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Are you looking for an easy and simple finishing method for full contour crowns? How about using CERABIEN ZR FC Paste Stain?

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Thanks to constant efforts in research and development, leading dental companies have managed to introduce new products that allow for less invasive techniques, standardized or simplified procedures and better outcomes on a regular basis. With so many different materials available on the dental market, however, it seems difficult to decide which products are best suited to fulfill the individual requirements. A direct comparison obtained through testing of all products in the dental office is simply impossible due to the great number of available solutions. Laboratory investigations provide information about specific product properties, but usually cannot create the overall picture. Moreover, the results of different tests are barely comparable due to variations in test conditions. Clinical study results are very useful as they shed light on clinical (long-term) performance of selected materials, but they are usually published years after a product’s launch. Hence, they are not available in the early stages. A great source of information are practice-based evaluations, as they support potential users in identifying high-quality dental materials.

One of the institutions conducting and publishing practice-based clinical evaluations and product performance tests is the US-based DENTAL ADVISOR. Once per year, the dental materials and equipment with the best performance receive a Top Product or Preferred Product Award. The list of winners is published online (www.dentaladvisor.com) and in the January-February issue of the DENTAL ADVISOR. In 2022, numerous products from Kuraray Noritake Dental Inc. were among the award winners.

Top Product Awards

Minimum intervention dentistry has gained increasing popularity in recent years. A product that even allows for a non-invasive approach is TEETHMATE™ DESENSITIZER for hypersensitivity treatment. This year, the product won a Top Award from the Dental Advisor for the eighth year in a row.

The material was designed to create hydroxyapatite (HAp), which is able to occlude open dentinal tubules and enamel cracks. This leads to a significant reduction of hypersensitivities when applied to exposed, mechanically treated or freshly prepared dentin. When used in the context of restorative treatment, TEETHMATE™ DESENSITIZER does not have a negative effect on the bond strength of dental adhesives or cements. A six-month clinical evaluation conducted by the DENTAL ADVISOR involving 27 patients with gingival recession-related hypersensitivity revealed that the use of the product is very effective in providing immediate and even long-term (six-months) hypersensitivity relief. This resulted in an excellent rating with a score of 96 percent.

Delivering a strong and durable bond to enamel and dentin is one of the preconditions for minimally invasive direct restoration procedures. A self-etch adhesive that offers more than just a reliable bond is CLEARFIL™ SE Protect. The product received a Top Product Award in the category Direct Restoratives, Bonding Agent: Self-Etch for the fourth time. It is based on the formulation of the gold standard two-step self-etch adhesive CLEARFIL™ SE BOND, but contains an extra MDPB monomer offering an antibacterial cavity-cleansing effect and fluoride for long-term fluoride release. The honoring of the DENTAL ADVISOR is based on a material test carried out by 13 DENTAL ADVISOR consultants and editors in their dental offices for six weeks. Due to its excellent performance, CLEARFIL™ SE Protect received a 98 percent clinical rating.

Great handling and aesthetic outcomes are probably the major benefits CLEARFIL MAJESTY™ ES Flow has to offer. For the seventh year in a row, the Top Product Award in the category Direct Restoratives, Composite: Highly Filled Flowable went to this material.

The universal flowable composite that also became the Editor’s Choice comes in three different levels of flowability, from high to super low*. This enables the user to choose the right viscosity for every clinical situation – with the high flowability variant being the perfect choice for cavity lining and as a resin coat in IDS (Immediate Dentin Sealing) procedures, and the super low flowability option being specifically suited for direct veneer procedures and even for build-up of posterior cusps etc. The universal flowable composite was tested by 29 consultants of the DENTAL ADVISOR in more than 900 clinical applications. The evaluated properties – placement/handling, aesthetics, viscosity and polishability – were rated “excellent”. This led to a recommendation rate of 100 percent and a 98 percent overall clinical rating.

*DENTAL ADVISOR evaluated only the standard level of flowability (Low), because other two variants are not available in US.

Preferred Products

Among the 2022 Preferred Products are two truly universal solutions: The time-saving CLEARFIL™ Universal Bond Quick and easy-to-use PANAVIA™ SA Cement Universal.

