Virtual Kick-Off KATANA Zirconia Symposium

Lecture 1 of 3, Prof. Dr. Beuer
Watch how Prof. Dr. Beuer explains his experience with the new material. Two in one: Combining High Strength and High Translucent Zirconia.

Lecture 2 of 3, MDT Rondoni + MDT Rossi
Watch the recording of the KATANA Zirconia YML Online Symposium on July 3rd 2021, the second lecture plus hand-on which details the experience of MDT Rondoni and MDT Rossi with this new material.

Lecture 3 of 3 + Q&A, MDT Nondas Vlachopoulos
Mister Vlachopoulos deepdives in to a full procedure executed with the new material and demonstrates how liquid ceramics compliment the material establishing a very high-end aesthetic result.

BY PETER SCHOUTEN

ZIRCONIA
CRYSTALLISATION

Zirconia is here to stay in dentistry. Since its introduction some two decades ago, the possibilities for use of zirconia have increased enormously. But how is this compound produced? What happens during sintering, what types are available, and how are the desired shape and shade of the final product achieved?

PSZ or Partially Stabilised Zirconia was the first of the zirconium oxides to be used in dentistry. This type of zirconia was stabilised using yttria, and is currently no longer in use. It consisted of a mix of monoclinic, tetragonal and cubic crystals. For many years, the so-called Y-TZP variety was used (yttria tetragonal stabilised zirconia polycrystal). This has outstanding flexural strength (> 1,000 MPa), however, a non aesthetic opaque white appearance. It consists for mostly of tetragonal crystals with a diameter of some hundreds of nanometres. Approximately 3 mol% yttria is added to keep the material stable at room temperature;
this variety is therefore sometimes described as 3Y zirconia. New varieties, such as cubic zirconia, were developed with the aim of improving the aesthetic
properties of the material. Cubic zirconia is characterised by high translucency but has a lower flexural strength. However, although the flexural strength of this type is considerably lower than that of the tetragonal version, it is nevertheless much higher than that of lithium disilicate. This form also contains a higher amount of yttria, ranging from 4 to more than 5 mol%.

CRYSTAL PHASES

We currently know of zircona crystals in three major shapes.

Monoclinic

Normally, zirconia exists only at room temperature in the monoclinic phase. Monoclinic zirconia has low strength and translucency.

Tetragonal
These zirconia crystals are metastable and only exist at room temperature after stabilisation, mainly by adding yttria.
Although tetragonal zirconia is strong, it has limited aesthetic properties.

Cubic
Cubic crystals are stable and provide improved translucency. Due to the addition of a higher percentage of yttria, cubic
zirconia work pieces are not as strong as tetragonal ones. On the other hand, they are highly aesthetic and therefore
suitable for monolithic restorations, even in the anterior zone.

CRYSTALLISATION PROCESS
Zircona is almost invariably offered as a partially sintered material. In this form it is always opaque white, and the true
colour and translucency is only apparent after sintering. During sintering, the material shrinks to its ultimate size; a
multitude of small crystals merg to form larger crystals, but although the crystals themselves increase in size, the total
volume decreases. This shrink factor is therefore taken into account in the software, so that the end product is not only
colourfast after sintering, but is also sizewise correct.

Small crystals merge into larger ones during the sintering process.

KATANA™ Multilayer HTML before (left) and after sintering.

The KATANA™ Zirconia family of multi-layered CAD/CAM blanks has a new member: KATANA™ Zirconia YML (yttria multi-layered). Based on Kuraray Noritake Dental Inc. (KND) proprietary multi-layer technology, this new material offers multiple layers with different levels of chroma and translucency PLUS different concentrations of yttria in a single blank. We talked to two experts from Kuraray Noritake Dental’s Research & Development Department in Japan, Atsushi Matsumoto and Yuta Tajima, about the new product and its specific features.

Mr. Matsumoto, Mr. Tajima, KND already offers a broad range of zirconia materials covering virtually every indication. Why did you decide to start developing yet another dental zirconia?

