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

A clinical case created by Dr. Shoji Kato of Takanawa Dental Office, Japan

PRODUCTS USED IN THIS CLINICAL CASE

KATANA™ Zirconia Multi-Layered Series

Our KATANA™ Zirconia series brings naturalness to all
prosthetics. Make natural veneers and natural full contour
prosthetics out of zirconia. Plus large dentin-like frameworks.
KATANA™ Zirconia UTML is a high translucent disc, which meets
the requirements of highest translucency level for anterior crowns
and veneers. All layers are highly translucent, whereby the color
saturation is reduced in the incisal area. The transparency of the
natural enamel is copied and the abutment shade is absorbed.

KATANA™ Zirconia STML is a multi-layered zirconia disc
where light is transmitted in the incisal area and blocked in
the cervical area. Due to its color and translucency gradient,
more opacity in the cervical area and more translucency in the
incisal area are achieved.

KATANA™ Zirconia ML, the pioneer of zirconia with a
natural color gradient, is made for large dentinal frameworks.
Its natural opacity makes it the ideal base to cover it with
hand-made ceramics. 

PANAVIA™ V5
One Cement. All cement indications. One prime procedure.
Start with priming the tooth using PANAVIA™ V5 Tooth
Primer. Then prime and roughen the prosthetic using
CLEARFIL™ CERAMIC PRIMER PLUS and apply the pre-mixed
cement. PANAVIA™ V5 comes in five aesthetic shades and
the original MDP assures a durable bond. On the tooth and
the prosthetic.

CLEARFIL™ CERAMIC PRIMER PLUS
The universal prosthetic primer for almost all prosthetic surfaces.
It durably bond to ceramics (lithium disilicate, zirconia), hybrid
ceramics, composite resins and metals. The original MDP monomer
bonds to metals and metal-oxides such as zirconia. Silane coupling
agent γ MPS guarantees a strong adhesion to composites, glassceramics
and hybrid ceramics. This perfect mixture of ingredients
will give you long lasting adhesion to virtually all dental materials.

By Paul de Kok, Amsterdam (KVPA) Periodontic Clinic & ACTA

Picture 1

The Patient
Joris reported to the clinic with two discoloured composite two discoloured class IV composite restorations in tooth 11 and 21 11 and 21 (picture 1). These vital teeth were traumatized in his childhood. He was not satisfied with the aesthetics of the restorations neither with the overall shape and colour of the two teeth. It was therefore decided to make porcelain facings for tooth 11 and 21.

Picture 2

The preparation
In order to limit the sacrifice of healthy tooth tissue while still creating sufficient space for the porcelain, a preparation was chosen with an incisal reduction of 1.5mm and a buccal reduction of 0.5mm. A so-called depth cutter – a diamond drill with 0.5mm deep recesses – was used to achieve this (picture 2).

Picture 3

To be able to adjust the shape of the mid-line to the new facings, cutting was carried out centrally through the contact. From the distal aspect the contactpoint was remained. The thin shoulder was positioned equi-gingivally, so that a dry operative field could be achieved without damage to the gingiva.

The preparations were then finished using fine drills and polishing discs. The existing, well bonded diamonds composite restorations were left in situ (picture 3).

Picture 4

Since the transparent facings are very thin, the colour of the cut teeth is significant. The colour of the cores was therefore matched using the Natural Die colour guide (picture 4). Finally, impressions were made. Temporary restorations were placed by means of 4 spot etching points and bonding.

Picture 5

Cementation
To combine superior aesthetics with adequate strength, pressed lithium disilicate restorations were chosen for Joris. Prior to cementing the facings, they were tried for size and checked for marginal integrity, contact points, occlusion/articulation and aesthetics. Then the correct cement colour was established by testing the facings with various try-in colours PANAVIATM V5 Universal (A2); Universal (A2) appeared to be the most appropriate colour in Joris’s case. The teeth were then polished with pumice and the facings were cleaned with alcohol, after which the teeth from 14 up to and including 24 were isolate by a rubber dam.
An incisor clamp was placed on the first teeth to be cemented. The facing was tried for fitting once more to ensure that it was free of contact with the rubber dam or the clamp and that the operative field of the preparation was totally dry (picture 5).

Picture 6

The facing was etched with 9% fluoricacid (picture 6) for 20 seconds to achieve micro-mechanical retention.

