429 Too Many Requests

In 1978, Kuraray shook up the dental market with the introduction of CLEARFIL BOND SYSTEM F, the world’s first total-etch adhesive system. Having inaugurated the era of adhesive dentistry, we steadily introduced new dental products over the following years. In 1983, Kuraray introduced the PANAVIA EX resin cement. By utilising our patented MDP monomer technology developed in-house, PANAVIA EX enabled Kuraray to set the industry standard for adhesion—a position we have held in the decades since. This year marks the 40th anniversary of Kuraray’s entry into the commercial dental products market, providing a perfect opportunity to reflect on how far we have come since.

Kuraray—Rooted from a true trailblazer 
Founded in June 1926 by Magosaburo Ohara in Kurashiki in Japan, Kuraray has transcended our humble origins as a producer of rayon to become a leading global manufacturer of medical products, materials, textiles, chemicals, resins and much more. Our commitment to research and development in the fields of chemistry and engineering has led to many market firsts and a reputation as a pioneer of new products and technologies. 

A history of innovation
From the very beginning, Kuraray has been focused on the manufacture of high value-added products. At the time of the business’s birth, rayon was a new type of synthetic material, and over the ensuing years, Kuraray was able to master its production. In 1950, we became the first company in the world to develop the technology to mass-produce POVAL (polyvinyl alcohol), paving the way for the production of the new synthetic fibre Vinylon in the same year. CLARINO, a water-resistant synthetic leather substitute for shoes, bags and other items, was released in 1964 after extensive research and testing, and quickly collected international awards for its technology.

Kuraray’s continued emphasis on independently developed proprietary technologies and techniques, rather than relying on imported alternatives, has enabled our company to provide original, high-quality products for a variety of different industries. High on this list is dentistry.

The Kuraray Noritake Dental era
In April 2012, Kuraray Medical and Noritake Dental Supply merged to form Kuraray Noritake Dental. By bringing together the materials and technologies developed by each of these market-leading companies, Kuraray Noritake Dental has continued to deliver dental bonding agents, ceramics and other reliable products to over 90 countries worldwide. The KATANA Zirconia range, for example, employs our unique multi-layered zirconia technology to provide a ceramic restorative material with superior translucency and perfect blending properties, while rapid bond technology ensures that CLEARFIL Universal Bond Quick delivers a lasting bond faster and easier than ever. 

Through a focus on research and production, Kuraray Noritake Dental is ideally positioned to continue providing leading-edge solutions to dental issues both now and in the future. 
 

SYMPOSIUM
DIRECT AND INDIRECT ADHESIVE AESTHETIC RESTORATIONS BASED ON MINIMALLY INVASIVE APPROACH

Zirconia restorations are continuously advancing due to the development of high-translucency multilayered full-contour materials allowing both minimally invasive preparations and highly aesthetic solutions. Effective adhesive techniques are a key factor for the long-term clinical success of such restorations. Three renowned lecturers will cover the topic illuminating most relevant aspects regarding latest material trends and different clinical options.

Prof. Beuer will focus on the aesthetic possibilities with full-contour Zirconia restorations preferably in the aesthetic zone.

Prof. Kern will focus on Zirconia-based resin-bonded fixed dental prosthesis (RBFDP) as an interesting long-lasting minimal-invasive alternative i.e. to implants and conventional C&B’s.

Prof. Tagami will focus on direct bonding strategies for achieving the high quality minimally invasive aesthetic restorations with reliable bonding technology. He will also touch the option with universal bonding agents and their use in direct and indirect applications.

FOR MORE INFORMATION VISIT LONDON.KURARAYSYMPOSIUM.INFO

Kuraray Noritake Dental concludes a patent license agreement with 3M In March 2018, Kuraray Noritake Dental Inc. (President: Kiyoyuki Arikawa), with its Head Office in Chiyoda-ku, Tokyo, concluded a license agreement with the 3M Company, whose Head Office is in Saint Paul, Minnesota, USA. The agreement concerns a patented method for producing multilayered ceramics, European patent No. 2024300, held by Kuraray Noritake Dental Inc.

