KATANA™ Zirconia – layered in 4 levels,
from dentine to incisal
KATANA ™ Zirconia from Kuraray is one of the pioneers in the field of polychrome zirconias. Kuraray is no longer just selling the blanks with which you conquered the German dental market many years ago. Constant development has allowed the range of the well-known multilayer zirconia manufacturer to grow.
The following materials are now available depending on requirements:
| Abbreviation | Description | Flexural strength | Colours |
| UTML | Ultra Translucent Multi Layered | 557 MPa | A1; A2; A3; A3,5; A4; B1; B2; B3; B4; C1; C2; C3; C4; D2; D3; D4; ENW; EA1; EA2; EA3 |
| STML | Super Translucent Multi Layered | 2748 MPa | NW; A1; A2; A3; A3,5; A4; B1; B2; B3; C1; C2; C3; D2; D3 |
| HTML | High Translucent Multi Layered | 1.125 MPa | NW; A1; A2; A3; A3,5; A4; B1; B2; B3; C1; C2; C3; D2; D3 |
| HT | High Translucent | - | White; A1,5/B1-2; A2-3 |
Anyone who can remember the beginnings of KATANA ™ Zirkonia knows that for some time only colour groups such as A-Dark and B-Light were available. In line with market requirements, Kuraray has increased this enormously in recent years in order to remain competitive. Because the competition has long followed suit. At CADdent® we offer KATANA ™ zirconia, multilayer zirconia from Kulzer (Kulzer dima® Mill Zirconia ML) and our own brand MINDFAB (FAB Zirconia).
Indications and areas of application
As is usual in the zirconia sector, the following also applies to KATANA ™ zirconia: the more translucent the material, the lower its flexural strength and thus its stability. In order to still be able to cover the entire spectrum of indications, Kuraray relies on different materials for the respective area of application:
KATANA™ Zirconia UTML
Kuraray itself states on its homepage that the KATANA ™ Zirconia UTML is particularly suitable for inlays, onlays and veneers. Restorations with this ultra-translucent zirconia are also used in the anterior region. However, the material is not suitable for crowns in the posterior region and bridges.
KATANA™ Zirconia STML
The material KATANA ™ Zirconia STML is used for anterior and posterior crowns. Small (up to 3-unit bridges) can also be made from STML. As with UTML, it is also possible to manufacture inlays, onlays and veneers with STML. This material reaches its limits in long-span bridges.
KATANA™ Zirconia HTML
In order to be able to cover the entire spectrum of indications, Kuraray also offers a less translucent multilayer zirconia. KATANA ™ Zirkon HTML is intended for crowns in the posterior area, small (up to 3-unit) bridges and wide-span restorations. In terms of the nature of the material, inlays, onlays and veneers are also possible, but Kuraray recommends using UTML here due to the higher aesthetics.
KATANA™ Zirkon HT
The HT material from KATANA ™ is a monochrome material from which frameworks can be made that are later veneered with ceramic. Due to the lack of a color gradient, this material is intended for veneering frameworks, but not for monolithic crowns.
Colouring of KATANA™ multicolour materials
The milling blank is industrially coloured through four layers. The dentin layer - Kuraray calls it body layer - is the relevant one for the color selection. It corresponds to the selectable VITA shades and takes up 35 % of the height. It is followed by two transitional layers, each taking 15 % of the height. The translucent enamel layer again makes up 35 % of the blank height.
With KATANA ™ UTML two different colour groups are available. On the one hand the “standard colours” that correspond to the VITA shade guide, and on the other hand “enamel colours” that have a reduced chroma in the upper layer. The translucent look in the incisal area can be adapted by shading.
Challenges and limits of KATANA™ Zirconia
Because of its low flexural strength (due to its translucency) the requirements for margin, wall and connector thickness are very high. It can happen that users deviate from the manufacturer's specifications when designing. The more translucent the material, the thicker the margin, wall and connector thicknesses have to be - due to the decreasing flexural strength. However, the stability of the material cannot be guaranteed without compliance with the manufacturer's instructions.
Another challenge is the fixed colour gradient due to the industrial colouring of the milling blank. In bridges with a strong Spee curve, for example, there are unsightly results in the colour gradient. Depending on the height of the blank and crowns, unsatisfactory results may also occur here.
OUR CONCLUSION
In the field of aesthetic restorations, Kuraray offers a wide range of materials for every indication with its materials KATANA ™ Zirconia UTML, STML, HTML and HT. Compared to other highly translucent materials, it also has a relatively high flexural strength and therefore high stability. Apart from the challenge of correct parameter settings and positioning in the blank, there are hardly any disadvantages.