Root canal preparation may damage NiTi instruments resulting in wear and deformation. The aim of this study was to make a comparative evaluation of the surface topography of the cervical third of four different rotary systems, before and after being used twelve times, in 1.440 resin blocks with simulated root canals with standardized 45° curvatures, and analyzed by atomic force microscopy AFM. The blocks were divided into four groups and prepared according to the manufacturers recommendations: Group 1--K3®; Group 2--Protaper Universal®; Group 3--Twisted Files® and Group 4--Biorace®. After each preparation, the instruments were washed and autoclaved. A total of 240 instruments were selected, being 30 new instruments and 30 after having been used for the 12th time, from each group. These instruments were analyzed by AFM and for quantitative evaluation, the mean RMS (Root mean square) values of the cervical third of the specimens from the four groups were used. The result showed that all the rotary files used for the 12th time suffered wear with change in the topography of the cervical region of the active portion of the file (ANOVA p < 0.01). Classifying the specimens in increasing order, from the least to the greatest wear suffered, Group 3 (2.8993 nm) presented the least wear, followed by Group 4 (12.2520 nm), Group 1 (36.0043 nm) and lastly, Group 2 (59.8750 nm) with the largest amount of cervical surface wear.

Low-level laser therapy is a tool employed in the management of post-operative inflammation process and in the enhancement of reparative process. The aim of the study was to perform histological evaluation of dental and periodontal ligament of rats central upper-left incisor teeth re-implanted and irradiated with low-level laser (InGaAl, 685 nm, 50 J/cm2) 15, 30, and 60 days after re-implantation. Seventy-two male rats had the central upper left incisor removed and kept for 15 min on dry gauze before replantation. Laser was irradiated over the root surface and empty alveolus prior replantation and over surrounding mucosa after the re-implantation. After histological procedures, all slices were analyzed regarding external resorption area and histological aspects. We observed an increase of root resorption (p < 0.05) in the control group compared to the laser group at 15, 30, and 60 days. These results showed that the laser groups developed less root resorption areas than the control group in all experimental periods. Additionally, histological analysis revealed less inflammatory cells and necrotic areas in laser groups.

The aim of this study was to assess qualitatively, by means of SEM images, the cleaning of the dentin walls of root canals after chemical-surgical preparation using Endo-PTC cream with 0.5% and 1% sodium hypochlorite and different final irrigating solutions. Seventy-two single-rooted human teeth were divided into eight groups and prepared using Endo-PTC cream with sodium hypochlorite (NaOCl) at different concentrations, and irrigated with NaOCl at different concentrations. Final irrigation was performed with either EDTA-T or EDTA-C. The best results were obtained with Group 1, followed by Groups 5, 2, 7, 8, 3, 6 and 4. We can conclude that the use of 0.5% NaOCl during instrumentation and final flush of the root canals was more efficient in cleaning than was 1% sodium hypochlorite. EDTA-T was more efficient in removing smear layer than EDTA-C, and the cervical third presented better cleaning of the root canal walls than did the middle third, which showed cleaner dentin walls than the apical third.

The aim of this study was to make a comparative evaluation of the surface topography of the cervical third and tip of four different rotary systems, before and after being used 12 times, in resin blocks with simulated root canals with standardized 45° curvatures, and analyzed by scanning electronic microscopy (SEM). A total of 1,440 resin blocks with simulated root canals and standardized curvatures were used. The blocks were divided into four groups and prepared by the crown down technique according to the manufacturers' recommendations: Group 1 (G1)--K3®, Group 2 (G2)--Protaper Universal®, Group 3 (G3)--Twisted Files®, and Group 4 (G4)--Biorace®. After each preparation, the instruments were washed and autoclaved. A total of 24 instruments were selected, being three new instruments and three after having been used for the 12th time, from each group. These instruments were analyzed by SEM. To perform the evaluation, 24 micrographs were observed by 12 evaluators who attributed a score to the images according to a template. In the qualitative analysis of the cervical region and tip of new instruments, it was observe that the files of Groups G4 and G2 were the least rough and those of G1, the roughest. In the same manner, the cervical region of the instruments was qualitatively analyzed after the 12th time of using them, and there was no statistically significant difference at a level of 1% (ANOVA P < 0.01) between G2 and G4 as well as between G1 and G3. As regards the tip, it was observed that there was no statistically significant difference, at a level of 1%, between the groups: G1 and G3, G1 and G4, and between G3 and G4, and there was statistically significant difference at a level of 1%, between group G2 and the other groups, with G3 having the greatest roughness (ANOVA P < 0.01).

Prokopowitsch I. Estudio de la variación de la permeabilidad de la dentina radicular usando isótopos 99m Tc, después de la aplicación de láser de alta intensidad RESUMENObjetivo: Este estudio tuvo como objetivo evaluar las variaciones de la permeabilidad dentinaria radicular de dientes humanos después del preparo químico-quirúrgico e irradiación con láser de Er: YAG, Nd: YAG, a través de la utilización del radioisótopo tecnecio-99m ( 99m Tc) libre. Materiales y métodos: Canales de treinta raíces palatinas de primeros premolares superiores humanos fueron preparados y divididos, aleatoriamente, en 3 grupos experimentales: G1 (control), G2 (irradiación con láser de Er: YAG) y G3 (irradiación con láser de Nd: YAG). Las muestras recibieron en el interior del canal radicular, 99m Tc libre en cantidad suficiente para el llenado y colocados en tubos de ensayo contiendo 1 ml de solución salina. Después de 1 hora, la cuenta del isótopo radioactivo ( 99m Tc) fue realizada. Resultados: Después del análisis estadístico (ANOVA), fue verificado que los mejores resultados obtenidos en cuanto a la disminución de la permeabilidad se encontraron en el Grupo 3, seguido del Grupo 2 y del Grupo 1. Conclusión: Concluimos que irradiación con láser de Nd: YAG provocó una disminución significativa de la permeabilidad dentinaria del canal radicular. El láser de Er: YAG y el control en relación a la permeabilidad de la dentina de las paredes del canal radicular no presentaron diferencias estadísticamente significativas a nivel de 5%.Palabras clave: Endodoncia, permeabilidad de la dentina radicular, Er:YAG, Nd:YAG, radioisótopo tecnecio99m (DeCS Bireme). SUMMARYObjective: The objective of this study was to evaluate changes in root dentin permeability of human teeth after chemical-surgical preparation, and laser irradiation with Er: YAG, Nd: YAG, through the use of the radioisotope technetium-99m ( 99m Tc) free.Estudio de la variación de la permeabilidad de la dentina radicular usando isótopos 99m Tc, después de la aplicación de láser de alta intensidad Study of the dentin root permeability variation using 99m