Effects of Nd:YAG lasers on root canal walls: a light and scanning electron microscopic study.
OBJECTIVE
This study evaluated amounts of debris, smear layer, and recrystallized dentin on root canal walls treated with an Nd:YAG laser. The presence of carbonized material was also assessed.


METHODS
The root canals of 36 extracted incisors were prepared by stepdown and stepback techniques and divided into 4 groups. One group was not treated further, while 3 others were exposed to the laser beam at an energy density of 159, 239, or 318 J/cm2. The roots were split longitudinally, photographed, and examined using a scanning electron microscope. The amounts of debris, smear layer, and recrystallized dentin were recorded from horizontal bands around the root, 2, 6, and 10 mm from the apices.


RESULTS
Mean smear layer scores were similar for all groups at the 3 levels examined, ranging from 2.157 to 2.851 on a scale of 0.0 to 3.0. Mean debris scores were similar for all groups at the 3 levels examined, ranging from 0.774 to 1.408 on a scale of 0.0 to 3.0. Recrystallized dentin was recorded in all 3 irradiated groups at the 2-mm level, but only in the group irradiated with 318 J/cm2 at the 6- and 10-mm levels. Severe carbonization was recorded at the 2-mm level.


CONCLUSIONS
Use of the Nd:YAG laser did not reduce the mean amounts of debris and smear layer compared to a nonirradiated group. Carbonization was recorded in the apical part of the canal, but this is not obvious when only scanning electron photomicrographs are examined.
Barbakow
F
F
Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich, Switzerland. barbakow@zzmk.unizh.ch
Peters
O
O
Havranek
L
L
D003786:Dental Pulp Cavity / Q000648:ultrastructure; D006801:Humans; D007180:Incisor; D007834:Lasers; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D018915:Root Canal Preparation / Q000295:instrumentation*; D016369:Smear Layer