429 Too Many Requests

A Kuraray Noritake Dental é pioneira no campo dos adesivos dentários através do desenvolvimento do monómero original 10-MDP. Patenteado em 1981, o monómero foi utilizado dois anos mais tarde no cimento compósito PANAVIA™ EX e, desde então, constituiu a espinha dorsal de muitos outros produtos de sucesso. Agora, a empresa combinou o monómero MDP original com monómeros hidrofílicos de amida para desenvolver a tecnologia de ligação rápida (Rapid Bond Technology) por detrás de CLEARFIL™ Universal Bond Quick, a solução adesiva universal emblemática da história de sucesso e compromisso com a inovação da Kuraray Noritake Dental.

Os avanços na moderna tecnologia de colagem dentária levaram a uma redução do número de componentes necessários para os processos de decapagem total e self-etch. No entanto, o manuseio básico destes adesivos não mudou muito. Muitos adesivos requerem que se agite o frasco antes do uso, que se esfregue longamente o líquido e/ou que se espere um certo tempo. Com frequência, a aplicação de várias camadas é necessária. A dependência de monómeros de penetração lenta significa que, para os adesivos tradicionais em frasco, a aderência ao difícil substrato dentinário é um processo lento e sensível às técnicas.

Com a integração de monómeros de amida recentemente desenvolvidos, a Rapid Bond Technology confere à CLEARFIL Universal Bond Quick excelentes propriedades hidrofílicas e a capacidade de penetrar rápida e eficazmente na dentina húmida. Não há necessidade de esperar pela secagem ao ar após a aplicação antes de prosseguir - este tempo foi eliminado - e após a fotopolimerização, é criada uma selagem de cavidade forte e durável. O procedimento de adesão com CLEARFIL Universal Bond Quick é simples e eficaz e garante resultados clínicos previsíveis, graças à tecnologia de aderência rápida.

Absorção de água incrivelmente baixa

Um dos indicadores mais importantes do sucesso a longo prazo da ligação dentinal é o nível de absorção de água na matriz orgânica da ligação. Uma elevada taxa de absorção de água foi clinicamente ligada à contínua deterioração física das ligações, o que pode levar ao desenvolvimento de cáries secundárias. Por esta razão, optámos por manter o conteúdo do HEMA tão baixo quanto possível.

CLEARFIL Universal Bond Quick cria uma rede de polímeros altamente reticulada devido aos monómeros de amida utilizados na Rapid Bond Technology. Como resultado, a taxa de absorção de água é relativamente baixa, o que significa que estes polímeros reticulados são mais estáveis num longo prazo.

Aderência estética e eficaz

A tecnologia de aderência rápida não só fornece uma base para a excelência na aderência prolongada. A camada fina de película (5-10 μm) de CLEARFIL Universal Bond Quick dá às restaurações uma excelente estética e a sua rede de polímeros densamente reticulada reforça a estabilidade desta camada exterior, oferecendo resistência à descoloração periférica.

Ao combinar o monómero MDP original da Kuraray Noritake Dental com monómeros hidrofílicos de amida, a Rapid Bond Technology é o motor que alimenta o CLEARFIL Universal Bond Quick.

A possibilidade de utilizar diferentes tipos de materiais de zircónio, dependendo da indicação clínica, tem aspetos positivos e negativos simultaneamente: positivos porque permite aos técnicos de medicina dentária alcançar os melhores resultados possíveis em qualquer situação, negativos porque requer um armazenamento considerável e muitas decisões a serem tomadas. Para aqueles que preferem escolher um caminho mais eficiente sem comprometer o resultado final, KATANA™ Zirconia YML é a nova solução ideal.

De fato, a Kuraray Noritake estudou longamente a fórmula do seu novo disco nos seus próprios laboratórios de investigação, uma vez que a mistura de pós com características não homogéneas, se não for perfeitamente equilibrada, pode conduzir a situações de tensão interna elevada no material e ao consequente risco de rutura, mesmo após um longo período. Kuraray Noritake chegou à sua solução com o desenvolvimento do inovador disco KATANA™ Zirconia YML multicor, multitranslucidez e multidureza.

