The present state-of-the-art technology involves a plasma spray (PS) method of coating. The major drawback to this technology lies firstly in the lack of adhesion of the coating which can cause the implant to loosen resulting in severe inflammation. Secondly, the minimum deposition of 50 micrometers in coating thickness that the technique dictates means that some of the coating has to be reabsorbed before bone bioactivity can take place. The new technique, pulsed laser deposition (PLD), is able to produce thin (2 micrometers) homogeneous and very adherent layers of hydroxyapatite (calcium phosphate) on titanium or titanium alloy, without any substrate surface pre-treatment. The deposited layer follows the contours of the implant surface perfectly giving an even coating. Cylindrical implants which have undergone performance testing have revealed the superior capability of PLD. After 6 months, bone contact was 43% more than for a plasma sprayed coated cylinder and there were no cases of inflammation as compared with the several found when conventional coating was used. Importantly, there was no re-absorption of the coating which suggests that the coating thickness could be reduced even further.
Improved hydroxylapatite coatings for dental orthopedical applications
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