Picture 7

It was then rinsed with water for 20 seconds before being neutralised in a solution containing ceramic neutralising powder. CLEARFILTM CERAMIC PRIMER PLUS was then applied to the facing. This ensures chemical bonding between the facing and the composite cement thanks to the incorporated silane and MDP. The adjacent teeth were separated by means of a transparent strip, after which the preparation was etched with 35% phosphoric acid (picture 7). TOOTH PRIMERTM was applied after thorough rinsing with water and drying after it had taken effect for 20 seconds.

Picture 8

A thin layer of PANAVIA V5 cement was then applied to the facing. The facing was placed on the preparation with the application of light finger pressure. A microbrush was used to remove the major excess along the margins. The cement of the buccal and palatal aspect was light cured for 5 seconds. A sharp scaler and floss were used to remove the final excess. Glycerine gel was then applied to the outline to avoid oxygen inhibition during curing. The cement was finally light cured from both sides for 20 seconds, the glycerine gel was rinsed away and the margins were finished by means of a composite polishing stone. After placement of the first facing, the rubber dam clamp was moved to the neighbouring tooth so the cementation of the second facing could proceed. This facing was once more tried for fit, pre-treated and cemented in an identical manner (picture 8).

Picture 9

The result
The facings were checked a few weeks later (picture 9). Joris was very satisfied with the aesthetics of his two central incisors. The transitions from tooth to restoration were invisible and the gingiva was healthy.

Picture 10

The transparency, surface structure and gloss are better adjusted to the neighbouring elements and to Joris’s smile (picture 10).

Dentist:

Paul de Kok, Amsterdam Periodontics Clinic

Paul de Kok studied dentistry at the ACTA and is an authorised restorative dentist at the Amsterdam Periodontic Clinic (KvPA), where he treats referred patients with restoration and aesthetic issues. In addition, Paul teaches indirect restorative dentistry at the Oral Functional Anatomy faculty of ACTA as well as conducting research in the Materials Science department. He also delivers lectures about this discipline at both a national and international level.

Dental technician: Eric van der Winden, Oral Design Center Holland

PAUL DE KOK USED CLEARFIL CERAMIC PRIMER PLUS AND PANAVIA V5 FOR HIS CASE STUDY

Adhesive cementation of high-translucent zirconium oxide restorations

The definitive integration of full ceramic restorations throws up a lot of questions in everyday practice life. Many of these are answered in the “ACTA Report”. The Congress lectures (ACTA Congress) held by Prof. Matthias Kern (Kiel/Germany) and Daniele Rondoni, ZTM (Savona/Italy) have been condensed down to the essentials and presented in a practical manner. The focus is placed on zirconia materials and it’s adhesive, MDP based cementation.  

Until now, the preferred cementation method for dental zirconia was conventional luting. Through the establishment of high-translucent zirconia materials (e.g. KATANA^TM UTML/STML, Kuraray Noritake Dental), however, the standards have changed. The outstanding aesthetic properties of the new zirconias are to be supported through a composite resin cement. In the ACTA Congress held at the ACTA University (Amsterdam/Netherlands,), Prof. Matthias Kern and Daniele Rondoni, ZTM evinced exciting information on the subject. Prof. Kern underlined the significance of the MDP monomer for the reliable adhesive cementation of zirconia restorations. He is convinced that the chemical adhesion can only take place using MDP based resin cements (PANAVIA^TM, Kuraray Noritake Dental). Rondoni presented the advantages and the material properties of the new zirconias.

In the “ACTA Report”, the scientifically founded explanations, which have proven their worth in practice, have been summarised. The reader learns for example which prerequisites are required for adhesive cementation. In addition, valuable preparation and material-relevant processing guidelines are provided. The explanations on the functional method of the adhesive cementation and the MDP monomer are presented in an interesting way. The original MDP monomer was developed in 1981 by Kuraray in order to improve the bond strength on tooth structure and dental metal alloy. Today, MDP monomer (the basis of PANAVIA^TM resin cements) are characterised by their strong adhesion to metal(oxides) incl. zirconia.

PANAVIA^TM V5 is an aesthetic and adhesive resin cement for all cementation indications, based on MDP technology. Prof. Kern published a work on bonding to zirconia ceramic with MDP for the first time in 1998. His well-founded experiences are practically summarised in the “ACTA Report”.

