Case by Marco Valenti, DDS and Angelo Canale, CDT

When dental zirconia evolved into a highly aesthetic material suitable for the production of restorations with a monolithic design or minimal labial cutback, the amount of hand work (ceramic layering) was reduced. At the same time, however, every dental laboratory needed to have more blanks available, and the need for an indication-specific material selection complicated the planning process.

Some dental technicians love to play with different blanks and with a combination of automated and manual work steps to exactly meet the patient and indication-specific needs. Others, however, would like to take a faster and more standardized path to beauty. For the latter group, Kuraray Noritake Inc. has just introduced a true allrounder. KATANA™ Zirconia YML is based on newly developed raw materials with different yttria content integrated into the company’s multi-layer colour structure. As a consequence, KATANA™ Zirconia YML offers colour, translucency and strength gradation throughout the blank, resulting in an unlimited indication range.

That sounds promising, but does it really work in the laboratory and clinical environment? Are there any hidden challenges with regard to designing and manufacturing? And how beautiful are the outcomes? In order to assess the material’s properties in real life and to see how it performs in our hands, we decided to select a complex case and run a clinical test.

INITIAL SITUATION AND TREATMENT PLAN

This female patient was concerned about the aesthetics of her maxillary anterior teeth (Figs. 1 and 2). Several porcelain-fused-to-metal crowns in the anterior (both central incisors) and posterior region (three premolars) had unsightly dark margins and an unnaturally opaque core. The adjacent natural teeth appeared more translucent and their look was compromised by several composite restorations with discoloured margins. A missing right first molar had caused second molar to drift mesially (Fig. 3). In addition, the left canine was missing, but the space had been closed (Fig. 4). Figure 5 provides an occlusal view of the pre-operative situation.

Fig. 1. Facial view of the pre-operative clinical situation.

Fig. 2. Frontal intraoral view of the patient’s teeth.

Fig. 3. Lateral view of the upper and lower right quadrant.

Fig. 4. Lateral view of the upper and lower left quadrant.

Fig. 5. Occlusal view of the maxillary teeth.

All restorations in the maxilla needed to be replaced, and the patient set great value on a long-lasting aesthetic improvement of the situation. Hence, an all-ceramic material needed to be selected. An orthodontic correction of the malocclusion prior to restorative treatment was not an option, so that the restorations needed to be adjusted to the existing clinical situation. In order to provide for a smooth optical integration, we decided to use a single material for all restorations from the incisors up to the second premolars. This was a great chance to put the new KATANA™ Zirconia YML to a test! It was planned to use the material monolithically with zero cutback and to just paint on an ultra-thin layer of liquid ceramics (CERABIEN™ ZR FC Paste Stain).

CLINICAL PROCEDURE

The old restorations were removed and tooth preparation was carried out (Fig. 6). A minimally-invasive structure removal is supported by the fact that KATANA™ Zirconia YML has a minimum wall thickness of just 0.4 mm in the anterior and 0.5 mm in the posterior region. Then, a digital impression was taken with 3Shape TRIOS 3 (Fig. 7). The acquired data was matched with photographs of the patient’s face to design a virtual wax-up (Fig. 8) and mill a temporary restoration in the dental laboratory. The placement of this temporary allowed for an aesthetic and functional assessment as well as a clinical test drive of the planned definitive restorations (Fig. 9). In this set-up, the left first premolar took over the function and shape of the missing canine. The fact that the gingival margin was slightly higher in the region of the right compared to the left central incisor did not bother the patient, so that an alignment (gingivectomy) was not necessary.

Fig. 6. Situation after tooth preparation with a heavily discoloured central incisor.

Fig. 7. Digital impression taken after tooth preparation.

Fig. 8. Smile design for the production of the temporary.

Fig. 9. Temporary restoration in place.

PRODUCTION OF THE FINAL RESTORATIONS

After successful completion of the test drive, a digital impression was taken with the temporary in place (Fig. 10). Based on this impression and the information acquired during the test drive, four full-contour crowns, two partial crowns and one bridge were designed (Fig. 11 to 13). The bridge in the region of the right first premolar to first molar had a small cantilever pontic to fill the reduced space of the missing first molar.

