טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGodley Reut
SubjectSurface Modification of a Low Modulus Titanium-Niobium
Alloy for Use in Medical Implants
DepartmentDepartment of Materials Science and Engineering
Supervisors Professor Elazar Gutmanas
Dr. Irena Gotman


Abstract

The main requirements of hard tissue replacement materials are high mechanical strength, low elastic modulus and the ability to chemically bond to bone (bio-activity). While a number of bioactive glasses and ceramics have been developed, they cannot be used in loaded bones due to their inadequate strength. At the same time, metals that are sufficiently strong for such applications are intrinsically non-bioactive. Lately, it has been shown that Ti can be made bioactive by soaking treatment in basic solutions. Ti and Ti-6Al-4V α-β alloy have the lowest elastic modulus of the currently used surgical metals, however their stiffness is still high compared to that of human cortical bone. Meanwhile, β-Ti alloys, and especially those based on Ti-Nb, have significantly lower elastic moduli and, if made bioactive, can become attractive artificial bone graft materials.  

The main thrust of the present research was, therefore, the development of an alkali treatment for bioactivation of a low modulus β-Ti-45wt%Nb alloy. Electrochemical treatments were performed with the goal to form a bioactive surface layer on the metal for direct bonding to the bone tissue. Electrochemical and soaking treatments were performed on cp Ti, Nb and the Ti-Nb alloy as well. In order to test the bone bonding capability in vitro, the alkali treated samples were soaked in a simulated body fluid. The samples were examined and characterized using SEM + EPMA, HRSEM, XRD, XPS and AES. In addition, the alloy’s corrosion behavior was examined in vitro. 

The results show that a sodium titanate-niobate hydrogel layer is formed on the surface of the Ti-Nb substrate by the electrochemical treatment in NaOH. When exposed to SBF, a Ca-P layer is formed on the substrate. This suggests that a similar bonelike apatite layer could form on the surface of the alkali-treated Ti-Nb upon implantation. The bone bonding capability coupled with low elastic modulus and outstanding corrosion resistance make β-Ti-45wt%Nb alloy an attractive bone graft substitute material.