Demystifying Zirconia
The myth surrounding zirconia has persisted for many years. When it first entered our industry, it was white, opaque, hard, and difficult to utilize to its full extent. But time has passed – equipment, tools, materials, and knowledge have evolved significantly.
Today, we can fabricate monolithic zirconia restorations – ranging from a single tooth to full-arch bridges, supported by teeth or implants. These restorations now exhibit a lifelike, natural appearance and deliver excellent functionality.
To better understand zirconia, we can differentiate it by strength and translucency – characteristics that are often (but not always correctly) interpreted as indicators of “higher aesthetics”. Let’s explore the types of zirconia in the simplest possible way without getting too scientific:
Zirconia Types by Generation:
- 3Y Zirconia
- The original generation.
- Highest strength and highest opacity.
- Best used where maximum durability is needed, e.g., posterior bridges.
- 4Y Zirconia
- Offers a balance between translucency and strength.
- Available in multilayered or monochromatic pre-shaded forms.
- Suitable for both anterior and posterior restorations.
- 5Y Zirconia
- Provides the highest translucency among current materials.
- Ideal for anterior aesthetic zones, but limited in strength.
- Not recommended for long-span bridges.
- Comes in pre-shaded and multi-layered options.
- 6Y Zirconia
- A newer hybrid of 4Y and 5Y.
- Combines the translucency of 5Y with the strength of 4Y.
- However, translucent areas are inherently weaker.
- The lower to middle parts of the blank contain stronger, more chromatic, and opaque zones.
- Nesting strategy becomes critical:
- Ensure connectors in bridges are placed in the stronger areas to optimize mechanical performance while maintaining aesthetics.
Important Clinical Considerations:
High translucency does not always equal high aesthetics. Aesthetics are relative and case-dependent. For instance, in cases involving underlying dark structures, such as:
- Metal posts
- Metal abutments
- Discolored roots from endodontic treatment
…it is not advisable to use highly translucent zirconias like 5Y or 6Y. These materials would allow the underlying colors to show through, resulting in inconsistent aesthetics.
In such situations, a higher-opacity zirconia like 4Y is preferred to mask the substructure. If aesthetic blending is critical and adjacent dentition must be matched precisely, layering porcelain over 4Y zirconia is often necessary.