The purpose of this study was to compare morphological changes on the
dentin surface induced by laser light delivered perpendicular or paral
lel to the dentin surface. The surface of the dentin slices and the ro
ot canal walls were lased with argon, CO2, and Nd:YAG lasers. When the
laser beam was parallel to the dentin, the effects of the laser energ
y ranged from no effect to eroding and melting of the smear layer and
dentin in the samples. When the laser beam was perpendicular to the su
rface, all three lasers produced well-shaped craters. From this, it wa
s concluded that the angle of the laser beam in relation to the target
surface can be a deciding factor of how much energy will be absorbed
by the dentin and consequently of the morphological changes induced by
the laser.