SURFACE MODIFICATION OF TITANIUM AND TITANIUM ALLOYS TO ENHANCE BONE HEALING
Titanium and Its alloys have been used for many years as the material of choice for fabrication of dental, orthopaedic and maxillofacial implants, due to their excellent mechanical properties, biocompatibility, and the ability to osseointegrate with the surrounding bone. In order to improve the bioactivity and osseointegration of titanium implants, especially in compromised bone, surface modification of the implant surface and surface coatings have been introduced. There are different kinds of surface modification, such as, grinding, plasma spraying, sputter coatings, and alkaline treatment. More significantly, immobilization of drugs, such as, bisphosphonates, played an important role in enhancing the bone healing process. The main aim of the study is to develop and identify a facile surface modification method of immobilizing bisphosphonate molecules on commercially pure titanium and its alloy. 10mm discs of commercially pure titanium (CpTi) and titanium-aluminium-vanadium (Ti-6Al-4V) alloy were subjected to different surface treatments experiments; 1) the CpTi and Ti64 alloy surfaces were invested in phosphate bonded investment (Deguvest) and heated up to 900°C simulating superplastic forming process (SPF) creating an interaction layer on the surface upon which they were subjected to immersion in simulated body fluid (SBF) for 7 and 10 days, 2) the titanium surfaces were subjected to alkali treatment with 5M NaOH at 60°C for 24 hours, further more immersed in SBF solution for 7 and 10 days, 3) immobilization of sodium alendronate bisphosphonate on the pre treated titanium surfaces using microseeding method, and 4) tethering of Bioglass® and sodium alendronate bisphosphonate on the titanium surfaces using the electrohydrodynamic spraying method. The surface characterization of the treated surfaces was assessed using scanning electron microscopy (SEM/EDAX), Raman spectroscopy, surface roughness profilometer, and atomic force microscopy (AFM). In vitro cellular bioactivity and cytotoxicity were evaluated on the treated surfaces. This study established that both the interaction layer and its treatment further with simulated body fluids created a favourable interaction layer on the titanium surfaces, which induced the formation of apatite like layer on the surfaces when soaked in SBF solution. The interaction layer so formed was stable and not lost after physical methods of cleaning, thus can be considered to be a quick and inexpensive method of surface modification of titanium implants, during processing itself, which can enhance the bone healing and result in improved osseointegration. The surface modification of CpTi and Ti64 achieved with SPF and sodium hydroxide treatment and further treatment with SBF were further used to immobilize alendronate successfully, which yielded a simple method of incorporating bisphosphonates on implant surfaces, without causing any damage to the drug as no heat treatment or chemical crosslinking was required. Based on the cellular response to the investment treated titanium samples, sodium hydroxide treated samples followed by SBF treatment it can be concluded that these surfaces provide favourable conditions for cell growth, proliferation and differentiation when compared to the non-invested samples.
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