1992 Volume 3 Issue 1 Pages 57-64
Few reports have been made on Nd: YAG Laser in Operative dentistry. Thepurpose of this study is to examine the morphological changes of lased enamel and dentine by pulsed Nd: YAG laser which was developed by American Dental Laser Company, in advance of the clinical application to dentine hypersensitivity, removal of carious dentine and cavity preparation.
For this study, 100 extracted human anterior and molar teeth were used. The power of this laser device was 0 to 3 watts and its number of pulse was 10 to 30pps. Furthermore, the guide beam of 1mW He-Ne and the quartz fiber of 0.32mm in diameter were used. The experimental group was classified into two subgroups. One is the group of only laser irradiation, the other is that of laser irradiation and excavation, with or not black indian ink. The specimens were observed by LM, SEM and CRM. As a result, the lased enamel surface, painted with black ink under the condition of the power of 0.75 to 3 watts, the number of pulse 10 to 30pps and the exposure time of 1 to 60 seconds, showed the morphological findings like a cracker and a lava. Observing the sectioned surface of these lased enamel and dentine, the upper surface of 10μm in depth showed the melted and homogeneous structure like a lava. The findings of such a portion by SEM-EDX and CMR showed the high concentration of calcium and phosphorus due to the evaporation of organic components. The above findings were also observed on the lased dentine and almost all dentinal tubles were closed by the laser irradiation, in the cases of combining with an excavator, no carious dentine was confirmed by LM observation, CMR showed that about 10μm of the lased surface was a radiographic opaque zone. The orfices of dentinal tubles located on the cervical hyper sensitive dentine were closed by laser irradiation under the condition of 1W, 2OPPS and 1 to 3 seconds.
From the above results, unless there are dental pulp damages and induced pain by laser irradiation, this therapy could be concluded to be very effective for caries prevention, laser etching of enamel and dentine, removal of carious dentine and pain relief of hypesensitive dentine.