Summary of Kuraray Noritake Dental Inc. ceramic business

Kuraray Noritake Dental Inc. launched the zirconia disc that has been commercialized through the use of our layered ceramic production method in 2012. The product has multi-layered structure with four different colored zirconia powders that feature a smooth transition of color gradation between layers. We took advantage of the dental ceramic coloring technology we had accumulated through the development of porcelains. Success was achieved in controlling the shrinkage of the layers by optimizing the amounts of pigments added, thereby achieving great accuracy in terms of adaptation. In 2015, we also launched a new series zirconia which has the high degree of translucency of natural tooth enamel and is suitable for the esthetic restorations of anterior teeth. In January 2018, zirconia block joined the zirconia family as our new solution for the fabrication of zirconia restorations. This new product achieves a well-balanced combination of appropriate mechanical properties and good esthetics with a short baking time. Kuraray Noritake Dental Inc. is committed to developing new dental materials that contribute to the dental industry. Our products have become even more competitive on the global market because of our intense pursuit of technological innovation.

Read the official statement here

Volume 3 of our "BOND" newsletter is now published and ready to read!

Content Highlights

Future of dentistry

CLEARFIL Universal Bond Quick tested by clinicians

Interviews on what was seen on the ConsEuro 2017

Start Reading: BOND Volume 3

At Kuraray Noritake Dental, we understand that the most important factors for successful prostheses are strength and aesthetic appearance. With our KATANA Zirconia multi-layered series, we are proud to provide a range of materials with the translucency, colour gradient and durability to make every prosthesis as natural as possible, from veneers to full-contour restorations.

Launched in 2015, KATANA Zirconia UTML (Ultra Translucent Multi Layered) is the most translucent series at 43 per cent, a level equal to that of lithium disilicate or glass. This optimal translucency, combined with its natural colour gradient, allows the material to be used with confidence for veneers and crowns between natural teeth in the anterior region. KATANA Zirconia UTML is available in 20 shades in two shade groups (standard and enamel), with the reduced chroma of the enamel shades allowing for an enhancement of the translucency of the incisal area. As the flexural strength of KATANA Zirconia UTML—557 MPa—is 30 per cent higher than that of lithium disilicate, it can be reliably used to produce durable and aesthetic single restorations. 

KATANA Zirconia STML (Super Translucent Multi Layered) likewise has a natural colour and translucency gradient that transmits light in the incisal area while blocking it in the cervical area. This provides clinicians with the basis for beautiful full-contour prostheses, regardless of the abutment colour. With a translucency of 38 per cent and a flexural strength of 748 MPa—even higher than that of UTML, this series is recommended for up to three-unit posterior bridges, as well as crowns in the anterior and posterior regions.

The KATANA Zirconia ML (Multi Layered) and HT (High Translucent) series possess a flexural strength of 1,125 MPa, providing the highest level of mechanical strength in the KATANA line. Ideal for frameworks and long-span bridges, this series has a translucency of 31 per cent and ensures the aesthetic appearance of zirconia required by Kuraray Noritake Dental.

Give your brush a break

Often, the only way to ensure a prosthesis’s natural appearance is by dipping. With the KATANA Zirconia series, prostheses simply need to be milled and sintered to create natural aesthetics. To give them an even more natural look, the buccal surface can be stained with FC Paste Stain (Cerabien ZR).

Cementation with PANAVIA

Built upon the foundation of our original MDP monomer, PANAVIA cements are the best option for cementing prostheses or bonding to zirconia in a dental practice or laboratory. Both PANAVIA V5, developed for all indications, and PANAVIA SA Cement Plus, designed for ease of use, utilise the MDP monomer and have high bond strength to zirconia and durability. With PANAVIA cements, restorations can be cemented adhesively, expanding the options for use with zirconia.

No other resin cement offers such ease of use and consistency in procedure. Indeed, the unrivalled simplicity and predictability of PANAVIA V5 is nothing less than astonishing.

Always the same cementation procedure. Always the special PANAVIA V5 Tooth Primer for the pretreatment of the tooth. And always CLEARFIL CERAMIC PRIMER PLUS to prime the restoration. 

In 1983, Kuraray introduced the PANAVIA EX resin cement and, with it, our patented MDP adhesive monomer. Since then, the MDP monomer has repeatedly been clinically proved and has set the industry’s adhesive standard for over 30 years. PANAVIA V5 is the newest addition to the PANAVIA cement line and sets a new adhesive benchmark for resin cements by providing self-cure dentine bond strengths equal to our gold standard light-cure bonding agent CLEARFIL SE BOND.

PANAVIA V5 is able to provide strong bonding not just to hydroxyapatite but to metals and zirconia as well. It can be used for all clinical cementation indications, including on crowns, veneers, inlays/onlays, bridges, crowns/abutments on implants, and posts. With PANAVIA V5, you always follow the same procedures prior to prosthetic cementation: roughen and prime the prosthesis, prime the tooth, and apply the cement to the prosthesis.

