Eliminating effect of Er, Cr: YSGG laser irradiation on the smear layer of dentin

Jingtao Yu, MD, DDS, and Lu Yan, MD, DDS

College of Stomatology, China Medical University, Shenyang, P. R. China

Purpose: To observe morphological changes and elimination of smear layer on the dentin exposed to Er, Cr: YSGG laser using different energy and irradiating distance.
Materials and Methods: Twenty-two first premolars were selected and slices with 1.5 mm thickness were prepared by horizontal sectioning through the middle third of the teeth crown. The occlusal surface having been coated by smear layer were to be treated. Each dentinal slice was irradiated under the laser with different irradiating distance (<2 and 3 mm) and different energy (1, 2, 3, 4, and 6 W). After routine preparation for microscopic observation, the specimens were observed with a scanning electron microscope.
Results: Laser with energy of 2-6 W and irradiating distance below 2 mm could effectively remove the smear layer from the dentin. Dentinal tubule orifices were diminished or partly occluded. With the energy of irradiation increased, the elimination of the intertubular dentin increased; on the other hand, laser with energy beyond 4 W and irradiating distance of 3 mm can also effectively eliminate the smear layer.
Conclusion: Energy of 2-3 W (irradiating distance below 2 mm) and energy of 4-6 W (irradiating distance about 3 mm) are recommended settings with which Er, Cr: YSGG laser can effectively remove the smear layer from the dentin surface. (Int Chin J Dent 2004; 4: 56-60.)
Clinical Significance: As a new, valid, and safe method, Er, Cr: YSGG laser selected proper setting can be applied in the clinical practice to remove the smear layer from dentin surface.
Key Words: dentin, Er, Cr: YSGG laser, scanning electron microscopy, smear layer.