Dada a elevada resistência da camada interior e a translucidez da camada exterior, esta nova geração de zircónio multicamadas oferece todas as características necessárias para tratar uma ampla gama de indicações com excelentes resultados estéticos num único procedimento simples.

KATANA™ Zirconia YML reinventa a tecnologia original multicamadas desenvolvida por Kuraray Noritake Dental há mais de uma década. As novas matérias-primas são caracterizadas por diferentes concentrações de ítrio (óxido de ítrio), integradas na conhecida estrutura multicamadas com quatro gradações de cores. O resultado é um disco com um equilíbrio perfeito de gradientes de cor, translucidez e resistência à flexão.

O novo zircónio, com uma resistência mínima à flexão de 1.000 MPa em todas as camadas de dentina, cumpre os requisitos de uma ampla gama de indicações, incluindo restaurações monolíticas de tamanho considerável. Devido à bem comprovada gradação de cor e à excecional translucidez da camada de esmalte, o potencial estético de KATANA™ Zirconia YML é tão elevado que muitas vezes é suficiente optar por um design monolítico da restauração desejada e um acabamento de baixa complexidade como o polimento, ou a microestratificação com Internal Stain+CZR FC Paste Stain.

As várias camadas do bloco são perfeitamente integradas entre si graças a um procedimento interno que assegura o fácil posicionamento da restauração no disco, uma transição invisível entre as camadas da estrutura (indispensável para resultados estéticos impecáveis), a máxima precisão de ajuste e um comportamento previsível a longo prazo da restauração.

Esta tecnologia de ponta de produção e composição do material tem uma vantagem adicional: um processo de sinterização ultrarrápido com duração de apenas 54 minutos, disponível para coroas unitárias e pontes com um máximo de 3 elementos. As propriedades óticas e mecânicas das restaurações obtidas com o processo de sinterização rápida são comparáveis às obtidas após ciclos de sinterização de 90 minutos, ou de 7 de horas.

Para mais informações sobre KATANA™ Zirconia YML, clique aqui.

A introdução de compósitos universais, universais não só em termos de campo de aplicação, mas também ao nível da adaptação de cor, marca efetivamente o advento de um novo tipo de compósito. Isto leva a uma reinterpretação do termo "compósito universal".

CLEARFIL MAJESTY™ ES-2 é uma linha de compósitos nanohíbridos. Hoje em dia, os compósitos nanohíbridos são comummente utilizados como compósitos universais. Apresentam um elevado teor de enchimento, são duráveis com excelentes características de polimento1.

A última variante da gama CLEARFIL MAJESTY ES-2 é CLEARFIL MAJESTY™ ES-2 Universal, o novo compósito universal para o qual expandimos a definição de universal para incluir a cobertura cromática.

Em restaurações posteriores, um único material numa única cor é suficiente para cobrir toda a gama VITA™, tornando desnecessária a determinação da tonalidade. Para as secções frontais, estão disponíveis duas opções de cor: uma variante mais clara e uma mais escura (UL e UD). A variante mais clara é utilizada na gama A1-A2 e a variante mais escura para tonalidades a partir de A3. A sobreposição entre UL e UD é suficiente para garantir que não seja necessária uma determinação específica da tonalidade.

Finalmente, para situações que requerem mais leveza e brilho, está disponível uma tonalidade UW adicional.

O que torna o CLEARFIL MAJESTY ES-2 Universal único em comparação com outros compósitos universais ou monocromáticos?
A diferença com CLEARFIL MAJESTY ES-2 Universal é que uma restauração bem sucedida e correspondente quanto à cor pode ser criada sem a utilização de um compósito adicional opaco (bloqueador), não só no caso de cavidades mais pequenas, mas também no caso de restaurações maiores de classe I e II. Mesmo nos sectores frontais, uma excelente restauração de classe IV pode ser alcançada com CLEARFIL MAJESTY ES-2 Universal e não apenas restaurações de pequenas lesões de classe III ou V.