Aesthetic stability in shading 

When it comes to maintaining shade in aesthetic cementation, conventional composite cements tend to discolour over time. With PANAVIA V5, Kuraray Noritake Dental presents an amine-free paste in five different shades—Universal (A2), Clear, Brown (A4), White and Opaque (only in self-cure mode)—that has been scientifically proved to demonstrate a lower level of post-curing colour variance than amine-based cements do. In addition, the new PANAVIA V5 try-in paste allows you to accurately simulate the shading of your cementation before it has been performed. As part of Kuraray Noritake Dental’s continued commitment to excellence in adhesion, this combination aims to enable the continued stability and natural appearance of the cement shading after curing.

PANAVIA V5 Tooth Primer

Almost all dual-cure resin cements available have been scientifically demonstrated to require light curing to achieve an acceptable bond strength. Thanks to Kuraray Noritake Dental’s focus on research and development, the MDP monomer-based PANAVIA V5 Tooth Primer contains a new catalyst that solves this issue. It provides an accelerated curing process from the moment the cement touches the primer, which, in turn, leads to a high degree of conversion from monomer to polymer. PANAVIA V5 presents a milestone in adhesion, as it offers improved bond strength for all tooth structures, even when used in the self-cure mode.

Prime with CLEARFIL CERAMIC PRIMER PLUS

PANAVIA V5 is designed for use in conjunction with CLEARFIL CERAMIC PRIMER PLUS, a stable universal primer that contains both Kuraray Noritake Dental’s original MDP monomer and a silane monomer. This allows it to bond to all silica-based ceramics (including lithium disilicate), zirconia, composites and metals. It provides excellent bond strengths to all of these materials, as well as procedural simplicity.

To find out more about integrating PANAVIA V5 into your restorative workflow, visit www.kuraraynoritake.eu/en/panavia-v5.html

When it comes to the aesthetic performance of restorations in the anterior region, a key aspect to consider is translucency—the ability of the material to let light pass through it without becoming transparent. As teeth are naturally quite translucent, it is often noticeable if a restoration is of a low-translucency material, as it will not blend in. In addition, if the material is of a different colour to the surrounding teeth, it will likely appear unnatural. As the originators of multi-layered zirconia technology, Kuraray Noritake Dental is proud to present our KATANA Zirconia range, a ceramic solution for restorative procedures that, owing to its superior translucency and variety of shade options, blends with the surrounding dentition perfectly.

Though it has been used in restorative dentistry since around 2000, zirconia’s popularity as a metal-free alternative has risen dramatically with the recent development of high-translucency options. Whereas older generations of this material possessed an unnatural, chalk-like whiteness that diminished its appearance, newer versions combine mechanical performance with visual superiority to effectively mimic the shading differences between the enamel and dentine layers. Our KATANA Zirconia line is at the forefront of this new standard, as its enamel-like translucency and durability make it suitable for full-contour zirconia crowns, veneers and inlays/onlays in the anterior region. KATANA Zirconia’s multi-layered technology builds upon our emphasis on research and development to provide a highly aesthetic and biocompatible restorative material. 

A pioneering spirit

Much of the advancement in zirconia’s translucency has been the result of innovations in the powder that forms the basis of the discs. Whereas a vast majority of zirconia manufacturers rely on a single, shared provider of this powder, Kuraray Noritake Dental’s powder is proprietary and processed in-house. This pioneering spirit allows KATANA Zirconia to have as natural a translucency and colour as possible—the KATANA Zirconia UTML (Ultra Translucent Multi Layered) series possesses a translucency of 43 per cent and is available in 16 standard shades and four enamel shades, making it an ideal and harmonious fit for almost all anterior restorations between natural teeth.

Our KATANA Zirconia disc range consists of several options designed for full-contour zirconia prostheses, from single crown to full arch: KATANA Zirconia UTML, STML (Super Translucent Multi Layered), ML (Multi Layered) and HT (High Translucent). The multilayer build-up of KATANA Zirconia means that, like in natural dentition, the translucency of restorations made with this material is higher in the incisal than in the cervical areas. Each of the KATANA Zirconia series possesses different translucency and mechanical properties, allowing clinicians to cover a wide range of restorative cases in the anterior and posterior regions.

