CAD Ceramics

8/3/2019 CAD Ceramics

1/5

clinical | EXCELLENCE

The term all-ceramics covers a variety of materials,

which differ quite considerably in the way they are

processed and in the type of properties they exhibit.

Special materials are available for a wide variety of

requirements. As a result of the rapid developments

in this field, it is becoming increasingly difficult to

maintain an overview of all the available products.

From an economic point of view, however, it is

important to focus on a select few systems.

Materials that can be processed usingCAD/CAM equipment include silicate and

oxide ceramics. Their strength and stability

are considered to be their most important properties.

Standardized and comparable values are available,

which allow a general classification. Therefore,

these ceramics are categorized as showing high,

medium or low strength. Generally, highly resistant

ceramics should be preferred because of their dura-

bility. Nevertheless, high-strength ceramics are very

difficult to process. Only a few CAD/CAM systems

are capable of machining these very strong mate-

rials. An alternative solution involves using green

bodies, which attain their final desired hardness only

after they have been machined.

Apart from being easier to process, ceramics of

lower strength demonstrate optical advantages, such

as natural-looking translucency and fluorescence,

which are of importance in places where highly aes-

thetic restorations are required. In addition, the

possibility or necessity of adhesive cementation is a

decisive criterion for certain indications.

There is no such thing as a universal ceramic.

The success of the treatment largely depends on the

correct choice of material for the case at hand. This

constitutes an exacting task for the dental team con-

sisting of the dentist and the dental technician. The

consistent and systematic development efforts of

Ivoclar Vivadent have produced two product lines,

IPS Empress and IPS e.max, which offer a suit-

able ceramic material for every indication.

IPS Empress CADThis material is a leucite glass-ceramic, which is

classified as a low-strength ceramic. The formation

of leucite crystals produces internal stresses, which

are responsible for generating the best possible

strength values in this category.The ceramics uncomplicated handling and

highly aesthetic appearance make up for its lack of

strength. The blocks can be machined in a straight-

forward procedure using CEREC or inLab milling

equipment. They are supplied in two levels of

translucency (HT - high translucency and LT - low

translucency) for different clinical situations. In

addition, the Multi Block, which features a natural-

looking transition of shade, brightness and

translucency, has been developed for more sophis-

ticated restorations. In most cases, the restorations

merely have to be polishing or glazed to achieve the

desired aesthetic effect. If needed, the IPS Empress

Veneer Kit provides a comprehensive selection of

materials for applying additional ceramic layers

and characterizations.

The indication range of this system includes

inlays, partial crowns and all-ceramic anterior and

posterior crowns. Furthermore, IPS Empress CAD

is particularly suitable for fabricating veneers

because of its highly aesthetic appearance. The

material comes in a wide selection of shades and

exhibits what is known as the chameleon effect.

Therefore, it is ideal for fabricating fully anatomic

restorations at chairside with the CEREC system.

However, it also produces outstanding results when

The world of CAD ceramicsA look at the demands placed on all-ceramics

By Dr Andreas Kurbad

There is

no such thing

as a universal

ceramic. The

success of the

treatment largely

depends on the

correct choice

of material for

the case at hand.

This constitutes

an exacting task

for the dental

team consisting

of the dentist

and the dental

technician...


2/5


Figure 1. The traumatic fracture in the front tooth was treated

with a composite filling, which showed signs of wear after

several years of service.

Figure 2. A minimally invasive preparation is carried out

before the ceramic veneer is placed.

Figure 6. The veneer is cemented with the adhesive technique

using Variolink Veneer.

Figure 7. Veneers show excellent aesthetic adaptation and have

a long service life.

Figure 8. The exact recreation of the natural surface texture is

of major importance in the fabrication of veneers.

Figure 9. The translucency of the IPS Empress ceramic and of

the Variolink Veneer cementation material allows restorations

to blend in smoothly with the existing tooth structure. Therestoration cannot be distinguished from the natural teeth.

Figure 3. After milling, the IPS Empress

CAD ceramic is characterized with the

IPS Empress Veneer Kit.

Figure 4. The areas of the veneer which

will cover the undamaged tooth structure

are only 0.3 mm thick.

Figure 5. An IPS Empress CAD Multi Block

is used. This block features a natural-look-

ing transition of shade and translucency.


3/5

it is processed in the laboratory. The application of wash pastes

ensures the smooth adaptation of the veneering ceramic to the

base material. Nonetheless, certain clinical concessions must be

made because of the low strength of this material. Thinly tapering

preparation margins must be avoided in areas that are exposed to

high mechanical loads. Consequently, crown preparations must

have a right-angle shoulder, which should not be wider than 1mmand have a rounded internal edge in accordance with the princi-

ples of non-invasive preparation and pulp protection. The

adhesive technique must be used for cementing the restorations.

Nevertheless, the working procedure of the conventional adhesive

technique, as it is prescribed for Variolink II, can be simplified

by using a system such as Multilink Automix. However, in areas

where aesthetics are very important and for the cementation of

veneers in particular, Variolink Veneer should be used, as it has

been specifically developed for these applications. In preparation

for adhesive cementation, the ceramic is etched with hydrofluoric

acid and then silanized.

