Clinicians who wish to provide patients with excellent dental restorations often choose zirconia crowns. These crowns are chosen over conventional PFMs (Porcelain Fused to Metal) or full-gold crowns due to their superior strength, durability, and excellent aesthetics. Some dentists exclusively use zirconia over all-ceramic restorations, particularly when restoring a single tooth. Zirconia crowns require shoulder or chamfer margins for best results. They may be fabricated from solid full-contour zirconia, high translucent zirconia or layered zirconia. High translucent zirconia and layered zirconia can be either screw-retained or cemented.
Most dental practices are switching from the conventional PFM crowns and moving towards the use of zirconia for creating fixed dental restorations. Because zirconia crowns and bridges possess excellent esthetics and are virtually indestructible, zirconia is becoming the most popular material for making dental crowns and other restorations.
Solid or Layered Zirconia?
Solid zirconia, or “monolithic zirconia,” is opaque, which is why it’s generally recommended for posterior crowns. Solid zirconia contains more stabilizers than high translucent zirconia, making it more durable to withstand forceful chewing and grinding. This material is particularly suitable for patients who may grind their teeth. Only minimal clearance is required for this type of restoration, and there is low wear on opposing teeth. Solid zirconia is also very effective for masking highly discolored dental preps, specifically those that have darkened due to previous dental treatments, such as a post and core or a restored dental implant.
Layered zirconia is more translucent and opalescent, but unlike solid zirconia, it is especially suitable for anterior crowns. Although generally used for anterior crowns, layered zirconia may also be used for posterior crowns if there is sufficient clearance. When done skillfully, the very best aesthetic results can be achieved. Both solid and layered zirconia crowns have a strength and consistency that is comparable with traditional PFM restorations, yet they provide far superior aesthetics.
Zirconia HT (High Translucent) , at 590-720 MPa, is much stronger than porcelain-fused-to-metal (PFM) restorations and maintains a natural and vibrant translucency.
The product is 100% metal-free, a feature that prevents gingival darkening and removes the possibility of exposing metallic margins if gum recession begins. They are naturally esthetic, transmit the color of adjacent teeth, and can be matched to any shade, making high-translucent zirconia suitable for bridges up to 3 units in length.
Using Zirconia HT can save your patients more than three hours since there is no need for shading liquids or drying time. Due to its inherent natural fluorescence in any lighting condition—whether daylight, sunshine or black light—restorations will always look natural. No special fluorescent glaze is required.
The high biocompatibility of zirconia will not cause allergies in patients who have allergic reactions to PFM restorations. Quite a few dental patients are allergic to the alloys used for the fabrication of PFM crowns. If you have a patient who faces these allergies, this is a sign that zirconia should be used when making restorations. In fact, zirconia possesses excellent biocompatibility, making the crowns and bridges prepared from zirconia extremely safe for clinical use inside the mouth.
Advantages of Choosing Zirconia Crowns
Zirconia crowns are highly biocompatible, as the smooth surface helps to reduce plaque accumulation. Layered zirconia crowns are extremely durable. Even though the porcelain used for layering does not have the strength of solid zirconia, they are designed to bond with the zirconium substructure, making chipping or fracturing extremely rare. The material also promotes a healthy tissue response.
Due to a wide variety of factors including chemical composition and processing requirements, there are many ways zirconia can be manufactured to suit the needs of the patient. This customization minimizes the margin for error and ensures excellent fit for each individual.
Zirconia is suitable for patients with metal allergies or who would prefer to have metal-free restorations.
Zirconia is metal-free, which prevents darkening around the gingival area. This eliminates the possibility of metal margins becoming exposed due to gum recession.
The translucent nature of this material can transmit the color of adjacent teeth and it is manufactured in a wide variety of shades, making it easy to accurately match the color of the patient’s natural teeth.
Using computer-aided design and manufacturing processes provide patients with a precise fit, reducing the chair-side time required for adjusting and cementing these restorations.
Zirconia crowns can be conventionally cemented in place by using Bisco’s Z-Prime Plus, then applying the bonding agent of choice to prep, followed by dual-cure resin cement.
Zirconia crowns are comfortable for patients, as they do not transmit hot and cold in the same way as conventional PFMs.
Are There Any Disadvantages of Having a Zirconia Crown?
The disadvantages of zirconia crowns are minimal. The toughness of the material has raised some concerns about friction against the tooth root and wearing down opposing teeth. Frequent check-ups, however, help to reduce the possibility of damaging opposing teeth. Initially, only bone-white substructures could be produced for zirconia crowns, which could sometimes create problems in achieving an aesthetically-perfect appearance. Now, however, the newer generation of materials are pre-shaded and can be fabricated to provide highly aesthetic and naturally-perfect restorations with minimal tooth reduction, meeting or even exceeding patient demands for high-quality work! Currently, the demand for zirconia far exceeds the demand for PFMs, and these older-style restorations are becoming a thing of the past.
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