“The KATANA Zirconia range demonstrates our commitment to providing aesthetic and reliable products for clinicians worldwide,” said Eileen Tan, European Product Manager at Kuraray Dental Benelux. “With KATANA Zirconia, you can bring true naturalness to your prostheses.” 

Peter Schouten, Technical Manager at Kuraray Europe Benelux

Before universal adhesives were available, two major techniques were used: total-etching adhesives, which basically work with phosphoric acid etching on enamel and dentine; and self-etching adhesives, which can be used with or without the option of etching enamel selectively. Prior to the introduction of self-etching adhesives in the late 1990s, dentists used mostly total-etching techniques. While this procedure achieves strong enamel bonding, it can also be very technique-sensitive and involves several steps. As a consequence, dentists welcomed the development of simplified adhesives. In 2011, the new generation of universal adhesives was introduced, with the aim of replacing all previous generations.

The development of universal adhesives was firstly due to the success of self-etching adhesives, but total etching was still advocated. The result, a universal adhesive, must be considered a self-etching adhesive with a phosphoric acid conditioning option on enamel and/or dentine. Maximum flexibility resulting from the freedom of choice in etching technique and the preference of the practitioner was thus obtained.

CLEARFIL Universal Bond Quick, manufactured by Kuraray Noritake Dental, is a single-component light-curing bonding agent indicated for all direct and indirect restorations in combination with all etching techniques (total-etching, self-etching or selective-etching). The adhesive is also indicated for the surface treatment of zirconia- and silica-based ceramics. When compared with other one-bottle universal adhesives, CLEARFIL Universal Bond Quick exhibits RAPID BOND TECHNOLOGY. We asked Peter Schouten, Technical Manager at Kuraray Europe Benelux and a chemist with decades of experience in the dental industry, about his views on universal adhesives and CLEARFIL Universal Bond Quick.

Dental Tribune: Since the introduction of the first universal adhesive, a new generation of adhesives has been created that has enjoyed increasing popularity since then. What is your opinion about the system?

Peter Schouten: For me, the term “universal” remains debatable. There is no clear definition of a universal bonding system yet. When we look at what different manufacturers are saying about universal bonding systems, the term to me applies primarily to the etching technologies and the ability to adhere to all substrates currently used in dentistry, such as silica- or metal-based materials. In this case, we can really speak of “universal”.

What are the advantages and disadvantages of self-etching and total-etching technologies? How are universal adhesives positioned in relation to them?

In my home country of the Netherlands, there is a large group of self-etching users. In many other countries, most dentists still use the total-etching approach. And, of course, there are reliable three-step total-etching systems on the market. However, etching of dentine removes hydroxyapatite and creates a layer of collagen. Afterwards, the dentist tries his or her best to penetrate this layer again with a bonding system. Why not preserve the hydroxyapatite and create a reliable bonding to the hydroxyapatite itself? This is the basis of the gold standard two-step self-etching bonding, our CLEARFIL SE BOND. Now universal adhesives—at least CLEARFIL Universal Bond Quick—provide the advantage that dentists can use any etching technique without worrying about results that are less than optimal. It really is an open system.

How do universal adhesives perform on wet and dry dentine, as well as enamel, in combination with all etching technologies?

I am a strong believer in the self-etching technique as we have proven already. The wetness and dryness of dentine is always an issue in total-etching techniques. With CLEARFIL Universal Bond Quick, the instruction is to rinse and dry. Our universal adhesive has the capability of penetrating the dentine surface quickly and completely.

Kuraray is a pioneer in adhesive systems: the company introduced total-etching bonding in the 1970s and innovative self-etching technology in the 1990s. The secret to success of all universal adhesives seems to be the incorporation of the adhesive molecule MDP (10-methacryloyloxydecyl dihydrogen phosphate) developed in 1981 by Kuraray. What is the function of MDP?

Kuraray has over 40 years of experience in the development of phosphate monomers. In 1976, we had already developed Phenyl-P. By far the most important ingredient in our current bonding systems is the original MDP. We never would have reached the level at which we are today without this phosphate monomer. MDP is capable of creating a long-lasting bond to calcium in hydroxyapatite and to other metals. As MDP can chemically bond to Ca2+ ions, it forms stable, insoluble MDP–Ca salts present as nano-layers at the adhesive interface.

Kuraray Noritake Dental introduced CLEARFIL Universal Bond Quick at this year’s International Dental Show. According to the company, CLEARFIL Universal Bond is the best one-step adhesive ever developed. Briefly, what do you find noteworthy about the bonding agent?