The restorations were milled from KATANA™ Zirconia YML. Despite the varying levels of flexural strength within the blank, virtual positioning of the restorations in the disc is extraordinarily easy. For the restorations produced in this case, it is only necessary to respect the minimum wall thickness and connector cross section recommended by the manufacturer. When long-span restorations (with more than three units) are planned, half of the connector cross sectional area needs to be positioned in the lower half of the blank. This is the case if a restoration is placed in the middle of the disc, independent of its size.

Fig. 10. Digital impression taken with the temporary restoration in place.

Fig. 11. Computer-aided design of the final restorations.

Fig. 12. Aesthetic assessment of the virtual design.

Fig. 13. Functional assessment of the virtual design.

FINISHING

Figures 14 and 15 show the sintered restorations on the resin models after the addition of individual textural features with hand instruments. A seamless multi-layer structure without transition lines and with a warm body area is obtained. For an even more natural appearance, some individual effects and glaze were added using the CERABIEN™ ZR FC Paste Stain kit from Kuraray Noritake Dental Inc. (Fig. 16 to 19).

Fig. 14. Frontal view of the restorations on the resin models.

Fig. 15. Occlusal view of the restorations.

Fig. 16. Frontal view of the final restorations.

Fig. 17. Lateral view showing the bridge and the anterior crowns in the first quadrant.

Fig. 18. Lateral view showing the crowns in the second quadrant.

Fig. 19. Occlusal view of the lifelike restorations.

TREATMENT OUTCOME

The restorations were placed with the adhesive cementation system PANAVIA™ V5 (Kuraray Noritake Dental Inc.). Figure 20 shows the treatment outcome immediately after cementation. The material masks the discolouration of the underlying tooth structure very well and offers a nice translucency in the incisal area.

FINAL SITUATION

Fig. 20. Treatment outcome.

A TRUE ALLROUNDER

Our test project confirmed that KATANA™ Zirconia YML is a high-quality material with a great aesthetic potential and no limits with regard to the indication range. It is surprisingly easy to design and position the restorations in the virtual blank and after milling, the surfaces are smooth, the margins are sharp and stable, and the fit is accurate. Micro-layering with paste stain is often sufficient for lively outcomes. This makes the new KATANA™ Zirconia YML the material of choice for anyone placing great value on a high level of automation, the standardization of laboratory workflows and efficient and easy procedures.

Dentists:

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.”

One for all: With KATANA™ Zirconia YML (yttria multi-layered), Kuraray Noritake Dental Inc. has launched a true allrounder covering traditional and new zirconia indications. At the KATANA™ Zirconia YML Virtual Kick-Off Symposium on July 3, 2021, professionals from the clinical and technical field as well as scientific experts from Kuraray Noritake Inc. provided insights into the properties and benefits of the innovation. We had a conversation with three of them about the specific features of KATANA™ Zirconia YML and its potential role in the dental practice and laboratory. Mathias Fernandez Y Lombardi, EU Scientific Manager Dental Ceramics & CAD/CAM Materials, provided insights from inside the company, while Prof. Dr. Florian Beuer MME, Charité – Universitätsmedizin Berlin and MDT Nondas Vlachopoulos, owner of the dental laboratory AestheticLab in Athens, shared their external perspectives.

Prof. Dr. Florian Beuer MME and Mathias Fernandez Y Lombardi during the conversation at the Kick-Off Symposium in Munich.

MDT Nondas Vlachopoulos virtually attended the meeting.

What are the most important features and benefits of the new KATANA™ Zirconia YML?

Mathias Fernandez Y Lombardi: KATANA™ Zirconia YML is a 5^th generation zirconia featuring next-generation multi-layered technology: it offers colour, translucency and flexural strength gradation in one disc – for a virtually unlimited indication range. As it may be used as the only zirconia or even ceramic CAD/CAM material in a laboratory or milling centre, it is designed for everyone who would like to simplify and standardize laboratory procedures. It may be sintered within 54 minutes, offers a high accuracy of fit and may be finished using time-saving techniques.

The new discs presented at the KATANA™ Zirconia YML Virtual Kick-Off Symposium.

Multi-layered structure of KATANA™ Zirconia YML.

What are the benefits of using a single zirconia for every indication from the dental technician’s perspective?

