ISSN 1061-3862, International Journal of Self-Propagating High-Temperature Synthesis, 2010, Vol. 19, No. 2, pp. 157–167. © Allerton Press, Inc., 2010. 157 1 1. INTRODUCTION It is known that nitinol, an intermetallic phase of nickel and titanium of NiTi stoichiometry, possesses properties of super-elasticity, damping and a shape memory effect. It is currently under consideration as an implant material [1–5]. However fears concerning this alloy have been expressed compared to pure tita- nium implants. These fears are related to the presence of nickel in the intermetallide. Knowing the harmful effect of nickel for the human body, medics have expressed some doubts regarding the biocompatibility of nitinol, despite a body of experimental work testify- ing to its advantages. In general, the contact surface between an implant and living bone tissue should be sufficiently rough to provide secondary fixation of the alien implant by bone ongrowth and ingrowth (into pores) [6, 7]. Because of even “smooth” (machined) titanium den- tal implants have a long history of success [8], there is a tendency towards surface roughening (by blasting, etching, coating, etc.) of metallic implants [9]. In this regard a porous surface of the implant is far more pref- erable than a smooth one. It has been shown previ- 1 The text was submitted by the authors in English. ously that nitinol can be synthesized for 3-dimen- sional implant production by overlapping the selective laser sintering (SLS) and SHS techniques [10, 11]. The SLS technique involves rastering a laser across a powder composition to both transform reactants to products and to sinter the formed material. SLS method concerns to Rapid Prototyping and Manufac- turing technology (RP & M) distinctive feature of which is high efficiency and reproducibility. We were the first who combined the processes of SHS and selective laser sintering. SHS reaction was conducted in a laser spot moving over the surface of reactive pow- der mixtures such as Ni–Al, Ti–Al, Fe–Ti or Ni–Ti [12–15]. Spatially selective sintering at high resolution and exact adjusting the energy of laser beam allowed us to control SHS reaction and obtain a desired shape of synthesized items such as implants [16–24]. The SHS process is an exothermic combustion reaction that transforms reactants, normally the ele- mental powders, to products by the passage of a hot synthesis wave. The technique can generate enormous temperatures (3000°C) and is routinely used to join railway tracks through the termite in order to prevent its transition by the thermal explosive process (Al + Fe 2 O 3 ). In the combined SHS/SLS process, the SHS Porous Titanium and Nitinol Implants Synthesized by SHS/SLS: Microstructural and Histomorphological Analyses of Tissue Reactions 1 I. V. Shishkovsky a, b , M. V. Kuznetsov c , and Yu. G. Morozov c a Lebedev Physics Institute, Samara Branch, Russian Academy of Sciences, ul. Novo-Sadovaya 221, Samara, 443 011 Russia b Samara State Medical University (SamSMU), ul. Chapaevskaya 89, Samara, 443 099 Russia c Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, ul. Institutskaya 8, Chernogolovka, Moscow, 142432 Russia e-mail: kuznets@ism.ac.ru Received January 20, 2010; in final form, March 3, 2010 Abstract—The comparative microstructural analyses and histomorphological studies of tissue reactions to porous titanium and nitinol implants synthesized by Selective Laser Sintering (SLS) are presented for a rat model for bone implants. It was discovered that the surface of porous pegs of titanium and nitinol made by SHS/SLS has a significantly favorable structure to the mechanical interlocking with bone and soft tissues. Histological analysis of decalcified paraffin sections after implant removal could only show that trabecular bone structures and marrow cavities were observed around the porous implants. In the connective tissue of the remaining implant beds the following cells: macrophages, fibroblasts, adipocytes and lymphocytes are discernible. It was shown that the nitinol synthesized by combined SHS/SLS technique has a developed and ordered microstructure. Keywords: SHS, selective laser sintering (SLS), porous implants, histological and morphological analyses, biointegration. DOI: 10.3103/S1061386210020123