The most remarkable thing is RAPID BOND TECHNOLOGY, enabling us to introduce the benefit of no waiting. This technology works in three steps: first, rapid penetration; second, fast polymerisation; and third, quick formation of a hydrophobic, hydrolytically stable bonding layer. It took our research and development lead Dr Yamato Nojiri many years to develop a cocktail of amide monomers that is superhydrophilic and turns after curing into a stable hydrophobic polymer. The addition of this amide monomer makes it possible to skip the waiting step. Fast polymerisation is achieved by a modified photoinitiator, releasing twice as many radicals in comparison with other initiators. The quickly formed stable bond derives from the combined action of MDP and the amide monomer. MDP bonds to calcium and amide monomer turns into a highly cross-linked hydrophobic polymer network.

The motto of CLEARFIL Universal Bond Quick is “Universal. Easy. Reliable.” Could you please explain that further?

I think that clinicians will be very satisfied with the bonding agent’s performance and wide indication range. It definitely will be used mainly for direct restorations with light-curing composite resins, but also for core build-ups, cavity sealing, treatment of exposed root surfaces and hypersensitive teeth. The pretreatment of the tooth can be done with any of the three etching procedures before applying this adhesive. For selective enamel etching and total-etching, phosphoric acid needs to be applied. I recommend K-ETCHANT Syringe etching gel. It is left in place for 10 seconds, followed by rinsing and drying. The product is very easy to use and not technique-sensitive. The result is a reliable bond because of the use of our proven MDP technology combined with the cross-linked hydrophobic polymer network.

Does CLEARFIL Universal Bond Quick adhere to any dental substrate (lithium disilicate, zirconia and metals)?

Yes, it does. CLEARFIL Universal Bond Quick is the ideal bonding agent in most situations. Bonding to tooth structure and to most direct and indirect filling materials can be performed with CLEARFIL Universal Bond Quick. For the pretreatment of silica-based ceramics (glass-ceramics); however, we advise the use of CLEARFIL CERAMIC PRIMER PLUS for the most optimal results.

What is known regarding combining universal adhesives with light-curing, dual-curing and self-curing composites without the use of primers? Can the dentist really combine them without any problems?

It can be used with all light-curing composites and compomers, with the exception of silorane-based composites. For use with self- and dual-cure composites, CLEARFIL DC Activator is needed. This catalyst activates the dual-curing mechanism of this adhesive. However, the addition of CLEARFIL DC Activator to the adhesive is not required when using it with CLEARFIL DC CORE PLUS or PANAVIA SA Cement Plus.

What do you see for the future of universal adhesives? 

As long as we still need adhesives to bond our composites to tooth structure, I'm almost certain that single-bottle universal adhesives will become the most used systems. In vitro tests have shown good results. A universal, easy-to-use adhesive with few treatment steps and a short working time reduces the risks of errors. Of course, relevant long-term clinical research results are needed to prove the quality. Kuraray Noritake Dental, with its leading adhesive technology, will surely remain the leader in this field.

Reliable adhesive cementation of zirconia

10-Methacryloyloxydecyl Dihydrogen Phosphate is a bit of a tongue-twister for anyone who is not a chemist by profession, so in everyday communication, this adhesive monomer is referred to by the three initial letters: MDP. MDP is indispensable in the dentistry business. For example, reliable adhesive cementation of zirconia restorations would not be possible without MDP. This adhesive monomer was developed by Kuraray Noritake Dental in 1981.

Requirements
Indirect restorations in modern dentistry must fulfil at least three requirements. First of all, they must be tissue-saving. This implies that a full crown is not the first choice, because approximately 70% of the tooth tissue has to be sacrificed for such a restoration. Nevertheless, full crowns are often still indicated by virtue of their mechanical retention. But given that the retention which can be achieved by adhesive cementation is now sufficiently reliable, a less invasive restoration than a crown should be chosen more often. And this choice may very well be for a zirconia restoration. Combined with the preliminary sandblasting of such an adhesive restoration, this choice is now an appropriate one thanks to MDP.

Durability is the second requirement for an indirect restoration. This quality of a restoration is largely associated with the flexural strength of the restoration material. While it has become clear that zirconia achieves the best durability scores, it should be pointed out that the cementation method also contributes significantly to the durability of a facing, inlay, onlay, etching bridge etc., which can nowadays all be realised in zirconia.

