Comparative evaluation of phosphoric acid, EDTA and saline, with and without ultrasonic irrigation for smear layer removal- a SEM study

Background: Smear layer can be a source of infection in the root canal. However, different physical and chemical agents are available for smear layer removal. Aim: The aim of this study was to compare the effectiveness of six different irrigation techniques for removing the smear layer in vitro using scanning electron microscopy (SEM). Materials and Methods: Eighteen single rooted human maxillary anterior teeth were accessed, instrumented, and subjected to various irrigation techniques: 37% phosphoric acid, 17% EDTA and saline, alone and with ultrasonic irrigation for 30 seconds, respectively. The irrigated samples were sectioned and assessed using SEM. Three photomicrographs (1000X) were recorded for each sample (coronal, middle, and apical). Takeda et al., scoring system was used to evaluate the smear layer left as observed in the images. Kruskal‐Wallis test was used to calculate the statistical difference at 5% level of significance. Results: In 30 second, 37% phosphoric acid with ultrasonic irrigation showed the best results followed by 37% phosphoric acid alone and saline with ultrasonic irrigation. 17% EDTA with ultrasonic irrigation was least effective. Conclusion: The results of the present study has shown that phosphoric acid solution may be considered as a favorable agent used for smear layer removal in endodontic therapy and its effectiveness can be enhanced using ultrasonics. for their ability to remove the smear layer. [10] The predictability of smear layer removal decreases as we go from the coronal to the apical region of the root and this could be attributed to the wider canal orifice coronally that tapers apically. [5,11,12] Various methods have been tested to increase the penetration of irrigating solutions into the apical third of the root canals like enhancing the irrigating solution by adding surfactants and using ultrasonics. [13,14] The various chemical agents used are sodium hypochlorite, chelating agents like EDTA solutions at concentrations ranging from 15‐17%, and organic acids like citric acid (5–50%), and polyacrylic acid (5‐40%) or other acids like phosphoric acid (5‐37%). [10,15] Phosphoric acid has been extensively used to remove the smear layer from coronal dentin as it is a commonly used etchant before a composite restorative material. [16‐18] and its performance in root dentin has been evaluated in only few studies. [15,19,20] Literature search reveals that there are only a few studies concerning the effect of the various agents on the smear layer removal. Also, differences exists in the methodologies, time intervals and concentrations of the solutions tested which limits the ability to make valid comparisons between Correspondence to: Dr. Parag M Wani, C‐block 600, Section‐25, Manera Road, Near Shree Hospital, Ulhasnagar ‐ 421 004, Thane, Maharashtra, India. E‐mail: paragwani45@yahoo.com Introduction Smear layer is debris retained on dentin after hand or rotary instrumentation. [1] It is made up of two parts: A superficial one, which is 1‐5 microns thick and loosely adhering to the underlying dentin and the smear plug that is about 40 microns is packed in the dentinal tubules. [2] It has been found that the smear layer debris consists of ground dentin, predentine, pulpal remnants and odontoblast processes and in the case of infected teeth it contains bacteria. [3] Many researchers believe that the smear layer should be removed as this layer harbors the survival and multiplication of the bacteria and can result in them re‐entering the dentinal tubules and re‐infecting the canals. [4,5] The antimicrobial action of the medications in the dentinal tubules can be altered in an undesirable fashion due to the smear layer. [6] The ability of the sealer to penetrate the dentinal tubules and thereby the adaptation of the root canal filling to the root canal might also be compromised due to the presence of this smear layer. [7‐9] Various chemical agents as well as some physical agents like ultrasonics and lasers in combination or alone has been tested Department of Conservative Dentistry and Endodontics, Gaurdian College of Dental Sciences and Research Centre, Thane, 1Department of Conservative Dentistry and Endodontics, D.Y. Patil University’s Dr. D.Y. Patil Dental College and Hospital, Pimpri, Pune, 2Consulting Endodontist , Pune, Maharashtra, India