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KMID : 0355219950200020429
Journal of Korean Academy Oral Medicine
1995 Volume.20 No. 2 p.429 ~ p.448
Effects of Pulsed Nd:YAG Laser Irradiation and Fluoride Compound Application on Acid Resistance of Bovine Teeth


Abstract
This study was designed to determine the most effective concentration of fluoride and levels of laser irradiation for the remineralization of decayed teeth. After irradiation with a pulsed Nd:YAG laser and the topical application of fluoride, phosphate and fluoride concentration in enamel were measured And then the changes on surface enamel using an scanning electron microscope were observed
Samples by extracting healthy, permanent, mandibular bovine teeth with no caries were obtained. Among them 371 healthy samples were selected and artificial carious lesions were made. 20 samples were assigned to each experimental group.
After irradiation with a pulsed Nd:YAG laset with total energy densities of 10J/cm2, 20J/cm2 and 30J/cm2 for each group. On the teeth,- 2% NaF, 1.9% NH,F, 1.6% TiF4, Elrnex gel(amme fluoride) and 1.23% APF gel were applied. After pH circulatory procedures, concentrations of fluoride with an lonalyzer (Orion Research. Model 901, USA) and phosphates with a UV/Vis spectrophotometer (Uvikon 860, Kontron Co., Switzerland) were measured. By etching the teeth in layers and measuring fluoride concentrations, a profile of fluoride penetration according to depth could be developed. And also the changes on the surface of the enamel using an electron scanning microscope were observed.

The comparative analysis yielded the following results ;

1. Phosphate concentration was low in all groups compared with the control group except for teeth treated Elmex gel, irradiated with 10J/cm2 and 30J/cm2 energy densities. Teeth treated with APF gel and 30J/cm irradiation had the lowest phosphate concentration.
2. Among all groups, fluoride concentrations in tooth enamel were highest in APF gel and NaF groups irradiated at 30J/cm2. The APF gel group had the highest fluoride concentrations across all energy densities.
3. In the APF gel group, and the NaF group, the greater the energy density of the laser, the higher the fluoride concentrations in the enamel.
4. In all groups, the concentration of fluoride in the enamel by depth tended to decrease with depth.
5. Under the scanning electron microscope, under the condition of irradiation with 20J/cm2, enamel crack was detected for the first time. In the NH4F group, spherical deposits were found on the surface of the enamel, and in the TiF4 group the surface of enamel was covered with an irregular, thin membranous mass in places. In the APF gel and NaF groups irradiated with lOJ/cm`, spherical and irregular particles covered the teeth. When these groups were irradiated at 20J/cm2, they were covered with amorphous crystals.

These results suggest that one could obtain more effective anticariogenic effects without damage to teeth when less than 20j/cm- energy densities and APF gel are used.
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