Basic Research-technology
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
M
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
JOE — Volume -, Number -, - 2014
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 .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
3
Basic Research-technology
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
Whitbeck et al.
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.
References 1. Gorni FG, Gagliani MM. The outcome of endodontic retreatment: a 2-yr follow-up. J Endod 2004;30:1–4. €stby B. Chelation in root canal therapy: ethylenediamine tetra-acetic acid 2. Nygaard O for cleansing and widening of root canals. Odontol Tendskrift 1957;65:3–11. 3. H€ulsmann M, Heckendorff M, Lennon A. Chelating agents in root canal treatment: mode of action and indications for their use. Int Endod J 2003;36:810–30. 4. Bystr€om A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35–40.
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5. Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions: part 3. J Endod 1983;9:137–42. 6. C¸alt S, Serper A. Time-dependent effects of EDTA on dentin structures. J Endod 2002;28:17–9. 7. Bramante CM, Betti LV. Comparative analysis of curved root canal preparation using nickel-titanium instruments with or without EDTA. J Endod 2000;26:278–80. 8. Silva e Souza PA, des Dores RS, Tartari T, et al. Effects of sodium hypochlorite associated with EDTA and etidronate on apical root transportation. Int Endod J 2014;47: 20–5. 9. Schneider SW. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol 1971;32:271–5. 10. Bramante CM, Berbert A, Borges RP. A methodology for evaluation of root canal instrumentation. J Endod 1987;13:243–5. 11. Elliott JC, Dover SD. Three-dimensional distribution of mineral in bone at a resolution of 15 mm determined by x-ray microtomography. Metab Bone Dis Relat Res 1984;5:219–21. 12. Nielsen RB, Alyassin AM, Peters DD, et al. Microcomputed tomography: an advanced system for detailed endodontic research. J Endod 1995;21:561–8. 13. Rhodes JS, Pitt Ford TR, Lynch JA, et al. Micro-computed tomography: a new tool for experimental endodontology. Int Endod J 1999;32:165–70. 14. Peters OA, Sch€onenberger K, Laib A. Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J 2001;34: 221–30. 15. Stern S, Patel S, Foschi F, et al. Changes in centering and shaping ability using three nickel-titanium instrumentation techniques analyzed by micro-computed tomography (mCT). Int Endod J 2012;45:514–23. 16. Freire LG, Gavini G, Cunha RS, dos Santos M. Assessing apical transportation in curved canals: comparison between cross-sections and micro-computed tomography. Braz Oral Res 2012;26:222–7. 17. Loizides A, Eliopoulos D, Kontakiotis E. Root canal transportation with a ni-ti rotary file system and stainless steel hand files in simulated root canals. Quintessence Int 2006;37:369–74. 18. R€odig T, H€ulsmann M, Kahlmeier C. Comparison of root canal preparation with two rotary niti instruments: Profile 0.04 and GT rotary. Int Endod J 2007;40: 553–62. 19. Gonzalez Sanchez JA, Duran-Sindreu F, Albuquerque Matos M, et al. Apical transportation created using three different patency instruments. Int Endod J 2010;53: 550–64. 20. Camps JJ, Pertot WJ. Relationship between file size and stiffness of stainless steel instruments. Endod Dent Traumatol 1994;10:260–3. 21. Camps JJ, Pertot WJ. Relationship between file size and stiffness of nickel titanium instruments. Endod Dent Traumatol 1995;11:270–3. 22. Wildey WL, Senia S, Montgomery S. Another look at root canal instrumentation. Oral Surg Oral Med Oral Pathol 1992;74:499–507. 23. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18: 269–96. 24. Verdelis K, Eliades G, Oviir T, Margelos J. Effect of chelating agents on the molecular composition and extent of decalcification at cervical, middle and apical root dentin locations. Endod Dent Traumatol 1999;15:164–70. 25. Cameron JA. The use of ultrasound and an EDTA-urea peroxide compound in the cleansing of root canal: an SEM study. Aust Dent J 1984;29:80–5. 26. Zurbriggen T, del Rio CE, Brady JM. Postdebridement retention of endodontic reagents: a quantitative measurement with radioactive isotope. J Endod 1975;1:298–9. 27. Stewart GG, Kapsimalas P, Rappaport H. EDTA and urea peroxide for root canal preparation. J Am Dent Assoc 1969;78:335–8. 28. Heling I, Irani E, Karni S, Steinberg D. In vitro antimicrobial effect of RC-Prep within dentinal tubules. J Endod 1999;25:782–5. 29. Wainwright WW, Lemoine FA. Rapid diffuse penetration of intact enamel and dentin by carbon 14-labeled urea. J Am Dent Assoc 1950;41:135–45. 30. Lewinstein I, Hirschfeld Z, Stabholz A, Rotstein I. Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin. J Endod 1994;20:61–3. 31. Caldwell JL. Change in working length following instrumentation of molar canals. Oral Surg Oral Med Oral Pathol 1976;41:114–8. 32. Davis RD, Marshall JG, Baumgartner JC. Effect of early coronal flaring on working length change incurved canals using rotary nickel-titanium versus stainless steel instruments. J Endod 2002;28:438–42.
Effect of EDTA Preparations
5
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
M
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
JOE — Volume -, Number -, - 2014
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 .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
3
Basic Research-technology
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
Whitbeck et al.
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.
References 1. Gorni FG, Gagliani MM. The outcome of endodontic retreatment: a 2-yr follow-up. J Endod 2004;30:1–4. €stby B. Chelation in root canal therapy: ethylenediamine tetra-acetic acid 2. Nygaard O for cleansing and widening of root canals. Odontol Tendskrift 1957;65:3–11. 3. H€ulsmann M, Heckendorff M, Lennon A. Chelating agents in root canal treatment: mode of action and indications for their use. Int Endod J 2003;36:810–30. 4. Bystr€om A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35–40.
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