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Publication:
Journal of Oral Laser Applications

Year 2002
Volume 2 , Issue 2

Back
Pages: 107 - 113

Class V Micropreparation Using Picosecond Nd:YAG Pulsed Laser: Micromorphological and Chemical Evaluation

Rosane de Fátima Zanirato Lizarelli/Vanderlei Salvador Bagnato

Purpose: In this study, we used a picosecond Q-switched mode-locked Nd:YAG laser (Antares, Coherent) to perform Class V micropreparations in enamel and dentin with various operating parameters. Materials and Methods: Three extracted sound human molars were used. The molars were kept in a humid environment to avoid dryness. The laser beam operating with 100 picosecond (ps) pulses, was focused by a biconvex lens (f = 80 cm) which produces a spot size with a Gaussian waist close to 50 mm. For enamel, the repetition rate of the laser was fixed at 100 Hz, and the average laser power was scanned from 600 mW to 1.3 W. For dentin, the repetition rate of the laser was fixed at 15 Hz and 100 Hz, and the average laser power was scanned from 600 mW to 800 mW. The samples were fixed in an x-y-z translation stage. The Class V cavities were prepared and examined under SEM. Results: In enamel, SEM observation revealed that the highest average power produced more well-defined margins and less dehydration than did lower power settings. Picosecond pulsed Nd:YAG laser at 100 Hz and 800 mW cut enamel around the prismatic structure. In dentin, SEM showed the margins of all micropreparations to be well-defined. Cracks produced by thermal stress were present. Smear plugs were removed and dentinal tubules opened. In all samples and with all energy parameters tested, the ratio of calcium to phosphorus atoms was increased. Under lower average power, the ratio was increased more in enamel (29.8%) than in dentin (14.9%). Under higher average power, the irradiated dentin surface was more enriched with calcium atoms (30.4%) than was enamel (9.5%). Conclusion: It is possible to used short laser pulses (picosecond) to prepare Class V micropreparations in enamel and dentin with well-defined margins and without thermal or mechanical damage. The picosecond Nd:YAG pulsed laser seems a promising method for the future of operative dentistry.

 

 
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