Page 41 - Journal of Laser Dentistry 1

lased group, resulting in clean root canal walls. The temperature increase on radicular surface varied depending on the power output and also the morphologic alterations of the dentinal walls were closely related to the thermal effect of laser irradiation. The morphologic changes in dentin walls caused by near infrared laser irradiation (from 803 to 1064nm) have been also extensively investigated and different outcome resulted closely related to the power and operative modality used and the type of associated irrigating solution. (10)

When considering different output powers and irrigant solution, the results showed a variety of changes from smear layer removal to dentine fusion. Such results confirmed that smear layer and debris are also removable with Diode laser, however cleaning all root canal walls is still difficult. If the energy level and duration of application are inadequate, a certain degree of thermal damage and morphological changes in dentin structure are observable (11), so that gated mode is advisable, also according to Moritz (12) and Benedicenti (8) studies.

A study from Alfredo E et al (2009), using 980-nm diode, reported a laser-modified surface with smear layer, fissures, and no visible tubule in the specimens treated in NaOCl wet canal. The samples rinsed with EDTA and laser irradiated presented instead absence of smear layer, partially opened tubules and some melting areas, concluding that laser promoted similar alterations on dentine morphology, depending to the type of surface pretreatment. (13,14) A recent research from Hmud R. et al in 2010 (15) investigated the role of diode laser (940 and 980 nm) in inducing cavitation in water-base media by the formation and implosion of water vapour as a mechanism of cleaning and deridment of the root canal. The study suggested that laser power played a more important role than pulse frequency or pulse

interval, due to the need of thermal energy to vaporize the water; the optimal laser-initiated cavitation occurred when weak (3%) peroxide solutions were used as the target irrigant, rather than water.

A SEM study from da Costa Ribeiro A. et al showed fusion and resolidification of the dentin surface (16), with partial removal of debris on the specimens irradiated when the diode laser was used in continuos wave associated to sodium hypoclorite irrigation. These alterations of the dentin surface appeared to be less evident in the group treated in gated mode associated to EDTA irrigation. The reduced thermal effect togheter to the use of EDTA solution as chelant irrigants, have the double result of a reduced thermal damage and more chelating, debridment and cleaning action of EDTA.

Conclusion

The results of this study indicate that the diode laser, besides its great decontaminating action, is useful for removing smear layer and debris from root canal walls, only when used with appropriate chelant irrigants. The use of diode laser in combination of EDTA irrigation have a synergistic effect, increasing treatment efficacy and leading to significantly better cleaning and debriding of the root canal.

Bibliograpy

1. Baumgartner JC, Cuenin PR. Efficacy of several concentrations of sodium hypochlorite for root canal irrigation. J Endod 1992; 18(12):605-12.