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

Raw material production

Pre-shaded dental zirconia typically consists of metal oxides, including zirconium oxide, yttrium oxide and aluminium oxide, as well as additives like binders and colour pigments or ions. Most manufacturers of dental zirconia obtain pre-fabricated powder from an external industry partner, the most popular option being Tosoh Corporation. In contrast, Kuraray Noritake Dental relies on an end-to-end in-house process. This includes the production and addition of the components forming the company’s innovative multilayered technology, which makes it possible to match the shades in the polychromatic blanks precisely to the colours of the VITA classical A1-D4 shade guide.

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

Since more powder production steps are carried out in-house, this gives the company full control of the quality of the raw materials, their grain size and the purity of the formulation. It also allows for a precise alignment of the mechanical and optical product properties. Properties of zirconia restorations that are affected by the powder quality and composition include translucency and shade appearance, flexural strength, ageing behaviour and sintering performance.

Blank pressing

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

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

Pre-sintering

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

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

A KATANA™ Zirconia blank ready for milling.

Fast sintering for the laboratory

The unique procedure has a positive impact on the surface smoothness after milling and can significantly shorten sintering times. In fact, the speed sintering program offered for all variants of KATANA™ Zirconia is the fastest one on the market. In the dental laboratory, the sintering times may be reduced to 90 minutes^*for single-tooth restorations and bridges of up to three units.

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

Overview of the recommended sintering protocols.

Fast sintering for chairside

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

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

Unique KATANA™ Zirconia properties

Together, these efforts taken by Kuraray Noritake Dental to produce dental zirconia of exceptionally high quality make all the difference. The KATANA™ Zirconia series - KATANA™ Zirconia Ultra Translucent Multi Layered (UTML), Super Translucent Multi Layered (STML), High Translucent Multi Layered (HTML) and KATANA™ Zirconia High Translucent Mono Layered (HT) - have a homogeneous, high-density structure with low porosity and a high level of purity. This optimises the performance of the blanks during machining.

Surface roughness

SEM image, magnification 33X, of competitor material surface roughness. Image courtesy of Dr Kunkela, Kunkela Research Academy.

SEM image, magnification 33X, of KATANA Zirconia surface roughness. Image courtesy of Dr Kunkela, Kunkela Research Academy.

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

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

Excellent marginal fit

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

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

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

KATANA™ Zirconia Block has hardly any common features with the zirconium oxide that captured dental laboratories two decades ago and was used as a framework material. In many cases, the innovative zirconia serves as a functionally and aesthetically sensible alternative to high-strength glass ceramics. Its flexural strength is higher than that of lithium disilicate, its translucency on a level with the LT variant of the ceramic and its surface – if smoothly polished – antagonist-friendly causing low wear. Apart from its natural translucency, the multi-layered structure of KATANA™ Zirconia Block with four gradient shades precisely imitating natural colour gradients found in anterior and posterior teeth leads to highly aesthetic outcomes.

In order to exploit the full potential of the cubic zirconia KATANA™ Zirconia Block, users of the CEREC system need to adopt slightly different automatic and manual processing strategies than for glass ceramic processing. The following answers to frequently asked questions provide information on the most important differences and tips and tricks that help achieve the best possible results.

COMPUTER-AIDED DESIGN

What is the best position of the restoration in the block to leverage all benefits related to the multi-layered structure?

Ideally, a restoration is positioned in the middle of the block. In addition, the selected block should be one shade darker than the determined shade. This will lead to a natural shade appearance of the resulting restoration. If the restoration is placed at the upper margin of the block, parts of the body shade – and with it chroma – are lost, which makes the restoration appear too light.

How are chipping effects in the area of the milling sprues (most often occurring in bridges) effectively prevented?

Marginal chipping in these areas might appear due to an uneven force distribution during milling. The problem is easily overcome by designing two milling sprues per crown or bridge unit.

COMPUTER-MANUFACTURING

Is wet or dry milling the best option to process KATANA™ Zirconia Block?

The best results are obtained with dry milling. This procedure also leads to time-savings, as there is no need for drying after processing.