A razão pela qual a Kuraray Noritake Dental Inc. chega onde outros não podem, é principalmente devido à tecnologia de difusão da luz (LDT). Ao integrar esta tecnologia em compósitos com a translucidez correta, a luz é difundida e refletida de tal modo que o compósito se integra perfeitamente com a estrutura dental envolvente.

Outros compósitos são baseados no efeito camaleão, enquanto Kuraray Noritake Dental Inc. acrescenta uma dimensão extra com a tecnologia de difusão da luz. Com o efeito camaleão, a luz passa através do material sendo refletida pelas paredes da cavidade. A cor percebida da restauração é, portanto, a cor das paredes da cavidade. Se a cavidade for demasiado grande, requer mais material de enchimento, a luz deve ir mais longe e uma parte considerável desta é absorvida. Neste caso, o brilho da restauração é reduzido e a cor das paredes da cavidade já não é refletida com precisão.

A nossa tecnologia LDT permite a difusão da luz no próprio compósito, para além de ser refletida a partir das paredes da cavidade. Consequentemente, CLEARFIL MAJESTY ES-2 Universal é um compósito particularmente tolerante. Esta característica está presente em todos os compósitos da família CLEARFIL MAJESTY ES-2.

CLEARFIL MAJESTY ES-2 Universal é o resultado de uma sofisticada tecnologia de enchimento, matriz e silano e oferece uma solução para todos os seus trabalhos de rotina em material compósito. Uma restauração sempre impecável onde a determinação da tonalidade é uma coisa do passado.

Referência

¹ Ilie, N., & Hickel, R. (2011). Resin composite restorative materials. Aust Dent J, 56 Suppl 1, 59-66. doi:10.1111/j.1834-7819.2010.01296.x

Desde que apareceu pela primeira vez no mercado sob a denominação “CLEARFIL SA Cement”, a série de cimentos autoadesivos Kuraray Noritake PANAVIA SA Cement tem evoluído constantemente, passando por várias fases de desenvolvimento. Ao longo do tempo, realizaram-se várias melhorias que culminaram no nosso mais recente produto: PANAVIA SA Cement Universal. Estas melhorias incluem: a potencialização da resistência de aderência ao tecido dentário, o aumento da temperatura de armazenamento à temperatura ambiente e o prolongamento do período de armazenamento para três anos. O que não mudou é a facilidade de remover o excesso de cimento, a tolerância à humidade e a integração do monómero MDP original.

O monómero MDP permite a aderência de PANAVIA™ SA Cement Universal ao tecido dentário, metais e zircónio. Até recentemente, a ligação química a materiais de matriz de vidro, tais como cerâmica e vitrocerâmica, incluindo disilicato de lítio e os compósitos, só era possível através da adição de um primer à base de silano.

Com a introdução de PANAVIA SA Cement Universal, a etapa de silanização tornou-se supérflua, devido à integração da inovadora molécula LCSi de silano, permitindo, portanto, ter um único procedimento universal sem a necessidade de qualquer primer adicional.

LCSi

Em palavras, parece simples adicionar o silano à massa. Na realidade, há limitações. Uma delas é a dificuldade de manter o silano sob a forma de γ-MPS(gama-metacriloxipropiltrimetoxissilano) ativo por um período prolongado. Isto deve-se, em parte, à natureza hidrofílica do γ-MPS: de fato, o contacto com a água em condições ácidas provoca a hidrólise de grupos alcóxicos do silano. Por esta razão, é preferível utilizar um silano mais hidrofóbico e por conseguinte mais estável, evitando o seu contacto com água e ácidos antes do tempo.

A Kuraray Noritake já utiliza silano de cadeia longa LCSi nos compósitos CLEARFIL MAJESTY Posterior e CLEARFIL MAJESTY ES Flow há algum tempo, mas esta é a primeira vez que é utilizado num cimento.

