Table 1.
Studies included in the review and their results obtained
| Surface modification | Author | Year | Method | Result |
|---|---|---|---|---|
| Ion implantation | Gavini et al.[13] | 2010 | Nitrogen ion implantation | Increases the number of CTF |
| Wolle et al.[14] | 2009 | Argon and nitrogen ion implantation | Argon ion implanted file showed double the number of CTF than nitrogen ion implanted file | |
| Rapisarda et al.[15] | 2001 | Nitrogen ion implantation | Increased wear resistance | |
| Conrad et al.[16] Tendys et al.[17] | 1987 1988 | PIII of TiN | Increased wear resistance | |
| Thermal nitridation | Rapisarda et al.[18] | 2000 | TiN coating | Improved cutting ability |
| Lin et al.[19] | 2007 | TiN coating | Greater corrosion resistance when exposed to 5.25% NaOCl | |
| Li et al.[20] | 2006 | TiN coating | Increased cutting efficiency and corrosion resistance | |
| Cryogenic therapy | Kim et al.[21] | 2005 | Cryogenic therapy | Higher microhardness, increased austenitic phase, increased cutting efficiency |
| Vinoth Kumar et al.[22] | 2007 | Deep CT | Improved cutting efficiency, no effect on wear resistance | |
| George et al.[23] | 2011 | Deep CT | Increased cyclic fatigue resistance | |
| Electropolishing | Anderson et al.[24] Tripi et al.[25] da Silva et al.[26] Lopes et al.[27] Condorelli et al.[28] Praisarnti et al.[29] |
2007 2006 2013 2010 | Electropolishing | Increased cyclic fatigue resistance |
| Herold et al.[30] | 2007 | Electropolishing | Does not prevent microfractures | |
| Bui et al.[31] | 2008 | Electropolishing | Electropolished files less resistant to cyclic fatigue | |
| Kaul et al.[32] | 2014 | Electropolishing | Eliminated manufacturing flaws but produced a weak surface highly vulnerable to fresh crack development | |
| Vapor deposition | Schäfer[33] | 2002 | PVD to NiTi K-files | 26.2% increase in cutting efficiency |
| Chi et al.[34] | 2017 | Titanium–zirconium-boron surface layer via PVD | Highly smooth file geometry with greater cyclic fatigue resistance | |
| Bonaccorso et al.[35] | 2008 | PVD and immersion in sodium chloride | Enhanced corrosion resistance, and better pitting resistance | |
| Qaed et al.[36] | 2018 | PVD | Electropolished files performed better than physical vapor-deposited files | |
| Surface functionalization | Cora et al.[37] | 2020 | 2% silver ion dip-coating | Increased efficiency against Enterococcus faecalis without influencing cutting efficiency |
CT: Cryogenic treatment, TiN: Titanium nitride, PIII: Plasma immersion ion implantation, CTF: Cycles to fracture, PVD: Physical vapor deposition, NiTi: Nickel–titanium