Biomedical Engineering Reference
In-Depth Information
9.4. Infiltrated ceramics
Infiltrated ceramics were invented in the 1980s by M. Sadoun. The
crystal content reaches 74% of the material by volume and infiltrated
ceramics cannot be considered as etchable because of the small
amount of glass. These materials are used to produce frameworks,
either by using the original hand-crafted manufacturing process called
slip casting, or by the milling of CAD-CAM blocks. There are three
different materials depending on the chemical nature of the crystalline
matrix, with increasing mechanical resistance and opacity: spinell-
based (MgAl
2
O
4,
In-Ceram Spinell, Vita Zahnfabrik, Bad Säckingen,
Germany), alumina-based (Al
2
O
3
, In-Ceram Alumina) and a mix of
alumina and zirconia (two-thirds Al
2
O
3 and one-third
ZrO
2,
In-
Ceram Zirconia). The relative opacity of these materials can be useful
in masking colored tooth tissues. Despite their excellent clinical
behavior and background [KER
12,
SEL
13,
GAL
14], infiltrated
ceramics are being progressively abandoned and replaced by high-
strength polycrystalline ceramics, such as zirconia.
9.5. Polycrystalline ceramics
9.5.1.
Alumina
Polycrystalline ceramics appeared in the 1990s with CAD-CAM
systems, which are able to predict and manage the significant
retraction of the material occurring during the solid-phase sintering.
They are not considered to be “bondable” materials, since they are not
etchable, and so are not recommended to perform partial restorations.
The first marketed material was alumina (Procera Alumina,
Nobelbiocare, Zurich, Switzerland). Its indications are similar to
alumina-based infiltrated ceramics: they can be used for prostheses of
up to three elements for anterior teeth (incisors and canines)
(Figure 9.3). Despite its advantages, particularly in terms of optical
properties, alumina is being progressively replaced with zirconia for
economic purposes.
