Effect of EDTA Preparations on Rotary Root Canal Instrumentation Evan R. Whitbeck, DDS, MS,* Kelli Swenson, DDS, MS,* Patricia A. Tordik, DMD,* Shayne A. Kondor, MSAE,* Terry D. Webb, DDS, MS,* and Jirun Sun, PhD† Abstract Introduction: The aim of this study was to evaluate whether rotary instrumentation using saline, EDTA 17% solution, or RC-Prep (Premier Dental, Philadelphia, PA) resulted in differences in root canal transportation. The secondary objective was to assess if instrumentation using these agents caused changes in the working length and canal volume. Methods: Moderately curved mesiobuccal roots of 24 maxillary molars were standardized in length and randomized into 1 control and 2 experimental groups. The canals were instrumented with 0.04 taper rotary files to size #30. All groups were irrigated with saline. Group 1 was also irrigated using EDTA 17% solution (Pulpdent Corp, Watertown, MA), and in group 2, RC-Prep was used. X-ray micro–computed tomographic scans and working length measurements were made before and after instrumentation. Three-dimensional models were created from the pre- and postinstrumentation scan data and compared for volume changes. Centroid points were calculated in cross-sectional slices of the canals, and transportation was determined by measuring the distance between the pre- and postinstrumentation points. The data were analyzed with 1-way analysis of variance (a = 0.05) and the Tukey post hoc test. Results: Less transportation was observed in group 2 than in group 1 (P = .001) and the control group (P = .014). Transportation in group 1 and the control group was not significantly different. Canal volume in group 1 was increased relative to group 2 (P = .004) and the control group (P = .022). No significant differences in the working length were observed. Conclusions: The use of chelating agents during root canal instrumentation did not significantly increase apical transportation. (J Endod 2014;-:1–5)
Key Words Chelating agents, EDTA, root canal preparation, transportation, x-ray micro–computed tomographic imaging
aintaining the original canal morphology during endodontic treatment, including minimizing transportation, has been shown to increase healing by up to 40% (1). EDTA was introduced to endodontics in 1957 and was advocated to decrease instrumentation time, with minimal effects on the oral tissues and root canal instruments (2). Despite a lack of evidence showing improved outcomes, contemporary indications for EDTA include canal lubrication during rotary instrumentation (3), enhanced antibacterial activity (4), and smear layer removal (5,6). It is unclear whether EDTA use during instrumentation increases apical transportation. More deviation was reported in curved canals prepared with EDTA (7), but the concentration, volume, and contact time of the chelator was not disclosed (7). Prolonged use of EDTA has been shown to cause excessive erosion with increased tubule aperture size (6). Conversely, 0.08-mm apical transportation was reported among curved canals prepared with a 6-minute, intermittent EDTA irrigation versus no deviation in a saline control, but the difference was not significant (8). Root canal curvature can be assessed several ways. Schneider (9) drew 2 lines on a radiograph and measured the acute angle formed. When measured before and after instrumentation, the angulation change indicates canal transportation. Canal preparation and transportation can also be assessed by photographing cross-sections of teeth before and after instrumentation (10). Each technique has limitations. The Schneider technique measures curvature in 1 plane, whereas photographing cross-sections requires disassembly and reconstruction of the specimen. X-ray micro–computed tomographic (micro-CT) imaging is a newer technology available to researchers. With voxel resolutions as small as 15 mm (11), computer software can fabricate 3-dimensional (3D) models of the internal and external tooth surfaces with great accuracy (12, 13). Studies have used micro-CT scanning to evaluate changes in canal volume, surface area, and transportation after instrumentation with different filing systems (14, 15). This technique is nondestructive (13) and superior to other methods for assessing canal transportation (16). Despite these benefits, no studies have used micro-CT imaging to assess canal transportation when instrumenting curved canals with chelating agents. The primary objective of this study was to evaluate whether rotary instrumentation using saline, EDTA 17% solution, or RC-Prep (Premier Dental, Philadelphia, PA) resulted in differences in root canal transportation. The secondary objective was to determine if instrumentation using these agents caused changes in the working length or canal volume. The experimental hypothesis was that apical transportation increases when chelating agents are used.