Este silano exclusivo possui um longo separador de hidrocarbonetos (a cadeia de hidrocarbonetos entre o grupo do silanol e o grupo do metacrilato) que o torna mais repelente à água e estável comparativamente à pequena molécula de γ-MPS. Assim, a reação com as partículas de sílica em materiais à base de vidro ocorre de forma mais ordenada e rápida. O resultado é uma ligação otimizada à superfície e uma maior resistência à hidrólise.

O objetivo de contrastar a degradação de silanos na PANAVIA SA Cement Universal exigiu estudos longos e aprofundados. No final, decidiu-se separar os componentes mais hidrofílicos dos hidrófobos, para que só entrassem em contacto entre si durante a mistura da massa. Isto permitiu-nos obter um prazo de conservação de três anos, mesmo à temperatura ambiente.

Investigação

Não são apenas os nossos dados internos que provam a aderência com materiais de vidro de qualidade comparável, se não superior, que podem ser alcançados com PANAVIA SA Cement Universal em relação à sua versão anterior, PANAVIA SA CEMENT PLUS, utilizado em conjunto com CLEARFIL CERAMIC PRIMER PLUS. Os primeiros resultados de um estudo independente confirmam os nossos dados internos.

Com PANAVIA SA Cement Universal, oferecemos agora um cimento de resina autoadesivo que permite a aderência direta a praticamente qualquer tipo de material, sem a utilização de primer ou outros agentes adesivos separados.

Saiba mais sobre PANAVIA SA Cement Universal, clique aqui.

Por Peter Schouten, Technical Manager Kuraray Europe Benelux

Did you know that a complete removal of temporary cement from the abutment tooth with a rubber cup and pumice paste or an ultrasonic scaler is usually impossible? In most cases, some visibly undetectable residues remain on the surface. They will negatively affect the bonding performance of the permanent cementation system you selected. KATANA™ Cleaner is our answer to this problem! Applied after conventional temporary cement removal, it provides optimal conditions for permanent cementation.

All relevant details are revealed in this scientific report.

Universal applicability of dental materials – this is a feature highly valued by the products’ users. It allows them to slim down the range of materials needed, which leads to reduced stock inventory and facilitates the establishment of universal workflows. With fewer variables and inconsistencies, all members of the practice team will know exactly what to do and how to do it, which mean less errors and consistent outcomes.

As one of the leading developers and providers of bonding agents, cements and composite filling as well as indirect restorative materials, Kuraray Noritake Dental strongly supports the universality trend in dentistry. Popular examples of universal products for direct restoration procedures are CLEARFIL™ Universal Bond Quick, a one-step dental bonding agent that works with or without a separate etching step, and the filling material CLEARFIL MAJESTY™ ES Flow.

Indirect restorative workflows are streamlined e.g. with PANAVIA™ SA Cement Universal, a self-adhesive resin cement indicated for all kinds of restorative materials, which is always used according to the same universal protocol.

Prior to the use of this product, the dental practitioner should consider cleaning the tooth and the restoration with KATANA™ Cleaner indicated for extra- and intra-oral use and providing optimal conditions for a strong and durable bond.

Both products recently received very positive ratings from the evaluators of Clinician’s Report. Click here to see the evaluations!

By Marco Stoppaccioli

In today´s society, due to higher life expectancy, greater and more responsible attention to one´s body, we have developed a culture more sensitive to personal well-being. Consequently, more patients with total removable prostheses request stabilization of their prostheses through implant treatment which offers the most effective and valid response to this need.

The demand for implant treatments has increased significantly during the last decade, specifically from patients with long-term full prostheses resulting in considerable bone resorption¹, but are hesitant to undergo complex bone regeneration interventions (Photo 1).

These rehabilitations require great commitment and professional skills. In addition to restoring a complex series of aesthetic-functional parameters that have been lost. Innovative products were developed, not only the restoration of the dental, but also, the orthopedic aspects of the procedure.