The KATANA™ Zirconia series has indeed received high praise and great feedback from the market. Users particularly appreciate the remarkably high strength of HTML, the well-balanced aesthetic and strength properties of STML, and also the high translucency of UTML. Although there has been a large increase of zirconia materials in the dental market recently, we have received many requests from our customers for a more universal material that offers the excellent properties of all variants of KATANA™ Zirconia in one product. This product should allow them to fabricate all kinds of restorations from a single disc, from single crowns to full bridges, while maintaining high aesthetic and mechanical properties for both anterior and posterior restorations. As the developer of the KATANA™ Zirconia series, the invention of KATANA™ Zirconia YML is our response to these desires expressed by our customers.

What is the main difference between KATANA™ Zirconia YML and the other available products of the KATANA™ Zirconia Multi-Layered Series?

All layers of KATANA™ Zirconia UTML, STML and HTML are produced from the same basic powder composition and therefore offer the same strength throughout the whole blank. Depending on the case specific requirements, users need to select the most suitable type of material, either a high-strength zirconia or a highly translucent variant. KATANA™ Zirconia YML is an all-in-one zirconia suitable for all cases: It consists of a high-translucency enamel layer, an intermediate layer offering well-balanced strength, translucency and colour, and a high-strength body layer. The raw materials used for this product are developed and produced by KND exclusively for YML. This is another milestone in advanced product development KATANA™ Zirconia.

We have received many requests from our customers
for a more universal material.

In general, the currently available zirconia materials with an integrated strength gradient do not have a very positive image in the eyes of many dental technicians and specialists, due to the fact that in the incisal area, the materials seem to be insufficiently strengthened. This can lead to fractures when it comes to long-span restorations, especially if they are inadequately positioned within the blank. How carefully did KND focus on these problems and how did they try to solve them in order to stand out from the competition?

The current yttria-based multi-layer products on the market are facing complicated limitations in connector position in large cases, such as full-arch restorations, due to the lack of an ideal combination of aesthetics and strength. To overcome this challenge, KND developed well-balanced raw materials of high strength and high aesthetics, and by including these raw materials in the intermediate layer between the enamel and body layers. The result is that even for long-span restorations, it is very simple to position the connectors thanks to its excellent balance between high strength and high aesthetic properties. Due to these unique attributes incorporated in our new product, the risk of deformation and breakage is avoided.

Another problem is the often clearly visible line between the different layers containing different amounts of yttrium oxide, which can be seen at a more detailed inspection after sintering. How did you address this issue?

At KND, we achieved both, adequate translucency gradation and invisible transition lines, even for zirconia layers with different yttria content. This has been accomplished thanks to our multi-layer zirconia manufacturing technology refined over many years, which includes mixing the appropriate amount of each layer's boundary to intentionally avoid transition lines. In addition, the newly developed interlayer raw materials and a newly designed sintering schedule were the keys to success.

How is it possible to have a sintering protocol that works for different zirconia components within the KATANA™ Zirconia YML blank and allows for the shortest sintering times ever?

The amount of shrinkage during sintering is determined by different factors such as the number and quantity of additives (yttria, alumina etc.) it contains. If the shrinkage ratio of each layer is different, transition lines are likely to appear between the layers, which might produce tensions in the material structure. The newly developed raw material for KATANA™ Zirconia YML enables us to control and unify the shrinkage ratio for all layers, even for raw materials with different yttria contents.

The use of proprietary raw materials produced in-house with excellent properties suitable for high-speed sintering was the main precondition that allowed for the development KND’s high-speed sintering schedule (54 min for restorations up to 3-unit bridges), which is available for all products of the KATANA™ Zirconia multi-layered series. This option improves the efficiency of the dental technician’s work and simplifies the workflow.

Are there any differences in milling and adjusting KATANA™ Zirconia YML compared to competitor products?

All KATANA™ Zirconia products from KND have an appropriate hardness with less chipping during the milling process thanks to the raw materials manufactured and refined in-house. Also, after the sintering procedure, it offers excellent chipping resistance, especially during very challenging marginal adjustments.

