Year : 2006 | Volume
: 9 | Issue : 1 | Page : 36--42
Comparative evaluation of the effect of two different concentrations of EDTA at two different PH and time periods on root dentin
R Sudha, VR Sukumaran, Jaya Ranganathan, Narasimha Bharadwaj
Department of Conservative Dentistry & Endodontics, Sree Balaji Dental College & Hospital Pallikkaranai, Chennai 601 302, India
Department of Conservative Dentistry & Endodontics, Sree Balaji Dental College & Hospital Pallikkaranai, Chennai 601 302
The aim of the study was to evaluate the effects of two different concentrations of EDTA at two different pH values for lmin & 10 min applications respectively on root dentin. 54 human maxillary incisors instrumented to size 60 to apical foramen were sectioned at the middle third (8mm sections) longitudinally into two equal mesial and distal halves. The sectioned specimens were irrigated for I and 10 min respectively using EDTA of concentrations 17% & 10% at 7.5 and 9 pH. The amount of demineralization and removal of smear layer was evaluated by phosphorus liberation, surface roughness studies and SEM analysis. Optimum results were obtained with EDTA at 10% concentration at 9 pH for 1 min.
|How to cite this article:|
Sudha R, Sukumaran V R, Ranganathan J, Bharadwaj N. Comparative evaluation of the effect of two different concentrations of EDTA at two different PH and time periods on root dentin.J Conserv Dent 2006;9:36-42
|How to cite this URL:|
Sudha R, Sukumaran V R, Ranganathan J, Bharadwaj N. Comparative evaluation of the effect of two different concentrations of EDTA at two different PH and time periods on root dentin. J Conserv Dent [serial online] 2006 [cited 2020 Jun 2 ];9:36-42
Available from: http://www.jcd.org.in/text.asp?2006/9/1/36/41307
The preservation or elimination of smear layer has been a focus of speculation and debate in the speciality of Endodontics for many years. Recent research concurs with the view that the smear layer itself can be contaminated and has the potential to harbor & protect bacteria within the tubules. Hence, researchers deem it prudent to remove the smear layer to allow disinfection of the entire root canal system ,, .
Various irrigating solutions have been tried among which EDTA has been popular as the most effective chelating agent for the removal of smear layer. Chelators were first introduced into Endodontics by Nygaard-Ostby (1957) who recommended the use of 15% EDTA solution with pH 7.3  . Its chelating action was used to demineralize the smear layer, open up the dentinal tubules and increase the dentinal permeability to intra canal disinfectants.
The inadvertent use of EDTA in terms of longer duration, inappropriate pH and concentration have led to erosion of dentin, reduction in bond strength of dentin adhesives to root dentin and misdirection of root canal instruments in the presence of softened dentinal walls. The purpose of this study was to compare the effects of two different concentrations of EDTA solutions (10%&17%) at two different pH values (7.5&9.0) for two time intervals (l min & 10min) on root dentin.
Materials & Methods
Fifty four freshly extracted intact non carious human permanent maxillary central and lateral incisors with fully formed apices were selected. Following removal of debris, tissue tags and calculus, the teeth were stored in physiologic saline and radiographs were taken to confirm the presence of a single canal.
Following access opening, cleaning and shaping of all teeth were performed by enlarging the canals with Kfiles to size 60 and then to size 80 using the step back technique. Coronal flare was produced by using no. 2 through no. 5 Gates Glidden drills up to middle third to facilitate better flow of irrigants. 10 ml of 5% NaOCI solution delivered with 18 gauge needle placed in the coronal third of the canal without binding was used during the entire procedure. After instrumentation, 8 mm of the middle third region of the root was measured, marked and sectioned for the study. The sectioned middle third was then cut longitudinally into two equal mesial and distal halves with the help of fine diamond disc using a low speed straight hand piece resulting in 108 sections of 54 teeth. The outer surfaces of the cut specimens were coated with 2 coats of nail varnish for phosphorous liberation and surface roughness studies. The specimens selected for SEM were not coated.
17% and 10% concentrations of EDTA were prepared by weighing 17gms & 10gms of disodium salt of EDTA respectively. The solutions were divided into two equal quantities for each concentrations and pH adjusted to 7.5 and 9.0 for both concentrations by adding an alkali (NaOH) and ascertained with pH indicator strips. 108 sections were divided into 9 groups with n = 12. 2 sections from each group were earmarked for examination of smear layer using SEM. The remaining 10 sections were treated with the prepared EDTA solution with varying pH 7.5 & 9; varying concentration 17 & 10% for a period of 1 & 10 min.