Photo 1: Upper and lower Jaw situation models.

Initially, the dental-skeletal rehabilitations involved the exclusive use of metal posts combined with acrylic materials.

In recent decades, we have witnessed an evolution in the surgical techniques and materials used, among these, zirconia² has a significant and highly innovative role. The main reason for its success is due to the possibility of being able to use it anatomically through a simple and effective protocol thanks to CAD CAM technology.

Zirconia, created to be covered with ceramic coatings, has undergone a profound evolution: from an exclusively structural material with high strength but low aesthetic appeal, it has become anatomical, constituting an alternative to layered restorations. Thanks to research and innovation, optimizing chemical and physical parameters³ in the dental industry, we now have a wide range of products, including multi-layer zirconia.

In more analytical terms, it offers a very valid response to the translucency, which is inversely proportional to the flexural strength. On the market this material class oscillates between 550Mpa and 1200Mpa of flexural strength. This characteristic identifies its indication range, specifically depending on the yttrium oxide content, which acts as a stabilizer of zirconia.

For dental-skeletal rehabilitations, the protocol involves the use of multi-layer monolithic zirconia with marked characteristics of flexural strength but lower translucency which determines a limit in the aesthetic sense. On the other hand, the use of multi-layered zirconia with high translucency cannot be considered suitable, due to its lack of flexural strength, despite fully meeting the requirement for naturalness.

To date it can be said that there is no zirconia that offers high mechanical properties combined with high translucency, two fundamental aspects for successful restorations.

Considering these factors, the idea was born to generate an innovative and experimental protocol capable of supporting, on the one hand, the ability of CAD/CAM systems to copy exactly a project or even better, a functionalized provisional implant, and on the other, to associate the use of two zirconia with different characteristics: one extremely tough, white colored zirconia with 1125 MPa (KATANA™ HT Kuraray Noritake) and the other super translucent multi-layered zirconia with 750 MPa (KATANA™ STML Kuraray Noritake).

OPERATIONAL PROTOCOL

In dental-skeletal rehabilitations, success depends on a precise diagnosis by the clinician, aimed at the functional and aesthetic restoration of the case. It is a fundamental task of the dental technician to translate this information through the creation of a wax-up, both analog and digital.

Photo 2: Digital wax-up.

Photo 3: Analog wax-up.

Thanks to digitization, with a 3D printer, it is possible to realize the wax-up quickly and economically in a prototype, capable of allowing the clinician to perform an initial test in the oral cavity.

Photo 4: From design to 3D prototype.

Once the adequacy of the prototype under study has been certified, the next phase involves the construction of the provisional implant which, placed in the oral cavity for a specified time, provides the fundamental information from an occlusal point of view, both in static and dynamic conditions.

The first strength of this protocol is to capture all information about the provisional implant and transfer them to the final work through digital systems. In other words, the provisional implant itself becomes the design of the final product.

Photo 5: Temporary result of analog project.

Photo 6: Acquisition of temporary arches refitted on the models.

FINAL PROCEDURE: OPERATING PHASES

Once the scans of the temporary implant have been acquired in the digital platform, the structural frame obtained by reduction of the temporary implant file is generated. The framework will be made by using KATANA™ HT white colored zirconia (Kuraray Noritake Dental Inc.) with a flexural strength of 1125 MPa. This choice is attributable to an adequate toughness of the material and an effective aesthetic chromatic response on the pink ceramic coating.

Photo 7: Structural framework.

Photo 8: White zirconia framework, 1125 MPa (KATANA HT).

Once the structural file is generated, it is called up within the modeling software to create the anatomical components that will be divided into quadrants.

Photo 9: File divided into three seqments.

The selected material is multi-layered KATANA™ Zirconia STML by Kuraray Noritake Dental Inc. with a flexural strength of 750 MPa and high translucency. KATANA™ Zirconia STML shows an optimized balance between mechanical and optical characteristics.

