Structural, mechanical, chemical and electrochemical characterization of experimental titanium alloys for dental implants

Author(s)

Jairo Matozinho Cordeiro

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2017-02-17

Examining board members

Valentim Adelino Ricardo Barão; Wirley Gonçalves Assunção; Antônio Pedro Ricomini Filho

• Advisor: Valentim Adelino Ricardo Barão

Abstract

This study aimed to provide a summary of several aspects of titanium (Ti) alloys for using as dental implants. Existing information about the mechanical, chemical, electrochemical and biological properties of the main alloys developed over the past few years were deeply reviewed to provide scientific evidence in favor of using Ti-based alloys as alternative of commercially pure titanium (cpTi) with its alloys in the clinical scenario. Subsequently, an in vitro study was carried out aiming to evaluate the structural, mechanical, chemical, electrochemical and biological properties of binary and ternary Ti alloys containing zirconium (Zr) and niobium (Nb). The experimental alloys were developed (in %wt): Ti-5Zr, Ti-10Zr, Ti-35Nb-5Zr and Ti-35Nb-10Zr, and machined into discs with 10 mm in diameter and 2 mm in thickness. CpTi and Ti-6Al-4V alloy discs were used as controls. Microstructural analysis was performed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties such as Vickers microhardness and elastic modulus were evaluated. The surface characteristics were analyzed by dispersive energy spectroscopy (EDS), X-ray excited photoelectron spectroscopy (XPS), atomic force microscopy (AFM), surface roughness (Ra, Rq, Rt, Rz) and surface free energy. The electrochemical assessment consisted of standard tests conducted in a body fluid solution (pH 7.4) to simulate the blood plasma. The albumin adsorption was measured by the bicinchoninic acid method. Data were evaluated through one-way ANOVA and Tukey test (? = 0.05). Ti alloys can be modified by thermomechanical processes affecting their microstructure and consequently their mechanical properties. CpTi and Ti-Zr alloys presented only ? phase in their microstructure. Ti-6Al-4V and Ti-35Nb-5Zr alloys showed a ? + ? structure. The ? phase was detected for the Ti-35Nb-10Zr alloy. It has been observed in the literature better properties for Ti alloys, such as low elastic modulus, high tensile strength, satisfactory biocompatibility, adequate corrosion resistance, and safety. Additionally, Ti alloys exhibited similar in vivo survivability when compared to cpTi. In the in vitro study, all alloys had a superior microhardness when compared to cpTi (p <0.05). The elastic modulus was statistically lower for Ti-Nb-Zr alloys (p <0.05). All materials presented in their constitution specific elements of each alloy in addition to carbon and oxygen. In general, all groups had a native oxide layer on their surface formed mainly by TiO2. CpTi presented the highest surface roughness (p < 0.05). Ti-10Zr alloy had lower surface energy than the control group (p < 0.05). Ti-10Zr alloy presented the best electrochemical behavior due to the combination of higher values of polarization resistance and lower values of capacitance (p < 0.05). Ti-Nb-Zr alloys had the lowest electrochemical stability (p <0.05). All materials exhibited similar albumin adsorption (p > 0.05). The superiority of Ti alloy when compare to cpTi is evident in many ways. However, there is no scientific evidence to ensure the full replacement of this material in vivo. In vivo studies with the new Ti alloys should be encouraged in order to consolidate their use as cpTi substitutes. ?-type alloys have been shown to be more promising for biomedical applications. Despite this, the binary ? Ti-Zr alloy showed the best combination of mechanical and electrochemical properties and may be considered an important candidate to fabricate dental implants (AU)

• FAPESP's process: 14/26853-2 - Structural, mechanical, chemical and electrochemical characterization of experimental titanium alloys for dental implants
• Grantee: Jairo Matozinho Cordeiro
• Support Opportunities: Scholarships in Brazil - Master