Shot peening increases resistance to cyclic fatigue fracture of endodontic files

Abstract

The objective of this study was to assess the resistance to fatigue fracture of conventional nickel–titanium files after undergoing shot peening. Forty NITIFLEX endodontic files, number 30, were divided into two groups; one was submitted to shot peening treatment and the other was not. All instruments were tested for fatigue fracture in simulated canals with a TRI-AUTO ZX endodontic motor. One file of each group was subjected to a residual stress analysis by XRD. Finally, the fractured surface was observed and elemental analysis performed by means of SEM and EDX. Roughness analysis was made by focal variation microscope. The shot peening group showed greater resistance to fatigue fracture; there was no difference in the length of the fractured fragments. XRD results showed the presence of residual compression stresses in the file submitted to shot peening, a decrease in the interplanar spacing, and an increase in the full-width-at-half-maximum and the microstrains. SEM and EDX showed a ductile fracture with zones of fatigue and an equiatomic ratio between the nickel and titanium. Surface roughness increased after the file was subjected to the shot peening procedure. In conclusion, shot peening increases the resistance to fatigue fracture due to the presence of residual compression stresses in files manufactured from a conventional nickel–titanium alloy.

Effect of shot peening on corrosion resistance of additive manufactured 17-4PH steel

“…A schematic representation of the changes within the surface layer is shown in Figure 1. As can be seen in Figure 1, SP can close cracks formed in the manufacturing process [10]. Shots can be made, for example, from steel, glass, ceramics, or nutshells [11].…”

Surface Engineering Strategies to Enhance the In Situ Performance of Medical Devices Including Atomic Scale Engineering

“…Treated samples took 585 s to fracture while untreated samples fractured at 174 s, and the length of fractured fragment was noted as 5.35 and 5.03 for treated and untreated samples, respectively. It was concluded that resistance to fracture was enhanced by hardening of surfaces, plastic deformation, and residues of compression stresses [165]. The shot peening method has several advantages and disadvantages, which are mentioned in the Table 8.…”

A Critical Review of Laser Shock Peening of Aircraft Engine Components

“…[18][19][20][21][22][23][24][25] While conventional SP can improve the fatigue resistance of components by introducing a large CRS on the target surface, the depth of the CRS layer is limited. [26][27][28] Other limitations of SP include poor thermal and mechanical stability of the CRS, [29][30][31] a significant increase in target surface roughness, and difficulty in realizing automatic control. [20] LPB and DR work similarly, and a stable layer of CRS introduced by LPB and DR has been demonstrated to improve the fatigue performance of various metallic materials.…”