Biomedical Engineering Reference
In-Depth Information
Figure 9.6.
a) Veneering ceramic artisanal stratification process, with a brush, to
produce a felsdpathic onlay. The ceramic is directly sintered on an investment die
replica; b) before sintering; c) after sintering
Figure 9.7.
Sintered ceramic block for a CAD-CAM manufacturing process
9.3.2.
Reinforced glass ceramics
Reinforced glass ceramics for dental applications started to be
developed in the 1980s, in the wake of Adair and Grossmann's work
[ADA
84,
GRO
73], and is still experiencing growing success in single-
unit prostheses. The size and the number of crystals in these materials
are optimized due to specific thermal treatments done industrially,
inducing and controlling crystal formation in the glass. Currently, the
obtained sintered material is made in the form of a cylinder, which is
softened in a special furnace by the dental technician, and then injected
into a mold to create the restoration. It is also available in the form of
CAD-CAM blocks for chairside or dental laboratory systems.
Depending on the nature of the crystals, their mechanical properties and
indications vary significantly (Figure 9.4). Due to the number, nature
and elongated shape of crystals (Figure 9.8), glass ceramics reinforced
with 70% by volume of lithium disilicate (Li
2
Si
2
O
5)
crystals are nearly
three times more resistant in terms of flexural strength than glass
