Bioactive Silica Based Coating on Stainless Steel Implants

CERE, SILVIA; JOSEFINA BALLARRE

Handbook of Sol-Gel Science and Technology, second edition

Springer

Lugar: New York; Año: 2016; p. 1 - 505

Biomedical prosthesis devices are used for replacing a body part that is missing or has loosen functionality. Metallic materials are most commonly used for load bearing implants and internal fixation devices (Chen and Thouas 2015). Some featured properties of a metallic material are its high tensile strength, high yield strength, resistance to cyclic loading (fatigue), resistance to time dependent deformation (creep) and its corrosion resistance. They generally find applications in the fabrication of implant devices such as hip joint prosthesis, knee joint prosthesis, dental implants, cardiovascular devices, etc. The most commonly used metals and alloys for medical devices include stainless steels (AISI 316L/317L, ASTM F138), commercially pure titanium and its alloys and cobalt-based alloys and, to a lesser extent, tantalum, zirconium and noble metals such as platinum and gold. It is important that their degradation by wear and/or corrosion is negligible (Duran et al. 2004). The metals used as permanent intracorporeal implants require the formation of a passive oxide film to prevent oxidation. The oxide is spontaneously formed on the metallic surface and limits the transport of metal ions across the oxide-solution interface. The passive film should be non-porous and fully cover the metal surface and also remain on the surface under mechanical stresses. The lower the amount of atomic defects in the oxide film, the more effective is the protection (Jacobs et al.1998). The oxide formed on stainless steel alloys is susceptible to suffer localized corrosion in the body environment. Protective biocompatible coatings applied onto the alloys can delay the rejection on harmful ions to the surrounding hence improving the corrosion resistance of the stainless steel in body fluid (Hansen 2008). Cemented and cementless prosthesis are used in orthopedic surgery and vast discussion about advantages and drawbacks of one procedure over the other are claimed based on their relative cost, surgery procedure and postoperative quality of life among others (Pennington et al. 2013). Cementless prosthesis are generally preferred for young active patients since there is more bone conservation, less probability of loosening and also, for patients who are allergic to methylmethacrylate. An study presented on cementless primary total hip arthroplasty shows satisfactory results in the short time and tend to improve in time, being promising in the case of a revision surgery (Rothman and Cohn 1990). The surface of the prosthetic metallic devices can be modified in order to promote bioactivity and hence not require the use of cement to attain fixation to the host. Coatings can be formulated with that goal and applied onto the metal to be bioactive and promote cell proliferation and osseointegration (Goriainov et al. 2014). In this chapter, the performance of silica based sol gel coatings with the addition of different bioactive particles (hydroxyapatite, wollastonite, glass or glass ceramic) applied onto stainless steel AISI316L is analyzed in terms of in vitro analysis (surface, electrochemical and bioactivity) and preliminary studies about in vivo behavior.