KATANA Zirconia UTML

KATANA Zirconia STML

KATANA Zirconia ML

AESTHETICS
Aesthetic acceptability is the third requirement for a modern indirect restoration. This means that porcelain baked on metal has become a thing of the past; full-ceramic materials are now the standard. Zirconia still has a relatively poor reputation in terms of aesthetics due to the extreme whiteness of the earliest examples from the turn of the century. Types of zirconia are now available with varying translucencies, and there are even so-called multi-layer varieties (KATANA Zirconia ML, STML and UTML by Kuraray Noritake), and these new zirconia no longer have to be porcelain-baked. Obviously, baking is still possible, and partial baking is a choice that is frequently made. One of the results of a multi-layer build-up is that the transparency is higher incisally than cervically, as it is in natural elements; the light falls through the incisal margin, but is blocked at the cingulum of the restoration. With a modern zirconia material such as KATANA Zirconia ML, this variable transparency goes hand in hand with a natural colour gradient from cervical to incisal. In a given colour, A1 for example, the cingulum has the corresponding dentine shade body and it passes to incisal in the appropriate enamel colour via two transition shades.

These veneers were made from KATANA Zirconia UTML and coloured using CERABIEN ZR External Stain

SURFACE
The new zirconia materials are changing the way dental technicians operate, as illustrated by the experience of Daniele Rondoni, a renowned dental technician. This professional, from Savona in Italy, has specialised in the use of Multi-Layering technology for ceramic materials (Tecnica della Multistratificazione in Ceramica). According to his philosophy, the choice of restoration materials should be so wide that customised solutions can be realised. Among other things, he believes that there will still be room for baked porcelain on a core of lithium disilicate or zirconia. Using baked porcelain, the dental technician can modify the surface texture of an aesthetic restoration to lend, as it were, a certain age to the restoration.

As for surface structure, the fact that the material allows for the smooth polishing of the occlusal plane is crucial to counteract abrasion by the antagonist and to maintain the occlusal balance. In this respect, the hardness of the material selected is not the main factor; the smoothness and resistance of the surface are far more important.

FLEXURAL STRENGTH
When selecting material for restorations, the dental technician also has the option to choose KATANA Zirconia Ultra Translucent Multi-Layered for veneers or anterior crowns; a zirconia with a translucence comparable to that of glass. This translucence is especially important with anterior restoration which is to be fitted between flawless natural elements, a situation that often occurs after anterior traumas. Such a restoration effected using KATANA Zirconia UTML harmonises with the neighbouring natural teeth, not least because this type of zirconia does not cause the frequently-occurring white appearance common in anterior crown. The modern aesthetic zirconia materials of the second generation are sintered at a temperature of 1,550°. This temperature is maintained for two hours. The dental technician needs to be aware that this temperature differs from the sintering temperature for KATANA Zirconia High Translucent Multi-Layered (1,500 °C). Wide-span bridges can be realised with the latter product, whereas the size of bridges made from KATANA Zirconia Super Translucent Multi-Layer remains limited to a maximum of four elements. KATANA Zirconia UTML can be used for small anterior bridges, but is more suitable for anterior crowns and veneers. The reason for this is that the flexural strength of these highly aesthetic zirconia materials is lower than the flexural strength of the standard zirconia, in which the flexural strength – 1,125 MPa – is sufficient for the production of durable widespan bridges. The flexural strength of the highly aesthetic zirconia varieties (approximately 750 MPa (STML) and 550 MPa (UTML)) is amply sufficient to ensure the durability of solitary aesthetic restorations and limited-span bridges.

Minimum wall thickness of KATANA*

* Maintain 0.8 mm thickness of pressed ceramic in all areas. When trimming of the zirconia framework the framework should be at least 0.4 mm.

PREPARATION
Flexural strength is not the only decisive factor for durability; the method of preparation is also crucial to properties of this material. Chamfer preparation is the required form of preparation,
with no knife-edge outline, no deep shoulder and, obviously, no undercuts. Since the restorations are fixed adhesively, parallel walls or grooves in the preparation are undesirable, and sharp
edges and transitions must be rounded off. If a preparation for a full crown has nevertheless been made, a substantial height difference between the vestibular and palatal/lingual outline is
contra-indicated.
 

Using the new zirconia materials means that a thickness of only 0.4 to 0.8mm need be removed for a veneer in the incisal and cervical area, and only 0.5mm is required in the labial plane,
which corresponds with the requirement to save tissue. For inlays, too, only 1mm is sufficient to achieve a durable result. If the inlay is extended to an onlay, 1mm is also sufficient for the
area where the cusps are capped. For a full crown in the lateral parts, a 1mm space must be kept as a minimum, which thickness must also be maintained for the upright walls of the preparation.