Is there anything else that sets KATANA™ Zirconia YML apart from other products with an integrated strength gradient?

Yes, KATANA™ Zirconia YML offers reduced sintering deformation, thanks to in-house developed raw materials, based on proprietary technology to control shrinkage rate. Moreover, we offer a wide range of shades (14), which is another important aspect (apart from the material’s well-balanced aesthetic properties and absence of transition lines) for the creation of lifelike restorations. Finally, since three out of four layers meet the conditions for an ISO class 5 classification, there are few restrictions on the design variation of the prosthesis.

Why should a dental technician consider using KATANA™ Zirconia YML instead of any other dental zirconia (in your opinion)?

Atsushi Matsumoto:

It is now possible for dental technicians to produce strong and aesthetic restorations with just one material, KATANA™ Zirconia YML. This allows for a reduced inventory, while working time is significantly shortened due to the possibility of high-speed sintering.

Yuta Tajima:

To my mind, the most convincing properties are excellent firing accuracy due to well-balanced material properties across all layers, the wide range of shades available and the great design flexibility even when designing long-span bridges. Last but not least, the trusted quality of the KATANA™ brand and the label “Made in Japan” are reasons to opt for this new product.

All blanks from the KATANA™ Zirconia Series stand out from other dental zirconia materials due to their particularly fine-grained, densely pressed microstructure, which is the basis for a superior surface quality, edge stability and the resulting accuracy of fit. What is the secret behind this exceptionally high blank quality?

Since we do not know the correlation between marginal stability properties (chipping, etc.) and material compositions, structures etc., it is very difficult to answer this question. It may depend on the structures of the zirconia crystals, the raw material itself, the correct strength level after pre-sintering or any other minor factor during the manufacturing process of the disc. All these factors together, of course, are important.

We are using pigments developed by KND, which have an excellent colour stability without fading even after the final sintering procedure.

Even if the restoration margins have been milled to a very thin profile, they still show smooth margins without any chipping.

A clear advantage of the KATANA™ Zirconia series, much praised by KND's Key Opinion Leaders, is its colour stability and shade match to the "VITA classical shade guide". Can you explain the importance of an in-house conducted addition of additives and color pigments in form of metal oxides to satisfy the user and distinguish KATANA™ Zirconia from competitors’ products?

We are using pigments developed by KND, which have an excellent colour stability without fading even after the final sintering procedure. The particle size is appropriately controlled. In addition, our professional "colour mixing" staff, reflecting the opinions of clinically experienced dental technicians both inside and outside the company, have achieved a pigment mixture that shows only a slight change in shade even in cases with different thicknesses.

What is your vision with regard to future developments in dental zirconia?

Since the introduction of zirconia on the dental market, many significant material advances have been achieved. Today, there are high-strength, low light-transmitting zirconia materials up to high light- transmitting, low strength zirconia materials available on the market. Furthermore, there are now also high light-transmitting, low strength zirconia materials in mixed systems (YML series) offered. Our foremost goal is to develop the ultimate zirconia in near future, combining both high strength and high light transmission, which breaks the general expectation of a compromise between strength and translucency within zirconia materials.

Interview with Mathias Fernandez Y Lombardi, EU Scientific Manager, Kuraray Europe GmbH

Kuraray Noritake Dental Inc. reinvented its original zirconia multi-layer technology by integrating newly developed raw materials with different yttria content into the proven multi-layer colour structure. The material that is based on this innovative technology, KATANA™ Zirconia YML, offers a well-balanced flexural strength, chroma and translucency gradation throughout the blank.

According to pilot users of the new zirconia discs, the greatest benefit of using KATANA™ Zirconia YML is in the true empowerment of the laboratory. We asked Kuraray Noritake’s EU Scientific Manager Dental Ceramics & CAD/CAM Materials, Mathias Fernandez Lombardi, to explain how the new material is able to positively affect work routines in the dental laboratory.

The greatest benefit of using KATANA™ Zirconia YML is in the true empowerment of the laboratory.

Mathias Fernandez Lombardi, who should consider working with KATANA™ Zirconia YML?