Methods From the *Naval Postgraduate Dental School, Bethesda; and †Dr Anthony Volpe Research Center, American Dental Association Foundation, Gaithersburg, Maryland. Address requests for reprints to Dr Evan R. Whitbeck, Naval Postgraduate Dental School, 8955 Wood Road, Bethesda, MD 20889-5628. E-mail address: [email protected]
0099-2399/$ - see front matter Copyright Published by Elsevier Inc. on behalf of American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2014.07.023
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Tooth Selection Twenty-four deidentified maxillary molars from an inventory of extracted, human teeth stored in 1% chloramine-T (Ricca Chemical Company, Arlington, TX) were selected as specimens. Each was examined under a dental operating microscope at 8 magnification (Global Surgical Systems, St Louis, MO) and radiographed in the mesiodistal and buccolingual planes. Teeth with root caries, cracks, resorption, incomplete apices, or <10 mm in root length were excluded. Teeth with ribbon-shaped or unidentifiable mesiobuccal (MB) canals were also excluded. Using Schneider’s technique (9), only teeth with MB roots curved from 10 –30 in both planes were included.
Effect of EDTA Preparations
Basic Research-technology Specimen Preparation The palatal root of each tooth was removed. Endodontic access cavities were prepared using carbide burs (Dentsply Maillefer, York, PA), and the primary MB canal orifice was located. Without coronal flaring, an ISO #10 FlexoFile (Dentsply Maillefer) was placed into the canal to ensure patency. Tooth length was standardized to 19 mm by removing coronal tooth structure; the working length for each specimen was 18 mm. All measurements were confirmed with a #10 file and a digital caliper (Digimatic Caliper; Mitutoyo America Corp, Aurora, IL). Specimens were mounted in modified polypropylene centrifuge tubes (Thermo Fisher Scientific, Waltham, MA) using acrylic resin (Varidur; Buehler LTD, Lake Bluff, IL). The distobuccal root was embedded into resin to align the MB root perpendicular to the long axis of the tube. A hole was cut in the centrifuge tube over the access cavity to enable root canal instrumentation. Randomization and Experimental Groups The 24 specimens were assigned a reference number and randomized into 3 groups (n = 8) using the random sequence generator at www.random.org. The first 8 numbers returned were assigned to the control group, the next 8 to group 1, and the final 8 to group 2. Control specimens were irrigated with 2.0 mL 0.9% saline (Baxter Healthcare Corp, Deerfield, IL) between files. In group 1, the canals and pulp chamber were flooded with EDTA 17% solution (Pulpdent Corp, Watertown, MA) before using each file. Canals were irrigated with 2.0 mL 0.9% saline between each file. In group 2, the pulp chamber was filled with RC-Prep and carried into the canals using files. Saline irrigation was performed between files, as in the other groups. All liquid irrigants were delivered using a 30-G, side-vented needle (Max-i-Probe; Dentsply
Rinn, Elgin, IL). Both chelating agents were used according to manufacturers’ instructions.
Canal Preparation All specimens were instrumented using a crown-down technique with 0.04 taper nickel-titanium rotary files (ProFile; Dentsply Tulsa Dental Specialties, Tulsa, OK) to a master apical file size #30. A pilot study determined the average instrumentation time for each canal to be 9 minutes. Therefore, the total instrumentation and irrigant contact time for each tooth was standardized to 9 minutes. Micro-CT Scanning All tooth specimens were scanned individually using a micro-CT device (Scanco mCT40; Scanco Medical, Bassersdorf, Switzerland) at an isotropic resolution of 18 mm, I = 114 mA, E = 70kVp, and an integration time of 300 ms before and after establishing the working length and canal instrumentation. Change in Working Length The distance from the coronal reference point to the apical foramen was measured before and after instrumentation using a size #10 file. The difference in length was recorded for each specimen. 3D Modeling Preinstrumentation and postinstrumentation models of the MB canal were created using 3D modeling software (Mimics 15.0; Materialise, Leuven, Belgium). Micro-CT data were imported as a set of planar grayscale images spaced at regular intervals along the axis normal to the image plane. Thresholding was performed to segment the voxels within the root canal by capturing only those within a specified range of gray
Figure 1. (A) A centerline was fit to the preinstrumentation model (red). (B) After superimposing the models, planes were created perpendicular to this centerline at 1-mm increments from D0–D8 in the preinstrumentation (red) and postinstrumentation models (green). (C) A cross-sectional view of the superimposed preinstrumentation (red) and postinstrumentation (green) planes at D5. In each cross-sectional plane, computer modeling software was used to calculate the centroid points (black). The movement of the centroid point between the preinstrumentation and postinstrumentation models (yellow arrow) was defined as transportation and measured (mm).
