Did you know that humans make up to 30,000 decisions every day? Especially in the busy laboratory environment, decisions often have to be made blazingly fast and under time pressure. At least there is one decision we can spare you: Choosing your all-ceramic material! The reason is that we offer you an all-rounder for everyday laboratory use—reliable, safe and with top colour fidelity—KATANA™ Zirconia YML.

The new KATANA™ Zirconia YML is suitable for every indication and delivers uncompromising outcomes. Its special blank structure results from a combination of newly developed raw materials with different yttrium oxide content. This makes KATANA™ Zirconia YML the all-rounder that allows its users to standardize, streamline and simplify their procedures. Save decision-making time and use the time gained for the really pleasant things in everyday laboratory work, like perfect aesthetic finishing, planning or talking to the patient.

KATANA™ Zirconia YML and the path to perfection

Simply beautiful—the KATANA™ Zirconia story is epitomized by enthusiasm for all-ceramics and a passion for aesthetics. Dental technicians' wishes were taken into account, as were the findings of science and materials technology. The state of the raw materials, the purity of the powders, as well as the homogeneity and density of the blanks—the material properties are specifically matched. In conjunction with a meticulously designed in-house manufacturing process, the result is the dependable high material quality for which KATANA™ Zirconia is known and loved.

The success of KATANA™ Zirconia is based on a remarkable feature: Only KATANA™ Zirconia is made using Kuraray Noritake Dental Inc.'s unique, patented raw material technology*. Kuraray Noritake Dental Inc. is one of the few zirconia manufacturers with exclusive access to its own raw material. On this basis, it has succeeded time and again in setting new pioneering trends on the market. The company was the first to launch multi-layered zirconia—its Original Multi-Layered Technology—on the market. Now, with KATANA™ Zirconia YML, a new era in multi-layered zirconia is beginning.

*EP2024300

What makes KATANA™ Zirconia YML so special?

The answer is easy: predictable outcomes. Users benefit from reliable performance, accurate results and easy use. Its high colour fidelity makes the KATANA™ Zirconia Multi-Layered series so distinctive, as does the precision and perfection that zirconia provides. All the masterly competence of dental specialists in one disc! Dental technicians benefit from high cost-effectiveness and productivity. Assured colour fidelity and precision also provide for relaxed working.

New raw material technology

KATANA™ Zirconia YML is based on a new raw material technology derived from decades of zirconia experience. The zirconia imparts translucency as well as flexural strength, together with its proven multilayer colour structure. The special structure results from a combination of new raw materials with different yttrium oxide content. This makes KATANA™ Zirconia YML the ideal all-rounder with which work processes can be standardized, streamlined and simplified.

KATANA™ Zirconia YML combines raw materials with different yttrium oxide content. The result is an all-rounder material with colour, translucency and strength gradation.

More simplicity in the dental lab

The high density and homogeneity of the material provides for excellent marginal quality and edge stability. Seamless multi-layered technology produces a natural appearance with smooth colour and translucency gradients, no transition lines, and more besides. Highly aesthetic results are achieved with minimal effort. Thanks to the high colour stability, dental technicians achieve the desired aesthetics without laborious post-processing. The reliable predictability of the outcomes makes work even more fun.

Monolithic anterior and posterior crowns are half polished and half individualized with CERABIEN™ ZR FC Paste Stain and then glazed. (Images courtesy of DT Enrico Ferrarelli and MDT Daniele Rondoni)

More assurance in the dental lab

The individual layers in the multi-layered blank are optimally matched and shrink homogeneously in the final sintering process. The result is a high level of dependability and optimum quality of results. KATANA™ Zirconia YML is made using Kuraray Noritake Dental Inc.'s patented raw material technology, whereby even the raw material comes from within the company. This represents a clear advantage over most other zirconia manufacturers, as it allows every parameter to be fine-tuned. The variables are optimized for reliable application—down to the smallest detail. This means highly accurate fitting in everyday laboratory work. Retro-adaption or repeated fabrication do not even arise. And if you need to step up the pace: Harmonious material structure and high zirconia competence are prerequisites for optional high-speed sintering too, which is a valuable asset for every dental lab.