KATANA™ Zirconia YML is designed for laboratories and milling centres with a strong focus on simplification. With its strong body and highly translucent enamel layer, it offers exactly the properties required for an unlimited indication range. Being perfectly suited for the production of durable monolithic long-span posterior bridges and of highly aesthetic anterior crowns or partial restorations, KATANA™ Zirconia YML is a true all-rounder that eliminates the need for another zirconia or even ceramic CAD/CAM material. At the same time, it supports highly automated production procedures and requires minimal hand work.

What are the benefits of using a single material for every indication?

Several benefits are related to the use of a single, all-round material. It leads to a reduced number of blanks to be stored, which simplifies inventory management and minimizes the storage space needed. Moreover, it facilitates standardization of laboratory workflows. Using the same material every time means that there are no differences in the basic design and milling parameters like minimum wall thicknesses and connector strengths, in the sintering protocols and finishing options to be taken into account. Hence, errors are less likely to occur and routines are easily established. Finally, the risk of cross-contamination is eliminated when a single material is processed with the available equipment (milling machine, milling and finishing tools, and sintering furnace). Predictable outcomes and flawless aesthetics are usually the result.

What are the benefits related to the use of KATANA™ Zirconia YML as the only ceramic CAD/CAM material?

I guess that the most important argument is that aesthetic outcomes are easily and efficiently achieved with KATANA™ Zirconia YML for all kinds of restorations, even for long-span bridges. It is usually sufficient to produce monolithic restorations for the posterior region, which are just polished or glazed. Anterior restorations may be designed monolithically or with minimal cut-back, and the user may choose between CERABIEN™ ZR (CZR) FC Paste Stains and CZR Internal Stains plus glaze to obtain a natural look. Another benefit of KATANA™ Zirconia YML is its seamless multi-layer structure combined with an extraordinary blank quality.

Why is this seamless structure and high blank quality important for users?

The seamless multi-layer structure, that is a smooth transition from one layer to the next, is the precondition for structural integrity and flawless aesthetics. It ensures that the material is free of transition lines, offers accurate dimensions after sintering (due to uniform shrinkage) and shows a reliable long-term performance not compromised by internal tensions. In KATANA™ Zirconia YML, a completely homogeneous composition, with carefully aligned CTE-values and shrinkage ratios in all parts of the blank, is responsible for this benefit.

Aesthetic outcomes are easily and efficiently achieved with KATANA™ Zirconia YML for all kinds of restorations, even for long-span bridges.

For its development, Kuraray Noritake Dental leveraged its long-standing expertise in dental ceramics and the advantages of an end-to-end in-house blank production process, without which it would have been impossible to reach the requested quality level. Due to the fact that the material is so well aligned, it was even possible to develop a 54-minute sintering programme that produces equally good results as the proven 90-minute or 7-hour programmes and becomes the go-to option for all rush cases. With this feature, KATANA™ Zirconia YML becomes the “jack of all trades” material: It offers highest comfort and security like an SUV, but when it comes to speed, it is in no way inferior to a sports car.

The above sintering recommendations represent only a guideline; depending on each individual furnace and condition, some adjustments might be necessary. If the 54 or 90-minute sintering program is not programmable in your furnace, it is not possible to set the furnace according to one of these schedules. *The material is removed from the furnace at 8000C. A furnace with a configurable YML sintering program is required.

Users who have already tested ceramic materials with a strength gradient know that positioning of long-span restorations in the blank can be tricky. What are the rules to be respected when positioning a long-span bridge in a YML blank?

Positioning of restorations in KATANA™ Zirconia YML discs is extraordinarily easy. The reason is that the gap between the lowest flexural strength found in the enamel area and the highest flexural strength found in the lowest body layer is comparatively small. Moreover, the Body Layer 1 that is found adjacent to the enamel layer already offers a flexural strength that is higher than the 800 MPa requested for bridges with four or more units. Consequently, users are on the safe side whenever they place their long-span restorations in the middle of the blank. More specifically, half of the connector cross section needs to be in the lower half of the disc, which is quite different from other materials with strength gradation that allow for connector positioning in the body area only. KATANA™ Zirconia YML restorations with a maximum of three units may be positioned in any layer. In this context, the fact that the thickness of each layer increases proportionally with the height of the disc comes as a benefit: The enamel layer is large enough to exploit its aesthetic potential in single-unit or small bridge cases.

