This study investigated a new method for the removal of intracanal broken instruments using laserwelding.
Twenty-four tips of K files, 10mm in length (diameter: 0.35mm), were used in the first experiment. After ahollow stainless-steel tube was inserted into the tip, an optical fiber (∅=400 μ) was introduced into the tubeto touch the tip, and a Nd: YAG laser was irradiated (output energy: 300mJ, 400mJ, 500mJ, 600mJ 10 pps 1sec). Then, a tensile test was performed.
In the second experiment, 30 tips of K files (diameter: 0.25mm, 0.30mm, 0.35mm, 0.40mm and 0.45mm) wereused. After setting as in the first experiment, the Nd: YAG laser was irradiated at 400mJ, 10 pps for 1 sec, and the tensile test was performed.
Data were analyzed by one-way ANOVA and the Tukey-Kramer test (P<0.05).
The results were as follows:
1. In the first experiment, laser welding was successful in all samples. The maximum load of the tensiletest in the 300mJ, 400mJ, 500mJ and 600mJ groups was 2.10-1.29kgf, 5.86-1.42kgf, 5.29-1.18kgf and 5.17-1.17kgf, respectively. The value of the 300mJ group was statistically lower than that of any other group.
2. In the second experiment, laser welding was successful in all samples except three samples in the 0.25mm group. The maximum load in the 0.25mm, 0.30mm, 0.35mm, 0.40mm and 0.45mm groups was 0.91-0.61 kgf, 2.73-0.91kgf, 5.86-1.42kgf, 6.40-0.86kgf and 6.52-1.06kgf, respectively. The values of the 0.25mm and 0.30mm groups were statistically lower than those of the other groups.