Permeability, morphologic and temperature changes of canal dentine walls induced by Nd:YAG, CO2 and argon lasers

The permeability, temperature and morphologic changes of the wall of the root canal induced by Nd:YAG, CO2 and argon lasers were studied, The changes were evaluated according to the presence or absence of a smear layer, Root canals of 140 human single-rooted teeth were enlarged using a step-back technique. Permeability was evaluated by the extent of 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 delivered into the canal by means of a flexible optical fibre or metal tip, There were statistically significant differences in permeability between 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 canal, all three laser types induced permeability increases in groups with a smear layer, In the apical third, statistically significantly decreases in permeability were observed among CO2 laser and Nd:YAG compared with control group (P < 0.01), Rises in temperature ranged from a minimum 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.