Biomedical Engineering Reference
In-Depth Information
3
Nanostructural Chemically Bonded
Ca-Aluminate Based Bioceramics
Leif Hermansson
Doxa AB
Sweden
1. Introduction
Biomaterials are based on a broad range of materials, such as organic polymers, metals and
ceramics including both sintered and chemically bonded ceramics (silicates, aluminates,
sulphates and phophates). The biomaterials can be made prior to use in the body in a
conventional preparation of the material. The need for in situ in vivo formed implant
materials makes the chemically bonded ceramics especially potential as biomaterials. These
ceramics include room/body temperature formed biomaterials with excellent
biocompatibility. Ca-aluminate as a biomaterial has been evaluated for over two decades
with regard to general physical, mechanical and biocompatible properties. The Ca-
aluminate based materials exhibit due to their unique curing/hardening characteristics and
related microstructure a great potential within the biomaterial field. The presentation in this
chapter aims at giving an overview of the use of Ca-aluminate (CA) as a biomaterial within
odontology, orthopaedics and as a carrier material for drug delivery. The examination deals
with aspects such as; the chemical composition selected, inert filler particles used, early
properties during preparation and handling (working, setting, injection time, translucency,
radio-opacity), and final long-term properties such as dimensional stability and mechanical
properties (fracture toughness, compressive and flexural strength, hardness and Young´s
modulus). One specific topic deals with the sealing of the Ca-aluminate biomaterials to
tissue - a key in the understanding of the mechanisms of nanostructural integration.
2. Overview of properties of chemically bonded ceramics
The Ca-aluminate bioceramics belong to the chemically bonded ceramics, which are usually
presented or known as inorganic cements (Mangabhai, 1990).
Three different cement
systems - Calcium phosphates (CP), Calcium aluminates (CA) and Calcium silicates (CS) are
discussed in some details in this section. Ceramic biomaterials are often based on
phosphate-containing solubable glasses, and various calcium phosphate salts (Hench, 1998).
These salts can be made to cure
in vivo
and are attractive as replacements for the natural
calcium phosphates of mineralised tissues. The Ca-phosphate products are gaining ground
in orthopaedics as resorbable bone substitutes. Biocements are often based on various
calcium phosphate salts - sometimes in combination with Ca-sulphates (Nilsson, 2003).
These salts can be made to cure
in vivo
and are attractive as replacements for the natural
