking shades with optimal light transmission, resulting in highly esthetic, life-like restorations.10-13 Providing fit and function with outstanding strength, IPS e.max Press offers superior performing and esthetically pleasing all-ceramic pressed restorations.14
While zirconium-oxide ceramic IPS e.max ZirCAD is the material of choice for large restorations exposed to high masticatory forces, IPS e.max ZirPress is specifically designed to press onto IPS e.max ZirCAD and other ZrO2 frameworks with a CTE of 10.5 to 11.15 The fluorapatite glass-ceramic IPS e.max ZirPress ingots are indicated for zirconium-oxide–supported gingiva portions, single-tooth restorations, anterior and posterior bridges, inlay-retained bridges, and implant superstructures.15 Used with press technology, IPS e.max ZirPress ingots press over zirconium-oxide frameworks with less time and effort and produce an esthetic, highly functional, and extremely accurate-fitting restoration. Available in three levels of translucency (HT, LT, and MO) and four bleach shades, two gingiva shades are also available for fabricating the gingival portion of the restoration.15
The All-on-4 treatment concept can be used in combination with a full-arch zirconia substructure and a variety of implants, such as NobelActive™, to provide edentulous patients with stable, functional, esthetic, and comfortable prosthesis.16-18 Additionally, a provisional prosthetic set-up can be screwed onto the implants after surgery to facilitate approval and completion of customized and single-unit restorations.17-21 Because the technique and implants can accommodate a broad range of prosthetics and abutments, high-strength zirconia substructures fabricated with CAD/CAM processes are possible.21