Positioning of long-span restorations in the middle of the disc.

What would you recommend dental technicians who would like to empower their laboratory or milling centre?

I can truly recommend testing KATANA™ Zirconia YML in the laboratory environment to see how it handles and to assess its potential. The exceptional blank quality and seamless integration of the different layers, the ease of positioning and processing efficiency are factors potential users need to experience in real life to understand what they mean for their daily work. Similarly, the aesthetic outcomes need to be assessed in the clinical environment for an authentic impression of the natural look and feel obtained. I am sure that KATANA™ Zirconia YML will be able to convince virtually everyone who wants to empower the laboratory with an easy-to-use, efficient universal zirconia solution that fits virtually every patient’s and every dentist’s needs! Kuraray Noritake Dental knows that dental technicians and practitioners are in need of products that support their striving for simplification, standardization and increased efficiency so urgently needed in present times. Therefore, our product innovations are all focused on delivering more performance with less effort. KATANA™ Zirconia YML is the latest addition to a whole series of materials pursuing this goal.

Minimum connector cross-sections are to be respected during the computer-aided design of KATANA™ Zirconia YML restorations.

Mathias Fernandez Y Lombardi

EU Scientific Manager
Dental Ceramics & CAD/CAM Materials
Kuraray Europe GmbH

2013
Successful completion of an apprenticeship as a dental technician at Seuthe dental laboratory in Plettenberg, Germany

2018
Successful completion of dental technology studies at the University of Osnabrück, Germany. Graduation as an engineer in dental technology

Since March 2018
Employee of Kuraray Europe GmbH

Daniele Rondoni, hammasteknikko (CDT)

Tavallisesti hammaskeraamin esteettisyyttä – erityisesti sen läpikuultavuutta – voidaan parantaa vain taivutuslujuuden kustannuksella. Kararay Noritake Dental -yhtiön Uusi KATANA™ Zirconia on erilainen. Rungon alaosan taivutuslujuudella 1,100 MPa:a ja korkealla läpikuultavuudella rungon yläosassa ja inkisaalisesti esteettisyydelle ei ole indikaatiorajoja, kuten alla oleva tapaus osoittaa.

Kuva 1. KATANA™ Zirconia YML -materiaalista toteutetut 4-osaiset ja 6-osaiset sillat jyrsinnän ja sintrauksen jälkeen. Vestibulaaripinnan luonnollinen rakenne on tärkeä edellytys monoliittisten restauraatioiden esteettisyydelle.

Kuva 2. Kahden sillan frontaalinäkymä mallin päällä CERABIEN™ ZR FC Paste Stain -tuotteen (Kuraray Noritake Dental Inc.) ultramikrokerroksen levittämisen jälkeen.

Kuva 3. Värjätyt ja lasitetut restauraatiot ja niiden läpikuultavuus valossa.

Kuva 4. Potilaan suuhun sementoidun 6-osaisen sillan bukkaalinäkymä.

Kuva 5. Potilaan suuhun sementoidun 6-osaisen sillan bukkaalinäkymä.

Tämän uudentyyppisen monikerroksisen zirkoniumoksidin avulla voidaan valmistaa esteettisiä monoliittisia restauraatioita myös etualueella. Eri kerrosten lujuuseroista huolimatta materiaalilla voidaan toteuttaa lujuudeltaan erinomaisia restauraatioita ja materiaalin hyvä läpikuultavuus inkisaalialueella takaa luonnollisen lopputuloksen sintrauksen jälkeen. Ultramikrokerrokset ja monoliittisen pinnan lasitus takaavat lopputuloksen, johon potilaat ovat tyytyväisiä.

