Australian Journal of Basic and Applied Sciences, 3(2): 1122-1129, 2009 ISSN 1991-8178 Corresponding Author: M.F.A Fouda, Inorganic Chemistry Department, National Research Centre, Dokki, Cairo, Egypt. 1122 Does the Coating of Titanium Implants by Hydroxyapatite affect the Elaboration of Free Radicals. An Experimental Study M.F.A Fouda, A. Nemat, A. Gawish. and Ayman R Baiuomy 1 2 3 4 Inorganic Chemistry Department, National Research Centre, Dokki, Cairo, Egypt. 1 Dept. of Surgery and Dental Medicine, National Research Centre, Dokki, Cairo, Egypt, 2 Faculty of Dental Medicine Girls’, Al Azhar University. 3 Dept. of Pharmacology, National Research Centre, Dokki, Cairo, Egypt, 4 Abstract: This study was carried out to throw some light on the mechanisms affecting the reaction of tissue surroundings titanium implants either coated with hydroxyapatite or not, especially the oxidative and nitrooxidative stresses as well as the level of NO in the blood stream. In addition to study the effect of the number of discs on the free radical status in the body and the histological reactions. Forty albino rats were used in this study; they were divided into two groups 20 rats. Group I receiving 50 coated implants with Hydroxyapatite (HA) and was subdivided into G Ia consists of 10 rats receiving one implant and GII b consists of 10 rats receiving four implants. The other group receive 50 uncoated titanium implants; subdivided into G IIa consists of 10 rats receiving one implant and G II b consists of 10 rats receiving four implants. EPR technique using 4-hydroxytempo free radical as an indicator of the balance between all free radical species from one side and NO as well as antioxidants from other side had been used. The results suggest that ROS generated from coated Ti-alloy may be involved in creating appropriate conditions for healing. Moreover; the titanium implants coated with hydroxyapatite leads to the reducing state in the cells faster than that without coating due to inhibition of formation of oxidizing and nitroxidizing species. The histological examination reveals no difference in the capsule thickness of both groups. Conclusions: the coating of titanium implants with hydroxyapatite leads to attaining of reduced state in the cells, which enhance the healing process in comparison with the uncoated implants. Key words: implants, Hydroxyapatite coated implants, Free radicals, Antioxidents, EPR. INTRODUCTION Dental implants have gained steadily increased clinical importance over the last decades, which have led to the rapid development of various different dental implant designs (Rungsiyakull et al, 2008). Biomaterial implants are used in a variety of anatomical locations such as dental implants, orthopedic or cardiovascular prosthesis for vessels or heart valves. The importance of the implant surface with respect to tissue reaction has been recognized with regard to maintain a controlled tissue interface (Beumer et al, 1994). Commercially pure titanium and titanium alloys including Ti6AL4V that possess high oxidation number and high acidity are widely used in manufacturing of dental and orthopaedic implants. Both mechanical and surface properties of such implants play an important rules in the subsequent biological processes (Rigo et al, 2004). The experimental results obtained by numerous investigators (Koklubo et al , 2003& Rigo et al, 2004), showed that the bioactivity of titanium surfaces is not high enough to induce the direct growth of bone tissue and good bone fixation before several months. So that several efforts were directed to the modification of metal surfaces which are often employed as a mean of controlling tissue – titanium interactions and shortening the time of bone fixation (Koklubo et al, 2003). The coating of titanium dental implants with hydroxyapatite (HA) offers the combination between the strength of the metals with the bioactivity of hydroxyapatite ceramic materials (Koklubo et al, 2003& Rigo et al , 2004). Histological study proved that coated dental implants with hydroxyapatite be highly bioactive with extensive new bone formation and attachment (Lobato et al, 2008) HA-coated implants had the most effect on osteoblastic differentiation, inducing a greater expression of an array of osteogenic markers; the HA coated surface may have a greater ability to enhance osteogenesis (Knabe et al, 2004) Furthermore, the HA coating was reported to produce clinical benefits in treatment time . reduction and early loading (Iezzi et al , 2007). In that respect, several techniques are usually, followed in