Improving the Surface Properties of Nickel-Titanium Endodontic Files

Objectives: Current technology has evolved of various treatments to enhance the surface properties of dental instruments for improving their efficacy during clinical use. In endodontics, shaping systems with a flexible core and a hard surface has developed technologies with increasing flexibility and increased cutting efficiency. Physical vapor deposition (PVD) is used to produce thin films and coatings on various surfaces. This study presents a novel surface treatment using a Boron/Nitride (B/N) layer applied onto the surface of endodontic files using PVD, and evaluation of the surface topography compared with non-coated files by AFM, SEM and surface profilometry.
Methods: A non-coated MTwo (VDW, Munich, Germany) 0.06 taper size 25 endodontic file was coated with 0.5 µm thick Boron/Nitride (B/N) layer using the PVD technique. The surface topographies were analysed and compared with a non-coated MTwo size 25, 0.06 using atomic force microscopy (AFM), laser surface profilometer, and scanning electron microscopy.
Results: AFM showed an average Ra of 29.1 μm for the B/N coated file, and 36.9 μm for the uncoated file. The laser profilometer showed an average roughness of 7.4 μm for the coated file, and 14.1 μm for the uncoated file. SEM and AFM showed that the B/N coated files had a cellular-like coating distributed on the surface. SEM elemental analysis showed for the coated files a ratio of Ni/Ti (wt%): 21/40, whereas for the uncoated sample was 39/40.
Conclusions: A B/N PVD coating creates a layer on a file with significantly reduced surface roughness. The applications of PVD coatings such as B/N can be an effective option for the improvement of NiTi endodontic instruments.