When opting for wet milling: Are there any particularities that need to be respected for KATANA™ Zirconia Block?

Those users opting for wet milling and utilizing the same machine for the processing of zirconia and glass ceramics should implement a system utilizing three water tanks. One tank is filled with wash water, the tank used for processing of glass-based ceramics is filled with water and additives (such as Dentatec, Dentsply Sirona) and the one used for processing of zirconia contains purified/distilled water without any additives.

Moreover, a prerequisite for a high quality of the manufactured restorations is that the machine is cleaned thoroughly every time before a different material is processed.

The following components need to be cleaned:

• the milling tools
• the interior of the machine
• the water tank(s)
• all filters

Typically, zirconia reacts to milling additives (Dentatec) in the water with a reduced translucency, so that their use cannot be recommended. Residues of glass ceramic particles found on milling tools, in the water or in the interior of the machine might also have a negative impact on the aesthetic appearance of KATANA™ restorations (typical effect: white spots on the surface).

When is it necessary to replace milling tools used for the processing of KATANA™ Zirconia Block?

It is recommended to replace the tool sets every 10 to 15 units. At this time, the degree of tool wear amounts to approximately 50 percent. Those who continue using the tools accept an increased risk of weakening the oxide ceramic’s microstructure: worn milling tools are likely to produce micro cracks and micro chipping. When these defects occur between the different units of a bridge, they increase the risk for chipping and fractures.

MANUAL POST-PROCESSING

Are there any specific measures to be taken when removing the block from the machine?

When machining is completed, the restoration should be touched only by individuals wearing gloves. Even after thorough washing, bare hands will release fats, which may lead to smear formation and a reduced translucency of the oxide ceramic material.

How are the restorations cleaned after sprue removal?

Powder residues should be removed after processing with a gentle stream of air. Alternatively, a fine (and obviously clean) brush may be used for the removal of the zirconia dust. Powder residues remaining on the restoration surface might lead to the occurrence or white spots or to smear formation. Steam-cleaning of the restoration should be avoided as this measure dramatically increases the pores in the material and alters the material properties.

When is the right time to add fissures and texture to the surface of the restoration and how is this task accomplished?

Ideally, all those details that cannot be incorporated by a milling machine (surface texture, fissures etc.) are added in the restoration’s pre-sintered state, i.e. between milling and final sintering. Diamond milling tools for oxide ceramics should be used at a low speed (7,000 to 10,000 rpm) for this purpose.

TANK MANAGEMENT: CLEANING PROCEDURE AFTER USING GLASS CERAMICS

Be sure the glass ceramic cooling-water tank is installed. Press the Pump button on the touch panel to wash away any glass ceramic powder that is inside the milling chamber. Then, thoroughly flush milling debris from the milling chamber filter and milling powder from beneath the milling chamber filter.

FINAL SINTERING

What are the particularities to be respected during final sintering of restorations made of KATANA™ Zirconia Block material?

Zirconia restorations are subject to volumetric shrinkage (approximately 20 percent) during sintering. Therefore, it is essential to not place the restoration on a rigid carrier during sintering. If the volume of the restoration is reduced while the volume of the carrier is not, the risk of fracture is high. Ideally, the restoration is placed on its largest side.

What measures should be taken to avoid discoloration of a restoration during sintering?

Discoloration (usually leading to a green-yellowish appearance) might be the result of contamination of the sintering furnace with metal oxides. These metal oxides originate from other materials processed in the furnace. They are released during sintering and absorbed by the restoration. Running a decontamination programme on a regular basis is an effective measure that helps prevent discoloration. For this purpose, white zirconium oxide (either collected from odds and ends of non-shaded blanks or purchased) is placed in the furnace chamber and a sintering programme is started. As the furnace CEREC® SpeedFire does not offer a specific decontamination programme, there is no way around working a fiddle: the user simply creates two separate jobs for the sintering of two single crowns, but sinters them together. The second job is used for the decontamination cycle. During this procedure, the white zirconium oxide absorbs the metal oxides, which has a cleaning effect on the furnace.

