An assessment of techniques for dehydrating root canals using infrared laser radiation

Infrared lasers have been used for debridement and sterilisation of both soft and hard tissues, but there have been few studies of such laser applications in endodontics. The present laboratory study was undertaken to examine the feasibility of using pulsed infrared laser radiation to remove moisture from root canals (with an adjunctive sterilising effect). Canals were prepared in extracted teeth and a standardised technique used to fill the apical half of the root canal with saline. Pulses of CO2 or Nd:YAG laser energy were delivered into the root canal system via miniature applicators and residual fluid determined, as well as temperature changes on the root surface. With the CO2 laser, long pulse durations were effective at dehydrating the canals, but elicited deleterious thermal changes both locally within the canal as well as on the root surface. With Nd:YAG laser treatment, large temperature increases on the root surface occurred even with low powers and low pulse frequencies, and extended times were necessary for dehydration. With higher powers and pulse frequencies, complete dehydration could be achieved in less than 60 seconds, however root surface temperatures increased approximately 25 degrees, and the radicular dentine was damaged by the production of plasma. Dehydration of root canals could not be achieved safely with these two infrared lasers, and damage to both radicular dentine and the periodontal ligament would occur if these techniques were to be applied clinically. Alternative methods which do not exert significant thermal effects should be investigated.