Alumina and Zirconia Ceramic for Orthopaedic and Dental Devices

Abstract

Ceramic materials are made of an inorganic non-metallic oxide. Usually ceramics are divided into two groups: silicon ceramics and aluminous ceramics. Ceramics are also divided into crystalline and non-crystalline depending on inner molecular organization. Depending on their in vivo behaviour, ceramics are classified as bioresorbable, bioreactive or bioinert. Alumina and zirconia are bioinert ceramics; their low reactivity togheter with their good mechanical features (low wear and high stability) led to use them in many biomedical restorative devices. Their most popular application is in arthroprosthetic joints where they have proven to be very effective, that make their use suitable especially in younger, more active patients. Also dental use of these materials was proposed to achieve aesthetic and reliability of dental restorations. 2. Mechanical and chemical features of bioceramics 2.1 Alumina Corundum known as α-alumina is the alumina ceramic used for biomedical application,. In nature single crystals of this material are known as ruby if containing Cr2O3 impurities, or as sapphire if containing titanium impurities which give them blue colour. Al 2 O 3 molecule is one of the most stable oxides because of high energetic ionic and covalent bonds between Al and O atoms. These strong bonds (Alumina DG(298K) =1580 KJ/mol) leave the ceramic unaffected by galvanic reactions (absence of corrosion, e.g. absence of ion release from bulk materials and from wear debris). Adverse conditions such as strong acidic or alkaline environment at high temperatures didn't corrupt allumina properties. Under compression allumina showed good resistance but under tensile strength shows its brittleness. at room temperature alumina does not show plastic deformation before fracture (e.g. no yield point in stress-strain curve before fracture), and once started fractures progress very rapidly (low toughness K IC). Tensile strength of alumina improves with higher density and smaller grain size. A careful selection of raw materials and a strict control of production process are performed by manufacturers to optimize allumina mechanical properties. Introduction of low melting MgO in the ceramic process enhanced mass transport during solid state sintering so that www.intechopen.com

In vitro/In vivo assessment and mechanisms of toxicity of bioceramic materials and its wear particulates

“…An Ames test and carcinogenic/mutagenic tests conducted on alumina and zirconia ceramics conrmed that these materials did not elicit any in vitro carcinogenic effects. 77 However, in one particular study, the subcutaneous implantation of solid and porous disks of alumina in a rat induced sarcoma at an incident rate of #25%, which was signicantly lower than the tumor incident rates reported in the literature for metals and medical-grade plastics. However, the same tests with ceramic particles did not produce any risk of neoplasms.…”

Functionally graded ceramics for biomedical application: Concept, manufacturing, and properties

“…Bioinert ceramics, such as Al 2 O 3 and Yttria‐Stabilized ZrO 2 (hereafter labeled as Y‐TZP), are characterized by high strength, hardness and wear resistance, but they are nearly inert, meaning that they show a negligible interaction with the surrounding living tissues . They are mainly used for high load‐bearing applications, such as hip prostheses for orthopedics and dental implants and restorations .…”

The influence of stem taper re-use upon the failure load of ceramic heads

“…The use of ceramic heads in total hip arthroplasty is constantly increasing due to their good wear characteristics, biocompatibility and reduction of fretting corrosion risk [1,2]. They are used especially in young patients and clinical results are very good [3].…”