CLEARFIL™ Universal Bond Quick became a Preferred Product of the Dental Advisor consultants for the third time. The universal bonding agent may be applied using the self-etch technique or – together with K-ETCHANT syringe – in the selective enamel etch or total-etch technique. Containing our rapid bond technology – a combination of the original MDP monomer with innovative hydrophilic amide monomers – the adhesive works instantly and without the need for extended exposure times, application of multiple layers or extensive rubbing into the tooth structure. The fast and easy application procedure was one of the main reasons for the consultants of the DENTAL ADVISOR to select CLEARFIL™ Universal Bond Quick as a Preferred Product and Editor’s Choice with a 98 percent score in a clinical evaluation.

PANAVIA™ SA Cement Universal became a Preferred Product in 2021 and 2022, won a Top Product Award in 2020 and is listed as the Editors’ Choice. The self-adhesive universal resin cement contains the unique LCSi monomer. This monomer is a silane coupling agent, which has a unique long carbon chain in its molecule. LCSi monomer establishes a durable, chemical bond with porcelain, lithium disilicate and composite resin without the need for a separate silane containing primer. The other key technology present in the formulation is the original MDP monomer, which provides for chemical reactiveness with zirconia, dentin and enamel. Together the technologies make it possible, that PANAVIA™ SA Cement Universal produces a strong and durable bond with virtually every restorative material without the need for a separate primer. Its handling characteristics, aesthetics and gingival friendliness received very good to excellent ratings from 31 clinical evaluators, who used the cement in 516 applications. The result of the overall clinical rating was 96 percent.

Finally, CLEARFIL™ Ceramic Primer Plus became a Preferred Product in 2019, 2020, 2021 and 2022, and received the Editors’ Choice label due to its excellent performance in the clinical evaluation. It contains the original MDP monomer and a silane monomer, which ensure excellent bond strength to all kinds of restorative materials, i.e., to silica-based ceramics, zirconia, composites and even metals. Users benefit from procedural simplicity as the product is just applied and dried to the bonding surface after the recommended pretreatment. In a clinical evaluation, the product received a recommendation rate of 96 percent and a 96 percent overall score from the DENTAL ADVISOR consultants.

Conclusion

Most of the Kuraray Noritake Dental products that received an award this year are based on resin technologies, one of our key competencies. In the 1980s, we developed the original MDP monomer, a functional monomer, which is an essential component of any adhesive product we introduced down to the present day, including the award-winning CLEARFIL™ SE Protect, PANAVIA™ SA Cement Universal, CLEARFIL™ Universal Bond Quick and CLEARFIL™ Ceramic Primer Plus. This is only one of our many areas of expertise. We also provide users with preventive products and a whole range of restorative materials – from composite filling materials like CLEARFIL MAJESTY™ ES Flow to dental ceramics like KATANA™ Zirconia UTML, STML, an updated HTML PLUS and the brand-new KATANA™ Zirconia YML. We see the winning of the awards as a positive proof of a reliable product performance that supports dental practitioners in reaching their own goals.

In 1976, Kuraray introduced its first adhesive monomer—the phosphate monomer Phenyl-P. Over the following years, the company’s commitment to research and development saw continued efforts to improve and refine this monomer’s molecular structure. Kuraray eventually achieved this goal by creating a molecule with greater capability to adhere to the tooth structure, low solubility and effectiveness in bonding to metal: the MDP monomer.

Developed and then patented by Kuraray in 1981, the MDP monomer remains, to this day, the leading functional monomer for reliable adhesion to various substrates including enamel and dentine. Research has repeatedly shown that products that utilise this monomer create long-term, durable and stable bonds to dental tissues, non-noble metals and zirconia ceramic. Simply put, it is hard to know where adhesive dentistry would be without the MDP monomer.

An unmatched level of purity

One of the secrets behind the success of Kuraray Noritake’s MDP monomer is its uniquely high-quality nature. The patent that Kuraray held on the monomer has expired, opening up the market for other manufacturers to synthesise their own MDP. However, a study conducted by Yoshihara et al.¹ found that, of the three adhesive MDP monomers they examined, differences in purity levels were visible and affected the intensity of nano-layering and resultant bond strength. Unsurprisingly, the bond strength displayed by Kuraray Noritake’s original and highly pure MDP was the highest measured.

“It’s very clear that the MDP monomer is one of the most effective monomers available, given its primary chemical binding potential to hydroxyapatite,” Prof. Bart Van Meerbeek, a leading authority on dental bonding agents, said in an interview with Dental Tribune International.

“Essentially, a universal adhesive that contains a high concentration of very pure MDP monomer should perform the best,” he added, when asked about universal bonding systems.

