General Properties of Titanium - Research Paper Example

?Titanium has several uses nowadays, one of the most important being in the medical industry. Various uses also exist within the realm of this industry: the use of titanium and its alloys in medical implants is one of the most well known. Titanium is an attractive option due to it being readily available, extremely strong and most importantly non corrosive even in the presence of body fluids. While adverse effects have been recorded with some implants, they have been attributed to the other metals alloyed with titanium and it appears titanium is going to keep being used as a viable option in the foreseeable future in implants. 1. Introduction Titanium is a metal that is found abundantly on earth and had several uses in many fields. It can exist in 3 separate forms in nature and numerous alloys have been formed with other metals which only serve to increase its uses. One area where titanium has been found to be of utmost importance is in the medical industry. Medical implants with titanium or titanium alloys incorporated in them have been developed and made use of in the past few decades. This paper will examine the use of titanium in medical implants and its properties that contribute to this success, in particular its property of being non corrosive. 2. General properties of titanium Titanium is a transition metal which is found in the earth’s crust (Balazic et al, 2007). It is the fourth most abundant metal on earth and is found all over the world in volcanic and alluvial deposits. While ores such as rutile and ilmeinite are plentiful, titanium reacts with nitrogen, hydrogen and oxygen and is not easy to extract from its ore (Brunette et al, 2001). Extraction involves very expensive methods and a mere 5% of pure titanium is extracted from an ore usually (Brunette et al, 2001). The density of titanium is about half of that of steel though it is as strong as steel (Balazic et al, 2007). Titanium is an allotropic element and can exist in three different forms in nature. The alpha form exists at room temperature and is a hexagonal crystal structure that is closely packed. The beta form exists when titanium in solid form is heated to a temperature above 883 C. it also exists when liquid titanium solidifies (Brunette et al, 2001). Mixing titanium with other metals makes it possible to make alloys that are stable at room temperature in either the alpha or the beta form. Metals commonly used to make stable the alpha form include aluminum, tin and oxygen. The beta form can be stabilized using metals like chromium, iron or vanadium. Using mixtures of both of these stabilizers leads to the production of alpha+beta titanium alloys (Brunette et al, 2001). 3. Uses of titanium Titanium has uses in many different fields including aerospace, power generation, automotive, chemical and petrochemical, sporting goods, dental and medical applications (Rack and Qaz, 2006; Sibum, 2003; Wang, 1996 from Balazic et al, 2007). The commercial aspects of titanium were only exploited in the 1940s (Balazic et al, 2007). Starting in the 1960s, titanium was used as a material in medical implants (Balazic et al, 2007). Now, over a 1000 tonnes or 2.2 million pounds of titanium are used in implants all over the world every year (The Titanium Information Group, 2003). Titanium alloys have also been used in the medical industry and there are three main types of alloys which have been developed: alpha titanium alloys, beta titanium alloys and alpha+beta titanium alloys (Balazic et al, 2007). Of these, it is primarily beta alloys that are used in medical applications (Brunette et al, 2001) Some of the most common alloys that have been used include Titanium-Aluminum-Vanadium and Nickel-Titanium (Nitinol) (Balazic et al, 2007). Some of the main uses in implants are for bone or joint replacements, dental implants, maxillofacial and craniofacial uses, cardiovascular devices and external prostheses (The Titanium Information Group, 2003). It has also been used in medical fasteners and fixation devices (Brunette et al, 2001). 