Nondas Vlachopoulos: The use of a universal zirconia solution with a high aesthetic potential and well-aligned mechanical properties allows dental technicians to reduce their inventory and streamline their procedures – from designing to finishing. Nowadays, we all know that, in order to optimize the outcomes, it is essential that we develop a deep understanding of a material’s properties, respect its design parameters (like minimum wall thicknesses) and adhere to the sintering protocols. It is much easier to accomplish this for a single material than for many different ceramics, and the potential for errors is minimized with a single-material approach. With KATANA™ Zirconia YML, this approach enables us to produce very different outcomes depending on where the restoration is placed in the multi-layered blank.

What are the benefits of using KATANA™ Zirconia YML as the only ceramic material from the dental practitioner’s perspective?

Florian Beuer: To my mind, the most important benefit of using a single zirconia every time lies in a simplified documentation. When different ceramic materials are used in the dental laboratory, we need to keep track of the material selected in every single case. Only in this way, it is possible to make the right cementation decisions (regarding cement selection and the appropriate pre-treatment of the restoration). In addition, when it comes to failure of the restoration, we need to know which material was used to prove that it has been processed correctly and is suitable for the actual indication. This is much easier when a single material is used every time. Zirconia is predestined for this approach as it is forgiving, supports minimally invasive preparations and – in case of KATANA™ Zirconia YML – almost everything can be done with it.

What are the secrets of KATANA™ Zirconia YML that allow for excellent treatment outcomes despite the one-for-all approach?

Mathias Fernandez Y Lombardi: KATANA™ Zirconia YML is based on a completely new, seamless multi-layer technology combining different, newly developed raw materials with varying yttria concentrations in a single blank. The inhouse development of the powders and their precise adjustment of each other in terms of properties like shrinkage and coefficients of thermal expansion are prerequisites for a smooth transition from one layer to the next. Only if the layers are very well integrated, it will be possible to reliably produce even long-span restorations with a delicate design, perfect fit and flawless aesthetics (without transition lines). The aesthetic properties were also optimized by integrating clinical instead of purely technical translucency.

Please explain the term clinical translucency.

Mathias Fernandez Y Lombardi: Usually, translucency of dental materials like zirconia is measured in its white, pre-shaded state. This so-called technical translucency value is increased by adding yttria to the formulation, which makes the zirconia itself appear brighter (increasing the whiteness). The translucency of the final restoration, however, is also affected by pigments and other additives in the formulation. Consequently, monolithic restorations made of different materials with the same technical translucency value may vary widely in terms of their actual, clinical translucency, which affect the overall aesthetic potential. The formulation of KATANA™ Zirconia YML has been optimized by carefully selecting and combining the right additives to obtain a natural, tooth-like translucency.

Translucency and shade appearance of KATANA™ Zirconia YML (left column) compared to various other 5^th generation zirconia materials.

Nondas Vlachopoulos, is this measure of optimizing the clinical translucency a key feature enabling the one-for-all approach of KATANA™ Zirconia YML?

Nondas Vlachopoulos: The positive effect attributed to this measure is noticeable, as KATANA™ Zirconia YML has a particularly warm and natural appearance especially in the body area some other materials with flexural strength gradation are lacking. This leads to an exact colour match with the VITA classical A1-D4 shade guide, and reduces the need for manual shade adjustments. This is important for a one-for-all approach, as the material should be a perfect basis for the production of monolithic restorations, which are not covered by a thick porcelain layer able to mask any imperfections. However, there is another key feature that facilitates the zirconia’s use for virtually every indication: Its exceptional design flexibility. It enables users to control the translucency and overall aesthetics by positioning the restoration quite freely within the blank. For restorations with up to three units, there is a complete freedom of placement. Larger restorations with four or more units need to be positioned in a way that at least 50% of the connector cross-section is in the bottom half of the disc. This is easily accomplished and gives us optimal options to exploit the various properties of each layer depending on the aesthetics and strength needed in each specific case.

Positioning guidelines for KATANA™ Zirconia YML.

What is the recommended finishing procedure?

