Abstract
Ti–6Al–4V alloy has been widely used in the orthopedic and dental fields owing to its high mechanical strength and biocompatibility. However, this alloy has a poor bone-bonding capacity, and its implantation often causes loosening. Osteoporosis increases with the aging of the population, and bisphosphonate drugs such as alendronate and minodronate (MA) are used for the medical treatment. Reliable and multifunctional implants showing both bone bonding and drug releasing functions are desired. In this study, we developed a novel organic-inorganic composite layer consisting of MA-containing gelatin and calcium-deficient calcium titanate (cd–CT) with high bone-bonding and scratch resistance on Ti–6Al–4V alloy. The alloy with the composite layer formed apatite within 7 days in a simulated body fluid and exhibited high scratch resistance of an approximately 50 mN, attributable to interlocking with cd ± CT. Although the gelatin layer almost completely dissolved in phosphate-buffered saline within 6 h, its dissolution rate was significantly suppressed by a subsequent thermal crosslinking treatment. The released MA was estimated at more than 0.10 μmol/L after 7 days. It is expected that the Ti alloy with the MA-containing gelatin and cd–CT composite layer will be useful for the treatment of osteoporosis bone.
Highlights
Ti–6Al–4V alloy is widely used for load bearing implants, since it is biocompatible comparatively to pure Ti metal, while it shows superior mechanical strength and corrosion resistance [1]
Among the inorganic surface coatings, the calcium-deficient calcium titanate formed by the Ca-heat treatment developed by the present authors has unique surface characteristics of nano-scaled 3D network morphology, high scratch resistance, chemical durability, and abundant Ti–OH groups [17,18,19]
We have shown that the Ti–6Al–4V pedicle screw treated with calcium-deficient calcium titanate (cd–CT) had a remarkably increased extraction torque compared with the untreated screw [7]
Summary
Ti–6Al–4V alloy is widely used for load bearing implants, since it is biocompatible comparatively to pure Ti metal, while it shows superior mechanical strength and corrosion resistance [1]. This alloy is poor in its bone bonding ability, and often results in the loosening of the implants [2,3]. In order to confer bone-bonding on Ti and its alloys, various types of inorganic coatings including a plasma spray apatite coating [4,5], titanate or titania coating by solution and heat [6,7], hydrothermal [8] and anodic oxidation [9] as well as surface roughening by blasting and acid etching [10] have been developed. We have shown that the Ti–6Al–4V pedicle screw treated with cd–CT had a remarkably increased extraction torque compared with the untreated screw [7]
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