Zirconia Crowns/Bridges
An ideal material for making dental bridges/crowns must be strong enough to withstand the force of mastication, should look similar to the natural teeth, should be biocompatible, and versatile enough to be engineered and customized to patient’s needs. Although, in past, many materials like resin, gold and porcelain have been experimented with and used, porcelain fused with metal (PFM) has been the most widely used. Metals are used for their strength and porcelain is fused over it for an aesthetic look.
Recently, zirconia-made bridges and crown have started gaining popularity. Zirconia or zirconium dioxide is made from zirconium metal and finds its utility in dentistry due to its biocompatibility and durability.
Metal Free Zirconia Bridges and Crowns
Zirconia emulates ceramic properties, boasting exceptional strength and offering a natural aesthetic akin to real teeth. It serves as an excellent foundation for ceramic layering and can be stained to achieve an authentic tooth-like appearance. There are many advantages of zirconia bridges/crowns, some of which are listed below:
Zirconia bridges/crowns stay strong even at a thickness of 0.5mm as compared to crowns made of porcelain fused to metal (PFM) which are around 1.5 to 2mm thick, hence they are bulky and take a lot of space. It implies that the tooth that needs to be prepared for the crown will have to be reduced more.
Many patients may develop allergic reactions to the metal under the porcelain crowns, leading to inflammation of the gum and infections. Zirconia bridges/crowns, on the other hand are highly biocompatible. The body doesn’t identify the crowns as foreign body, hence do not trigger an allergic reaction.
Porcelain fused on metals crowns can chip away easily as compared to zirconia crowns as they are free of metal.
Types of Metal-Free Zirconia Bridges/Crowns
There are mainly two types of Zirconia Bridges/Crowns – Monolithic crowns and Layered Crowns.
Monolithic crowns
These zirconia crowns are made only of zirconia and have outstanding strength and aesthetics. Monolithic zirconia crowns are used for replacing the posterior teeth.
The posterior teeth are crucial for chewing and have cusps and grooves on their upper surface to aid in the efficient crushing of food particles. However, when these teeth require replacement, metal coated with zirconia crowns may succumb to chipping over time due to the rigorous forces of chewing, resulting in a flattened tooth surface.
Flattened tooth surface are inappropriate for chewing; in addition, it may also cause pain and discomfort. Monolithic zirconia crowns overcome all these shortcomings; they have the necessary cusps and grooves for chewing and are resilient against chipping.
Layered crowns
Layered crowns are made of zirconia and layered with ceramic materials for mimicking the translucency of natural teeth. These layered crowns have the same strength and durability as zirconia, and can be made in shades that resemble the natural teeth.
Difference between Porcelain Fused to Metal, Layered Metal free Zirconia and Monolithic Metal free Zirconia
| Porcelain Fused To Metal (PFM) | Layered Zirconia | Monolithic Z0rconia |
|---|---|---|
|
|
Ideal for anterior teeth |
Ideal for posterior teeth |
|
Chipping of porcelain is seen over time |
Ceramic layering is less likely to chip as the chewing forces are less in the front teeth |
No chipping or fracture |
|
Abrade opposing natural teeth |
Does not affect the opposing natural tooth |
Does not affect opposing natural tooth |
|
Good strength |
High esthetics |
High esthetics |
|
Metal Exposure makes it unesthetic |
Great esthetics – mimicking natural tooth |
Tooth colored |
|
Gum tattoo is seen |
No gum tattoo |
No gum Tattoo |
|
More tooth reduction for metal and porcelain layers |
Less tooth reduction |
Less tooth reduction |