Mathias Fernandez Y Lombardi: In principle, all designs and finishing options are available for KATANA™ Zirconia YML – from a monolithic design individualized with liquid ceramics to microlayering after a minimal vestibular cutback or even full ceramic layering on frameworks. As the aesthetic potential of the zirconia is already high, however, we believe that in most cases, the first option is absolutely sufficient. In this case, a monolithic restoration is milled and the surface subsequently treated with our liquid ceramic system CERABIEN™ ZR FC Paste Stain. The pastes are easily applied in ultra-thin layers, very well controllable and wear resistant.

Anterior and posterior crown made of KATANA™ Zirconia YML after sintering (left part) and after sintering and finishing with CERABIEN™ ZR FC PASTE STAIN (right part).

Nondas Vlachopoulos, what is your preferred finishing procedure for restorations made of KATANA™ Zirconia YML?

Nondas Vlachopoulos: In the posterior area, I often opt for monolithic restorations individualized with CERABIEN™ ZR FC Paste Stain. The technique leads to beautiful outcomes a large majority of patients would love to see even in the anterior region. However, as orders for the production of anterior restorations coming my way are usually placed by clinicians and patients with the highest possible aesthetic demands, I often go for a framework design and full porcelain layering with CERABIEN ZR Porcelains. The materials (like EX-3 portfolio for metal frameworks) are based on synthetic feldspathic porcelain with a structure and particle distribution very similar to natural dentin and enamel. All in all, I like the fact that I can select the most suitable finishing technique for every individual case, and I believe that it is often possible to reduce the finishing effort to a minimum.

Clinical translucency, design flexibility, mechanical properties: Apparently, the differences between the available zirconia materials – even of the 5^th generation – are huge. How can users ensure that the material they select is of high quality and offers favourable mechanical as well as optical properties?

Florian Beuer: When the first-generation zirconia materials appeared on the dental market, laboratory testing revealed that there are huge differences in quality between materials of different manufacturers. Although independent studies comparing the properties and behaviour of 5^th generation zirconia are still scarce, it may be assumed that differences do exist. My recommendation is to select a several materials from well-known manufacturers supporting clinical studies, compare the study results already available, and test the selected options in the laboratory setting. Directly comparing design concepts, the processing quality and final appearance will most likely reveal which material is a dental technician’s favourite. I am sure that KATANA™ Zirconia YML is among the materials worth being tested.

Thank you for this insightful conversation.

A while ago Mr. Takuro Nagura of Kuraray Noritake Dental put in an appearance at the Mardent Dental Trade event in Breda to provide some practice-oriented information to the attending dental technicians about the application of CERABIEN ZR FC Paste Stain in combination with KATANA™ Zirconia. The result was a fruitful afternoon, filled with questions, insights and tips.

Those in attendance were all dental technicians with ample experience of working with KATANA™ Zirconia. Mr. Takuro Nagura was therefore able to enjoy the experience of being surrounded by a group of enthusiastic KATANA™ fans, all of whom also use Noritake porcelain and PANAVIA™ V5 to their full satisfaction. The excellent aesthetics, perfect fit and ease of use were frequently-heard endorsements in favour of the use of Kuraray Noritake Dental products.

The session began with an introductory presentation, with an in-depth focus on the technical properties of the materials, instructions for baking, shade taking and staining techniques. Then it was time for the group to get started themselves. A KATANA™ Zirconia UTML molar and front crown had been prepared for each participant, and these were then characterised by means of CERABIEN ZR FC Paste Stain. The shades A+, Grayish Blue and Reddish Brown were used as starting points.

The entire front crown was first treated with glaze, after which external stain was applied; first in a horizontal direction, whereby dentine A+ was used cervically and enamel Greyish Blue incisal. Finally, dentine A+ was also applied vertically to emphasize the marmelon structure. Mr. Nagura offered the useful tip of first scratching in the eventual necessary crack lines with a sharp instrument such as a needle, and then colouring them in with external stain.

Glaze was initially applied to the full surface of the molar too, after which external stain was applied horizontally. A+ was used for the cervical and occlusal plane, with enamel Greyish Blue for the occlusal cusps. A+ was then applied to the vertical lines, and the fissures were finally coloured in using Reddish Brown.

