Effects of Nd:YAG-laser irradiation on monolayer cell cultures.
OBJECTIVE
The clinical applications of Nd:YAG lasers on oral soft tissues include a wide field of surgical and periodontal procedures. This in vitro study focuses on the histological effects of Nd:YAG-laser irradiation on a fibroblast monolayer cell culture especially with regard to thermal damage and cell necrosis. The results of this basic research study provide us with clear power settings for a safe soft tissue laser treatment.


METHODS
Two hundred forty multiwell cell cultures and 24 micro-slide Leighton tubes were laser treated. Laser irradiation was performed with a commercial free-running pulse Nd:YAG laser and a quartz fiber with a diameter of 200 microns on L-929 fibroblast cell cultures. The variable parameters were pulse energy (30-120 mJ), pulse rate (20-100 Hz), power output (1.5-3.0 W), and time of irradiation (10-60 s). The cultures were analyzed with help of vital staining, autoradiography, and cytomorphology examination.


RESULTS
Depending on the different settings the laser irradiation caused inhibitions of the DNA metabolism rate and the cell division rate, a degeneratively changed cytomorphology up to cell pyknosis. An increasing pulse energy, pulse rate, or an increased time of irradiation created an extended diameter of the pyknotic cell zone.


CONCLUSIONS
The laser beam creates an exactly bordered damage between cells. The cells had a very good inherent mobility, but the border between eliminated and unloaded cell zone was sharp, even after an incubation of 24 h. These stable results prove that the laser can be applied up to a micrometer distance. With the help of cell clusters it was proved that the laser beam is also able to eliminate exactly one monolayer. Cells which had been covered by another cell layer (in a cluster) were not eliminated.
Gutknecht
N
N
Clinic of Conservative Dentistry, Periodontology and Preventive Dentistry, Medical Faculty of the Technical University of Aachen, Germany.
Kanehl
S
S
Moritz
A
A
Mittermayer
C
C
Lampert
F
F
D001345:Autoradiography; D002455:Cell Division / Q000528:radiation effects; D002478:Cells, Cultured / Q000528:radiation effects; D004247:DNA / Q000528:radiation effects; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D007834:Lasers / Q000009:adverse effects; D009061:Mouth Mucosa / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D009336:Necrosis
D004247:DNA