- Email: [email protected]
Smear layer removal with passive ultrasonic irrigation and the NaviTip FX: a scanning electron microscopic study
Smear layer removal with passive ultrasonic irrigation and the NaviTip FX: a scanning electron microscopic study Shweta Goel, MDS,a and Sanjay Tewari, MDS,b Rohtak, Haryana, India DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS, POSTGRADUATE INSTITUTE OF MEDICAL SCIENCES
Objective. The aim of this study was to compare the effect of continuous, intermittent passive ultrasonic irrigation (PUI) and active scrubbing of irrigants with NaviTip FX (Ultradent, South Jordan, UT) in removing smear layer. Study design. Forty single-rooted teeth were randomly divided into 5 test groups and subjected to final irrigation with 17% EDTA followed by 2.5% NaOCl for 1 minute each using different activation methods: no activation (control), brushing with NaviTip FX, continuous PUI with irrigant delivered at pulp chamber, continuous PUI with irrigant delivered through the ultrasonic unit, and intermittent PUI. Specimens were examined under scanning electron microscope, and the data were analyzed using Friedman 2-way analysis of variance, Kruskal-Wallis, and Mann-Whitney U tests. Results. NaviTip FX and intermittent PUI showed significantly lower smear score than other groups at the 3 mm level (P ⬍ .05). Conclusions. Both brush and intermittent ultrasonic activation were effective in the removal of smear layer from the apical third. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:465-470)
Removal of pulp tissue and elimination of microorganisms and their toxins from the root canal system is one of the most important objectives of root canal therapy.1 This is usually achieved by a combination of mechanical instrumentation and irrigation. The efficacy of irrigation depends on its ability to remove dentin debris and smear layer that occur following instrumentation of root canal.2 McComb and Smith3 were the first to describe the smear layer in instrumented root canals through the use of scanning electron microscopy (SEM). Possible deleterious effect may occur if the smear layer and debris are not removed during root canal treatment. Microorganisms remaining in the smear layer after the instrumentation of an infected root canal space can survive and reinfect the canal.4,5 The smear layer has also been shown to hinder the penetration of intracanal disinfectants6 and sealers7,8 into dentinal tubules. Although not substantiated in clinical trials, it would appear to be prudent to remove the smear layer before filling an instrumented root canal. The effectiveness of irrigation relies on both the mechanical flushing action and the chemical ability of irrigants to dissolve the tissue. The flushing action from the syringe irrigation is relatively weak, and passive a
Assistant Professor. Senior Professor and Head. Received for publication Feb 5, 2009; returned for revision Apr 2, 2009; accepted for publication Apr 17, 2009. 1079-2104/$ - see front matter © 2009 Published by Mosby, Inc. doi:10.1016/j.tripleo.2009.04.023 b
ultrasonic irrigation (PUI) has recently been reported to increase the flushing action and improve the efficacy of irrigants in removing remnants of pulp tissue and debris.9-12 Studies on smear layer removal by PUI are inconclusive. Smear layer removal is less predictable in the apical third as compared with the coronal and middle third of the root.13-16 This could be attributed to comparatively smaller apical canal dimensions hindering the penetration of irrigants and resulting in limited contact between canal walls and irrigants.17 Two flushing methods can be used during PUI, namely, a continuous flush of irrigant from the ultrasonic handpiece10,17 or an intermittent flush method using syringe delivery.18,19 Abbott et al.15 reported that intermittent PUI did not enhance the removal of smear layer, and Cameron19 found that intermittent flush irrigation with EDTAC followed with 4% sodium hypochlorite left a minimum smear layer restricted to the apical seat. Van der Sluis et al.20 found both continuous and intermittent flushing equally effective in debris removal from artificially prepared grooves in the apical third; however, no study has compared the effect of continuous and intermittent flushing in the removal of smear layer with EDTA. To aid in root canal debris and smear layer removal, a few attempts have been described that use cotton wrapped around an endodontic file or a broach,21 or an endobrush.22,23 Recently a 30-gauge irrigation needle covered with a brush (NaviTip FX, Ultradent, South Jordan, UT) was introduced into the market. A review of the literature revealed that only 1 study reported the 465