Examples of staining with fc paste stain

Case by Dt Giuliano Moustakis

When producing restorations for the upper anterior region, the first thing that comes to a dental technician’s mind is the selection of a material that matches the colour and translucency of the patient’s natural teeth. The aim behind this action is to provide a perfect optical integration of the restorations to be produced. In order to achieve this optical integration, however, dental technicians need to focus on the surface morphology as well. The following clinical case is used to demonstrate how restorations with the right colour, translucency and texture are able to create a stunning, natural smile, even in complex cases.

The female patient had a periodontally compromised dentition with a missing maxillary lateral incisor and mandibular prognathism. Spacing was present in both jaws, but the patient decided not to undergo orthodontic treatment due to the challenging periodontal situation and the associated risk of losing additional teeth. Instead, a cosmetic camouflage was planned. As the existing direct restorations on the upper central incisors were in need of replacement, the restoration of choice was an all-ceramic, five-unit bridge. Knowing that this situation would best be solved with a material that offers high flexural strength in the body area (strictly mandatory for five-unit bridges) and high translucency in the enamel part (required to imitate nature in the anterior region), the new KATANA™ Zirconia YML was selected. Thanks to its multi-layer structure with colour, translucency and flexural strength gradation (achieved through yttria content gradation), this material offers exactly the desired properties. We decided to use it with a slight vestibular cutback and microlayering with CERABIEN™ ZR (CZR) porcelain.

Fig. 1 Pre-operative clinical situation with a Class III Malocclusion, a missing lateral incisor, spacing and periodontally compromised teeth in both jaws.

Fig. 2 Lateral view of the pre-operative situation.

Fig. 3 Shade determination in the dental office.

Fig. 4 Maxillary central and lateral incisors and right canine after tooth preparation.

Fig. 5 Printed models of both jaws based on an intraoral scan. This view reveals the discrepancy between the upper and lower jaws that needs to be camouflaged.

Fig. 6 Vestibular and incisal reduction and surface texturing on the pre-sintered restorations made of KATANA™ Zirconia YML. Integration of mamelon structures with a round-end straight carbide bur.

Fig. 7 Integration of horizontal growth grooves with a coneshaped instrument (Panther Stone 040).

Fig. 8 Translucency of the reduced bridge after sintering.

Fig. 9 KATANA™ Zirconia YML structure on the model after sintering.

Fig. 10 Silicone index revealing the space generated in the cutback procedure.

Fig. 11 Evaluation of the camouflage effect.

Fig. 12 Try-in of the zirconia structure.

Fig. 13 Sandblasted bridge ready for microlayering.

Fig. 14 Bridge after the application of internal stains and a single layer of CERABIEN™ ZR Body (A3B) and CERABIEN™ ZR Luster Porcelain (LT1, LT Royal Blue, LTx and LT Coral mixed with Incisal Aureola).

Fig. 15 Chromatic map of the microlayering procedure.

Fig. 16 Palatal view of the restoration.

Fig. 17 Bridge after the first bake and the addition of LT1.

Fig. 18 Finished restoration. In order to optimize the look of tooth and gingiva parts, a final layer of CERABIEN™ ZR FC Paste Stain and Glaze was added.

Fig. 19 Palatal view of the restoration after finishing.

Fig. 20 Try-in of the bridge for aesthetic and functional evaluation.

FINAL SITUATION

Fig. 21 Treatment outcome.

CONCLUSION

This clinical case shows that KATANA™ Zirconia is an innovative material with high aesthetic potential. Despite flexural strength gradation, there are no severe design restrictions that limit the indication range. Instead, it is easy to design and produce even long-span bridges. Furthermore, due to the material’s high aesthetic potential, a monolithic design with zero cutback and paste staining with liquid ceramics is often an option. If users want to add a porcelain layer, a simplified and time-efficient microlayering approach is highly recommended. In any case, a natural surface morphology should be integrated, as it is essential for an aesthetic outcome.

Dentist:

DT GIULIANO MOUSTAKIS

Using different zirconia materials depending on the indication and on patient-specific needs allows for the best possible outcomes, yet comes with the danger of mixing up processing protocols. Kuraray Noritake Dental Inc. (Kuraray Noritake Dental) eliminates this problem by offering a complete portfolio of KATANA™ Zirconia Multi-Layered materials with harmonized sintering schedules. The latest member of the KATANA™ Zirconia Multi-Layered Series, KATANA™ Zirconia HTML Plus, is available since September 1, 2021. In addition to the aligned sintering schedules, it offers an increased translucency and optimized colour without compromising its flexural strength.

