Er : YAG and alexandrite laser radiation propagation in root canal and itseffect on bacteria

Objective: The objective of this study was to compare the bactericidal effe ct of the Er:YAG (wavelength 2.94 mu m) and the Alexandrite (wavelength 0.7 5 mu m) laser radiation. The spreading laser energy in the surrounding hard dental tissues round the root canal was evaluated and the bactericidal eff ect of both these different laser wavelengths was analyzed. Summary Backgro und Data: The use of a laser to clean and shape the root canal space is the latest method used for cleaning of root canals. The interest in laser endo dontics was concentrated on the possibility to extirpate the contents of th e root canal, to sterilize and to "melt" the walls of the root canals, The previous reports were performed with CO2, excimer, argon, Nd:YAG, Ho:YAG, a nd Er:YAG lasers, Methods: Er:YAG laser system (2.94 mu m, energy 100 mJ or 300 mJ, repetition rate 1 Hz, 30 pulses) and alexandrite laser system (0.7 5 mu m, energy 250 mJ, repetition rate 1 Hz, 30 pulses) were prepared and t hree experimental arrangements were used during the measurements, First the energy transport through the tooth tissue was observed (frontal and side e xperimental setups) and then, the bactericidal effect was evaluated, Result s: It was demonstrated that due to the absorption in the hydroxyapatite and water content in the dentin, the Er:YAG laser radiation is fully absorbed in the root canal wall. This direct influence of the radiation could be exp ected only close to the sapphire tip. It was found that the tissue, which w as not directly affected by the laser radiation, cannot be disinfected by t he subablative effect of Er:YAG laser radiation. In the second part of the experiment the real bactericidal effect of Er:YAG ablative energy (300 mJ) could be observed. It was also shown that the alexandrite laser radiation w ith a wavelength of 0.75 mu m spreads through the canal system space and le aks into the surrounding tooth tissues. Both lasers have bactericidal effec t, Conclusions: The pulsed Er:YAG and alexandrite lasers can be efficiently used for killing dental bacteria but the spreading of their radiation in t he tooth tissues are different.