Ultrastructural changes of human dentin after irradiation by Nd:YAG laser.
OBJECTIVE
The use of Nd:YAG laser has been proposed for endodontic treatment. However, its ability to reduce dentin permeability, which is important for the success of root canal treatment, remains controversial.


METHODS
Nd:YAG laser irradiation was performed in pulsed mode on human dentin. The parameters were: pulse energy (100 mJ), rate (10 pps), and total irradiation time (4 seconds). The crystalline phases, electron diffraction patterns, morphology, and microstructure of specimens after laser irradiation were observed by dark-field emission transmission electron microscope (TEM).


RESULTS
Three ultrastructural zones could be delineated in the dentin: (1) an outer zone with an ordered columnar structure composed of hydroxyapatite and beta-tricalcium phosphate, (2) an intermediate zone composed of an amorphous substance (about 40-70 nm in diameter), and (3) an inner zone of well-crystallized hydroxyapatite grains. These three zones were free of pores or voids.


CONCLUSIONS
Our study demonstrated that laser-irradiation might be used to reduce dentin permeability.
Lee
Bor Shiunn
BS
Department of Dentistry, National Taiwan University Hospital, Taipei 10016, Taiwan.
Lin
Chun Pin
CP
Lin
Feng Huei
FH
Lan
Wan Hong
WH
D003745:Dental Enamel Permeability / Q000528:radiation effects*; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure*; D006801:Humans; D028022:Low-Level Light Therapy; D008854:Microscopy, Electron