| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1994: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The first laser machine, which was invented by Maiman in 1960, has been used extensively in several areas of scientific research, including medicine and dentistry. The carbon dioxide (CO_2) laser became available about 20 years ago. The beam is well absorbed by water and hence by biological tissues. Although there are some reports in the literature describing the effects of laser irradiation in vivo on enamel, dentin, and pulp, relatively little histological information is available regarding the response of the alveolar bone and periodontal ligament with the light and electron microscopy.
In the present study, we compared the difference of healing process and histological changes in the time course between the laser treated group and the control group in which defects were made by a dental bur instead of laser irradiation. Rabbit mandibles were irradiated by a CO_2 laser and bone defects until reaching the tooth were mede. The comparative studies were performed by means of the histolog
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ical method, microradiography, the fluorescent labeling method, and the TUNEL method. The results obtained were as follows.
1) Laser irradiation on bone, periodontal ligament and tooth caused significant changes in overall tissue architecture.
2) Debris and charred bone tissue and the lack of a granulation tissue plug which usually forms following drilling with a dental bur were found in the defectafter lasing, .
3) Formation of new bone directly againt carbonized bone surfaces was not shown.
4) Necrosis of osteocyte (sequestra formation) was observed in a wider area at the laser treated group, while the control group had no such findings.
5) Control group with the dental bur showed the formation of new bone after 2 weeks, however, healing process of bone was not ocmpleted in 4 weeks.
6) Carbonized and degenerated necrotic layrs as well as the defectivecavities remained at 4 weeks.
7) TUNEL positive areas extended parallel to the tooth axis along a periodontal space from the center of an laser irradiated site.
These results indicated that CO_2 laser irradiation adversely effects osseous and periodontal tissues in a wide area and the delay of the wound healing process might be caused by the remaining carbonized layrs. Less
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