Today sandblasting and MDP is the proven formula to reliable adhesive cementation of zirconia.

The “ACTA Report” is a recommended read for all dentists and dental technicians who have integrated full ceramic restorations into their everyday working lives. Well-founded and practical!    

For more information

Email dental.eu@kuraray.com or phone +49-(0)69-305 85 980

You can read the full report  here.

PRESS RELEASE

EXPERTS PRESENT IMPORTANT FINDINGS ON THE ADVANCED BONDING PROPERTIES OF THE NEW ONE-BOTTLE UNIVERSAL ADHESIVE: CLEARFIL™ UNIVERSAL BOND QUICK

Hattersheim, Germany – January 2017  

The 2nd December 2016 saw the annual Kuraray Noritake Expert Symposium in Frankfurt with more than 60 leading adhesives and composites experts from universities all over Europe meeting to discuss and share new advances in the world of adhesive technology, notably CLEARFIL™ Universal Bond Quick: the new one-bottle universal adhesive by Kuraray Noritake Dental which is to be launched in Europe in February. Prof. Dr. Bart Van Meerbeek from the KU Leuven - BIOMAT - University Hospitals Leuven/Belgium, acted as Symposium Moderator.

Starting off the day’s proceedings, Yusuke Fujimura, Technical Manager and Chief Developer at Kuraray Noritake Dental demonstrated how, unlike most other bonding agents, CLEARFIL™ Universal Bond Quick works instantly, removing the need for waiting time, extensive rubbing or multiple layer application. This was followed by Professor Dr Bart Van Meerbeek who discussed the problems associated with conventional total-etch methods whereby strong phosphoric acid is applied to the dentin, dissolving the natural tooth protector hydroxyapatite and exposing the collagen matrix. He posed the fundamental question:” Why demineralise the tooth with strong acids only to remineralise it again?”

Also on the agenda were four individual studies, each tested far over and above the legally-required ISO standards, providing insights into the fact that the longevity prognosis for bonded restoration is absolutely dependent on both the quality of the adhesives and the effect of the procedural steps. Luc Randolph, Materials Research Engineer at the University of Louvain-la-Neuve/Belgium, reported on shear bond strength tests using the new universal adhesive CLEARFIL™ Universal Bond Quick concluding that: “Among the all-in-one universal alternatives, the new CUBQ technology appears equally efficient despite the absence of waiting time after application, making it a more user-friendly and convenient option than its competitors.”

Prof. Dr. Amélie Mainjot from the University of Liège/Belgium went a step further demonstrating highly positive bond results for zirconia which showed, even after thermocycling, comparable bond strength to Vita Mark II class-ceramic instead of pre-test failures when not treated with CLEARFIL™  Universal Bond Quick.

Finally, Prof. Dr. Mutlu Özcan from the University of Zurich/Switzerland, concluded that, whereas the described method of air-abrasion increases the adhesion results for the majority of adhesives, air-abrasion may not be needed for CLEARFIL™ Universal Bond Quick.

Over the course of the day the speakers presented many enlightening research results which participants were able to take away with them. However, before they left, Prof Van Meerbeek called for a panel discussion so that speakers could collaborate with the audience on requests for future development and findings.

CLEARFIL™ Universal Bond Quick is launched in Europe on the 1st of February 2017. 

Read the full report: Kuraray Noritake Symposium Report (PDF: 360 Kb)

Kuraray celebrates its 90th anniversary in 2016. We take the opportunity of this occasion to offer you a glimpse of the history of Kuraray from a new perspective. The name Kuraray represents more than 8,300 employees and an annual turnover of approximately 3.7 billion euros. Kuraray was founded in Kurashiki, Japan, in June 1926, by Magosaburo Ohara. Kuraray began with the domestic production of Rayon, a synthetically produced cellulose fibre referred to as artificial silk, a new and innovative product at the time. 

The name KURARAY is derived from the location: Kurashiki and the product manufactured: Rayon. The development of this branch of production developed very quickly in Japan, with many other major manufacturers establishing themselves during this period. Whereas others recruited their technicians and experts from elsewhere, Kuraray established the Kyoko Research Laboratory, which was managed by the University of Kyoto to generate expertise and support for the development of the required technologies. Ohara also committed himself to cultural and social projects. The building of an art gallery and the financing of an orphanage represent only two of his many projects in Kurashiki. The Ohara Museum of Art was the first private museum of Western art in Japan.

