Additives Used in Chemically Bonded Bioceramics - Nanostructural Bioceramics: Advances in Chemically Bonded Ceramics - page 31

temperature raise, which may damage surrounding tissue, and too
slow hydration is inappropriate from a practical clinical aspect.
So depending on the main system selected for a given application
retarders or accelerators may be necessary to use. The processing
agents also affect rheological properties and contribute to desired
consistency. For Ca-aluminate-based systems a Li salt is often used
as an accelerator [4]. For tri-Ca-phosphate (TCP) citric acid is often
used as a retarder [2]. Retarders and accelerators often belong to the
know-how of the commercial producers of biomaterials.

4.1.3 Fillers Used in Chemically Bonded Bioceramics

Important complementary additives in CBBCs are inert filler
materials. The inert fillers in CBBCs are introduced to contribute
to general properties related to homogeneity and microstructure
and to improve mechanical properties such as strength and wear
resistance. Inert fillers are also introduced to control specific
properties related to the inherited property of additives. Slowly
resorbable phases may influence the biologically related properties
of biocompatibility, bioactivity, and antibacterial properties. In Table
4.2 below is presented the contribution of some additives to specific
properties [1, 5-7].

Table 4.2 Examples of additives and specific properties achieved

Additives Improved property of the CBBCs

Glass Transparency

ZrO Radio-opacity

2

Pre-hydrated phases Transparency

Ca-phosphates Bioactivity

SrF Antibacterial properties 2

The amount of fillers can also be used to control the porosity of
the final products [8]. CBBCs always contribute to a certain amount
of nanoporosity. To reduce the total porosity inert solid fillers may
be added [4].