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Basic Research-technology values. The range of gray values captured was varied slightly between specimens to maximize the accuracy of the segmentation. Modifications were made using software tools to eliminate noise and smooth the edges of the model. The final voxel set was interpolated to yield a surface model and stored in Standard Tessellation Language format. Because the enamel was not altered during root canal preparation, it was segmented and used to superimpose the preinstrumentation and postinstrumentation models.
Assessment of Changes in Root Canal Volume and Transportation After superimposing the models, the crown, pulp chamber, accessory canal anatomy, and root canal beyond the working length were removed using a program similar to engineering computer-aided design software (3Matic, Materialise). Volume changes were calculated using the software after inputting the voxel size from the micro-CT machine. To assess transportation, a centerline was created within the preinstrumentation model (Fig. 1A). Starting at the working length, 9 planes (D0–D8) were drawn perpendicular to the centerline at 1mm increments, creating multiple cross-sectional slices of the canal (Fig. 1B). The postinstrumentation model was sectioned using the same planes. The centroid point in each cross-section was identified and its position compared between the preinstrumentation and postinstrumentation models. The linear distance between these points was defined as canal transportation and was measured in millimeters (Fig. 1C). The mean canal transportation was calculated by averaging the 9 measurements obtained from each tooth. Statistical Analysis Two-way analysis of variance (ANOVA) was used to test for an interaction between the canal cross-sectional level (D0–D8) and irrigant (saline, EDTA 17% solution, or RC-Prep) on canal transportation. One-way ANOVA was used to compare the effect of irrigant on mean canal transportation, change in volume, and change in working length (a = 0.05). The Tukey post hoc test was conducted when the ANOVA indicated a significant difference among the means compared (a = 0.05).
Results Two-way ANOVA indicated no interaction between canal level and either chelating agent on transportation (P = .227). One-way ANOVA was then conducted to determine if canal level affected transportation. At D6–D8, the canal level influenced transportation (P < .0005, Fig. 2), but no relationships were identified from D0–D5 (P > .05). One-way ANOVA identified significant differences in the mean canal transportation (P = .001) and canal volume (P = .003) with respect to the chelating agent used (Fig. 3A and B). Less mean canal transportation was observed in group 2 (0.059 0.052 mm) when compared with group 1 (0.085 0.062 mm, P = .001) and the control group (0.080 0.054 mm, P = .014). There was no difference in the mean canal transportation between the control group and group 1 (P = .762). A significant increase in postinstrumentation volume was observed in group 1 (2.45 0.76 mm3) compared with the control group (1.490 0.84 mm3, P = .022) and group 2 (1.20 0.55 mm3, P = .004). There was no difference in postinstrumentation volume between the control group and group 2 (P = .714). No significant changes in the working length were observed among the 3 groups (group 1 = 0.186 0.200 mm, group 2 = 0.099 0.085 mm, and control group = 0.095 0.127 mm; P = .382).
Discussion The primary objective of this study was to evaluate whether using saline, EDTA 17% solution, or RC-Prep influenced canal transportation. Transportation may occur because of the physical properties of the files or as a result of chelating agents or irrigants used during canal preparation. In this study, most transportation measurements were 0.010 mm or less, with values as high as 0.019 mm observed in coronal sections of the canal. Transportation of this magnitude is consistent with previous reports that used ProFiles and size #10 patency instruments (17–19). Because modulus of elasticity increases exponentially as a function of file size (20, 21) and stiffer files are more likely to transport canals (22), greater transportation was expected and observed in the coronal regions (D6–D8) of the canals. Three different agents were used during tooth preparation. In the control group, saline was used exclusively. With no chelating ability, saline primarily removes debris created during instrumentation. Because
Figure 2. Neither the use of chelating agents nor the canal level influenced transportation from D0–D5. The canal level influenced transportation at D6, D7, and D8, but the agent used during preparation had no effect. *Significance among the means at different canal levels; bar indicates no significance.