A monomer with many applications

The first Kuraray product to use the MDP monomer was PANAVIA EX resin cement. Introduced in 1983, PANAVIA EX quickly became known as a facilitator of reliable adhesion, and the PANAVIA family of adhesive resin cements, including PANAVIA V5 and PANAVIA SA Cement Universal, still employs the MDP monomer to provide first-class bonding for dental professionals worldwide.

Of course, the MDP monomer forms the backbone of a number of products in Kuraray Noritake Dental’s current CLEARFIL range of bonding systems, such as the gold standard CLEARFIL SE BOND, a mild two-step self-etching, light-cured bonding agent. CLEARFIL Universal Bond Quick, the company’s universal single-step dental bonding agent, utilises rapid bond technology. The synergistic combination of the original MDP monomer and hydrophilic amide monomers works to create a lasting bond faster and more easily than ever.

There have been more than 40 years of evidence, and the conclusion is clear: Kuraray Noritake Dental’s MDP monomer has changed dental bonding for the better.

Learn more about the MDP monomer here.

References

1. Yoshihara K. et al. Functional monomer impurity affects adhesive performance. Dent Mater. 2015 Dec;31(12):1493–1501.

A newcomer in the PANAVIA family – PANAVIA Veneer LC. Cementation of the veneers can be a challenging task, but with this specialist product in house, outstanding results can be achieved with ease.

Check out the video to learn about the features of PANAVIA Veneer LC and the resulting benefits.

Finishing of six anterior elements with gingival flange produced from high-strength KATANA™ Zirconia – from surface morphology adjustments to micro-layering.

FOREWORD

Innovative high-translucency, multi-layered variants of zirconia feature well-balanced optical and outstanding mechanical properties. Their use allows for better outcomes of laboratory-based digital workflows and makes it possible to fulfil the increasing functional demands we are facing in the clinical environment. Depending on individual, case-specific needs, laboratory technicians can select a suitable zirconia and the distinctive technical approach delivering the desired outcomes. For this purpose, it is essential to develop a deep understanding of the available materials, their chromatic adaptability and general aesthetic potential, the design and finishing options and their correct technical implementation as well as the most important case-specific selection criteria. In combination with advanced laboratory-based communication skills, this knowledge will enable us to fulfil or even exceed the patient’s expectations by delivering a highly aesthetic, functional restoration.

Let us assume that a six-unit anterior bridge with gum area on implants is needed. For the ideal prosthetic solution, white aesthetics is fundamental, but a perfect harmony will only be achieved if the gingival texture and colour is reproduced in a natural way, as the gingiva is considered the “aesthetic frame” of the dental restoration. Our solution is a monolithic restoration made of KATANA™ Zirconia YML, finished using a 3D micro-layering technique with CERABIEN™ ZR.

OBJECTIVE

In this Master Course, you will acquire the theoretical knowledge needed to select the appropriate zirconia and finishing technique for every individual case and the practical skills required for the finishing of the six-unit bridge with gum area – from surface texturing to 3D micro-layering on teeth and gums.

YOU WILL LEARN TO:

✔ Select the appropriate type of KATANA™ Zirconia ML
✔ Re-finish pre-sintered zirconia
✔ Optimize the sintering process
✔ Re-finish and prepare the zero cut-back elements
✔ Accomplish micro-layering with CERABIEN™ ZR porcelain
✔ Perform mechanical finishing and polishing

For more information please visit: https://www.danielerondoni.com/courses/

By Dinesh Sinha, BDS, PHD, Senior Technical and Marketing Manager Dental Division, Kuraray America, Inc.

Since the early 2000’s, the global all-ceramic restoration market, including that for zirconia, has been growing rapidly. Increasing market demand resulted in various dental manufacturers marketing different dental zirconia types that can be used in many dental prosthetic applications. Today, dental ceramists play a key role with the latest CAD/CAM technology to provide high performance zirconia prosthetics with more precision and aesthetics for treatment needs.

