PERMEABILITY, MORPHOLOGIC AND TEMPERATURE-CHANGES OF CANAL DENTIN WALLS INDUCED BY ND-YAG, CO2 AND ARGON-LASERS

The permeability, temperature and morphologic changes of the wall of t he root canal induced by Nd:YAG, CO2 and argon lasers were studied, Th e changes were evaluated according to the presence or absence of a sme ar layer, Root canals of 140 human single-rooted teeth were enlarged u sing a step-back technique. Permeability was evaluated by the extent o f methylene blue dye penetration into the tubules, Temperature changes were measured using a thermovision system, and morphological changes were evaluated by scanning electron microscopy, Laser energy was deliv ered into the canal by means of a flexible optical fibre or metal tip, There were statistically significant differences in permeability betw een lased groups with and without a smear layer in the cervical third of the root canal following lasing, In the middle third of the root ca nal, all three laser types induced permeability increases in groups wi th a smear layer, In the apical third, statistically significantly dec reases in permeability were observed among CO2 laser and Nd:YAG compar ed with control group (P < 0.01), Rises in temperature ranged from a m inimum of + 10.1 degrees C (CO2 laser) to a maximum of + 54.8 degrees C (argon laser), All three laser devices appeared capable of producing a glazed-like surface and craters.