iDentistry The Journal January 2017 | Page 6

The Journal Finite-element analysis (FEA) of carbon-fiber reinforced PEEK (CFR-PEEK) implants suggested that they could induce lesser stress [6] shielding than titanium . However, since PEEK dental implants have not been used widely clinically, it is unknown if there is a difference between the bone resorption around PEEK and titanium implants in human subjects. Moreover, a more recent FEA study by Sarot et al. suggests there is no difference between the stress distribution around PEEK and titanium dental implants [7] . Indeed, more clinical trials are vital to conclude whether or not PEEK implants produce lesser stress-shielding than titanium implants. Unmodified PEEK is inherently hydrophobic in nature, with a water- [8,9] contact angle of 80–900 and bioinert . Indeed, studies have shown that there is no significant effect of unmodified PEEK on the proliferation rate of cells in vitro [10] . On the contrary, some studies have observed an increased protein turnover in cells in contact with conventional- [11] and CFR-PEEK . Animal studies have suggested that PEEK can survive for up to 3 years while inducing non- [12] remarkable localized inflammation . Nevertheless, quite a few studies suggested that there is no significant difference between the osseointegration of PEEK and conventional implant materials such as zirconia and titanium [13] . Conversely, recent proteomic studies have indicated that PEEK inhibits mRNA processing that may lead to a decreased cellular proliferation rate on the surface and cytotoxic [14] effects may be produced in the long-term . Nonetheless, the same proteomic studies have found no difference between the bioinertness of [15] PEEK, zirconia and titanium . Although unmodified PEEK, is considered as a biointert material however, there has been no conclusive evidence of osseoconductive effects of PEEK in vivo and in vitro. Hence, in its unmodified form, the long term survival rate of PEEK implants is questionable. In order to improve the mechanical and biological proper-ties, a number of modifications have been attempted in PEEK materials. Fig 2 : Applications of polyetheretherketone (PEEK). 10 3 1 15 5 Vol. 13 12 No. 1 2 3 May-August Sept-Dec 2017 Jan-April 2016 2016