More flexibility in the dental lab

High flexural strength in the dentin area, yet high translucency in the enamel area—these features allow KATANA™ Zirconia YML to cover every all-ceramic indication. The zirconia is suitable for producing long-span monolithic bridges as well as thin-walled crowns, cut-back frameworks for micro-layering and even veneer restorations. Due to this versatility, it is possible to replace other ceramic CAD/CAM materials in the laboratory. This makes inventory management so much easier!

Is it a good idea to start processing translucent zirconia in the dental office? Learn why two experts – Dr. Mike Skramstad and Dr. Sameer Puri said that it may change everyone’s way of practicing dentistry for the better. In their lecture, the two experts described their chairside workflow in detail, including finishing and polishing steps.

October 7^th, 2022 marked the 10^th anniversary of the dental divisions of Kuraray and Noritake becoming Kuraray Noritake Dental Inc. For this celebration, ten internationally renowned experts shared their scientific, technical and clinical know-how in the virtual symposium titled “Up to now and from now on: From innovation to simplification”.

We prepared and uploaded the recording of this second lecture so you can watch it at your convenience.

USING THE NEXT-GENERATION SELF-ADHESIVE CEMENTS

by Dr. Tomohiro Takagaki.

INTRODUCTION

In recent years, the use of CAD/CAM systems for the production of indirect restorations has become increasingly popular. The shortage of young, qualified staff in the field of dental technology in Japan¹) is likely to contribute to a further increase of automated production techniques such as CAD/CAM, which require fewer manual production steps compared to traditional manufacturing techniques. Also globally, the number of restorations fabricated using CAD/CAM systems is rapidly increasing. This leads to an even more widespread use of innovative, tooth-coloured restorative materials such as zirconia, silicate ceramics and resins.

Demand for placing restorations using the principle of adhesion by resin cements is more and more increasing in daily clinical settings. However, it is difficult and complicated to condition the tooth and restoration surfaces using many primers correctly. In addition, the combination of many different components is time-consuming, complex and cost-intensive. Self-adhesive resin cements, which do not require conditioning the surface of teeth or some restorations with primers, have been released recently, and have become popular among dental practitioners. However, there are many reports²) on the dislodgement of resin-based CAD/CAM restorations and full-zirconia crowns that have been placed using self-adhesive cements. Hence, demand is high for a resin cement system that is both simple to use and reliable in performance.

In this document, I explain the fundamental technology of resin cement systems and their range of applications. In addition, I will introduce the method of using a next-generation self-adhesive cement, PANAVIA™ SA Cement Universal (Kuraray Noritake Dental Inc., Fig. 1), as an example.

- A commemoration of the company’s 10th anniversary -

Kiyoyuki Arikawa

After graduating from Kyushu University Faculty of Agriculture, Mr. Kiyoyuki Arikawa joined Kuraray. He has been involved in the dental materials business since joining the company, and this year marks his 38th anniversary.

Initially, he led the planning and development of products from the head office, and has won Kuraray's Merit Award for three products, including CLEARFIL™ SE Bond. In addition, since 2006, he has managed the dental materials business as General Manager of each subsidiary in Europe and the United States.

After that, he returned to Japan and served as president of Kuraray Noritake Dental from 2014 to 2020. Currently, he has handed over the president to his junior and is working as CTO.

To commemorate the 10th anniversary of Kuraray Noritake Dental Inc., I have been asked to write an article under the above title. Here in this article, I would like to write about my own impressions and some thoughts I had about the development and commercialization of various products I was directly engaged with. I was an employee of Kuraray before it was integrated with Noritake, so things described in this article will mainly be from the period during which I worked in the Dental Materials Division of Kuraray Co., Ltd. I would like to beg the readers' pardon for my failure to describe in detail Noritake Dental Supply’s products, which originated from that company’s brilliant history in the development and manufacture of dental materials.