Ohara considered the dreadful conditions in which employees commonly worked and lived at the time to be unacceptable; he was not a profit-driven employer, and attempted to solve such issues. He ensured that decent accommodation, fitness facilities and nursery schools were built to provide young employees, or families who had left their homes to work for Kuraray, with everything they needed for education and a healthy and culturally rich lifestyle.
One of the largest general hospitals in the west of Japan, the Kurashiki Central Hospital, was originally founded by Kuraray to promote the well-being of employees and their families. It is still considered to be one of the most famous hospitals in Japan.

With the production of Kuralon in 1950, developed from the in-house manufactured products PVA and vinyl acetate, Kuraray expanded to become the specialist chemical company it is today. Always intent on making a contribution to the good of society, Kuraray addressed the subject of environmental protection very early on. The visionary Ohara was aware of the seriousness of environmental pollution, and made great efforts to prevent it.

Internationally too, Kuraray has remained aware of its social responsibilities. After the war, a production facility was opened in China which helped to improve the poor post-war living conditions of the Chinese population.
Today, Kuraray is a leading global manufacturer of the specialist chemicals used in many aspects of daily life. Kuraray has always viewed its employees as its most important asset, and continues to do so to this day.

During my presentations I am often asked why clinical research into bonding systems is conducted using class V situations.

The non-carious class V lesion is most suitable for this type of research for a number of reasons. Unquestionably, the main reason is the fact that such lesions present little or no macro retention. It must be remembered that if a cavity presents macro retention, loss of adhesive strength in the bonding interface will not automatically lead to loss of retention.

Other major reasons (in no particular order) are that such lesions occur relatively often, but also that in general they are situated in an easily accessible area and do not demand complex restoration technology. The configuration factor is low (ratio between free and bonded areas) and does not therefore cause much shrinkage stress. In addition, both enamel and dentine are involved in the restoration, although in some studies efforts are made to limit bonding to enamel (for example, in Van Dijken et al., Clinical long-term retention of etch-and-rinse and self-etch adhesive systems in non-carious cervical lesions. A 13 year evaluation. Dent Mat 2007).

The restoration is then re-assessed periodically. Obviously, loss of retention is considered, and sometimes restorations are also assessed on marginal integrity, marginal discolouring and aesthetics.

Whenever a restoration goes wrong, this is noted as a failure. The survival/lifetime of restorations is expressed in an Annual Failure Rate; for example, an AFR of 4.6 means that, on an annual basis, 4.6% of the restorations failed in the course of the study.

Phosphoric acid, sometimes also called orthophosphoric acid, is a substance that is used frequently in the practice of dentistry, mostly in concentrations between 30 and 40%. It is a proven substance for the etching of enamel (Buonocore 1955). It also entails hazards, because contact with the eyes and skin may cause severe irritation, blistering and burns.

The substance should only be applied where its use is intended, and proper control is of the essence. The use of a coloured gel is therefore recommended, preferably of a thixotropic type. The application of a cofferdam is also definitely recommended, and the patient should wear protective glasses ( the practitioners should obviously also wear protective glasses). When removing the etching gel, the main volume should first be sucked away using a saliva ejector without a cap. The area should then be rinsed clean with a spray mist suction device under continued suction.

If the etching gel should unintentionally get onto the skin or, even worse, into the eyes, the affected area should be rinsed with plenty of water until the patient no longer feels any pain in the affected area. In such a case, it is recommended that medical assistance be sought.

This article is based on a publication in the British Dental Journal Vol 217 No.2 Jul 25 2014
Link to the publication. 

I would like to refer to a recently conducted study by Garcia et al. to reply to this question, which derives from practice. The study examines the effect of three desensitisers on the bonding strength to dentine of a composite cement.

The study concluded that the effect is dependent on the material. Gluma Desensitizer (Heraeus Kulzer) and Super Seal (Phoenix Dental) decreased the bonding strength, whereas TeethmateTM Desensitizer (Kuraray Noritake) improved the bonding strength. The researchers obviously consider it necessary to conduct further research into the workings of TeethmateTM Desensitizer, a cement that contains calcium phosphate.

Clinical significance:

TeethmateTM Desensitizer, a material containing calcium phosphate, may serve as a useful new generation of desensitisers for use prior to the cementing of indirect restorations.

Click here for the research abstract.