Zirconium oxide in practice and laboratory: Update 2024

Of course, zirconium oxide is no longer an insider tip, but it continues to surprise with new developments and perspectives. The focus of TEAM Talk #6 “Zirconium oxide in practice and laboratory – Update 2024” was therefore four key questions that were discussed from the various perspectives of dentistry, dental technology, materials science and the dental industry.

• What distinguishes a 3rd generation zirconium oxide from a 5th generation one?
• What influence does high-speed sintering have?
• How should zirconium oxide restorations be attached and what should be taken into account?
• 3D printing and zirconium oxide: what is the current status?

The recording of TEAM Talk #6 is freely accessible as a video to inform and inspire. We would like to thank all participants for their active participation and the enriching discussion.

What distinguishes a 3rd generation zirconium oxide from a 5th generation one?

The distinction between 3rd and 5th generation zirconium oxide is based on a few key properties:

• Composition: 3rd and 5th generation zirconium oxides are cubic-tetragonal zirconium oxides with high translucency. The difference lies in the aluminum oxide content; 0,05% Al₂O₃ in the 3rd generation compared to 0,02% Al₂O₃ in the 5th generation. In addition, in the 5th generation, additional grain growth stoppers are built into the material, which means that the grain size is relatively small for a 5Y-TZP ceramic.
• Strength and aesthetics: The change in grain size and reduction in alumina content in the 5th generation aims to increase mechanical strength without compromising translucency (aesthetics).
• The 5th generation was installed for the first time in a multi-generation zirconium oxide disc. Here the 4th generation is combined with the 5th generation in order to optimize the optical properties (basal opaque than occlusal). The strength is almost the same throughout the entire blank.

TEAM talk discussion

During the discussion, a significant shortcoming in communication on the part of some manufacturers was viewed critically. It's about missing information about different strength values ​​for multi-generation zirconium oxide. Users are faced with the challenge of wanting to objectively evaluate products and select them for their requirements. This often proves to be difficult, especially when manufacturers only provide average values ​​for the entire blank without going into specific values ​​for the individual layers. This is perceived as inadequate and even misleading. The average value does not provide a realistic insight into the performance of multilayer zirconia. It is much more important to know how the individual layers - be they made of 3Y-TZP, 4Y-TZP or 5Y-TZP - behave in terms of their strength. This represented a call to manufacturers. Only through detailed information can users make well-founded decisions, select products that meet both aesthetic and functional requirements, but above all position the restorations in the blank securely and with long-term stability.

What influence does high-speed sintering have?

The conventional sintering process of zirconia, which often takes more than seven hours, can be a limitation in certain situations. High-speed sintering offers an efficient solution with several advantages, e.g. b.

• Quick repetition of work in the dental laboratory
• Avoidance of temporary restorations, for example in geriatric patients (direct integration of the definitive restoration)
• Time savings for patients, e.g. B. in cases where it is difficult to arrange multiple appointments
• Competitive advantage through faster production times

This is made possible technologically High-speed sintering through special sintering parameters that allow the sintering time to be shortened to up to 30 minutes without negatively affecting the properties of the zirconium oxide. However, it is important to use zirconium oxide blanks specifically approved for high-speed sintering and special sintering furnaces. There are currently two different types of sintering furnaces for high-speed sintering on the market, which differ fundamentally technologically. A close look at the underlying technology is recommended.

TEAM talk discussion

The discussion about possible changes in the light-optical properties through high-speed sintering revealed an interesting area of ​​tension between subjective experiences and scientific findings. Some participants expressed the fear that the light-optical properties could change during high-speed sintering, especially with large-volume bridge pontics. However, these concerns are based on personal experiences or expectations rather than objective, scientifically based data. Scientific studies show that no significant changes in the light-optical properties of zirconium oxide are to be expected as a result of high-speed sintering. But…an important point is the regular calibration and cleaning of the sintering furnaces. Inadequate maintenance can lead to uneven sintering results, which can, among other things, affect the light-optical properties. In addition, the blanks that are approved for high-speed sintering must be specially adjusted in color, only then will the light-optical properties be correct after sintering.

How should zirconium oxide restorations be attached and what should be taken into account?

Gluing or cementing – any Method has its requirements and advantages. Adhesive bonding (bonding) increases the overall stability of the restoration and offers aesthetic advantages. However, it is technically demanding and requires careful application. Phosphate monomers (MDP) in the luting system are crucial for the adhesive luting of zirconium oxide. These improve the bond between the zirconium oxide and the fastening material. It is important to ensure that the MDP has a high degree of purity, as impurities affect the bond strength. Cementation is often used for less aesthetically demanding restorations and/or when the requirements for adhesive cementation (e.g. drainage, preparation design) are not met. Cements are less technically sensitive in their application. Adhesive fixation is generally recommended for bridges.

TEAM talk discussion

The discussion about adhesive bonding has shown that despite the many advantages of this method, debonding (separation of the restoration) can occur. This problem is primarily attributed to the technique sensitivity of adhesive fixation. Even small deviations from the manufacturer's instructions can increase the risk of debonding. It was pointed out to pay attention to the expiry date of the materials and not to use materials that are past their expiry date - without compromise. How the materials are stored also influences their effectiveness. To achieve optimal results, the manufacturer's instructions (temperature, humidity, light exposure) must be adhered to. In addition, it was recommended to work with a single vendor material system. A vendor's products are typically coordinated with each other, increasing compatibility and reducing the risk of problems such as debonding.

3D printing and zirconium oxide: what is the current status?

One of the most current topics in dental materials science is currently 3D printing of zirconium oxide. The current status reflects an exciting phase of technological development and clinical testing. Here are a few points summarized.

• Technical implementation: The additive manufacturing of zirconium oxide restorations is carried out by printing a slip that consists of a mixture of zirconium oxide particles and a photosensitive resin. The slip is selectively exposed and hardened. After this process, the printed workpiece must be debinded and then sintered.
• Clinical results: Previous research results and short-term clinical studies show promising results. What should be emphasized is the high visual consistency with natural teeth.
• Approval process and availability: Due to the complex approval process, there is currently only one manufacturer that offers an approved system for 3D printing of dental zirconium oxide. This highlights the challenges manufacturers face when introducing new technologies.
• Economic aspects: Although the additive manufacturing of zirconium oxide is technically feasible, from an economic perspective the processes are not yet fully developed. One factor is the long debinding time - burning out the organic binder - which makes the entire manufacturing process very time-consuming.

However, it seems to be a matter of time before additive manufacturing of zirconia finds wider use.

TEAM talk discussion

The discussion on the topic clearly showed that the expectations for this technology are high. One of the biggest advantages of 3D printing is the ability to precisely customize complex geometric structures. Theoretically, almost any geometry can be implemented, which can be particularly advantageous in complex cases. In contrast to milling, where the geometry is limited, 3D printing allows the production of restorations even at difficult preparation angles; without cutter radius correction. Another exciting aspect is the potential possibility of combining different types of zirconium oxide in one restoration. This means that different strengths, translucencies or colors can be achieved in a workpiece.

And so TEAM Talk #6 once again provided a platform for the exchange of knowledge and experiences. The lively discussions showed that continuous research and development as well as close collaboration between practice, laboratory, science and the dental industry are essential. This interdisciplinary exchange is characteristic of the EADT ev

For anyone who missed TEAM Talk #6 or would like to review the discussions again, the recording is now available as an on-demand video. We cordially invite you to watch this informative and inspiring TEAM Talk episode.