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use of these tips in the removal of debris and reported significantly better debris removal in the coronal third but not in the middle and apical thirds.24 However, their effect on smear layer removal was not studied. The purpose of the present study was to evaluate and compare the effect of intermittent and continuous passive ultrasonic irrigation with syringe irrigation in removing smear layer from the root canal wall. In addition, the effects of these methods were compared with the new cotton-coated irrigation needle NaviTip FX. MATERIALS AND METHODS Forty single-rooted noncarious extracted human premolars and canines with single root canals, fully developed apices, and straight roots were included in this study. The teeth selected ranged from 21 to 24 mm in length and were randomly and equally distributed over the different groups. The specimens were stored in 0.1% thymol solution throughout the experiment, and root surfaces were thoroughly cleaned of soft tissue and calculus using ultrasonic scaler. All root surfaces were examined at ⫻20 magnification in a stereomicroscope (RSM-9; Radical, Ambala, Haryana, India) for location of apical foramina, cracks, or resorption. Root surfaces having cracks, fracture, resorption, and apical foramina ⬎0.5 mm from the anatomic apex were discarded. Access cavities were prepared using diamond burs (Mani, Tochigiken, Japan), and Gates-Glidden burs (Mani) were used for the stepback preparation. Working lengths were set by deducting 1 mm from lengths of the files when they extruded just beyond the apical foramina. All preparations were carried out by the principal author. The preparation was begun with size 25 K-files (Dentsply Maillefer, Ballaigues, Switzerland) which bound in the canal at working length, and roots with wider apical foramina were discarded. The middle and coronal thirds of the canals were flared before apical preparation, with Gates-Glidden burs of numbers 2, 3, and 4 with stepbacks of 3, 5, and 7 mm, respectively, relative to the length of last instrument used. Instrumentation of the apical third was continued through 3 sequentially larger K-files, and thus the master apical file was size 40 in all roots. The stepback phase of the apical third begin with the size 45 K-file and 5 larger K-files up to 70. Patency of the apical foramen was maintained throughout preparation with a size 15 K-file. Root canals were thoroughly irrigated with 2 mL freshly prepared 2.5% NaOCl solution between each instrument using a 30-gauge needle which was inserted as far into the prepared root as possible without binding. Final irrigation in all of the groups was carried out with 10 mL 17% EDTA and 10 mL 2.5% NaOCl for 1 minute each. Samples were divided into 5 groups of 8
Fig. 1. 30-gauge NaviTip FX.
teeth each according to the method of activation of final irrigants: Group A (control): Irrigants were not activated and were delivered with a 30-gauge needle placed 1 mm short of working length without binding. Group B (NaviTip FX): A size 30 NaviTip FX (Fig. 1) was placed 1 mm short of working length, and intracanal push and pull strokes were performed along the canal wall (each with 6 mm amplitude reaching 1 mm short of working length) with concomitant delivery of irrigants, first with 10 mL EDTA then with 10 mL NaOCl for 1 minute. Group C (continuous activation with irrigant supply from needle): In this group passive ultrasonic irrigation was performed, using a size 10 K-file in a modified Suprasson P5 system (Satelec, Merignac, France) without the flow-through irrigation system in the following manner. The canal was filled with EDTA, and the ultrasonic file was placed into the canal 1 mm short of working length without touching the walls, so that it could vibrate freely. The ultrasonic file was activated at a power setting of 4 for 1 minute. During this time, irrigant was delivered continuously with needle near the canal orifice at the rate of 10 mL/min. The procedure was repeated similarly with NaOCl. Group D (continuous activation with irrigant supply from handpiece): In this group also, root canals were passively ultrasonically irrigated for 1 minute similarly to group C, but the irrigants were continuously delivered at a rate of 10 mL/ min through the unit. Group E (intermittent activation): In this group, PUI was done similarly to group C except that the file
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Table I. Mean smear layer scores (⫾SD) for the different groups at various levels Group
3 mm
6 mm
9 mm
A. Control B. Brush C. Continuous ultrasonic D. Continuous ultrasonic E. Intermittent
4.01 ⫾ 0.78* 1.29 ⫾ 0.18† 3.99 ⫾ 0.67*
2.82 ⫾ 0.57§ 1.62 ⫾ 0.63† 2.60 ⫾ 0.42§
1.99 ⫾ 0.75† 1.26 ⫾ 0.17† 1.49 ⫾ 0.40†
3.51 ⫾ 0.33*
2.24 ⫾ 0.45§
1.59 ⫾ 0.28†
2.08 ⫾ 0.51‡
1.78 ⫾ 0.50†
1.25 ⫾ 0.19†
*,†,‡,§Scores with the same letter indicate no statistically significant difference at P ⫽ .05.
