This study evaluated the cleaning efficacy of a root canal system by Nd:YAG laser and rotary instruments. Sixty single-rooted human teeth were divided into four experimental groups (n=15). In the first group the teeth were prepared with a step-back technique using conventional K-files. In the second and third groups, tooth preparation was carried out using Nd:YAG laser and rotary NiTi instruments, respectively. Teeth in the fourth group were prepared by combined laser and rotary methods. The smear layer remaining on canal walls was then assessed by scanning electron microscopy in the coronal, middle, and apical portions. The comparison of smear layer removal efficacy between groups was carried out by Kruskal–Wallis and Mann–Whitney U tests. The mean grades of smear layer removal in rotary-laser, rotary, laser and step-back techniques were 1.34±0.18, 2.2±0.28, 1.91±0.25, and 2.42 ±0.19, respectively. On the whole, differences between rotary-laser and rotary groups, step-back, and the three other techniques (rotary, laser, and rotary-laser) were significant at p=0.034. Based on the findings of this study, the cleaning efficacy of rotary, laser, and rotary-laser techniques were better than the step-back technique and the combined laser and rotary technique was the most efficient method.

The aim of this study was to evaluate the efficacy of smear layer removal from teeth following root canals using lasers (Er:YAG and Nd:YAG), NaOCl, 17% EDTA, and MTAD by scanning electron microscopy (SEM). Root canals were irrigated with 3 mL of 5.25% NaOCl after each file. Teeth were randomly divided into five groups. In the final irrigation, canals were irrigated with 5.25% NaOCl (Group 1, control), 17% EDTA (Group 2), or BioPure MTAD (Group 3). Laser groups were irradiated with Er:YAG laser (1.8 W, 120 mJ, 15 Hz) (Group 4) or Nd:YAG laser (1 W, 100 mJ, 15 Hz) (Group 5). The smear layer at the apical, middle, and coronal thirds of each root canal was imaged using SEM. Smear layer removal by EDTA was the most effective in all regions. The difference between EDTA and MTAD was statistically significant in the coronal and middle (p < 0.05), but not the apical (p > 0.05), regions. The difference between the control and laser groups was not statistically significant (p > 0.05). In all regions, the difference between 17% EDTA–MTAD and the control–laser groups was statistically significant (p < 0.05). Although improvement was observed in removal of the smear layer using alternative materials and techniques, application of a combination of EDTA and NaOCl remains an effective technique.

The regular periodontal practice of scaling and root planing produces a smear layer on the root surface that is detrimental to the readhesion of tissues during subsequent regeneration therapy. Although it has been demonstrated that gels containing the chelating agent ethylenediaminetetraacetic acid (EDTA) can assist in the removal of this contaminating layer, no quantitative method is yet available by which to evaluate the efficiency of the treatment. In this article, the power of atomic force microscopy (AFM) as a technique for monitoring and mapping the surfaces of dentinal roots is demonstrated. Roughness parameters of teeth that had been scaled and root planed were determined from AFM images acquired both before and after treatment with EDTA. The results confirmed that EDTA is an efficient cleaning agent and that dentinal samples free from a smear layer are significantly rougher than the same samples covered by a contaminating layer. AFM analysis is superior to alternative methods involving scanning electron microscopy because the same sample section can be analyzed many times, thus permitting it to be used as both the control and the treatment surface.