Nd: YAP Laser in the Elimination of Endodontic Nickel-Titanium Files Fractured in Rooted Canals (Part 1: Teeth With Minimal Root Curvature)

Background
Fracture of nickel-titanium (Ni-Ti) instruments in root canals is commonly associated with compromised outcomes in endodontic treatment. There is no single, universally accepted approach for managing this complication. The objective of this study is to evaluate the effectiveness of an Nd: YAP laser-assisted protocol in removing fractured Ni-Ti files in teeth with minimal root curvature (less than 15 degrees).
Methods
A total of 66 notched Ni-Ti files located at the apical third of the extracted teeth with minimal root curvature (less than 15 degrees) were included. The Nd: YAP laser was used with parameters set to a power of 3W, delivering 300 mJ per pulse. The fiber had a diameter of 200 µm, and the laser operated in pulsed mode at a frequency of 10 Hz, a pulse duration of 150 𝜇s, and an energy density of 955.41 J/cm2 per second. The safety of the irradiation parameters was proven in a previous study. The edge of the laser fiber was inserted in the canal until close contact with the fractured file was achieved during all the irradiation procedures. Total elimination and bypass of the instrument were considered a success while partial bypass, non-bypass, or lateral perforation were considered a failure. In addition, the average time required to bypass or eliminate the broken Ni-Ti files was recorded. Scanning electron microscopy (SEM) was used to evaluate physical modifications after irradiation, and X-ray emission spectroscopy was employed to calculate the percentage of nickel and titanium incorporated into the dentinal walls of the canals.
Results
Six samples were excluded from the study. From the 60 included, the success rate was 100%, with 71.66% (n=43) bypass and 28.33% total elimination (n=17) of the fractured instrument. The mean and standard deviation of the measured time for bypassing or completely removing the broken files was 7.463 ± 3.679 seconds. Chemical analysis revealed that Ni and Ti residues were predominantly present in the irradiated canal area with a mass percentage of 5.548 ± 4.621 and 7.371% ± 5.393 for Ni and Ti, respectively, at the impact area and decreased toward the apical region.
Conclusion
This study proposes a promising protocol using Nd: YAP laser for removing fractured Ni-Ti files in teeth with minimal root curvature that is less than 15 degrees.