Fig. 2. Scanning electron microscopic view at ⫻21 of a sample, showing the location of photographs taken at the 3 mm level along the horizontal line.
was activated only for intervals of 10 seconds. Between each interval, the canals were refilled with irrigant by placing the 30-gauge needle into the canal 1 mm short of working length. This procedure was repeated 6 times, so that total duration of ultrasonic irrigation was 1 minute. A final flush with 2 mL 2.5% NaOCl concluded the preparation in all of the groups, and all specimens were dried with paper points. Immediately after completion of root canal preparation, the samples were coded to allow for blinded evaluation of the samples. Root surfaces were grooved using separation disk to indicate level 3, 6, and 9 mm from the root apices, and specimens were decoronated. Specimens were split longitudinally in the buccolingual plane, taking care not to contaminate the canal with debris. Specimens were dehydrated in ascending grades of alcohol up to 100% and mounted on aluminum stubs. Gold sputter coating was carried out under reduced pressure in an inert argon gas atmosphere in Agar Sputter Coater P 7340 (Agar Scientific, Essex, U.K.) and specimens were examined under scanning electron microscope (Leo 435, VP, Cambridge, U.K.) operated at 15 KV. Serial photomicrographs were taken of the canal walls at ⫻400 magnifications at the 3, 6, and 9 mm levels as shown in Fig. 2. These serial photographs were placed adjacent to each other, forming a continuous horizontal examination strip at 3 levels. A 60-m-square grid was superimposed on the strip, from which smear layer scores were evaluated. The number of assessment units varied from 12 to 48 depending on root canal diameters. Amount of smear layer present in each of the “assessment units” were assessed and recorded using a 5-step scale based on the criteria described by Mayer et al.16:
Score 1: All dentinal tubules were open and no smear layer was present. Score 2: Some dentinal tubules were open and others covered by a thin smear layer. Score 3: Few tubules were open and the rest covered by a thin homogeneous smear layer. Score 4: All dentinal tubules were covered by a homogeneous smear layer without any open tubules visible. Score 5: A thick homogenous smear layer completely covered the canal walls. Two calibrated and blinded evaluators independently scored the samples. The scores were then compared, and if a difference was found the two evaluators jointly examined the sample. For each evaluation strip, average scores for smear layer were calculated from the raw data by dividing the sum of all individual scores by the number of assessment units. The code was then broken and each sample was assigned to its experimental group. Means recorded at the 3, 6, and 9 mm examination levels were statistically analyzed for significance (P ⬍ .05 ) within and between the groups using the Friedman 2-way analysis of variance (ANOVA), Kruskal-Wallis test, and Mann-Whitney U test. RESULTS Mean amounts of smear layer recorded at the 3 mm, 6 mm, and 9 mm levels in the 4 experimental groups and 1 control group are listed in Table I. Of a possible maximum of 5, mean smear layer scores in all 5 groups ranged from 4.01 ⫾ 0.78 to 1.25 ⫾ 0.19 (Table I). Representative SEM photomicrographs at the 3 mm level are shown in Fig. 3. Friedman 2-way ANOVA depicted significant difference between the different groups at different levels (3 mm, 6 mm, and 9 mm levels; P ⬍ .05). Significantly lower smear layer scores (P ⬍ .05) were found at the 3 mm and 6 mm levels in the brush and intermittent ultrasonic groups compared
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Fig. 3. Scanning electron microscopic view at ⫻400 of the apical portion of the root canal wall with 60-m-square grid used to score the smear score. A, Control: Large amount of debris and smear layer is present. B, Brush: Almost complete removal of smear layer and many dentinal tubule openings are seen. C, Continuous activation with irrigant supply from needle: All dentinal tubules are completely covered by a thick homogeneous smear layer. D, Continuous activation with irrigant supply from handpiece: Large amount of smear layer is present. E, Intermittent activation: small amount of debris and complete removal of smear layer are visible.
with the control and other experimental groups (Fig. 3, B and E). No significant differences in smear layer scores were recorded between the other experimental groups and the control group (Fig. 3, A, C, and D).