PANAVIA™ - A PRODUCT DEVELOPED TO BECOME AN OUTSTANDING BRAND IN THE RESIN CEMENT MARKET

In August 1984, I was assigned to Kuraray’s Dental Materials Division. On that day, when I first came to the office, a celebration was being held in commemoration of PANAVIA™ EX, a dental resin cement released the previous year that had just received the President’s Prize. PANAVIA™ EX was launched with thorough preparation, as a genuine adhesive resin cement, after the company had completed the expansion of the CLEARFIL™ lineup (F, FII, Core, SC and Posterior) that it had begun designing in 1978. PANAVIA™ EX's characteristics, which enable the application of adhesive bridge technique (thanks to its strong adhesion to enamel), were particularly acclaimed by many users around the world, making it a smash-hit product.

Parallel with that great success, we focused on discovering the cause of pulpal stimulation, a problem that sometimes occurred when PANAVIA™ was applied to dentine for luting restorations, and we sought measures to prevent this problem. At first, PANAVIA™ was released with a recommendation to condition the dentine with phosphoric acid in order to increase the strength of its bond to the dentine. However, its highly-hydrophobic paste composition seemed to prevent the MDP monomer from delivering a sufficiently strong bond to dentine. In addition, it appears that the phosphoric acid treatment opened the dentinal tubules, leading to the occurrence of pulpal stimulation. We performed fact-finding surveys and held many conferences with university researchers to resolve this problem of pulpal stimulation. Among the temporary measures we made to prevent the occurrence of pulpal stimulation without changing the existing specifications of the product, we decided to recommend against conditioning the dentine with phosphoric acid, at least in Japan. With the health insurance reimbursement system supplying a good tailwind for PANAVIA™, the common understanding sprang up spontaneously in the dental materials market: "Cases requiring strong adhesion, such as adhesion bridges, should be cemented with PANAVIA™ and those which can be treated with general luting should be cemented with glass ionomer cements."

Since then, five improved versions of PANAVIA™ have been put on the market, to sweep the resin cement markets overseas as well as in Japan. The improvements were made mainly for the purposes of increasing the range of crown restorative materials -- for example to include precious metals and ceramics -- that can be treated with this product, and in order to improve handling ease in the clinical setting. Here, I would like to emphasize that what lay behind our endeavor to improve PANAVIA™ was "realizing a reliable general luting material". In pursuit of this goal, we focused on improving the product by causing the resin cement to make a strong bond to dentine through chemical polymerization. I think that those efforts of ours indeed contributed to the evolution of the PANAVIA™ brand.

The efforts we have made since the launch of PANAVIA™ back there in 1983 have now come to fruition as PANAVIA™ V5, PANAVIA™ SA Cement Universal and, most recently, PANAVIA™ Veneer LC, a light-curing veneer cement with an extra-long working time. When we talk about its PANAVIA™, there is no avoiding mentioning the technologies behind those products, in particular, the development of the indispensable catalyst technology that was incorporated into them. Our catalyst technology is an excellent one that can also be applied to other products, and every day at our Niigata Development Department, R&D activities are still being carried out to improve it further.

Owing to our efforts, these days no complaints are ever heard about pulpal stimulation caused by PANAVIA™. On the other hand, in parallel with developments involving PANAVIA™, glass ionomer cements that have also evolved. These are also widely used and strongly supported by many users around the world.

Providing the characteristics glass ionomer users want is one of the directions we have followed, which has continued since the development of PANAVIA™.

Case by Dr. David Garcia Baeza and DT. Pilar Ballesteros Galan

Shade determination in the planning phase, shade evaluation at try-in: How is it possible to accomplish these highly important tasks in the production of lifelike anterior restorations without meeting the patient in person? A computer-based shade documentation and try-in system is a great solution. Download this clinical case example describing the aesthetic restoration of two maxillary anterior teeth to learn more about one such system and its use!

LOOKING TOWARD A UNIVERSAL FUTURE

At a glance, this issue is emblematic of our commitment to continuous innovation and improvement. Many of the articles focus on newly introduced or updated products and clearly demonstrate the science-backed reasoning that have guided their development.

A prime example of this approach is newly launched PANAVIA™ Veneer LC cementation system. By combining tried and tested components of our ever-popular and reliable PANAVIA™ V5 system with new nano-spherical filler technology, this specialist solution possesses excellent clinical and aesthetic properties.