KATANA™ Zirconia HTML Plus is based on its tried and proven predecessor KATANA™ Zirconia HTML and also offers a 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.

Careful in-house optimizations in the material composition and structure have paved the way for an increased translucency of 45 percent (compared to 43 percent KATANA™ Zirconia HTML) and an even more natural shade appearance of the manufactured restorations. The colour appears more vivid and more saturated, which leads to an improved optical integration with the adjacent teeth and gums. At the same time, the high flexural strength (1,150 MPa) is maintained, ensuring an unlimited range of indications.

When it comes to sintering, three options are available for single-tooth restorations and bridges with up to three units: a 54-minute high-speed sintering programme especifically valuable for remake and rush cases, a 90-minute programme and the traditional seven-hour sintering programme suitable for long-span restorations as well.

All three options and identical schedules are also available for the other materials of the portfolio: KATANA™ Zirconia UTML, KATANA™ Zirconia STML and the new KATANA™ Zirconia YML (yttria multi-layered) with additional flexural strength and translucency gradation. Due to this feature, standardizing manufacturing procedures for a minimized risk of errors and consistent outcomes becomes extraordinarily easy. More information about KATANA™ Zirconia HTML Plus and the whole product family is available at our website.

The inventor of the original zirconia multi-layer technology, Kuraray Noritake Dental Inc., has just introduced its latest development in the evolution of dental zirconia – KATANA™ Zirconia YML (yttria multi-layered). At the KATANA™ Zirconia YML Virtual Kick-Off Symposium on July 3, 2021, four world-renowned experts reported on their first-hand experience with this highly versatile material that complements the existing KATANA™ Zirconia Multi Layered Series very well.

The chairman of the event, Prof. Dr. Florian Beuer MME (Charité – Universitätsmedizin Berlin, Fig. 1), represented the perspective of scientific researcher and clinician. MDT Daniele Rondoni, MDT Roberto Rossi (Savona, Italy) and MDT Nondas Vlachopoulos (Athens, Greece) shared their impressions obtained from processing KATANA™ Zirconia YML in the laboratory setting and focused on possible indications and finishing methods.

Fig. 1 Prof. Dr. Florian Beuer MME.

Scientific facts about YML

Following the welcome speech of Kazumitsu Nakatsuka (Head of BU Medical, Kuraray Europe GmbH, Fig. 2), Prof. Dr. Beuer started a journey through the evolution of dental zirconia. He described the different steps taken to transform an opaque, white framework material into a translucent, tooth-coloured material with a multi-layered structure suitable for monolithic restorations. In this context, he explained that KATANA™ Zirconia YML is a fifth-generation dental zirconia featuring colour, translucency and flexural strength gradation. High strength in the lower (body) part of the blank makes the zirconia well-suited even for long-span bridges, while the high translucency in the upper part facilitates natural aesthetics (Fig. 3). As a result, the material is recommended for virtually every indication (Fig. 4).

Fig. 2 Kazumitsu Nakatsuka, Head of BU Medical, Kuraray Europe GmbH.

Fig. 3 Multi-layered structure of KATANA™ Zirconia YML.

Fig. 4 Overview of the KATANA™ Zirconia portfolio and the recommended indications: KATANA™ Zirconia YML is the only material that is suitable for all indications from single tooth restorations to long-span bridges.

In order to leverage the desired properties such as high translucency for an anterior crowns or high strength for a long-span bridges, the restoration simply needs to be positioned in the correct part of the blank. The design flexibility of KATANA™ Zirconia YML is high and restrictions are few: the connectors of bridges with more than three units simply need to be positioned in the lower half of the blank for sufficient strength.

Additional benefits of the new material are a controlled firing deformation and high accuracy of the manufacturing process leading to a precise fit, the option of fast processing with a sintering time of just 54 minutes for short-span restorations and aesthetics comparable to glass-ceramic materials. After sharing these facts, some scientific data and clinical pictures, Prof. Dr. Beuer confessed that zirconia is his favourite material: it is forgiving, allows for minimally invasive restoration procedures and is suitable for virtually every indication. He usually opts for veneered zirconia in the anterior and monolithic zirconia in the posterior area. Like with every innovative dental material, he is looking forward to seeing more clinical data being shared with the community in the forthcoming years.

