Zirconia: Taking Dental Restorations to the Next Level

Since the introduction of porcelain-fused-to-metal (PFM) crowns in the 1960s, the dental industry has sought materials with both the esthetic value of

porcelain, and the strength of noble metals to withstand the pressure of posterior occlusal forces.

Glass-ceramic materials that came along in the 1980s were confined to use on anterior teeth. In the early 2000s, researchers found that a toughened

version of the metal zirconia met the strength requirements needed for posterior teeth, although the esthetics of the material left much to be desired.

Today, with improved technology, zirconia now rivals PFMs and all-ceramic restorations both for strength and beauty.

A member of the titanium family of metals, zirconia has multi-industry uses and is ideal for use in both anterior and posterior crowns where it fulfills

functional requirements and can be custom shaded for quality esthetics.

Advantages

Zirconia is now the preferred material for crown and bridge fabrication, including implant-supported restorations. These are replacing metal-based

restoration as the choice of most dentists, lab technicians, and patients. Because it can withstand occlusal forces without causing wear on opposing teeth,

the material has quickly replaced full-metal and PFM’s as the material of choice.

Zirconia is more wear resistant than gold, retaining its shape and resisting the tendency to crack and erode by patients who brux. The flex strength

value (MPa) of zirconia is more than twice that of traditional lithium disilicate (glass-ceramic) making it the ideal material for posterior crowns and

bridges.

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While there is, as always with innovative technology, a learning curve for dentists new to working with zirconia, the techniques for tooth preparations

is basically the same as for porcelain and glass ceramic materials. A more conservative preparation of the patient’s original tooth structure is a distinct

advantage.

With zirconia, clearance may be as little as 1 mm, while lithium disilicate materials require 1.5 to 2mm and will not be as strong. A thicker chamfer is

preferable to a feathered margin to provide for minimum thickness at the margin while retaining the ability to taper it to the prep.

Traditional impressions or digital impressions can be used with equal success.

Concerns

As with all new materials and technology, dental zirconia does have its

drawbacks.

Many dentists are hesitant to use zirconia because there are fewer long-term research studies to assess its properties and compare the longevity of the

material to gold, porcelain, and lithium disilicate. However, the studies completed thus far all reflect positively on the future of zirconia crowns.

There is also a lack of ability to bond the material to the preps. Though, that might be seen as an advantage by some, since only cement is needed to

permanently seat the restoration. The hardness, while certainly considered one of zirconia’s advantages, might be a disadvantage when having to remove or

access through them for endodontic treatment.

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Chairside adjustments, while usually minimal, must be made safely, using diamond burs at slow speed with copious amounts of water, polishing wheels, and

cones specifically designed for use with zirconia.

Do not use carbide burs or diamonds at high-speed for adjustments due to microscopic fractures that can occur from the impact of the burs on the

material.