In an illuminating article about how resin cement systems can function during the era of digital dentistry, Dr. Tomohiro Takagaki explains the growing demand for a system that is easy to use and performs up to standards of the modern dentistry, utilising PANAVIA™ SA Cement Universal as an example.

Dr. Clarence Tam provided a clinical case regarding the use of CLEARFIL MAJESTY™ ES-2 Universal to create naturally-blended posterior restorations. An interview with Dr. Adham Elsayed further clarifies the advantages of this composite and how it can be used in everyday dental workflows.

A lively discussion with Dr. Karim Nasr sheds new light on what benefits the multi-layered KATANA™ Zirconia Block can bring to single-visit dentistry. And last but not least, Donald Jetter, provides an insightful overview of the influence that the famed MDP monomer continues to have on Kuraray’s CLEARFIL™ and PANAVIA™ product lines nearly four decades after its introduction to the dental market.

Click here to read. Happy reading!

Start Reading: BOND | VOLUME 9 | 08/2022

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BOND | SPECIAL EDITION | 06/2021

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Direct restoration procedures simplified

Some companies mainly make use of basic technologies developed by others to improve their products and introduce new ones, while other companies conduct fundamental research and technology development inhouse. Is this difference relevant for someone who uses the resulting products in the dental practice or laboratory on a daily basis? It is – as companies developing everything from scratch usually have a deeper understanding of the products and their production procedures, which makes it easier for them to modify specific features, solve existing problems and respond to market needs. This article describes the impact of several basic technologies developed by Kuraray Noritake Dental Inc. on the workflow of creating direct composite restorations.

Direct restorations – from complex to simple

Adhesive restorative dentistry using high-performance dental adhesives and resin composites is currently one of the most popular way of treating teeth with carious lesions. Nowadays, a single-bottle universal adhesive and one or two shades and opacities of universal composite are usually enough to create beautiful and durable outcomes, provided that the right materials are selected.

This, however, has not always been the case. For a long time, the techniques used to create direct restorations have been quite complex: adhesives were technique-sensitive multi-bottle and multi-step systems with long application times. Composite filling materials, on the other hand, only produced lifelike outcomes when many different shades and opacities were combined in the right way. And even if the complex procedures were carried out correctly, the risk of microleakage, discolouration and eventually secondary caries was comparatively high. Kuraray Noritake Dental Inc. focused on solving these issues quite early, starting with the utilization of the Original MDP Monomer developed in 1981.

Optimizing the bonding performance

The Original MDP Monomer addressed the issue of limited long-term bonding performance of adhesive systems. MDP’s hydrophilic (phosphate) group forms a particularly strong and long-lasting chemical bond with calcium found in hydroxyapatite, the main component of enamel and dentin. The formed MDP-Ca salt provides the basis for a stable, strong and durable hybrid layer. In combination with the resin in the bonding agent a tight seal of the cavity after light-curing is the result. Down to the present day, MDP is an essential component of any adhesive product from Kuraray Noritake Dental Inc., and it is the key component that made CLEARFIL™ SE Bond become the Gold Standard self-etch adhesive system.

However, convinced that dental adhesives should provide for more than just a strong and long-lasting bond, Kuraray Noritake Dental Inc. started to focus on solving another issue: the risk of demineralization and cavitation caused by bacteria remaining in the cavity. Based on its experience in developing other adhesive monomers, Kuraray Noritake Dental Inc. invented the MDPB monomer that has an antibacterial cavity cleansing effect. Different from antibacterial agents that might impair the bond strength of a subsequently applied adhesive, the MDPB monomer kills remaining bacteria without affecting the bonding performance. It is contained in the primer of the two-bottle self-etch adhesive CLEARFIL™ SE Protect and is immobilized by polymerization.

The bactericidal mechanism of MDPB is presumed to be similar to the well-known antibacterial agent CPC (Cetyl pyridinium chloride), which is in many toothpastes and mouth rinses.

