**2. Dental implants**

A dental implant is a material placed in or on the oral tissues that help to support the oral prosthesis. An ideal implant material should possess the following characteristics. It should be biocompatible and possess adequate strength, rigidity, good corrosive, and be capable of wear and fracture resistance. The principles of designing a dental implant should be much compatible with the physical properties of the material. Materials that are used for fabricating a dental implant can be considered according to the chemical composition of the implant and their biological responses. Many reports claim that these dental implants may be made from metals, ceramics, or polymers [8].

#### **2.1 Titanium and its alloys**

According to the American Society for testing and materials, there are six distinct types of titanium that are widely available as implant biomaterials. They are grade I, II, III, IV Cp Ti, various combinations of titanium, aluminum like alpha-beta alloy containing 6% Al and 4% V, alpha-beta titanium alloy containing 6% aluminum and 7% niobium, alpha-beta titanium alloy with non-ferrous metal. The physical and mechanical properties, such as tensile strength and osseointegration, elastic modulus, non-toxic nature, are quite different for the different alloys. The most important property related to the oxygen residuals in the metals and the other two titanium is considered as very low interstitial alloys. Among all the available alloys, the commercially prepared pure titanium alloys are generally considered as pure and mentioned

in Grade I, Grade II, Grade III, and Grade IV titanium and has wide applications in implant manufacturing. Some trace elements, such as carbon, oxygen, nitrogen, and iron, are also considered in this process. Although titanium possesses many strengthening characteristics, literature reports reveal that it evokes a stronger reaction in the host causing hypersensitivity reactions, failed implants with increased concentration of titanium in peri-implanted tissues, regional nodes, and pulmonary tissues based on animal models, allergy to titanium in the form of urticaria, pruritus of the mucosa or skin, atopic dermatitis, poor fracture healing, necrosis and immunosuppression and weakening of orthopedically implanted titanium [9].
