We have developed a new monitoring system to detect thermal damages in cavity preparation withan Er: YAG laser. The system consists of an optical fiber, a spectroscope and MOS linear image sensorwhich has high sensitivity and response speed. Emission line spectra of 560 nm and 590 nm in wavelength wereobserved when tissue charring, thermal cracks and deposition of molten materials were produced by theirradiation of laser beam. The intensity of the emission increased as the laser energy became higher. Theemission line spectra were not observed when the cavities were perforated without thermal damage.
This study compared pain relief effects after periodontal and endodontic surgeries between Nd: YAG laser irradiation and administration of anti-inflammatory drugs using the Visual Analogue Scale (VAS). Forty-three teeth in 20 patients were included in this study. The surgical procedure was as follows: the gingival flap was elevated root planing and bone defect debridement were done. In the experimental group (Exp) of 24 teeth in 10 patients, the Nd: YAG laser was irradiated to the root surface, bone defect and theinside of the gingival flap after root planing and bone defect debridement (3.0 W, 30 seconds, 3 times). Inaddition, the laser was irradiated around the mucogingival junction immediately after surgery (1.5W, 1minute, 3 times). In the control group (Cont) of 19 teeth in 10 patients, no intervention was made followingsurgery and anti-inflammatory drugs were taker as soon after surgery as possible. VAS was performedimmediately after surgery, at 1, 2, 3, 4, 5 and 6 hours in one day and at 1, 2, 3, 4, 5 and 6 hours in two days. Healing was uneventful in all patients. Statistical analysis by the Wilcoxon signed-rank test indicated that VAS of Exp was significantly higher than Cont between 1 hour and 3 hours in one day and VAS of Cont wassignificantly higher than Exp between 1 hour and 5 hours in two days (p<0.05). This study suggests that laser irradiation and anti-inflammatory drugs may have almost the same pain reliefeffect after periodontal and endodontic surgery.
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.