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Effect of EDTA Preparations
Figure 3. (A) The canals in group 2 (RC-Prep) showed less transportation when compared with those in group 1 (EDTA 17% solution) and the control group (saline). (B) The volume of the canals in group 1 (EDTA 17% solution) increased significantly more with instrumentation than those in group 2 (RC-Prep) or the control group (saline). *Significance; bar indicates no significant difference.
all instrumentation techniques remove some dentin from the root canal walls (23), the transportation observed in these teeth likely resulted entirely from the mechanical properties of the files. The teeth in the experimental groups were prepared with either EDTA 17% solution or RC-Prep. No difference in transportation was observed among canals prepared with saline or EDTA 17% solution. Canals prepared with RC-Prep showed less transportation than those prepared with EDTA 17% solution or saline. These results are consistent with a molecular analysis of chelating agents applied to root dentin in which neutral EDTA extracted significantly more calcium and phosphorus from the coronal two thirds of the root than RC-Prep (24). The increased demineralization occurring in the specimens prepared with EDTA 17% solution probably facilitated the greater transportation observed in these teeth. It is also likely that the polyethylene glycol base in RC-Prep inhibited the demineralization of dentin by the EDTA contained in this paste. A scanning electron microscopic analysis of root canal walls after preparation with sodium hypochlorite or an EDTA– urea peroxide–polyethylene glycol compound revealed a waxlike smear layer in teeth prepared with the chelating compound, attributed to the 4
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polyethylene glycol base (25). These results are also consistent with an autoradiographic study of teeth prepared using 2.5% sodium hypochlorite with an EDTA–urea peroxide–14C-labeled glycerol paste in which neither irrigation nor further preparation were able to completely remove the radioactive glycerol (26). In this study, the polyethylene glycol base may have prevented dentin demineralization in the specimens prepared with RC-Prep, decreasing the magnitude of transportation observed. The final component of RC-Prep, urea peroxide, increases the antibacterial action of this paste (27, 28). Although urea has been shown to readily penetrate tooth structure (29) and peroxides can decrease the microhardness of dentin (30), the fact that RC-Prep does not predictably remove the smear layer (24, 25) likely limited the impact of urea peroxide on this investigation’s results. The secondary objective of this study was to evaluate the effect of different irrigants on working length and canal volume. The canals prepared with EDTA 17% solution showed a greater increase in canal volume than those prepared with saline or RC-Prep. These results are also consistent with the aforementioned molecular analysis of chelating JOE — Volume -, Number -, - 2014
Basic Research-technology agents and root dentin (24). EDTA 17% solution likely demineralized coronal root canal dentin more so than saline or RC-Prep, facilitating the removal of dentin and increasing canal volume. No specimens showed significant changes in the working length. Although multiple studies have found that canals may shorten during preparation, the working length changes observed in this study were consistent with previous reports, although not statistically significant (31,32). The results of this investigation differ from those reported in a previous study that used E-speed film; nickel-titanium hand files; and an unspecified concentration, contact time, and volume of EDTA (7). This difference may have resulted from advances in technology and different methodology. This study used nickel-titanium rotary instruments, specific formulations and exposure times for EDTA, and micro-CT imaging with computer modeling technology, enabling 3D modeling of root canal systems and measurements on the order of micrometers. These methods likely improved the accuracy of the data obtained and are consistent with another study using similar methodology to examine transportation when canals were prepared with chelating agents (8).
Conclusions This study found less transportation when instrumenting canals with RC-Prep, increased canal volume when EDTA 17% solution was used, and no changes in the working length. With no difference in canal transportation between the control and EDTA 17% solution, this study failed to reject the null hypothesis. The use of chelating agents during root canal instrumentation did not significantly increase apical transportation.
Acknowledgments Supported by the Walter Reed National Military Medical Center Department of Research Programs. The authors would like to thank Dr Francois Tuamokumo, Department of Research Programs, Walter Reed National Military Medical Center, Bethesda, MD, for his statistical analysis of the data. The authors acknowledge that research protocol NNMC.2011.0071, Evaluation of Curved Root Canal Preparations Using Nickel-Titanium Rotary Files with Various Chelating Agents received applicable NNMC Institutional Review Board review and approval. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the U.S. Government. The authors deny any conflicts of interest related to this study.
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