While two-bottle self-etch adhesives has already simplified the adhesive procedure, single-bottle universal adhesives go the extra mile. It is a challenge to bring together ingredients distributed in multi step systems in one bottle without compromising the stability of the product. Current technology now makes this possible. To seal the surface as soon as possible after application, the penetration of the monomers into the dental tissue must be fast and efficient. However, the penetration is usually slowed down by monomers that need time to penetrate the tooth structure – especially wet dentin – and sometimes even need to be rubbed into it. That is why Kuraray Noritake Dental Inc. focused on developing the Rapid Bond Technology. It consists of the Original MDP Monomer combined with newly developed hydrophilic crosslinking amide monomers and is integrated in CLEARFIL™ Universal Bond Quick. The hydrophilic amide monomers provide for a rapid, deep and complete penetration of the dentin and form upon curing a densely cross-linked polymer network responsible for a strong and durable bond. Hence, waiting and rubbing times are eliminated and a tight and long-lasting seal of the cavity is established after light-curing.

Due to their hydrophilicity (water-affinity), the amide monomers of the Rapid Bond Technology penetrate dentin very well. After light-curing, the bond exhibits low water sorption and therefore high aging-resistance.

Optimizing direct restoratives

Combining multiple layers, shades and opacities: The use of highly complex layering techniques for the creation of lifelike composite restorations is luckily a thing of the past in many clinical situations. The reason: highly developed resin composites that blend seamlessly with the adjacent tooth structure. To provide for this favourable feature, Kuraray Noritake Dental Inc. has developed its proprietary Light Diffusion Technology (LDT). The technology is incorporated in special pre-polymerized fillers acting like millions of micro-prisms that transmit and refract light and colour from the surrounding tooth structure. Optimized in size, distribution and refractive index in relation to the matrix, the fillers offer unsurpassed natural blending.

The whole CLEARFIL MAJESTY™ composite line-up contains this proprietary filler technology. Its latest product – CLEARFIL MAJESTY™ ES-2 Universal – in which Kuraray Noritake Dental Inc. makes use of next level LDT allows for a single-shade technique with simplified shade selection: it is available in two shades for the anterior and a single shade for the posterior region, but blends in so nicely that it covers virtually every shade of the VITA classical A1-D4 shade guide.

Refracting and transmitting light in the right way for a great optical integration: light diffusion fillers of CLEARFIL MAJESTY™ ES-2 from Kuraray Noritake Dental Inc.

As a great optical appearance is not only dependent on optical integration and undetectable restoration margins, Kuraray Noritake Dental Inc. also developed fillers that provide for the rest – a natural surface gloss and long-term polish retention. The solution integrated in CLEARFIL MAJESTY™ ES Flow with its three levels of flowability is called Submicron Filler Technology, which consists of glossy submicron-sized fillers. These fillers are so small that light reflections show a natural effect even after wear. Kuraray Noritake Dental Inc.’s exceptional silane technology is used to join millions of those submicron fillers and keep them together over time. It allows for high filler loads in the low-viscosity composites and limits water uptake that would otherwise lead to degradation of the cured composite. The perfect balance between the glossy submicron fillers, light diffusion fillers, resin matrix and proprietary silane technology is responsible for a balanced combination of mechanical and optical properties.

Example of a single-shade restoration made of CLEARFIL MAJESTY™ ES-2 Universal.

Conclusion

Adhesive monomers, filler technologies and silane technology providing for a solid combination of fillers, clusters and resin matrix: Kuraray Noritake Dental Inc. clearly is a trusted expert in the field of adhesive restorations. The proprietary technologies developed during the past decades have definitely contributed to a better (long-term) performance of direct restorations, and to reliable and aesthetic outcomes more easily achieved.

- A commemoration of the company’s 10th anniversary -

Kiyoyuki Arikawa

After graduating from Kyushu University Faculty of Agriculture, Mr. Kiyoyuki Arikawa joined Kuraray. He has been involved in the dental materials business since joining the company, and this year marks his 38th anniversary.

Initially, he led the planning and development of products from the head office, and has won Kuraray's Merit Award for three products, including CLEARFILTM SE Bond. In addition, since 2006, he has managed the dental materials business as General Manager of each subsidiary in Europe and the United States.

