Corrosion of Biomaterials Used in Dental Reconstruction Dentistry

Abstract

although biologically inert, it has poor mechanical properties, on the other hand, steels, which have excellent mechanical properties do not show a good corrosion resistance). Titanium is a material reactive in water, air, or any other electrolyte where it covers spontaneously with a titanium oxide layer. It is considered an inert material, as in contact with the tissue, it is rapidly inactivated forming on its surface a thin, hard, and protective layer of oxide, in less than one second [9, 10, 11, 47]. The titanium oxide film formed spontaneously is continuously regenerating and it provides an in-depth protection for the metal towards chemical attack, including the aggressive attack produced by the liquids of the body. Titanium is still considered the ideal material in endosseous dental implant. It does not produce any magnetic effect, it does not produce any magnetic field to disturb the activity around the cells; oxides from the surface of the implant being very adherent and insoluble, and they prevent the release and direct contact between the potentially harmful metal ions and tissues (biological compatibility). Titanium does not produce organic-metallic compounds, which are toxic, or if they are produced, such organic-metallic are unstable. Surface of oxides, consisting of TiO, TiO 3 , Ti 2 O 3 , and Ti 3 O 4 attracts and binds biomolecules (Kasemo 1983). The major disadvantage of this metal is the difficulty to cast it. Today it is obtained by dissociation in vacuum at 1400°C having a purity of 99.85 to 99.95%. Titanium alloys are better tolerated than pure titanium because the oxide layer that forms is higher (of approx. 10-20 μm) [9, 10]. Recent researches have demonstrated that the oxide layer (TiO) considered so stable regenerates every nanosecond, and re-oxidation is a major advantage due to minimizing the risk of biodegradation. It has been proven that next to resistance to corrosion, biological compatibility, resistance and price, the alloys used in medicine are "conversion" alloys based on titanium. Resistance to corrosion can be increased by alloying with molybdenum, zirconium, rhenium, niobium, chromium, manganese. Biomedical titanium alloys are: Ti-Al-V, Ti-Al-Mo, Ti-Al-Cr, Ti-Al-Cr-Co. Frequent use of titanium alloy Ti-6Al-4V for implants is determined by a combination of the most numerous and more favourable characteristics, which include resistance to corrosion, durability, low elasticity module and the ability to adhere with bone and other tissues (osseointegration) [13, 14, 18, 20, 36]. However, there are a number of issues related to the effects the components of the alloy can have. Aluminium and vanadium are elements released into the tissue. Therefore, a number of titanium alloys have investigated (Ti-Al-Nb, Ti-Zr-Al) and it was demonstrated that the Ti-6Al-6Nb alloy has properties comparable to the Ti-6Al-4V alloy, but it shows a greater strength and resistance to corrosion [53, 55]. Analysis of possible reactions to prolonged contact of living tissues with the alignment elements of tit...

Wear and friction characterisation of some restorative dental materials

“…Here it can be also observed that the depth of the wear scar in the lubricated conditions is greater, however, the micrograph does not appear to show significant damage, only showing fractures and the presence of debris. This phenomenon is due to the fact that in the composite material it presented a chemical reaction known as corrosion, which in dental composite materials causes a swelling in the material, due to the separation of the polymeric chains due to the absorption of a solvent [27], which makes the material softer. Due to the corrosion suffered by the composite material, the attrition-corrosion phenomenon was generated, which caused greater wear in the lubricated condition.…”