The author's choice to divide the anatomical components into three segments has a dual purpose: the first is to have a better quality of the milling and the second is to reduce the material waste of the zirconia disc as much as possible.

Photo 10: The three segments after sintering.

Once the frameworks are obtained, before they are merged with each other, the anatomical parts are finished and polished; only the areas excluded from the functional part will be sandblasted. Special attention must be paid to the surface texturing of the anterior sectors⁵, with cutters, discs and rubbers dedicated for this purpose. The surfaces that remain shiny offer a lower abrasion coefficient than the natural tooth⁶; in fact, the abrasiveness depends on the surface smoothing. Polished zirconia has lower abrasion coefficients than lithium disilicate and layered ceramics⁷.

The adhesion between the anatomical and structural zirconia components is achieved by fusion with Noritake Cerabien ZR Low Fusion ceramic.

Photo 11: Anatomical components joined to the structural framework.

Once the adhesion between the zirconia components has been obtained, the first analog phase involves the creation of the gum parts, with dedicated pink gingival masses at a high temperature of 940 C° (CZR™ Tissue Kuraray Noritake Dental Inc.). The author selects three gingival masses with which the keratinized and vascularised parts are reproduced8, peculiar to the natural gingival tissue.

Photo 12: Used CZR™ Tissue porcelain.

Photo 13: Application of CZR™ Tissue porcelain.

Once the pink gingival parts are finalized, the coloring of the anatomical components will follow with the use of dedicated low temperature stains (CZR™ FC Paste Stain, Kuraray Noritake Dental Inc.) which, together with the high translucency of the anatomical zirconia, guarantees a high aesthetic result.

With gray, blue and black shades, it is possible to give a high degree of translucency to the incisal edges. With warm shades, like orange and yellow, the transitions of the anatomical crowns are emphasized, while with a few spots of strong color it is possible to give character and uniqueness to the teeth.

Photo 14: Used shades of CZR™ FC Paste Stain.

The low baking temperature of CZR™ FC Paste Stain guarantees the non-alteration of the gingival component. The final step involves glazing the sandblasted parts.

Photo 15: Final situation.

Photo 16: Occlusal view.

CONCLUSION

The strength of dento-skeletal rehabilitations made of monolithic zirconia, which is a stable, reliable and highly biocompatible material is, through the possibility of using CAD/CAM technology to make an exact copy of a case or, even better, a functionalized temporary implant.

Photo 17: Matching with wax-up.

The 1125 MPa zirconia is ideal for this type of prosthesis, however, does not offer an aesthetic quality. Therefore, the combination of two zirconia materials, one extremely strong and the other highly aesthetic, fully satisfies this requirement.

Photo 18, 19: Intra-oral situation.

BIBLIOGRAPHY:

1) Matteo Chiapasco, Eugenio Romeo La riabilitazione implantoprotesica nei casi compless, UTET S.p.A. 2003 Unione Tipografico-Editrice Torinese.

2) Piconi C. ,Rimondini L. ,Cerroni L. , La zirconia in odontoiatria, Masson, 2008.

3) Stawarczyk B., Ozcan M., Hallmann L., Ender A., Mehl A., Hammerle CH., Effect of zirconia sintering temperature on flexural strengh, grain size and contrast ratio. Clin oral investig, 2013.

5) Shigeo Kataoka, Yoshimi Nishimura , Morfologia naturale dei denti, Edizione internazionale Milano 2003
La riabilitazione implantoprotesica nei casi compless.

6) Oh W., Delong R., Anusavice K., Factors affecting enamel and ceramic wear: A literature review. J Prosthet Dent 2002.

7) Preis V., Bher M., Kolbeck C., Hahnel S., Handel G., Rosentritt M., Wear performance of substructure ceramics and veneering porcelains, Dent Mater, 2011.

8) Rutten L. & P., L’estetica su impianti, editrice MEA, 1999.

Thanks: Dr. Fortunato Alfonsi, Odt. Raoul Pietropaolo.

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.