After that, he returned to Japan and served as president of Kuraray Noritake Dental from 2014 to 2020. Currently, he has handed over the president to his junior and is working as CTO.

In the early 1980s, shortly after Kuraray entered the dental materials market, Noboru Makino, then Director of the Mitsubishi Research Institute, a major think tank in Japan, made a sensational announcement. He said: "The denture industry will overtake the automobile industry with the advent of an aging society." Many companies, including leaders in the chemical industry that were more or less involved with dental materials, paid attention to this announcement and joined the dental materials market in Japan, one after another.

Now that 40 years have passed since Mr. Makino predicted this thriving dental materials business, we notice that the patient's perception of dentures and the structure of the dental materials market have changed dramatically. First, as the population’s average age gets higher, patients no longer simply accept that inevitably they will end up using dentures. They want to use their own teeth, retaining their natural teeth as long as possible. This has led to an increased demand for implants and resin restorations. Furthermore, patients also began demanding more esthetic effects from their dental treatment and the dental materials market shifted its focus to the more esthetic aspects of adhesion-based dentistry and the development of new types of dental materials, such as those used for the fabrication and bonding of all-ceramic restorations. In parallel, with rapid advances in digital technology, it has become possible to fabricate made-to-order restorations using CAD/CAM systems, instead of using the metal casting method. Under these circumstances, new types of materials, such as zirconia suitable for the fabrication of restorations using CAD/CAM systems, were created to meet the esthetic drive-in dentistry.

This sequence of events illustrates that new technologies are fusing with existing market forces to create new markets based on shifting patient needs, suggesting that the winner in the market will be the company that quickly identifies user needs, creates new technologies, and meets those users' needs. In other words, both Kuraray and Noritake have formed new markets as a result of their earnest efforts to address and solve the problems users have presented to them. In fact, after Kuraray Medical merged with Noritake Dental Supply, I concluded that one thing the two companies had in common was the attitude of taking good care of their products’ users. We all understood their manner of use and the circumstances in which they used the products. We were all making all-out efforts to solve users' problems both before and after the marketing of products. Our determination to stand at the users’ sides and resolve any problems they have with our products as quickly and completely as possible seemed to me to differentiate our approaches from others.

The spread of the novel coronavirus, which caused a global pandemic, has drastically changed patients’ values as related to dental treatment. In the U.S., demand for chair-side zirconia blocks increased as a way to reduce the number of clinic visits, and there was a shift to more expensive treatment options, which was also seen during the Lehman Shock. Therefore, the preference for same-day treatment may become a major trend in dental treatment in the future. In addition, there are many other signs of changing patient needs, such as the widespread use of remote treatment and the rise of ethical consumption in support of sustainability.

In order for us to make further progress and continue to grow for another 20 or 30 years, we have to identify user needs correctly and in a timely manner, and continue to retain these same shared values held by Kuraray and Noritake, embodied in the statement: "We are determined to satisfy user needs”. That is, we need to root our ‘DNA’ within the company’s longstanding body of values, and retain our eternal enthusiasm for developing new markets. I think these ‘genes’ will be indispensable to our future growth.

Case by Dr. Yohei Sato, DMD, PhD, Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, JAPAN and Dr. Keisuke Ihara, CDT, i-Dental Lab, JAPAN

Fig. 1. The patient was referred to our hospital by an orthodontist. The chief complaints were improper esthetics of the teeth due to black triangles at the edges of the gaps between the teeth and occlusal wear of the teeth.

Fig. 2. On the basis of the pre-treatment diagnosis using a mockup, the abutments were prepared without anesthesia, keeping in mind that the enamel should be preserved to the extent possible.

Fig. 3. Since a fixation retainer was installed on the palate side, it was difficult to take impressions using silicone. Therefore, an intraoral scanner for impression taking was used.

Fig. 4. A layer of porcelain on each of KATANA™ Zirconia STML substrates was applied to complete the laminate veneer resto-rations. The inner surface of each restoration was sandblasted, being careful to prevent chipping.