DANIELE RONDONI, MDT

Tässä videossa hammasteknikko Kazunobu Yamada näyttää, miten hän sävyttää ja lasittaa uutta Katana Zirconia YML -zirkoniaa. Katso vaiheittain etenevä video erittäin esteettisen ja luonnollisen lopputuloksen saavuttamisesta erilaisilla FC Paste Stain -sävyillä.

Esittelemme Katana Zirconia -tuoteperheen uusimman jäsenen Katana Zirconia YML:n. Tässä vallankumoukseillisessa zirkoniakiekossa on monikerroksinen rakenne, joka parantaa paikkojen estetiikkaa merkittävästi. Haluatko tietää, miten voit kehittää hammaslaboratoriosi palveluja tämän huippulaadukkaan tuotteen avulla? Katso videolta lyhyt yhteenveto tämän käänteentekevän uuden zirkoniakiekon ominaisuuksista!

We are pleased to share with you short training videos for CERABIEN™ ZR (CZR) porcelain.

Check out the below working steps and learn more about how to achieve outstanding aesthetics using this tried and proven material.

It is strong, it is pre-shaded like natural teeth, and it is reliable: KATANA™ Zirconia HTML, the highest strength version among KATANA™ multi-layered zirconia series. Now, Kuraray Noritake Dental Inc. has carefully optimized the product to further improve its optical properties and to harmonize the sintering schedules with all other materials of the KATANA™ Zirconia Multi-Layered Series.

The new KATANA™ Zirconia HTML Plus offers all popular properties of its predecessor, including the multi-layered colour structure and uniform strength distribution throughout the blank. It is suitable for a variety of indications including long-span bridges with a minimum wall thickness of just 0.4 mm in the anterior and 0.5 mm in the posterior region. This allows for minimally invasive preparations, while the user may choose between a monolithic, cut-back or framework design combined with the preferred finishing technique.

The PLUS refers to additional benefits like the material’s improved optical properties: KATANA™ Zirconia HTML Plus offers an increased translucency of 45 percent (compared to 43 percent KATANA™ Zirconia HTML) and an even more natural shade appearance of the manufactured restorations. “As the colour of the restorations appears deeper, more vivid and more saturated, and the translucency is closer to that of natural teeth, a great optical integration is achieved straight away. This leads to a reduced finishing effort”, says Mathias Fernandez Y Lombardi, EU Scientific Manager Dental Ceramics & CAD/CAM Materials at Kuraray Noritake Dental. At the same time, the high flexural strength (1,150 MPa) is maintained, providing for an unlimited range of indications.

Like its predecessor and all other materials of the KATANA™ Zirconia Multi-Layered Series, KATANA™ Zirconia HTML Plus is the result of an in-house development, powder compilation and blank production process that is able to control every detail. This enabled our specialists to achieve a precise alignment of the desired properties, while maintaining a high blank quality that leads to the accurate milling results with smooth surfaces and regular edges users of KATANA™ Zirconia HTML are familiar with.

The unique powder composition and specific in-house blank production procedure also allowed us to streamline the sintering protocols. For single-tooth restorations and bridges with up to three units, three different protocols are available: a 54-minute high-speed sintering programme specifically developed for remake and rush cases, a 90-minute schedule and the traditional seven-hour sintering programme. The latter is also suitable for long-span restorations.

These three options and identical schedules are available for KATANA™ Zirconia HTML Plus, KATANA™ Zirconia UTML, KATANA™ Zirconia STML and the new KATANA™ Zirconia YML with additional flexural strength and technical translucency gradation. With this feature, it becomes extraordinarily easy to standardize procedures despite an indication-specific selection of the best-suited KATANA™ Multi-Layered Zirconia.

Mathias Fernandez Y Lombardi concludes: “KATANA™ Zirconia HTML Plus is completely in line with our philosophy of developing products that support their users in streamlining and simplifying procedures without limiting choices. Users may choose from a whole range of highly specialized or universal zirconia solutions, may opt for their preferred design and finishing technique, and can select the sintering protocol that suits their individual needs. At the same time, the manual effort is reduced and the risk of starting the wrong sintering programme is eliminated.”