| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1996: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Application of Er : YAG laser to apicoectomy
The purpose of this study was to compare apicoectomy using Er : YAG laser and the conventional cutting method in vitro.
Extracted single-rooted human teeth were used in this experiment. Root resection was performed with Er : YAG laser or a fissure bur mounted to a micro-motor. Resected root surfaces were evaluated with SEM.In addition, cutting efficiency of both methods and dye penetration of the cut surface were compared. After removing the tooth crown of 10 extracted single-rooted human teeth, root canal were cleaned, shaped and obturated. Then, the samples were randomly divided into two groups. Root resection by Er : YAG laser or micro-motor was performed, and working time was counted and the cut surface area measured. Then, all the root surfaces were sealed with nail polish except the resected surface. All roots were placed into 0.1% methylene blue dye for 7 days, rinsed and air-dried. Finally, they were split and the dye penetration from
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the resected surface measured and statistically analyzed.
The results were as follows : 1.There were no smear layr or debris left on the resected surface cut by Er : YAG laser, and the shape of the cut surface was irregular. On the other hand, both smear layr and debris were observed on the surface cut by the conventional method, and the cut surface was smooth. 2.The cutting efficiency of Er : YAG laser and micro-motor was 14.8 ((]SY.+-。[)7.3) sec./mm<@D12@>D1 and 4.4 ((]SY.+-。[)1.7) sec./mm<@D12@>D1, respectively. Cutting by Er : YAG laser significantly needed more time than that by micro-motor (t-test, p< 0.05). 3.Dye penetration length in the Er : YAG laser group and micro-motor group from the resected surface was 0.95 ((]SY.+-。[)0.37) mm and 1.07 ((]SY.+-。[)0.70) mm, respectively. There was no significant difference between the two groups.
Application of Er : YAG laser to retrograde cavity preparation
The purpose of this in vitro study was to determine if Er : YAG laser was capable of preparing retrograde cavities. The root canals of extracted single-rooted human teeth were prepared and obturated. Root ends were resected and the roots were randomly divided into two groups. Retrograde cavities were prepared with Er : YAG laser or an ultrasonic retro tip. Working time was counted and the rate of increase in the root canal area at the resected surface measured, and they were statistically analyzed. In addition, retrograde cavity surfaces were evaluated with scanning electron microscopy. On the other hand, retrograde cavities of 7 roots in each group were filled with EBA cement. The root surfaces were sealed with nail polish and all samples were placed into 0.1% methylene blue dye for 3 days. Finally, they were split and the dye penetration length was measured and statistically analyzed.
The results were as follows : 1.Working time of the Er : YAG laser group and ultrasonic group was 52 ((]SY.+-。[)27) and 176 ((]SY.+-。[)62) sec respectively. Er : YAG laser could prepare the retrograde cavity significantly quicker than ultrasonics. (Mann-Whitney U-test, p= 0.0001) 2.The rate of postoperative increase in the root canal area of the Er : YAG laser group and ultrasonic group was 212 ((]SY.+-。[)72) and 198 ((]SY.+-。[)58) %, respectively. There was no significant difference between the two groups (t-test, p=0.338). 3.There were nodebris, gutta percha or sealer left on the retrograde cavity surface prepared by Er : YAG laser. The shape of the retrograde cavity was spread and irregular at the resected surface. On the other hand, debris and sealer were observed at cavity surfaces cut by ultrasonic and the cavity was cylindrical in shape. 4.Dye penetration length from the resected surface in the Er : YAG laser group and ultrasonic group was 1.01((]SY.+-。[)0.18) and 1.30((]SY.+-。[)0.61) mm, respectively. There was no significant difference between the two groups. (t-test p=0.253) Less
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