CHARACTERISATION

Which techniques are best suited for an optical refinement of monolithic restorations made of KATANA™ Zirconia Block?

A material designed for this kind of refinement is CERABIEN™ ZR FC Paste Stain from Kuraray Noritake Dental. The paste-like shading solutions are filled with ceramic particles. Therefore, the optical effects achievable with these pastes are much more durable than those obtained with classical stains. As all pastes are fluorescent, it is possible to produce a natural long-term fluorescence effect without an additional work step. With just four shades of the liquid ceramic – A+, Grayish Blue, Value and Clear Glaze – it is possible to perfectly characterize 85 percent of all restorations made of KATANA™ Zirconia Block material. The firing temperature is 750 °C and the CTE values of CERABIEN™ ZR FC Paste Stain and KATANA™ Zirconia Block are precisely adjusted to each other. The product is also very well suited for glass ceramic characterization.

How is it possible to hold the restoration during characterization?

The easiest option is the use of putty material on a carrier. The crown is simply placed on the unset putty and then positioned on the carrier. The surface of the restoration should be cleaned with a gentle stream of air before applying the pastes. Thanks to the ceramic particles in CERABIEN™ ZR FC Paste Stain, the pastes stay put during processing and do not flow away.

POLISHING

How to ensure a low wear of the antagonist?

Zirconium oxide stands out due to its hardness, which makes careful polishing of the surface a prerequisite for clinical use. After characterization with CERABIEN™ ZR FC Paste Stain, polishing of all occlusal contact areas is mandatory as well. The polishing set Polierset KATANA™ Twist DIA even allows for intraoral use.

PLACEMENT

What kind of resin cement is recommended for the definitive placement of restorations made of KATANA™ Zirconia Block material?

The best possible results are obtained with PANAVIA™ V5. This adhesive resin cement system is responsible for the development of a particularly strong bond between the tooth structure and the restoration, which also has a strengthening effect on the restoration.

Time has always been limited in dental offices, and COVID-19 sanitisation requirements have constrained this even further. Streamlining procedures is a logical strategy for reducing chair time; however, this optimisation must still ensure a high treatment standard and aesthetic outcome.

The CLEARFIL MAJESTY™ ES-2 Universal shades concept from Kuraray Noritake Dental enables this: fast shade determination and creation of aesthetic, long-lasting direct restorations with a single shade in your regular cases; an opaquer or blocker is no longer needed.

CLEARFIL MAJESTY™ ES-2 Universal shades concept consists of a compact shade range:

• The universal (U) shade is for all posterior restorations.
• For the aesthetically more demanding anterior, the user is given two shade options: universal light (UL) and universal dark (UD).
• The universal white (UW) shade is employed for certain cases, such as the restoration of primary teeth.

This simplified shade concept works so well thanks to the integration of Kuraray Noritake Dental’s light diffusion technology, which makes restoration distort light in a similar way tooth structure does. Consequently, the applied material blends virtually invisibly into the surrounding tooth structure.

Convincing mechanical properties make CLEARFIL MAJESTY™ ES-2 Universal shades very well suited for posterior and anterior restorations alike. Just like other members of the CLEARFIL MAJESTY™ ES-2 family, this innovative product offers high strength, favourable wear and balanced shrinkage stress for reliable performance — even in load-bearing posterior areas. The material is easily polished and retains its gloss, yielding a natural-looking appearance that is particularly beneficial in the anterior region.

The CLEARFIL MAJESTY™ ES-2 Universal shades, available in preloaded-tip capsules and syringes, provide a time-saving and simplified means of realising aesthetic, strong and lasting restorations.

This is streamlining of direct composite procedures in optimum form - in short: intelligent simplification!

Clinical case by Dr Zorzin.

Volume 7 of our "BOND" magazine is now published and ready to read!

Content Highlights:

• Composites versus hybrid ceramics
• Flowable composites a universal solution?
• Universal adhesives, is one bottle sufficient?