Zirconia is a polycrystalline ceramic. This means that it is entirely composed of crystals, with no glass phase. The presence of an entirely crystalline microstructure brought strength to zirconia and gave initial formulations an opaque appearance with low translucency. The translucency of zirconia is improved by changing the atomic arrangement within the crystals of zirconia (most commonly known as translucent or aesthetic zirconia). There are several key factors dental ceramists should know when selecting zirconia:

1. Type/brand of zirconia

During the industrial process of making dental zirconia (zirconium dioxide), Yttria (Y₂O₃) is added to make refined zirconia stable at room temperature. Yttria also contributes to increasing the translucency of zirconia, but also conversely reduces its strength. The most common method of classifying zirconia is by Yttria concentration (i.e., 3Y, 4Y & 5Y). Many dental manufacturers use/buy zirconia from one large industrial ceramic manufacturer. This classification helps to understand and describe the properties of zirconia where the primary powder source is the same. 3Y is the strongest and least translucent, whereas 5Y is the highest translucency and lowest strength.

Fig. 1. Kuraray Noritake Dental Inc. original KATANA™ Zirconia powder.

Most dental zirconia manufacturers purchase raw zirconia powder from a third party. Only a few manufacturers like Kuraray Noritake Dental Inc. use their own proprietary original zirconia powder formulations (Figure 1). The company can thereby more accurately control the chemical and physical make-up, not only with Yttria concentration, but also parameters like grain or particle size, as well as sintering temperature. Kuraray Noritake has KATANA™ as an umbrella brand with three different options of strength and translucency in multi-layered formulations: KATANA™ HTML PLUS, STML and UTML.

2. Strength of dental zirconia

The most common method of measuring ceramic strength is by evaluating its flexural strength. The flexural strength test applies a force on the top of a ceramic specimen, which causes the specimen to bend and fracture. The International Standards Organization (ISO) and the American Dental Association have developed a standard for measuring the flexural strength of dental ceramics. Two methodologies are commonly used today. In the 3-point bend method (Figure 2), a rectangular specimen is used, whereas in the biaxial flexural strength method (Figure 3), a circular specimen is incorporated. Both tests are acceptable, however, ceramics tend to produce higher values when tested with the biaxial method over the 3-point bend method.

Furthermore, even in a 3-point bending test, if the span length (see Figure 2) of the specimen is decreased, it can produce higher values of flexural strength of the same ceramic. It is critical to understand testing parameters when selecting or comparing different ceramic brands. All materials should be tested under the same conditions, and by using the same methodology.

3. Multi-chromatic vs multi-translucent

Kuraray Noritake was the first dental manufacturer to introduce multi-layered zirconia as a commercial product in 2013. Different concentrations of pigment-containing zirconia powder are utilized to make the zirconia discs and blocks multi-chromatic.

Multi-chromatic: KATANA™ Zirconia HTML PLUS/STML/UTML (Figure 4) were developed based on the concept of “lifelike appearance”, accurately and naturally mimicking the color and translucency of natural teeth. It has a top enamel layer, two transition layers, and a base body layer. The unique manufacturing technology from Kuraray Noritake allows each powder layer to seamlessly blend within a gradient profile that eliminates any demarcation lines between the different layers. The Yttria concentration remains similar in all layers; therefore, the strength of the zirconia does not deviate from layer to layer. The pigments (chroma) are adjusted in a way that produces different chroma among the layers, where the translucency stays the same.

Multi-translucent: KATANA™ Zirconia YML (Figure 5) is the latest KATANA™ multi-layered disc, with a well-balanced combination of color translucency and flexural strength gradation. It is also manufactured using multilayer technology, with different Yttria content in each layer.

Strength differs in each layer, providing enamel with 750 MPa, the transition-body with 1000 MPa, and the base layer with 1100 MPa flexural strength. These layers are perfectly harmonized with each other, since all fundamental production steps, including purification, refining of the zirconia raw material and the addition of essential components such as Yttria, are all processed in-house by Kuraray Noritake.

4. Cleaning zirconia

During trial-fitting, the zirconia restoration might become contaminated with salivary proteins, thereby reducing the bond strength. KATANA™ Cleaner (Figure 6) can be used to remove contamination. This can be easily achieved by rubbing KATANA™ Cleaner on the intaglio surface, and subsequently rinsing it with water. KATANA™ Cleaner has a high cleaning effect, due to the surface-active characteristic of MDP Salt.

5. Bonding to zirconia

There are several clinical situations where zirconia restorations benefit from resin bonding: restorations that are less strong or thin, lack retention, or rely on resin bonding, (ex. resin-bonded fixed partial prostheses, onlays, or laminate veneers). Prof. Markus Blatz, DMD, PhD, University of Pennsylvania School of Dental Medicine and his group introduced a three-step approach, known as the “APC Zirconia Bonding Technique”.

