Zirconia or zirconium dioxide (ZrO2) is a highly attractive
ceramic material in prosthodontics due to its excellent mechanical properties
related to transformation toughening, which are the highest ever reported for
any dental ceramic and enhanced natural appearance compared to metal-ceramics. It
is widely used to build prosthetic devices because of its good chemical
properties, dimensional stability, high mechanical strength, toughness, and a
Young’s modulus (210 GPa) similar to that of stainless steel alloy (193 GPa).
The high initial strength and fracture toughness of
zirconia results from a physical property of partially stabilized zirconia
known as “transformation toughening”. Zirconia is a polymorphic material that has 3 crystal phases: monoclinic (m), tetragonal (t), and cubic (c). At room
temperature, zirconia is in monoclinic phase and transforms into tetragonal
phase at 1170°C, followed by a cubic structure at 2370°C. While cooling, the
metastable tetragonal zirconia is transformed into stable monoclinic zirconia.
The tetragonal to monoclinic (t→m) phase transformation is associated with a
large volume expansion (3-5%) that induces compressive stresses opposing crack
opening and acts to increase resistance to crack propagation. In vitro studies
of zirconia specimens demonstrate a flexural strength of 900 to 1200 MPa and a
fracture toughness of 9 to 10 MPa/m2. It is a bioinert, not soluble
metal oxide that also exhibits a favourable radio opacity and a low corrosion potential.
Zirconia frameworks can be produced according to two different CAD/CAM
techniques. In
soft machining technique, CAD/CAM systems
shape pre-sintered blocks, which involves machining enlarged frameworks in a
so-called green state. The enlarged pre-sintered zirconia frameworks are then
sintered in a sintering furnace to their full strength that is accompanied by
shrinkage of the milled framework by 25% to the desired dimensions. In
hard machining technique, fully sintered blocks are shaped.
The framework coloration is performed either adding metal oxides to the
zirconia powder, or embedding the frameworks in metal salt solutions after
machining. Glazing is created by firing a small coating of transparent glass
onto the surface or by heating the framework up to glazing temperatures for 1
to 2 minutes to get shiny glass surfaces.
Although zirconia has superior mechanical properties, its opaque white
color and insufficient translucency require glassy porcelain veneering on the
framework to achieve a natural appearance and acceptable aesthetics. However,
cracking or chipping of the porcelain veneer has been reported to be a major
complication of these restorations. The possible causes of porcelain veneer
cracking are; differences in coefficient of thermal expansion (CTE) between
framework and porcelain, firing shrinkage of porcelain, porosities, poor
wetting of veneering, flaws on veneering, inadequate framework design to
support veneer porcelain, overloading and fatigue.
Your future of excellent oral health with
Bright New Smile awaits you
Dr. Goswami – the Delhi Zirconia Crown
Dentist - owner of Specialist Full Contour Monolithic Zirconia CAD CAM Metal
Free All
Porcelain Full Ceramic Dental Crown & Bridge Dental clinic in East Delhi,
welcome people to have a detailed consultation to know about monolithic
zirconia full contour zirconia crowns or why choose Full Contour Monolithic Zirconia
All Porcelain Full Ceramic CAD CAM designed computer manufactured dental crowns
over conventional metal porcelain crown work.
Same team -- Affordable
cost -- Same location since last 18 yrs. (est. 2000).
That’s the real beauty of having Zirconia Dental Crown
Treatment from Delhi Dental Center.
Feel free to ask us for a free
consultation
Contact us at :: http://zirconiadentalcrownsindia.com/3m-lava-classic-zirconia-porcelian-ceramic-dental-crown-bridge-dentist-clinic-delhi-india/
Call us at – 9968288257 ,
011 – 22544207.
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