Start Reading: BOND | VOLUME 7 | 10/2020

Did you know that CERABIEN™ ZR FC Paste Stain has a layer of transparent liquid on top of the liquid ceramic?

This layer protects the material from dust and dirt.

Hence, it is best left in place.

The use of highly translucent, gradient pre-shaded zirconia brings more efficiency into the dental laboratory. Due to the advanced properties of the materials, e.g. from the KATANA™ Zirconia Multi-Layered Series, true-to-life restorations may be created without any or with only a small vestibular layer of veneering porcelain. This saves a lot of time usually required for manual work around steps in the veneering of zirconia frameworks. At the same time, this also allows for a reduced wall thickness, beneficial in the context of minimally invasive dentistry.

In order to leverage the high aesthetic potential and balanced mechanical properties of these types of zirconia, however, it is essential that the restorations are processed under ideal conditions. The most advanced materials with the highest translucency are particularly sensitive to contamination during and after wet milling, contamination of the furnace chamber, and temperature variations during sintering. Possible undesirable effects include a grayish appearance of the restorations and low chroma, green, yellow, blue or gray traces in the restorations, white spots on the surface and variations in colour and translucency.

If carried out on a regular basis, the following measures will effectively eliminate these effects. Hence, they will support users in ensuring consistently beautiful results.

Optimizing the milling process

Blue or gray traces visible in the final restoration are usually the result of contamination of the cooling water with extrinsic particles in the context of wet milling, (which is usually conducted in chairside procedures). In most cases, silica particles left over from the processing of glass or silicate ceramics with the same milling unit are the root of the problem. The effect is easily avoided by thorough cleaning of the milling chamber, the water tank and the filter insert of the milling machine every time a different material needs to be processed. Another solution is dry instead of wet milling, which offers additional benefits such as shorter processing time and better quality edges and surfaces.

Decontamination of the furnace chamber

In general, the chamber of the sintering furnace should be cleaned before sintering. Important measures include the removal of dust inside the sintering chamber and cleaning of the heating elements, both done with a soft brush. The use of compressed air is contraindicated.

Unwanted optical effects that occur on restorations due to contamination of the sintering chamber include white spots on the restoration surface, a blue-grayish appearance and low chroma, and green or yellow traces in the material. White spots on a restoration surface are usually indicators of contaminated alumina sintering beads or the use of the wrong instruments for surface modification and sprue removal. The effect is avoidable through a monthly or even more frequent replacement of the sintering beads (as soon as they show any signs of discoloration) as well as the exclusive use of fine-grid diamond instruments for adjustments prior to sintering.

Alumina sintering beads may be the cause of white spots on a restoration surface if not replaced on a regular basis.

The blue-grayish appearance and low chroma may be attributed to mineral residues from dipping liquids in the chamber. They are effectively removed with the aid of a decontamination program to be selected in the furnace menu, which is run after inserting several residual pieces of a highly translucent, white zirconia blank. As soon as the decontamination cycle is completed, the chromatic intensity of the residual blank parts indicates whether a second cycle is required. In order to prevent the occurrence of a grayish appearance in new restorations, it is recommended to perform a decontamination program at least once per month.

Pieces of a white zirconia blank left over after milling.

MoSi₂ heating elements: Regeneration needed

If a restoration appears to be green or yellowish, it is most likely that the furnace is equipped with aging molybdenum disilicide (MoSi₂) heating elements in need of regeneration or replacement. The inner part of the elements is made of molybdenum (Mo), which is usually covered by a protective layer of silica (SiO₂). This layer is naturally built up during sintering at a temperature range between 1,000 and 1,600°C. As the thickness of the layer grows, its intrinsic residual compressive stress increases. This stress, as well as possible extrinsic influences, e.g. originating from acidic dipping liquids, may finally lead to cracks and a breakup of the protective layer. Once damaged, the molybdenum core is exposed. At a low temperature range of 400 to 600°C, the molybdenum reacts with oxygen in the sintering chamber, a process referred to as pest oxidation. The resulting molybdenum oxide (MoO₃), together with ions or metal oxides from colouring agents, is responsible for the green-yellowish discoloration on the surface of the restorations.

