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.

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.

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.

By Dr Alessandro Devigus

Fig. 1. Initial situation with fractured PFM crown.

Fig. 2. Initial situation with fractured PFM crown – problem of deep bite.

Fig. 3. Situation after removal of old crowns and placement of retraction cord.

Fig. 4. Milled crowns before sintering with Speedfire.

Fig. 5. Crowns after sintering.

Fig. 6. Try-in of sintered crowns.

Fig. 7. Crowns after glaze and stain.

Fig. 8. Try-in of finished crowns.

Fig. 9. Crowns after adhesive cementation with PANAVIA™ V5 A2.

FINAL SITUATION

Dentist:

DR. ALESSANDRO DEVIGUS

Dr. Alessandro Devigus received his degree from Zurich University, Switzerland, in 1987. Since 1990 his working in his own private practice with a focus on CAD CAM and Digital Dentistry. He is also CEREC Instructor at the Zurich Dental School.

Dr. Alessandro Devigus is an active member of the European Academy of Esthetic Dentistry (EAED), founder of the Swiss Society of Computerized Dentistry, Neue Gruppe member, ITI fellow and speaker.

Dr. Devigus is editor-in-chief of the International Journal of Esthetic Dentistry, author of various publications and an international lecturer.

By Dr Alessandro Devigus

Fig. 1. Initial situation with fractured PFM crown.

Fig. 2. Initial situation with fractured PFM crown – problem of deep bite.

Fig. 3. Situation after removal of old crowns and placement of retraction cord.

Fig. 4. Milled crowns before sintering with Speedfire.

Fig. 5. Crowns after sintering.

Fig. 6. Try-in of sintered crowns.

Fig. 7. Crowns after glaze and stain.

Fig. 8. Try-in of finished crowns.

Fig. 9. Crowns after adhesive cementation with PANAVIA™ V5 A2.

FINAL SITUATION

Dentist:

DR. ALESSANDRO DEVIGUS

Dr. Alessandro Devigus received his degree from Zurich University, Switzerland, in 1987. Since 1990 his working in his own private practice with a focus on CAD CAM and Digital Dentistry. He is also CEREC Instructor at the Zurich Dental School.

Dr. Alessandro Devigus is an active member of the European Academy of Esthetic Dentistry (EAED), founder of the Swiss Society of Computerized Dentistry, Neue Gruppe member, ITI fellow and speaker.

Dr. Devigus is editor-in-chief of the International Journal of Esthetic Dentistry, author of various publications and an international lecturer.

By Dr Luca Dusi

For purely aesthetic reasons, this patient asked for the reconstruction of her cone-shaped upper right lateral incisor (12). The patient was offered a treatment including a first phase of orthodontic therapy aimed at recovering the space necessary to be able to reconstruct the lateral incisor to its ideal size. As the patient refused to undergo this orthodontic therapy, it was decided to restore the tooth with resin composite and match its size to the space already available.

The adhesive system used was CLEARFIL™ SE BOND 2, while the restoration was created with the new composite CLEARFIL MAJESTY™ ES-2 Universal. Although this material is designed for the single-shade technique with only two shades matching the anterior tooth shades, I decided to combine both pastes to achieve the best possible outcome. The shade UD (Universal Dark) was used to reconstruct the cervical and central portion of the lateral incisor. The incisal portion was restored with UL (Universal Light).

Fig. 1. Initial situation with a cone-shaped upper right lateral incisor (12).

Fig. 2. Image of the initial situation taken with a polarising filter for shade evaluation purposes.

Fig. 3. The new CLEARFIL MAJESTY™ ES-2 Universal composite with only two shades for the anterior region was chosen. It offers a good optical integration thanks to Kuraray Noritake Dental’s Light Diffusion Technology.

Fig. 4. Shade determination with the aid of cured samples of CLEARFIL MAJESTY™ ES-2 Universal UL (Universal Light) and UD (Universal Dark) on the tooth surfaces.

Fig. 5. Isolation with rubber dam.

Fig. 6. CLEARFIL™ SE BOND 2 used for the establishment of a strong bond between the tooth structure and the composite material.

FINAL SITUATION

Fig. 7. The universal composite blends in well with the adjacent teeth regarding its colour and surface finish.

Dentist:

• Graduated with honors in Dentistry and Dental Prosthetics at the University of Milan in 2010.
• In 2011/2012 and 2012/2013 he held the position of Adjunct Professor for the teaching of Prosthetic Technologies at the University of Milan-Bicocca.
• Member of SIdp (Italian Society of Periodontology) and AIC (Italian Academy of Conservation).

By Dr Luca Dusi

For purely aesthetic reasons, this patient asked for the reconstruction of her cone-shaped upper right lateral incisor (12). The patient was offered a treatment including a first phase of orthodontic therapy aimed at recovering the space necessary to be able to reconstruct the lateral incisor to its ideal size. As the patient refused to undergo this orthodontic therapy, it was decided to restore the tooth with resin composite and match its size to the space already available.

The adhesive system used was CLEARFIL™ SE BOND 2, while the restoration was created with the new composite CLEARFIL MAJESTY™ ES-2 Universal. Although this material is designed for the single-shade technique with only two shades matching the anterior tooth shades, I decided to combine both pastes to achieve the best possible outcome. The shade UD (Universal Dark) was used to reconstruct the cervical and central portion of the lateral incisor. The incisal portion was restored with UL (Universal Light).

Fig. 1. Initial situation with a cone-shaped upper right lateral incisor (12).

Fig. 2. Image of the initial situation taken with a polarising filter for shade evaluation purposes.

Fig. 3. The new CLEARFIL MAJESTY™ ES-2 Universal composite with only two shades for the anterior region was chosen. It offers a good optical integration thanks to Kuraray Noritake Dental’s Light Diffusion Technology.

Fig. 4. Shade determination with the aid of cured samples of CLEARFIL MAJESTY™ ES-2 Universal UL (Universal Light) and UD (Universal Dark) on the tooth surfaces.

Fig. 5. Isolation with rubber dam.

Fig. 6. CLEARFIL™ SE BOND 2 used for the establishment of a strong bond between the tooth structure and the composite material.

FINAL SITUATION

Fig. 7. The universal composite blends in well with the adjacent teeth regarding its colour and surface finish.

Dentist:

• Graduated with honors in Dentistry and Dental Prosthetics at the University of Milan in 2010.
• In 2011/2012 and 2012/2013 he held the position of Adjunct Professor for the teaching of Prosthetic Technologies at the University of Milan-Bicocca.
• Member of SIdp (Italian Society of Periodontology) and AIC (Italian Academy of Conservation).

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.

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.