Apical sealing is essential for the success of paraendodontic surgery, so any procedure that may favor an adequate sealing of the apical remainder should be performed. The purpose of this study was to evaluate the influence of diode laser irradiation on the apical sealing of root-end cavities with MTA retrofillings. Root canals in twenty extracted human teeth were shaped with K-files and filled with gutta-percha. The apexes were cut off and root-end preparations were performed. The roots were divided randomly in 2 groups. Group 1 (ten specimens) was retrofilled with MTA. Group 2 was irradiated with diode laser, with 1 W for 20 seconds, on the apical surface and root end cavity before retrofilling with MTA. The specimens had their external surfaces impermeabilized with cyanoacrylate, except for the apical surface, and were then immersed in 1% rhodamine B dye for 72 h and placed in plaster stone. After that, the specimens were submitted to longitudinal abrasion until half of the root remained. The linear dye leakage was observed in these mid-roots between the root canal wall and retrofilling. The linear dye leakage was measured with Image Lab software, and the results were statistically analyzed with Student's t test. There were no statistically significant differences between the two groups (p > 0.05). The diode laser irradiation did not improve the apical sealing of MTA retrofillings under the conditions of this in vitro study.

The laser therapy is an excellent adjunct clinical procedure in endodontic treatment in order to improve the cleaning and disinfection of the root canal system; however few studies in the literature investigated the possible use of this new technology in the clinical situations of retreatment. The objective of this study was to evaluate in vitro the use of the diode laser (810nm, continuous mode) in the removal of gutta-percha and AH Plus sealer from the root canal, with or without the use of a chemical solvent (eucalyptol). Root canal filling materials were irradiated by 810 nm diode laser (ZAP SOFTLASE, ZAP LASERS). The temperature changes at the outer root surface were verified in the apical third of 12 samples during the irradiation. Temperature increase from 2.47 to 9.35 ºC was observed. The specimens were randomly divided in 4 groups of 10 roots each, varying the parameter of laser irradiation and the use of eucalyptol. The groups were assigned as follow: Group I = irradiation (1.0 W) without the solvent use, Group II = irradiation (1.5 W) without the solvent use, Group III = irradiation (1.0 W) + solvent, Group IV = (1.5 W) + solvent. Mesio-distal and buccolingual radiographs were taken before and after retreatment and the area of remaining gutta-percha in the root canals was determined with the aid of: Adobe Photoshop and ImageLab softwares. The groups: G1xG3; G1xG4; G2xG4 presented statistical differences.Based on the methodology used, it was verified that the temperature did not exceed 10ºC and that the presence of the solvent made it possible to remove large amounts of root canal filing material, aiding the desobturation process when used in association to the diode laser.