APC Step A: Air-particle abrasion, then application of P: Primer and finally Step C: Composite resin. MDP-based resin cemented restorations exhibit better margins long term. MDP has shown a very stable chemical bond to zirconia. Kuraray Noritake invented and introduced the Original MDP monomer in 1981. All Kuraray Noritake PANAVIA™ cement (Figure 7) brands contain this original MDP monomer.

Kuraray Noritake is known for its legacy of inventing groundbreaking technologies in both resin and ceramic technologies. The company is committed to inventing the best quality materials that dental ceramists and dentists can use to treat their patients with confidence.

Dentist:

DINESH SINHA, BDS, PHD

First published in: A Journal of Dental Technology | November/December 2021

The KATANA™ Zirconia Multi-Layered series from Kuraray Noritake Dental Inc. (Kuraray Noritake Dental) is popular among dental technicians and dentists around the world, as it offers great mechanical and optical properties. The available materials have different levels of translucency and strength, and a multi-layered structure that facilitates the creation of lifelike restorations.

Furthermore, they are very well processable, which results in a high milling accuracy and smooth margins. Together, these properties are highly valuable for every dental office, as they result in precisely fitting, durable and beautiful restorations that help you exceed your patients’ expectations.

Clinical long-term success of these zirconia restorations, however, is not only determined by the material choice and laboratory processing alone. The way clinical procedures such as cementation and intra-oral adjustments are carried out have a decisive impact as well. In order to support you in your striving for a long-lasting bond between the tooth and the restoration, and to facilitate intra-oral polishing, Kuraray Noritake Dental has developed a wide variety of in-office products designed to make your life easier and your practice even more successful.

Remove bond-strength compromising proteins

When proteins present in blood and saliva are deposited on the bonding surfaces of teeth or dental restorations, the bonding performance of dental adhesives and self-adhesive resin cements will be compromised. As it is impossible to keep these surfaces free of oral fluids at try-in, effective cleaning strategies are required. In tests comparing different methods and cleaning agents, sandblasting and the use of KATANA™ Cleaner have been highly successful in removing the proteins from the bonding surfaces¹.

As KATANA™ Cleaner is a biocompatible material (unlike other often strongly alkaline zirconia cleaners), it is suitable for intra- and extra-oral use. Hence, it is the perfect solution for cleaning your KATANA™ Zirconia restorations as well as prepared enamel and dentin before cementation. The product has a high cleaning effect and is easy to use: simply rub it in for ten seconds, rinse and dry.

Obtain a reliable bond with fewer components

Fewer components and fewer procedure steps, this is what an increasing number of dental practitioners strives for when it comes to cementing zirconia restorations. For all of them, PANAVIA™ SA Cement Universal is the solution.

The self-adhesive resin cement contains the proprietary long carbon-chain silane coupling agent (LCSi Monomer) developed by Kuraray Noritake Dental that delivers a strong, durable chemical bond to porcelain, lithium disilicate and composite resin without the need for a separate primer. The original MDP monomer, also present in the paste, allows for chemical reactiveness with zirconia, dentin and enamel.

Therefore, the product is indicated for a wide range of indications (including adhesion bridges) without the need for separate priming and bonding. Another important fact is that excess removal requires a significantly lower force compared to other cements. This was already the case for product’s predecessor PANAVIA™ SA Cement Plus, as reported by a researcher from Tufts University in Boston, Massachusetts². For specifically demanding cases, you may increase the bond strength of PANAVIA™ SA Cement Universal to tooth structure with the aid of CLEARFIL™ Universal Bond Quick.

Choose the proven and familiar multi-step system

For all those who would like to stick to multi-step procedures they have trusted for years, PANAVIA™ V5 is the go-to product. It is suitable for all restorations, including those that demand the highest possible bond strength. It is the strongest cement Kuraray Noritake Dental ever developed, and with five shades, it is the most aesthetic one, too. This allows you to cement all tooth-coloured restorations with confidence, no matter whether they have a retentive or non-retentive design. PANAVIA™ V5 is designed to work perfectly with KATANA™ Zirconia, and is indicated for cementing a wide range of indirect restorations, and also for post-and-core procedures and amalgam bonding.

Create antagonist-friendly surfaces

Studies have shown that surface roughness of a restoration has a larger impact on the wear of the antagonist than the hardness of the dental material. This means that for an antagonist-friendly behaviour, the restoration surfaces need to be perfectly polished. This task is easily accomplished with TWIST™ DIA for Zirconia, which may be used after intra-oral adjustments or in the context of maintenance measures.

