Abstract
The overall success and long-term life of the medical implants are decisively based on the convenient osseointegration at the hosting tissue-implant interface. Therefore, various surface modifications and different coating approaches have been utilized to the implants to enhance the bone formation and speed up the interaction with the surrounding hosting tissues, thereby enabling the successful fixation of implants. In this review, we will briefly present the main metallic implants and discuss their biocompatibility and osseointegration ability depending on their chemical and mechanical properties. In addition, as the main goal of this review, we explore the main properties of bioactive glasses and silica-based ceramics that are used as coating materials for both orthopedic and dental implants. The current review provides an overview of these bioactive coatings, with a particular emphasis on deposition methods, coating adhesion to the substrates and apatite formation ability tested by immersion in Simulated Body Fluid (SBF). In vitro and in vivo performances in terms of biocompatibility, biodegradability and improved osseointegration are examined as well.
Highlights
Ceramics represent the class of materials that are more similar to bone in terms of composition, their intrinsic brittleness makes them unreliable for load bearing applications
316L SS implants—characterized by a double-layer hybrid organic-inorganic sol-gel coating with the high velocity suspension flame spraying (HVSFS) coatings, due to their high porosity and to the related larger surface area in contact with the dispersion of wollastonite particles deposited using dip-coating technique—were able to induce the Simulated Body Fluid (SBF)—despite the poor mechanical properties exhibited by suspension plasma spraying (SPS) bioactive glasses, which had hydroxyapatite deposition on their surface when immersed in SBF up to 33 days [62,157]
Mechanical and in vitro biological analyses have demonstrated that bioactive glass-based and silicate ceramic coatings could be promising coating materials for orthopedic and dental applications
Summary
Ceramics represent the class of materials that are more similar to bone in terms of composition, their intrinsic brittleness makes them unreliable for load bearing applications. Metallic biomaterials currently used in orthopedics have a higher elastic modulus (in the range between 44 and 205 GPa) as compared to that of natural bone (17–22 GPa) (see Figure 1b), resulting in stress shielding effect that leads to a reduced stimulation of bone formation and remodeling and, subsequently, to the loosening of the implants [18,19,20,21]. It means that the implants “shield” the surrounding bone from experiencing adequate loading, which is required for bone growth stimulation, and when the stress level decreases too much, bone resorption may occur. Coating behavior in vitro and in vivo will be discussed
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