(Ultra) micro layering: Aesthetics easily achieved

MDTs Daniele Rondoni and Roberto Rossi focused on easy-to-achieve aesthetics with KATANA™ Zirconia YML. They presented different clinical cases to demonstrate how they obtain beautiful outcomes with a monolithic design (zero cutback), a small vestibular cutback or a micro cutback, and appropriate stains and porcelains from the CERABIEN™ ZR series (Kuraray Noritake Dental Inc.). Restorations with a monolithic design are typically individualized with internal stains and the liquid feldspathic ceramic material CERABIEN™ ZR FC Paste Stain (Figs. 5 and 6) or FC Paste Stain only (Fig. 7), a procedure that was demonstrated in a hands-on session. FC Paste Stain allows for application in ultra-thin layers and yet, it creates desired 3D effect. When opting for a (vestibular) micro cutback, microlayering with internal stains and a single luster porcelain (LT1) completed in a single bake may be the solution. All techniques are easily implemented and possible only thanks to the high aesthetic potential of the base material (KATANA™ Zirconia YML), which reduces the manual processing effort and time without compromising quality and aesthetics.

Fig. 5 Recipe for the use of CERABIEN™ ZR Internal Stain …

Fig. 6 … in combination with CERABIEN™ ZR FC Paste Stain Clear glaze on a monolithic surface (presented by Daniele Rondoni and Roberto Rossi).

Fig. 7 Example of a Toronto bridge made of KATANA™ Zirconia YML A2, finished in the gum areas with CERABIEN™ ZR Tissue Kit and on the teeth with CERABIEN™ ZR FC Paste Stain (presented by Daniele Rondoni and Roberto Rossi).

When starting to work with a new zirconia, the speakers recommend to analyse its optical properties in different light conditions, compare it with other materials and use a spectrophotometer discover its specific optical behaviour. What the speakers like most about KATANA™ Zirconia YML is the fact that all indications are covered with a single material.

Combining different finishing techniques: High-end aesthetics

According to Nondas Vlachopoulos, KATANA™ Zirconia YML is a great solution that combines the strength of second-generation zirconia like KATANA™ Zirconia HTML and the very high translucency usually found only in materials with reduced strength like KATANA™ Zirconia STML. The speaker showed several clinical case examples from complex implant-based restorations to crowns on teeth and implants, which were all solved with the new material (Figs. 8 and 9). He usually applies monolithic zirconia individualized with CERABIEN™ ZR FC Paste Stain in the posterior area, while on the six anterior teeth, he opts for complex porcelain layering techniques leading to the exceptionally aesthetic results that have made him famous.

Fig. 8 Wear case solved with monolithic KATANA™ Zirconia YML restorations in the posterior and layered restorations in the anterior area (presented by Nondas Vlachopoulos).

Fig. 9 Maxillary left central incisor restored with a layered crown with a KATANA™ Zirconia YML coping on an implant (presented by Nondas Vlachopoulos).

Highly versatile material

In the discussion following the presentations (Fig. 10), two experts from Kuraray Noritake Dental Inc. – Mathias Fernandez Y Lombardi and Antonio Corradi – stressed that the high processing quality of KATANA^™ Zirconia YML is due to the end-to-end in-house production process, ensuring that the company has control over every detail. The speakers agreed that the new product leads to numerous benefits for dental technicians and clinicians, as it allows for standardized procedures, a reduced inventory and simply produces beautiful outcomes with the preferred technique.

Fig. 10 Discussion with the experts in the studio and online.

Watching the renowned experts, their presentations and the final discussion, it became clear to the participants that KATANA™ Zirconia YML is a true all-in-one solution suitable for virtually all types of restorations and finishing techniques. With its well-aligned composition and smooth transition from one layer to the next, it is a great choice for everyone striving for aesthetic and reliable outcomes. More information about KATANA™ Zirconia YML is available at our website.

If you would like to watch back the event recordings click here.

We are pleased to share with you short training videos for Super Porcelain EX-3 porcelain.

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

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