Recent Advances in Implant Biomaterials - A Review

Usage of Implants in dentistry is tremendously increasing in recent times. This has led to the invention of new biomaterials for dental implants by the researchers. Continuous evolution has occurred in the (cid:977)ield of dental implant biomaterials in the last two decades leading to the emergence of innovative biomaterials. This article summarizes the different implant biomaterials and the recent advances in this (cid:977)ield. The material science and they are various biological and physical properties affecting their treatment outcome are dis-cussed. Throughout the years, myriads of dental materials have been tried for replacement of missing tooth. Now titanium remains the gold standard as a dental implant material. Over the recent period, many Implant biomaterials have evolved. It includes composites, glass-ceramics, metal alloys, ceramics, glasses, and polymers. Nanotechnology is an emerging application in the branch of implant dentistry. Nanotechnology can improve the properties of dental implants for achieving good osseointegration. It is imperative for dental


INTRODUCTION
The biomaterial is a substance that is used to augment or replace any tissue or organ, thereby facilitating the function of the body. Implant materials should have ideal physical, chemical, mechanical and biological properties. Dental implant bio-material must be biocompatible and should function well when forces are applied. According to the biologic response or chemical composition, biomaterials used for manufacturing dental implants can be classi ied. (Table 1) (Sykaras et al., 2000).

Titanium and its alloys
Six types of titanium are used as dental implant materials. It includes CpTi and Ti alloys (ASTM). Based on oxygen residuals of metals, the properties of CpTi vary.
There are three structural forms of Titanium alloys which include alpha (α), beta (β) and alpha-beta. The alpha-beta combination alloy is commonly used in dental implants. They are used because of their low density, good strength, and high resistance to corrosion. They also have a low modulus of elas

Titanium Sensitivity associated with Dental Implants
Titanium hypersensitivity can result in several adverse reactions and rapid implant exfoliation (Mitchell et al., 1990;Preez et al., 2007). Review studies suggest that titanium hypersensitivity can lead to implant failure and such events are under-reported (Müller and Valentine-Thon, 2006;Chaturvedi, 2013). In contrast, some studies claim that the role of titanium in causing allergic reactions is unproven (Javed et al., 2013;Siddiqi et al., 2011).

Failure Mode of Titanium
Incidence of fracture of a titanium implant is from 0% to 6% (Balshi, 1996;Tolman and Laney, 1993). Implant fracture is caused by faulty implant design; manufacturing defects; a non-passive it of the framework or physiological and biomechanical overload (T and U, 1994;Zarb and Schmitt, 1990;Piattelli et al., 1998).

Ceramics as Dental Implant Coatings
Several types of ceramic coatings are used on dental implants (Table 2). It includes bioactive ceramics and inert ceramics. Coatings can be dense or porous with varying thicknesses.

Polymers
Several types of polymers are used as dental implant materials. Due to many disadvantages of polymers like poor mechanical properties, lack of adhesion to living tissues, and adverse immunologic reactions, the use of polymers as coatings for implants are not validated nowadays.

Rapid prototyping or additive manufacturing
Rapid prototyping or additive manufacturing is a new technology for manufacturing next-generation dental implants. Advantages of this technique include minimal material wastage and printing of multiple objects at a time.

Application of nanotechnology in dental implants
With the use of newer technologies, hydroxyapatite (HA) and calcium phosphates (CaP) are coated onto the surface of implants (Knowles et al., 1996). However, there are some controversial and contradictory reports as well, claiming HA coatings as not very bene icial (Wang, 2004). There is an increasing interest to use bio-glass in the fabrication of dental implant coatings. (Hench, 1991) But attempts to coat bioactive glass on metallic surfaces failed due to interaction between metal and glass (Wilson et al., 1993). It is dif icult to fabricate an ideal coating with a single technique or material. A combination of techniques and materials are required to manufacture a material with good properties and achieve a thickness in nanometers.

CONCLUSIONS
Dental implant biomaterials and their design have evolved over the period of time with the advance of biotechnology.
With recent advancements, researchers have successfully incorporated arti icial structures within biologic systems. Dental practitioners must have a good knowledge of osseointegration properties of different biomaterials used in dental implants for successful clinical practice. A prompt diagnosis and treatment plan is important for selecting a particular dental implant material according to the patients' needs.