The flexible polishing spirals with an innovative shape offer you various application benefits for excellent polishing results. TWIST™ DIA for Zirconia is highly suitable for occlusal surface polishing as the shape and contour of the zirconia restoration is maintained. As they are sterilizable, the spirals may be reused.

A winning team for reliable results

By using a restorative material, cleaning solution, cementation system and polishing spirals from Kuraray Noritake Dental, you will benefit from streamlined procedures and reliable results. The products are not only designed to work with each other, but also thoroughly tried and tested for combined use, so that you can carry out your procedures with utmost confidence.

References

1 Data source: Kuraray Noritake Dental Inc.
2 A. Roberta et. al., J Dent Res Vol #98 (Spec Iss A), #3624, Determination of Excess Removability of Self-adhesive Resin Cements

Superior bond strength and consistently predictable results from one universal cement – PANAVIA™ V5 is nothing less than astonishing. It’s suitable for all indications, irrespective of restoration type or materials to be bonded. Simply pre-treat the tooth with PANAVIA V5 Tooth Primer, then prime the restoration with CLEARFIL CERAMIC PRIMER PLUS and cement. That’s all there is to it.  

Check out this video demonstrating PANAVIA V5 cementation workflow of zirconia crowns.

What is the story behind the development of Clearfil Universal Bond Quick Flip-Top Cap?

With this video, we will walk you through the story behind its development.

Users of dental zirconia are really spoilt for choice these days. Countless manufacturers offer zirconia materials that differ in their mechanical and optical properties and indication range. What is not apparent at first sight is that the available products also differ with respect to the quality of the CAD/CAM blanks offered. Blank quality is highly dependent on the quality of the raw materials and is affected by different aspects during raw material processing, pressing and pre-sintering. This has a huge impact on the surface quality, edge stability, fit and processing requirements of milled restorations.

Raw material production

Pre-shaded dental zirconia typically consists of metal oxides, including zirconium oxide, yttrium oxide and aluminium oxide, as well as additives like binders and colour pigments or ions. Most manufacturers of dental zirconia obtain pre-fabricated powder from an external industry partner, the most popular option being Tosoh Corporation. In contrast, Kuraray Noritake Dental relies on an end-to-end in-house process. This includes the production and addition of the components forming the company’s innovative multilayer technology for a polychromatic blank structure and – in the case of "KATANA™ Zirconia" YML – additional translucency and flexural strength gradation.

At Kuraray Noritake Dental, the powder is produced in-house.

Since more powder production steps are carried out in-house, the company is given full control over the quality of the raw materials, their grain size and the purity of the formulation. It also allows for a precise alignment of the mechanical and optical product properties to achieve a smooth transition from one layer to the next. The result is a seamless colour structure and outstanding match of the shades in the polychromatic blanks to the colours of the VITA classical A1–D4 shade guide.

In those materials combining different yttria concentrations in a single blank, additional in-house alignment measures may be taken. In the case of "KATANA™ Zirconia" YML, a completely new raw material was developed to deliver a uniform shrinkage ratio and harmonized coefficients of thermal expansion across the blank und thus bring flexural strength gradation to perfection.

Properties of zirconia restorations that are affected by the powder quality and composition include translucency and shade appearance, flexural strength, ageing behaviour and sintering performance.

Blank pressing

Zirconia discs and blocks used for CAD/CAM processing are usually produced by uniaxial and isostatic pressing. In the uniaxial compaction process, pressure is applied to the powder from one direction (uniaxial) or two directions (biaxial), whereas the isostatic compaction process involves virtually equal pressure applied from all sides. Hence, isostatic pressing typically results in a more uniform density distribution throughout the blank and a higher material homogeneity. These factors are prerequisites for a predictable processing and sintering behaviour and affect the fit of the final restoration. For optimal mechanical and optical properties of the zirconia material, it is essential to avoid large porosities, air pockets and impurities caused by airborne particles that are trapped during pressing.

At Kuraray Noritake Dental, a unique and extremely meticulous pressing process achieves a uniform pressure distribution and low risk of contamination by airborne particles. This specific procedure reduces gravitation forces and contributes to having as high as possible density of zirconia material. All the high-level preparation processes from raw material production to pressing are responsible for the high edge stability and surface quality of restorations milled from "KATANA™ Zirconia".”