The degree of demineralization was estimated by the amount of phosphorous liberated using AutoAnalyzer (SCREEN MASTER 3000 BIO CHEM SYS INT S.R.I. ITALY). The surface roughness produced was evaluated by Surface Profilometer (WYKO SURFACE PROFILERS, ARIZONA) and SEM analysis was done to estimate the amount of smear layer removal. (JEOL-JSM-5610LV).
The results of phosphorus liberation and surface roughness were tabulated and statistically analyzed. Mean and standard deviation were estimated from all the sections. The mean values were compared by oneway ANOVA and Multiple range tests by TUKEY HSD procedure was employed to identify the significant groups at 5% level.
Conventional methods with common irrigants are ineffective in the removal of smear layer that can harbor bacteria, organic & inorganic residue which plays a pivotal role in the successful outcome of endodontic therapy. Smear layer not only prevents the anti-microbial effects of irrigants but also interferes with the close adaptation of the root canal filling material''' This led to the popular usage of chelating agents in endodontic treatment.[Table 1],[Table 2],[Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8],[Figure 9],[Figure 10],[Figure 11]
In this study, the significant effects of two concentrations of EDTA solutions prepared (in our Biochemistry laboratory) at two different pH values were evaluated and compared with respect to smear layer removal on root dentin. A step back method of preparation of root canal was done to ensure a free & adequate flow of irrigating solutions and maximize its effect on root dentin. The specimens were specifically preferred to be the mid-root region because it had a higher content of non-collagenous organic matrix & better calcification as compared to other regions of root  .The length of the sectioned specimens was standardized as 8mm so that equal & adequate amount of dentin was exposed to irrigation. The protocol of using 5 % Sodium hypochlorite separately was followed because on combining with EDTA the available chlorine was drastically altered thereby decreasing the flushing ability as reported by many researchers. 
Among the major factors that affect the cleaning properties of EDTA solutions on root canals, the pH of the solution is reported to play an important role  . The two different pH selected (7.5 & 9) were based on the fact that too acidic a pH, would result in protonation of EDTA as described below  : -
(1) EDTAH [-3] +Ca [+2] =EDTACa [-2] + H + (chelation)
(2) EDTAH [-3] + H + = EDTA H2 [-2] . (protonation )
The protonation of EDTA that prevails would result in insignificant demineralization; thereby, the pH chosen for the study were between neutral & alkaline.
From the results [Table 1] it is evident that 17% EDTA with a pH of 7.5 at 10 min exhibited maximum phosphorus liberation whereas minimum liberation was observed for 10 % EDTA at a pH of 9 for I min. This may be explained by the fact that pH affects calcium availability in several ways. Chelating efficiency of EDTA at a higher pH is reported to be greater due to increased ratio of ionized to non ionized molecules in the solution. This could be attributed to the fact that at a high pH, the excess hydroxyl ions will retard the dissociation of hydroxyapatite thus limiting the number of calcium ions available. On the contrary, at a low or neutral pH the binding of calcium ions will tend to increase the dissociation of hydroxyapatite and its availability for chelation ,, This may be further explained by the fact that the mechanism of action of EDTA is co-existent with protonation & chelation. Once the equilibrium is reached between them the action of EDTA becomes selflimiting 
The 10min application of EDTA does not have a pronounced demineralization when compared to 1 min application. This could probably be explained that although the reaction proceeds and acid accumulates, it is ultimately the protonation that prevails. As far as EDTA concentrations were concerned, both 10% and 17% displayed complete removal of smear layer, but the demineralization effects of 17 % EDTA was more significant which exhibited an greater erosion of the dentinal tubules as seen in SEM. SEM analysis revealed complete removal of smear layer and widening of tubules with 17 % EDTA at 7.5 pH for 10 min whereas 10 % EDTA at 9 pH for 1 min also exhibited complete removal of smear layer with no widening of the tubular structures.
The surface roughness evaluated by the 3D optical surface profilometer shows a marked increase in the surface roughness for EDTA groups which can be depicted as an increase in the number of peaks (red) and valleys (blue) - [Figure 10]. On the other hand 5% NaOCI (control group)- [Figure 11] displayed lesser number of peaks and valleys which demonstrates decreased surface roughness compared to EDTA clearly indicating the physical changes on the root dentin, although there was no statistical difference within the EDTA groups.
In the light of observation from the study, it may be suggested that EDTA at 10% concentration with pH 9 for 1 min exhibited optimum results in terms of smear layer removal, degree of demineralization & surface roughness without causing erosion of dentinal tubular structures. Research and trials are required to idealize the pH and concentration of EDTA to function as a suitable endodontic irrigant.
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