Fig. 5. After trial fitting, bonding inhibiting substances as blood and saliva were removed using KATANA™ Cleaner.

Fig. 6. Milling. CLEARFIL™ CERAMIC PRIMER PLUS, which contains the phosphoric ester monomer MDP, was applied and dried using compressed air.

Fig. 7. The surface of each tooth was cleaned and treated with K-ETCHANT Syringe for 10 seconds before washing it away with water and compressed air-dried the area.

Fig. 8. PANAVIA™ V5 Tooth Primer was applied and left it for 20 seconds, then compressed air-dried it.

Fig. 9. PANAVIA™ Veneer LC Paste was applied and the laminate veneer was seated. For this case, we treated six teeth during one session.

Fig. 10. The unpolymerized excess paste was removed with a brush. PANAVIA™ Veneer LC Paste is a light-cured type, which was designed to provide sufficient working time.

Fig. 11. This photo shows the results after the final light curing. Since the excess cement was easily removed, there were almost no cement residues.

FINAL SITUATION

Fig. 12. The photo shows the inside of the oral cavity one month after the fitting of the laminate veneer restorations. It can also be noted that the teeth’s marginal gingiva has been improved, thanks to the good fit of the laminate veneer restorations.

Some companies mainly make use of basic technologies developed by others to improve their products and introduce new ones, while other companies conduct fundamental research and basic technology development inhouse. Is this difference relevant for someone who uses the resulting products in the dental practice or laboratory on a daily basis? It is – as companies developing everything from scratch usually have a deeper understanding of the products and their production procedures, which makes it easier for them to modify specific features, solve existing problems and respond to market needs. This article describes the impact of two basic technologies developed by Kuraray Noritake Dental Inc. on the production of zirconia-based indirect restorations.

All-ceramic evolution

A milled monolithic or only minimally reduced core made of high-strength ceramics plus a micro-layer of porcelain: this is today’s success formula for the production highly aesthetic indirect restorations. The approach is by far less complex and time-consuming than traditional production and layering procedures, while its outcomes can be quite impressive. Concerning aesthetics and function, however, it is essential that the right types of material are selected and combined.

The core: Multi-Layered Zirconia Technology

When the first opaque zirconia framework materials conquered the dental market, leading manufacturers never grew tired of stressing that not all zirconia is alike. Instead, huge quality differences do exist depending on the raw materials selected as well as the processing techniques and equipment used for blank production. With an increasing aesthetic potential of the core materials and a decreasing thickness of the veneering porcelain on top, this fact becomes more relevant than ever.

When Kuraray Noritake Dental Inc. identified the need for more aesthetic zirconia core materials with a higher translucency and a tooth-like colour structure, it decided to develop a completely new type of dental zirconia. It started establishing a sophisticated raw material production, blank pressing and pre-sintering process inhouse. This was the basis for the development of the dental industry’s first polychromatic blank with a seamless colour structure and precise shade match with tabs of the VITA™ classical shade guide. In order to identify the best ingredients and procedures, the R&D team experimented with different raw materials, formulations and grain sizes, developed ways to optimize the purity of the ingredients and focused on perfectioning the homogeneity and density of the blanks and – of course – the integrity of the different layers. Currently, three different products based on this original Multi-Layered Zirconia Technology are available for dental laboratories: KATANA™ Zirconia UTML, KATANA™ Zirconia STML and KATANA™ Zirconia HTML PLUS. They offer different levels of translucency and flexural strength.

KATANA™ Zirconia Multi-Layered disc with four-layer colour structure.

Three different products with four-layer colour structure, differing in terms of translucency and flexural strength.

In June of 2021, Kuraray Noritake Dental Inc. introduced a new, next level Multi-Layered Zirconia disc – KATANA™ Zirconia YML. This time, the company responded to the marked need for a universal zirconia with a high aesthetic potential. The blanks offer colour, translucency and flexural strength gradation – with the highest translucency in the enamel and the highest flexural strength in the lowest body layer.

KATANA™ Zirconia YML: Multi-Layered Zirconia disc with colour, translucency and flexural strength gradation.

