title: A comparison of the morphological changes after Nd-YAG and CO2 laser irradiation of dentin surfaces.
abstract: The purpose of this study was to compare the morphological changes after Nd-YAG and CO2 laser irradiation on dentin surfaces with or without the smear layer. Eighty-one 3-mm-thick dentin specimens collected from the middle third of molar crowns were used. The dentin surfaces were ground to #320, #400, and #600 grit in series to create a smear layer. Half of the specimens were treated with 14% EDTA for 2 min to remove the smear layers. The lasers were applied on each specimen perpendicularly with 1-mm focus distance to the dentin surface for 4 s. The parameters for the Nd-YAG laser were 50 mJ, 100 mJ, and 150 mJ at 10 pps, 20 pps, and 30 pps, and for the CO2 laser were 2 W, 3 W, and 4 W at 5 ms x 20 pps, 10 ms x 10 pps, 20 ms x 20 pps, 50 ms x 2 pps, 100 ms x 2 pps, and 200 ms x 2 pps. The results showed that the Nd-YAG laser caused crater and melting of the dentin surface, especially in dentin specimens with smear layers. The CO2 laser produced extensive cracking lines on dentin surfaces with a smear layer, whereas surface erosion and crater formation were found on specimens without a smear layer. In conclusion, both the laser types and smear layer have a significant influence on the morphological changes of dentin surfaces irradiated by lasers.
authors.affiliation: Graduate Institute of Dental Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: W H
authors.initials: WH
authors.lastname: Lan
authors.forename: K W
authors.initials: KW
authors.lastname: Chen
authors.forename: J H
authors.initials: JH
authors.lastname: Jeng
authors.forename: C P
authors.initials: CP
authors.lastname: Lin
authors.forename: S K
authors.initials: SK
authors.lastname: Lin
mesh_terms: D002245:Carbon Dioxide; D003804:Dentin / Q000528:radiation effects*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008963:Molar; D009354:Neodymium; D016369:Smear Layer; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D002245:Carbon Dioxide; D009354:Neodymium