FIXATION
A wide range of possibilities have already been suggested for the durable fixation of zirconia-based restorations. All of these options have also been researched, but according to Prof. Matthias
Kern, there is no point in conducting further research into the best cementation procedure. This scientist and practitioner, who currently works at Kiel University, in Germany, has been involved
in the adhesive cementation of zirconia for nearly twenty years.Based on his wide experience, Kern is convinced that three requirements have to be met to achieve the reliable cementation
of zirconia. First of all, a rubber dam must be applied for the operation, which is obviously easier for partial restorations than for total restorations. It is not only from the perspective of tissuesaving that it is useful to keep the preparation limited for this reason. The second condition is that micro-mechanical adhesion needs to be achieved. For zirconia restorations, the necessary adhesion is obtained by sandblasting the surface. Obtaining chemical adhesion is the third condition. Based on extensive research, Kern is fully convinced that chemical adhesion can only be achieved by using MDP. His first publication on this subject dates back to 1998. It was the use of Kuraray Noritake’s PANAVIA, which did indeed contain MDP, which made it possible to achieve durable synthetic resin bonding to zirconia
after sandblasting.
 

SANDBLASTING
Dentists and dental technicians are apparently somewhat averse to sandblasting*, as evidenced by the extensive research conducted in an attempt to find an alternative. No such alternative has yet
been found. Efforts have been made to fuse a silica layer onto the zirconia to improve bonding, but according to Kern, the results of this procedure – the Rocatec method, for example – have been
disappointing. Nor is the silanisation of a zirconia restoration effective, because zirconia does not react to silan. Dentists who want to achieve the durable cementation of their zirconia restorations therefore have no other option than the purchase of a sandblasting device. Sandblasting can be carried out in a small cabin to prevent the surrounding area of the practice from being
affected. Soft air abrasion is carried out at 0.5 bar, while tight air abrasion is performed at 2.5 bar. The exact pressure is not all that crucial to the adhesion of the zirconia, providing that it is between
0.5 and 2.5 bar**. Kern advises sandblasting at a pressure of 1 bar, so that the surface to be bonded becomes somewhat rougher without this being visible to the naked eye. Obviously, the part of
the restoration that does not require bonding, such as the outside
of a veneer or the dummy of an etching bridge, has to be protected from the effect of the abrasive grains. It is also advisable to apply a colorant (waterproof marker pen) to the area to be sandblasted
prior to the operation. The colour disappears during sandblasting, making it easy to check that the entire adhesive surface has actually been abraded.

SANDBLASTING
Sandblasting of zirconia oxide at a lower pressure is a requirement for an effective adhesion. The
combination of sandblasting and MDP ensures both mechanical adhesion in the micro-roughness and
chemical adhesion between zirconia dioxide and MDP. There is extensive research material to corroborate the effectiveness of this method.

* It had long been assumed that the tetragonal and/or cubic structure would relapse into a
monoclinic state due to sandblasting, as a result of which fracturing would occur because
of the associated expansion. Sandblasting with aluminium oxide particles of 50 micron as a
maximum and a maximum air pressure of 2.5 bar does not, however, cause any damage.
** Airpressure is different from manufacturer‘s recommendation.

Adhesive monomer
The restoration surface can be cleaned using alcohol after the
sandblasting process. This step is optional. If the alcohol becomes
contaminated, for example, by saliva residues, the effect will be
negated, because the sandblasted surface would be contaminated
as well. The choice of the fixation procedure is relatively simple
provided MDP is used. This adhesive monomer was developed in
1981 by Kuraray Noritake Dental to improve the adhesive strength
to hydroxyapatite, and has proved its strength ever since. MDP is
not present in the glass ionomer cements (GIC’s), which, because
of their ease of use, are also sometimes used for the cementation
of zirconia restorations. ‘Don’t!’ warns Kern. It is clear from all the
studies that the composite cements containing MDP provide the
most durable results. The oldest known cement from this category
is PANAVIA EX, which was introduced in 1983. The optimised
PANAVIA V5 was presented recently as the single cement for
all cementation indications guaranteed to work according to a
predictable procedure. All the cements and bondings produced by
Kuraray Noritake contain MDP.