Restorations displaying greenish surface pigmentation.

Molybdenum disilicide heating element with a protective silica layer bursting off, leading to pest oxidation and the contamination of elements in the sintering chamber.

Regeneration firing, which involves a rapid heating rate and a long firing phase at approx. 1,450°C, aims at regenerating the layer of silica. This measure, however, works only a limited number of times, as a repeated process of pest oxidation and regeneration leads to aging of the heating element itself. Hence, it will ultimately lead to the need for replacement. The whole issue of pest oxidation may be effectively avoided by the use of a furnace with silicon carbide heating elements, which are highly aging-resistant and do not cause any discoloration. A positive side effect is that these types of heating elements deliver more constant temperatures.

Temperature control

Variations in translucency or chroma and pigmentation of restoration surfaces are often due to deviations of the actual sintering temperatures from the recommended temperature curve. The only way to solve this issue is temperature calibration. This measure is not only a prerequisite for aesthetic results, but also has a decisive impact on the mechanical properties of the restorations: if the maximum temperatures are too high, for example, the flexural strength of the zirconia materials may be expected to decrease¹.

Effect of temperature differences during sintering on restorations made of KATANA™ Zirconia UTML: The restorations were sintered at the same nominal temperatures in three different furnaces!

Temperature control is usually carried out with the aid of TempTABs or PTCRs (process temperature control rings). They are placed into the furnace on a sintering tray and typically processed by running a calibration cycle. After sintering, the tab or ring diameter is determined. As TempTABs and PCTRs exhibit controlled shrinkage, it is possible to calculate the actual sintering temperature based on the measured diameter. A conversion table supports the user in determining the deviation between the temperature actually reached and the temperature displayed on the furnace. Subsequently, the values displayed on the furnace are adjusted if necessary.

TempTAB on a sintering tray with restorations ready for sintering.

General recommendations

In order to set the stage for brilliant aesthetics and ideal properties of zirconia restorations, it is essential to ensure optimal processing conditions. Instead of troubleshooting carried out whenever discoloration appears after sintering, it is advisable to take the following actions on a regular basis as preventive measures:

• Cleaning of the milling machine’s water tank every time before starting to mill (wet milling only)
• Strict adherence to the sintering protocols recommended by the material manufacturer
• Removal of the dust from the sintering chamber and heating elements with a soft brush before each use
• Replacement of the alumina sintering beads whenever they show signs of discoloration (at least once per month)
• Exclusive use of fine-grid diamond instruments for sprue-removal and pre-sintering adjustments
• If possible: Use of furnace with silicon carbide heating elements
• Furnaces with molybdenum disilicide heating elements require constant visual control and regular regeneration cycles
• Running of a decontamination program with decontaminating powder or white zirconia residues (y-TZP) at least once per month
• Temperature control and calibration at least once per month

With these simple measures, it is possible to maximise the full potential of KATANA™ Zirconia Multi-Layered Series from Kuraray Noritake.

References
¹ Stawarczyk, B., Özcan, M., Hallmann, L. et al. The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio. Clin Oral Invest 17, 269–274 (2013).

Dentistry is currently experiencing an interesting evolution. While dentists are becoming increasingly specialised, the demand for products that can be used for all indications continues to grow. These systems and materials are part of a universal trend in dentistry—a trend that Kuraray Noritake Dental is extremely well suited to accommodate.

Advancing adhesive dentistry

As the technology has developed, dental adhesives have progressed from no-etching to total-etching and then self-etching systems. In 1978, Kuraray Noritake Dental introduced CLEARFIL™ BOND SYSTEM-F, the world’s first total-etching adhesive system. More than four decades later, the company is still setting standards with CLEARFIL™ Universal Bond Quick, a one-step dental bonding agent that can be used in total-etching, self-etching and selective-etching modes.

Combining Kuraray’s original MDP monomer with hydrophilic amide monomers, CLEARFIL™ Universal Bond Quick is designed to be less technique-sensitive than other one-step solutions and has been proved scientifically to deliver stronger, more stable bonds.