All Multi-Layered Zirconia discs and technology incorporated in them support the production of lifelike restorations with reduced hand work. No matter whether the user prefers to work with materials offering a uniform strength and selects them depending on the indication or with the universal solution: the finishing effort is reduced considerably due to the optimized translucency and natural colour gradation of the core materials. At the same time, the quality of the produced restorations is high thanks to regular margins, smooth surfaces and a precise fit (as a result of the homogeneous, high-density structure with low porosity and a high level of purity).

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

The micro-layer: Synthetic Feldspathic Porcelain Technology

Differences are not only found in zirconia, but also in the performance of veneering porcelains. They typically consist of feldspathic porcelain, and most of them are based on natural feldspar. Depending on where this feldspar is mined, it may have slightly different properties. That is why manufacturers of this natural feldspar-based veneering porcelains need to adjust their formulations from time to time, and handling and aesthetic properties might be somewhat different with every new system purchased. In the 1980s, these variations in the composition of natural feldspar led to unpredictable material properties causing difficulties in reproducing the natural tooth colour and even porcelain fractures and cracks appearing after firing of porcelain-fused-to-metal (PFM) restorations. A limited colour stability was also an issue.

For Noritake, one of the parent companies of Kuraray Noritake Dental Inc., these issues were reason enough to start developing a different kind of porcelain. After analysing the issues and weighing the possibilities, a completely new Synthetic Feldspathic Porcelain Technology was developed. It provides for stable coefficients of thermal expansion, particle distribution and colour, as it is no longer dependent on natural sources of feldspar.

Originally, this technology was used in Super Porcelain AAA (EX-3) introduced in 1987, a veneering porcelain for metal frameworks. However, the technology also formed the basis for the development of CERABIEN™ ZR Porcelain and CERABIEN™ ZR FC Paste Stain for porcelain layering on zirconia. This line-up of internal stains and porcelains was specifically developed for micro-layering on zirconia.

All products have one thing in common: as they are based on synthetic feldspathic porcelain, they offer consistent mechanical and handling properties and predictable shade effects. The material structure and particle distribution resemble those of natural teeth, supporting lifelike outcomes. A reduced effort is achieved with the liquid ceramic system CERABIEN™ ZR FC Paste Stain used on a monolithic restoration or one with a minimal cut-back (0.1 mm).

Different micro-layering approaches with CERABIEN™ ZR FC Paste Stain…

…and CERABIEN™ ZR Internal Stain plus Luster Porcelain leading to highly aesthetic outcomes.

Connecting elements: Touch-Cure and Monomer Technology

When needing to cement the finished prosthetic restorations on implant abutments or frameworks, it is essential to select a cementation system that is able to fulfil high aesthetic and functional demands. The PANAVIA™ family of resin cements from Kuraray Noritake Dental Inc. contains many different technologies that provide for a high bond strength to various substrates and a tight marginal seal. The key technology incorporated in any cement is the Original MDP Monomer invented by Kuraray in 1981. It is capable of establishing a particularly strong and long-lasting bond to enamel, dentin, metal and zirconia. The self-adhesive resin cement PANAVIA™ SA Cement Universal also contains the LCSi Monomer, a Long Carbon-chain Silane coupling agent. This monomer forms a strong chemical bond with resin composite, porcelain and silica-type ceramics (like lithium disilicate), so that the need for a separate silane component (a primer or adhesive) is eliminated when bonding these types of prosthetic restorations. PANAVIA™ V5, the strongest cement in PANAVIA™ line, is equipped with Touch-Cure Technology. It seals the interface between the tooth and the restoration to prevent micro-leakage, provides for a high polymerisation ratio even when dark-curing and hence delivers a strong bond in virtually every situation.

Conclusion

KATANA™ and CERABIEN™ are excellent partners that allow for a simplified approach to lifelike restorations. The high level of quality and reliable performance offered by the solutions are due to proprietary technologies and streamlined inhouse production procedures that really make a difference. And whenever needing to cement prosthetic restorations on implant abutments or frameworks, PANAVIA™ resin cement systems based on proprietary monomer and curing technology are a perfect choice.