Pre-sintering

The pre-sintering procedure is necessary in that it gives the pressed blanks the required stability to be machinable with milling tools. The selected temperature profile and duration of the pre-sintering cycle determine the material’s strength and processing properties and have an impact on the final sintering process.

The unique pre-sintering procedure carried out in the production facilities of Kuraray Noritake Dental results in blanks that are stable in their pre-sintered state. Although more stable, pre-sintered "KATANA™ Zirconia" is machinable with common diamond-coated milling tools without any increased risk of breakage or higher tool wear.

Fast sintering for the laboratory

The unique procedure has a positive impact on the surface smoothness after milling and can significantly shorten sintering times. In the dental laboratory, the sintering times may be reduced to 54 minutes* for single-tooth restorations and bridges of up to three units – an interesting option for rush cases and remakes.

*The material is removed from the furnace at 800 °C.

“KATANA™ Zirconia” YML speed sintered (90-minute sintering schedule), whereas the discs of competitors were sintered using typical overnight sintering schedules suitable for the particular material. Even with 90-minute sintering, KATANA™ Zirconia YML displays superior optical properties when compared to major competitors.

Uniform sintering schedules are offered for the whole "KATANA™ Zirconia" Multi-Layered Series.

Overview of the recommended sintering protocols.

Fast sintering for chairside

Using the "KATANA™ Zirconia" block with Dentsply Sirona’s CEREC system, it is possible to sinter single crowns up to three-unit bridges in 18–30 minutes without compromising the mechanical or optical properties.

The “KATANA™ Zirconia” block displays superior optical properties after 18 minutes of sintering compared with representatives of major competitors’ raw material after 30-minute and 60-minute sintering programs designed by Kuraray Noritake Dental based on the manufacturer’s recommendations.

Unique “KATANA™ Zirconia” properties

Together, these efforts taken by Kuraray Noritake Dental to produce dental zirconia of high quality make all the difference. The "KATANA™ Zirconia" series— "KATANA™ Zirconia" Yttria Multi Layered (YML), Ultra Translucent Multi Layered (UTML), Super Translucent Multi Layered (STML), High Translucent Multi Layered Plus (HTML Plus) and KATANA™ Zirconia High Translucent Mono Layered (HT)—have a homogeneous, high-density structure with low porosity and a high level of purity. In addition, "KATANA™ Zirconia" YML offers a seamless structure without transition lines despite flexural strength gradation. All these properties optimise the performance of the blanks during machining.

SEM images of non-polished “KATANA™ Zirconia” and a competitor’s material at 33× magnification. The four images of each material show the surface structure at different areas of a molar crown. In all areas, the surface of the restoration made of the competitor’s material is rougher and shows more porosity than the surface of the “KATANA™ Zirconia” crown directly after milling, according to Dr Josef Kunkela’s research results. One of the contributing factors to this result is the more densely pressed blanks with smaller grain sizes of “KATANA™ Zirconia”. (Courtesy of Kunkela Research Academy by Dr Josef Kunkela).

Surface roughness

An optimised processing behaviour leads to regular restoration margins, smooth surfaces and a precise fit of the restorations. The latter is due to the fact that the milling behaviour and volumetric shrinkage during final sintering are highly predictable, so that a user designing a 20 μm cement gap will get what he or she desires. Owing to the great control over optical properties and outstanding match to the VITA classical A1–D4 shades, "KATANA™ Zirconia" is considered to be one of the most aesthetic dental zirconia options available on the market.

Exellent marginal fit

SEM images revealing the fit of restorations made of two different materials (lithium disilicate and “KATANA™ Zirconia” Block STML) on a tooth abutment. The “KATANA™ Zirconia” restoration shows a more regular margin and more precise fit (with a cement gap of 19–21 μm) than the lithium disilicate crown (cement gap 26–45 μm). (Courtesy of Kunkela Research Academy by Dr Josef Kunkela).

Extremely regular margins of a “KATANA™ Zirconia” crown after milling, which is also a result of the favourable material structure.

In order to ensure all the desired material properties, including aesthetics and strength, one thing is essential: the machining carried out in the dental laboratory – milling and sintering - needs to adhere to the recommended protocols. This means that the milling machine and furnace should be cleaned and calibrated on a regular basis, which provides the conditions for optimised zirconia processing from the powder to the final, true-to-life dental restoration.

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