It is not just bonding agents that are becoming universally applicable either. A dental cement like Kuraray Noritake’s PANAVIA™ SA Cement Universal builds upon the success of previous generations of PANAVIA™ to deliver optimal bonding to dental tissue as well as to metal and zirconia materials. This self-adhesive resin cement always requires the same procedure, even when bonding porcelain, lithium disilicate and composites, without the need for a primer. The reason? It’s the addition of a unique long carbon chain silane.

Universal composites and cleaners

The silane technology behind PANAVIA™ SA Cement Universal can also be found in CLEARFIL MAJESTY™ ES Flow, a universal flowable composite suitable for all cavity classes. Its small, durable filler particles help to ensure excellent flexural and mechanical strength, while special cluster fillers provide a light diffusion effect similar to that of natural teeth. Creating aesthetically natural and reliable restorations is easier than ever with CLEARFIL MAJESTY™ ES Flow.

As the latest addition to the CLEARFIL MAJESTY™ ES series, CLEARFIL MAJESTY ES-2 Universal offers a smart and easy-to-use system that will work for the vast majority of your daily cases. Its light-cure, radiopaque restorative material which provides accurate color matching, high polishability and excellent physical properties, makes the product ideal for both anterior and posterior restorations. What makes this Universal series truly special is that the shades cover all shades of the VITA classical A1-D3 shade standard with a limited number of syringes/PLTs depending on the cavity class. If you opt for CLEARFIL MAJESTY™ ES-2 Universal, just a few shades will do the trick.

And when considering Kuraray Noritake’s forays into universal solutions, let us not forget the new KATANA™ Cleaner, a non-abrasive cleaner that, unlike other options on the market, can be used both intra- and extra-orally. Backed by extensive scientific research, the KATANA™ Cleaner comes with a single-handed delivery cap and an extremely straightforward method of application: simply apply with a rubbing motion for at least 10 seconds, rinse with water and air-dry before cementation.

Making dentistry more streamlined

The modern dental practice is often multidisciplinary in its nature, which can result in the need to store many more products than there might be space for. Through these universal products and others, Kuraray Noritake is aiming to make dentistry simpler and more efficient.

At Kuraray Noritake Dental Inc. we are proud that our products are being developed using innovative technologies, paying attention to detail and keeping in mind the needs of our customers.

We are committed to offering outstanding products that provide dental professionals with the flexibility for self-expression and creativity, adding value and delivering superb aesthetic results to each and every procedure.

Usability, simplicity and, of course, quality always in mind - providing dental professionals with materials that will make their daily practice stress free.

As a prove that our products meet the needs of dentists and lab technicians alike, we are happy to share with you the EC Certificates of Full Quality Assurance System that we have received from The Notified Body.  Those can be downloaded below.

Chairside products

Labside products

When it was first introduced to restorative dentistry in the early 2000s, zirconia was an opaque, unnatural-looking substance with a chalk-like whiteness. Two decades later, technological and material advances have meant that zirconia is now a highly aesthetic and durable ceramic solution for a variety of procedures. Leading the way is Kuraray Noritake Dental’s KATANA™ Zirconia series, which can now be integrated at every step of the restorative workflow.

The pioneering nature of KATANA™ Zirconia

Key reasons for zirconia’s improvements as a dental material are continued innovations in the powder that forms the basis of the discs. While a majority of dental zirconia manufacturers rely on a single shared provider of powder, Kuraray Noritake’s zirconia materials are unique in that they are produced in an end-to-end in-house process. From the proprietary powder technology through to disc pressing and pre-sintering, KATANA™ Zirconia is produced to ensure unparalleled purity and unmatched quality.

Multilayered technology

Three of the four types of KATANA™ Zirconia—UTML, STML and HTML—incorporate Kuraray Noritake’s original multilayered build-up technology. This innovative four-layer structure faithfully replicates the translucency and colour gradation of natural dentition, resulting in an eye-pleasing final restoration. Furthermore, each member of the KATANA™ Zirconia series possesses different translucency and mechanical properties, allowing clinicians to cover a wide range of anterior and posterior restorations.