Possibly because Kern conducted his research in Maryland for
two years, he has recorded remarkable results with adhesively
cemented Maryland bridges (etching bridges). It has also become
apparent that, most of the time, an adhesion bridge functions best
with only one wing. For example, if a one-wing zirconia adhesion
bridge is cemented using a cement containing MDP instead of
a lateral upper incisive adhesive, such an adhesion bridge may
remain in place for up to 20 years, to the satisfaction of both
dentist and patient. This restoration, with its survival rate of 95.2%
after five years, therefore qualifies as a permanent restoration.

And the same goes for an onlay bridge made from zirconia.
Sandblasting and MDP; the formula for the durable bonding
of zirconia restorations.

So bear in mind: MDP also stands for a Mega Durable Product.

PANAVIA V5 for the adhesive fixation of zirconia
Achieving a reliable bonding to zirconia – it can be done! Read all about it in the preceding article.

PANAVIA V5 is the successful successor to both PANAVIA F2.0 and CLEARFIL ESTHETIC CEMENT. Thanks to its excellent adhesive bond with both dental tissue and all indirect materials, superior aesthetics, and unambiguous processing, PANAVIA V5 is a popular bonding cement. PANAVIA V5
provides a single cement for all cementation indications and features an unambiguous procedure.

CONCISE INSTRUCTIONS FOR USE
1. Sandblast the zirconia surface to be bonded with aluminium oxide powder (30-50 μm) at low pressure, then clean the restoration in an ultrasound bath and allow it to dry.

2. Apply CLEARFIL CERAMIC PRIMER PLUS to the restoration surface, then proceed to Apply & Go. Dry the entire surface using a gentle air flow.

3. Apply PANAVIA V5 Tooth Primer to the element and leave it to take effect for 20 seconds. Dry the surface with air.

4. Apply PANAVIA V5 Paste to the restoration surface and
position the restoration.

Applying the paste.

Positioning
After placement, remove excess cement using a gauze, a small brush, or something similar.

5. Remove surplus cement and light-cure. Always take account of the self-curing time needed for opaque elements and the use of PANAVIA V5 Opaque..

Daniele Rondoni

Owner of a dental laboratory in Savona

Professor Matthias Kern

Christian-Albrechts University

In restorative dentistry, the core build-up is a crucial step that often has a high degree of difficulty and technique sensitivity. Pairing the brand new CLEARFIL Universal Bond Quick with the reliable CLEARFIL DC CORE PLUS, Kuraray Noritake Dental’s new CLEARFIL core build-up Kit ensures that post and core build-ups can be performed in a stress-free and streamlined manner with as few components as possible.

CLEARFIL Universal Bond Quick

CLEARFIL Universal Bond Quick is the latest universal bonding agent from Kuraray Noritake Dental. A one-step adhesive that can be used in total-etch, selective-etch and self-etch modes, it eliminates the need for waiting, rubbing or applying additional layers. Utilising a combination of Kuraray Noritake Dental’s patented MDP monomer with hydrophilic amide monomers, this dental adhesive is able to penetrate the dentinal surface faster than any other while delivering a stronger, more stable bond.

CLEARFIL DC CORE PLUS

A dual-curing (light-curing with chemical self-curing property), two-component core build-up material, CLEARFIL DC CORE PLUS provides the strongest bond build-ups available when used with CLEARFIL Universal Bond Quick. It is supplied in an auto-mix delivery system, maximising ease of use, and with two types of specially designed guide tips for bulk or intra-canal use, allowing access to deep root canals. CLEARFIL DC CORE PLUS feels and cuts like dentine when it is being prepared, and since its modulus of elasticity is close to that of dentine, occlusal stress can be dispersed. Its non-slumping formula ensures that it maintains its profile, eliminating the need for matrices

Together, the CLEARFIL Universal Bond Quick and the CLEARFIL DC CORE PLUS create a stress-free procedure for build-up restorations in as little steps as possible.. In addition, CLEARFIL Universal Bond Quick’s instantaneous adhesion complements the accelerator for self-curing CLEARFIL DC CORE PLUS possesses. Their combined outstanding properties ensure long-lasting and exceptional clinical outcomes.

“As the replacement for our highly successful CLEARFIL DC CORE PLUS Kit, the CLEARFIL DC CORE PLUS & Quick KIT is the latest example of our ability to take our rigorously-tested research and development and turn it into an optimal dental solution. This well-balanced combination eliminates the need for an activator (CLEARFIL DC Activator). With only two components, the CLEARFIL core build-up Kit demonstrates that excellence in adhesion can be quickly achieved with the right products,” says Mitsuru Takei, Head of Technical Services for Kuraray Europe GmbH.