Removal of broken tiles using pulsed Nd:YAG laser irradiaton

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This study investigated a new method for the removal of intracanal broken instruments using laser welding. Twenty-four tips of K files, 10 mm in length (diameter: 0.35 mm), were used in the first experiment. After a hollow stainless-steel tube was inserted into the tip, an optical fiber (q5 =40011 m) was introduced into the tube to touch the tip, and a Nd:YAG laser was irradiated (output energy: 300 mJ, 400 mJ, 500 mJ, 600 mJ; 10 pps; 1 sec). Then, a tensile test was performed. In the second experiment, 30 tips of K files (diameter: 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm and 0.45 mm) were used. After setting as in the first experiment, the Nd:YAG laser was irradiated at 400 mJ, 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 tensile test in the 300 mi, 400 mJ, 500mj and 600mJ groups was 2.10±1.29 kgf, 5.86±1.42 kgf, 5.29±1.18 kgf and 5.17±1.17 kgf, respectively. The value of the 300 mi 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 0.25 mm group. The maximum load in the 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm and 0.45 mm groups was 0.91 ± 0.61 kgf, 2.73±0.91 kgf, 5.86±1.42 kgf, 6.40±0.86 kgf and 6.52±1.06 kgf, respectively. The values of the 0.25 mm and 0.30 mm groups were statistically lower than those of the other groups.