IPS e.max CADThis material is a lithium disilicate and generally categorized as a

silicate ceramic. As a result of its special crystal structure, its final

strength is very high. Therefore, it is classified as a medium-

strength ceramic. The material is supplied in an intermediate

crystalline form (metasilicate) with an unusual blue colour. In this

state, the material can be machined, finished and cut back without

any problems. When all this work has been done, the ceramic has

to undergo crystallization firing for 25 to 35 minutes to obtain its

final strength. Most commercial furnaces can be used for this pur-

pose. The ceramic restorations are placed on a carrier material

(Object Fix) for the firing cycle. After crystallization firing the

materials colour and translucency is similar to that of natural

teeth. By bringing about a change in the crystal structure (trans-formation to a disilicate), the material also becomes considerably

stronger. Depending on the aesthetic requirements of the patient,

the ceramic can be stained and glazed or veneered or partially

veneered. The IPS e.max CAD ceramic is also available in two

levels of translucency. Although the more translucent material

IPS e.max CAD LT is preferred in most cases, the more opaque

material (MO) is useful when discoloured teeth or metal sub-

structures (e.g. implant superstructures) have to be masked. The

versatile IPS e.max Ceram, which is available in a wide range of

shades, is available for veneering and/or staining purposes.

This ceramic is mainly used to fabricate full crowns. However, it

can also be used for partial crowns and even veneers. Because of its

high final strength, the material can be used in areas where the adhe-

sive technique cannot be employed or if there is some doubt about


Figure 10. The veneer of the PFM crown has been damaged.

Figure 12. The natural-looking IPS e.max CAD ceramic

requires only very minimal characterization.

Figure 13. The originally blue block becomes a tooth-coloured

translucent ceramic restoration as a result of crystallization.

Figure 14. Exceptionally aesthetic results are achieved with theIPS e.max CAD LT ceramics.

Figure 11. The chamfer preparation remains unchanged

compared with the previous restoration.

Programat CS is the ideal firing and crystallization furnace

for dentists. The new Programat CS

is a furnace with vacuum capabili-

ties. Crystallization and glaze firings

of IPS e.max CAD restorations

can be conducted with ease in

the dental practice. The furnace

has 20 programs, is easy to

operate and features a controlled

cooling process.


4/5

whether the procedure can be carried out

properly. The ceramic is used to fabricate

various types of crowns. Depending on aes-

thetic and/or economic requirements, very

straightforward mono-ceramic or partially

or fully veneered restorations can be fabri-

cated. Mono-ceramic pieces are milled to

the desired final shape. Subsequently, crys-

tallization firing as well as stain and glaze

firing can be conducted in one time-saving

step. A more complex procedure involves

cutting back the crown. In this case, aesthet-

ically relevant areas are either left out in the

computer-aided design or mechanically

removed after the restoration has been

machined and then these areas are built up

with veneering ceramic. A chamfer or a

right-angle shoulder, which is created

according to minimally invasive principles,

is acceptable. IPS e.max CAD restorations

can be cemented with the conventional

cementation technique or the adhesive luting

technique. For the adhesive technique, the

ceramic is etched with hydrofluoric acid and

then conditioned with silane. Multilink

Automix is the product of choice for

achieving excellent bonding results.

IPS e.max ZirCADIPS e.max ZirCAD ceramic is based on

yttrium-stabilized zirconium dioxide. It is

classified as an oxide ceramic. It is one ofthe strongest dental ceramics, demon-

strating bending strengths of around 900

MPa. Most CAD/CAM machines are not

capable of milling the ceramic in its hard

final state. Therefore, it has to be

machined in what is known as a green

state and then sintered to obtain its final

strength. As sintering is conducted at very

high temperatures of over 1500C, a spe-

cial furnace is needed for this purpose.

The shrinkage of 20 to 25 percent, which

occurs during sintering, is taken into

account by the CAD/CAM equipment in

that it cuts the restoration in enlarged

form. Before compulsory veneering takes

place with IPS e.max Ceram, foundation

materials, also called liners, are applied.

The clinical uses of the material are

determined by two main properties. The

materials high strength allows it to be

used for almost every indication, with

crowns and above all bridges being the

most common indications. IPS e.max

ZirCAD is also the material of choice for

fabricating all-ceramic primary crowns.

However, compared with the previously

described silicate ceramics, zirconium

dioxide is less translucent. Therefore, in

situations where a high level of aesthetics

is desired and the high final strength

offered by this class of materials is not

absolutely necessary, silicate ceramics

should be preferred.The clinical procedure for IPS e.max

ZirCAD does not differ from that of conven-

tional metal-ceramics. The preparation of a

chamfer is recommended. Even though con-

ventional cementation is possible, it must be

noted that opaque cements that demonstrate

a strong inherent colour (eg zinc phosphate

cements) will have a negative effect on the

appearance of the restoration. Therefore,

glass ionomer cements should be used. The

adhesive technique may also be used to

place IPS e.max ZirCAD restorations. In

fact, it is unavoidable in the case of resin-

bonded bridges. For this purpose, the

bonding surfaces are sandblasted and coated

with zirconia primer. Easy-to-handle

bonding systems have firmly established

themselves for this technique. The self adhe-

sive Multilink Sprint is known to produce

satisfactory results in routine procedures.

AcknowledgementThank you to Kurt Reichel, the master

dental technician responsible for the labo-

ratory work shown in this article.

About the authorDr Andreas Kurbad is in private practice

in Viersen, Germany.

For more info, contact Geoff Staples,

Account Development Manager CAD/CAM

at Ivoclar Vivadent on 0400-616-598 [email protected]

Figure 15. Typical inhibited smile of a

patient with a metal-ceramic bridge.

Figure 16. Chamfer preparation is carried

out with standardized instruments.

Figure 18. Multilink Automix is used to

cement the finished bridge.

Figure 19. Multilink Sprint achieves a

self-adhesive bond quickly and easily.

Figure 20. A highly satisfactory result.

Figure 17. A framework is milled from

an IPS e.max ZirCAD block in enlarged

form to take into account the subsequent

sintering shrinkage.



5/5

CAD Ceramics

Documents

Transcript of CAD Ceramics