Nano-structural bioactive gradient coating fabricated by computer controlled plasma-spraying technology

Bioactive Glass—An Extensive Study of the Preparation and Coating Methods

Diseases or complications that are caused by bone tissue damage affect millions of patients every year. Orthopedic and dental implants have become important treatment options for replacing and repairing missing or damaged parts of bones and teeth. In order to use a material in the manufacture of implants, the material must meet several requirements, such as mechanical stability, elasticity, biocompatibility, hydrophilicity, corrosion resistance, and non-toxicity. In the 1970s, a biocompatible glassy material called bioactive glass was discovered. At a later time, several glass materials with similar properties were developed. This material has a big potential to be used in formulating medical devices, but its fragility is an important disadvantage. The use of bioactive glasses in the form of coatings on metal substrates allows the combination of the mechanical hardness of the metal and the biocompatibility of the bioactive glass. In this review, an extensive study of the literature was conducted regarding the preparation methods of bioactive glass and the different techniques of coating on various substrates, such as stainless steel, titanium, and their alloys. Furthermore, the main doping agents that can be used to impart special properties to the bioactive glass coatings are described.

Dissolution behavior of calcium phosphate nanocrystals deposited on titanium alloy surfaces

We have recently shown that a new implant surface design, achieved by the deposition of discrete nanocrystals of calcium phosphate on microtopographically complex titanium-based substrates, accelerates osteoconduction and also renders the implant surface bone bonding. Thus, we wished to examine the elution behavior of these calcium phosphate nanocrystals and their modulation in vivo. We first compared the total amount of calcium phosphate on these implants with that of plasma-sprayed implants, by measuring the eluted calcium using atomic absorption spectrophotometry. We then plotted their dissolution behavior in vitro as a function of pH relevant to physiological conditions. To assess their structural stability in vivo for periods of up to 1 month, we placed samples in diffusion chambers, implanted them in the abdominal cavity of rats, and examined their surfaces by scanning electron microscopy following retrieval. Our results show that these nanocrystals are stable at normal pH but, as expected, dissolve at acidic pH, and that they remain unchanged when exposed to body fluid in vivo for up to 1 month.