A zirconia series embedded in a system of products

Thanks to Kuraray Noritake’s emphasis on research and development, the KATANA™ Zirconia family is embedded in a complete system of products for polishing, staining, glazing, porcelain veneering and cementation in order to deliver outstanding treatment outcomes.

CERABIEN™ ZR FC Paste Stain allows for the easy characterisation of full-contour zirconia restorations. Available in 27 different shades, it delivers an extremely controllable transparency that enables the creation of highly aesthetic restorations.

When cementing a zirconia restoration during the trial fitting stage, the new KATANA™ Cleaner will surely come in handy. This non-abrasive universal cleaner from Kuraray Noritake helps to remove contamination, thereby delivering the bond strength patients deserve. Its relatively low pH value of 4.5 also means that, unlike other dental cleaners, it can be used both intra-orally and extra-orally.

Of course, when finally cementing the restoration, the dentist needs to be confident that the cementation will be both reliable and durable. PANAVIA™ V5 is Kuraray Noritake’s strongest cement yet and offers unrivalled procedural simplicity and predictability. This amine-free paste is available in five different shades that have been scientifically demonstrated to exhibit less post-polymerisation colour variance than amine-based cements. For aesthetic and stable cementation, PANAVIA™ V5 is the best option.

It is clear that, with the translucent KATANA™ Zirconia series and these associated products, Kuraray Noritake has established a fully integrated system that can work for almost any prosthetic workflow. KATANA™ Zirconia is key to durable metal-free restorations.

Phosphoric acid is not only used for etching enamel and dentin surfaces within dental bonding procedures, but also frequently as an intra- and extra-oral cleaning agent for tooth structure and dental restorations. But is phosphoric acid always the right choice?

Direct Restorations

Many bonding procedures are performed using self-etch adhesive systems. When applied to the prepared tooth surface, the acidic monomers in the primer and/or the bond partially remove and modify the smear layer, resulting in a thin hybrid layer. A substantial amount of hydroxyapatite crystals remain on the slightly etched surface, enabling both chemical and mechanical adhesion between the adhesive and the dental tissue. If the bonding surface in the cavity is contaminated e.g. with blood or saliva, and phosphoric acid is applied for cleaning and decontamination, it etches the tooth structure, too, resulting in the removal of HAp. This will prevent the desired chemical adhesion, between the bonding system and the tooth, which may lead to compromised bond strength. Hence, cleaning with phosphoric acid may have a negative effect in this context and cannot be recommended.

Great cleaning results with no negative effect on the performance of the dental adhesive are obtained with the universal cleaning solution KATANA™ Cleaner. It contains an MDP salt of triethanolamine (MDP-TEA), as well as 'free' MDP. With a pH of 4.5, KATANA™ Cleaner is essentially neutral, meaning that, unlike phosphoric acid, it does not remove hydroxyapatite from the tooth. However, it does still effectively eliminate any saliva and/or blood contamination.

Indirect Restorations

For materials containing glass, such as lithium disilicate and feldspathic porcelain, phosphoric acid is a tried-and-tested agent for removing contamination, such as deposits produced when etching these materials with hydrofluoric acid. However, routine use of phosphoric acid to remove contamination from indirect restorations may not be wise. In fact, its use on zirconia is not recommendable, as it could inhibit the desired chemical adhesion of phosphate monomers in the bonding agent to the surface of the zirconia restoration.

When cementing prosthetics using self-adhesive resin cements like PANAVIA™ SA Cement Universal or cements that use self-etching primers (e.g. PANAVIA™ F2.0 or PANAVIA™ V5), the use of phosphoric acid on dentin is not recommended for the same reasons as in the case of direct restorations.

No pitfalls, no restrictions

Unlike 35% phosphoric acid, KATANA™ Cleaner is a product that cleans reliably without inducing negative side effects – independent of the type of tooth structure, kind of restorative material and planned bonding procedure. Hence, it is a universal cleaning solution that allows you to streamline your procedures.