4. Desirable characteristics of titanium for medical implants Titanium is desirable for use in medical applications not only because it is extremely strong as has a low density but mainly because of its resistance to corrosion (Niinomi, 2002 from Balazic et al, 2007). The main properties that are necessary for biomedical uses are a resistance to corrosion, biocompatibility, mechanical behaviour, availability of the metal and whether it can be processed (Disegi, 2000; He and Hagiwara, 2006; Katt, 2004). (Disegi, 2000; He and Hagiwara, 2006; Katt, 2004 from Balazic et al, 2007). The resistance to corrosion is one of the most important properties of a metal that must be carefully considered when considering it for medical implants. As implants are exposed to bodily fluids, they must be inert enough to not react with any of these. The effects of corrosion on a medical implant would lead to the implant being degraded in the body and leakage of harmful metals into the surrounding tissues (Balazic et al, 2007). Titanium has been seen to be compatible with both soft and hard tissue (Brunette et al, 2001) and has been found to be corrosion resistant thanks to the formation of a layer of titanium oxide. This layer is stable and protects against corrosion within the human body. While it appears that corrosion is completely stopped due to this layer, this is not exactly the case. Corrosion is actually reduced substantially not completely stopped but this is adequate for the purpose of medical implants (Balazic et al, 2007). The oxide surface layer remains stable to a depth of 10nm (Tengvall and Lundstrom, 1992 from Balazic et al, 2007). In addition, at favourable conditions, a calcium phosphate layer is also formed on the surface of the titanium and this allows for excellent osteointegration with the bone. Ostiointegration with a bone refers to a metal implant being stable while in direct contact with the bone (Brunette et al, 2001). If, for some reason, either the titanium oxide layer or the calcium phosphate layer is damaged, there is the added advantage that these will regenerate automatically (Balazic et al, 2007). 5. Adverse effects reported with titanium in medical implants While the main advantage of titanium coated implants is its resistance to corrosion due to the oxide layer, it is also the oxide layer that causes problems. The formation of titanium oxide can reduce the pH at the border of the titanium and the coating. This may, in time, lead to dissolution of the coating (Balazic et al, 2007). Titanium is over time released into surrounding tissues and this does lead to discolouration but this seems to happen in a negligible number of cases (Brunette et al, 2001). However, titanium is said to be ‘physiologically indifferent’ so there have been no cytotoxic effects as a result (Brunette et al, 2001). On the other hand, the commonly used alloy of Titanium with 6% Aluminum and 4% Vanadium has shown some cytotoxic effects though these have mainly been attributed to Vanadium (Brunette et al, 2001, Balazic et al, 2007).it must be noted that is imperative to investigate the individual effects of each metal in an alloy on the body as opposed to the entire alloy itself. Nickel-titanium alloys have also had some adverse effects reported with use though it was Nickel that was implicated as the cause. In Nickel-implant alloys, nickel was observed to affect surrounding soft tissues in a toxic manner. Nickel was even seen to affect distant organs and damage them by its accumulation. It was also seen to be detrimental to bones (Balazic et al, 2007). Of these however, Nickel-titanium alloys still seem less reactive than alloys using Vanadium or even ones that use cobalt (Balazic et al, 2007) 6. Conclusion To sum up, it can be said that titanium is an extremely useful metal in a wide variety of functions, including in the use of medical implants. Titanium is ready available, it is of low density, is extremely strong and is able to alloy with several other metals to form alloys with desirable properties. In addition, the most important aspect of its use in medical implants is the fact that it is non corrosive. This property of not being corrosive has been linked to the formation of a layer of titanium oxide that does not react with bodily fluids. While some undesirable effects have been reported in cases where metal implants using titanium were used, it appears that these seemed to be as a result of other metals in the alloy such as vanadium or nickel. These effects seem to be a minute number of cases. Due to the properties mentioned above, titanium is an ideal metal to use in medical implants. It appears that use of titanium has increased drastically since the 1960’s when it was first used in medical implants and it does seem that this will only keep increasing in the foreseeable future. Works Cited. Balazic, M., Kopac, J., Jackson, M.J. and Ahmed, W. (2007) ‘Review: titanium and titanium alloy applications in medicine’, International Journal. of Nano and Biomaterials, (2007), 3–34. Web. Brunette, D.M.; Tengyvall, P.; Texter, M. and Thomson, P. Titanium in Medicine. Material Science, Surface Science, Engineering, Biological Responses and Medical Applications. Germany: Springer-Verlag, 2001. Print. The Titanium Information Group. Titanium Alloys in Medical Applications. January 11, 2003. Web. May 8 2011. Read More