Between group B and group E, the brush group was significantly better than intermittent ultrasonic group at the 3 mm level (P ⬍ .05). At the 9 mm level, all of the the groups were equally effective in smear layer re-
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moval; no significant difference was observed between various groups. When comparing the individual levels, in all of the the groups except brush and intermittent ultrasonic groups, lowest smear layer scores were recorded at the 9 mm level, followed by 6 mm and 3 mm level, with significant difference at the 3 levels (P ⬍ .05). In the brush group (group B), all 3 levels were clean with no significant difference in smear layer scores at the 3 levels examined. In the intermittent ultrasonic group (group E), no significant difference in smear layer scores were recorded at the 6 mm and 9 mm levels; however, significantly higher smear layer scores were recorded at the 3 mm level compared to the 6 mm and 9 mm levels. DISCUSSION The aim of the present study was to evaluate the methods to improve the removal of smear layer, particularly from the apical third of root canal. Significantly better smear layer removal with intermittent ultrasonic irrigation in the study could be related to better flushing of apical third. The syringe delivery of irrigant allowed full control of the procedure, because the depth of needle penetration in the canal and volume flushed through the apical region were known. It allowed for the continual deposition and renewal of irrigating solution within the apical third, leading to better flushing. Gutarts et al.12 also found that a passive ultrasonic irrigation resulted in better debris removal from the apical third of molars using the irrigating needle rather than the file for ultrasonic activation and related it to the continuous and better delivery of irrigant from the tip of needle in the apical portion. Our results do not agree with those of Abbott et al.,15 who reported that intermittent activation of EDTA followed by NaOCl was not effective in the removal of smear layer. In that study, they used a power setting of 1 with a size 20 K-file in the ultrasonic unit, and the irrigant was delivered with 25-gauge needle. Lower power settings and larger size of needle and file might have been responsible for the different results in that study. Similarly to previous studies,13,14,16 the present study did not find significantly better smear layer removal in the apical third in group C and group D. In group C, irrigant was delivered at the pulp chamber with needle, and in group D it was delivered through the ultrasonic unit at the rear end of the file rather than the tip. With these methods it is not possible to determine how much irrigant actually enters the root canal and flows through the apical part. Moreover ultrasonic vibration of the file along with narrow apical diameter of the root canal might have prevented flow of irrigating solution from the coronal to apical area. Also in the continuous ul-
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trasonic group, contact of the vibrating file on the EDTA-softened canal wall may have produced a new smear layer during final activation. With intermittent method, the file can better remain centered in the root canal for a smaller period (10 seconds instead of 1 minute), thus minimizing the chances of touching the root canal and creating smear layer again during final irrigation. Findings of the present study are not consistent with the study of Lui et al.,25 who found that 1 minute of continuous ultrasound with EDTA was effective in removing smear layer. The difference could be related to a better scoring method used in the present study. A 60-m-square grid was superimposed over the photomicrographs and the amount of smear layer was evaluated in each assessment unit. A grid scoring method may be more accurate to score smear layer than a single score examined per level, because it is often nonuniformly distributed.26 Also, magnifications of ⫻1,000 and ⫻3,000 used in that study might have resulted in an observational bias, because only a small area of the root canal wall can be observed in higher magnification. Results of the present study are also in contradiction to the study by Van der Sluis et al.,20 reporting that the intermittent ultrasonic method and continuous flow of irrigant through the device were equally effective in the removal of artificial debris from the artificially prepared groves. Removal of debris from the root canal space might be more difficult than the debris removal from artificially created grooves. In the present study, the NaviTip FX brushes showed almost complete removal of the smear layer and debris at the apical third, with no significant difference between the apical, middle, and coronal thirds. Continuous delivery of irrigant at the apical third and better mechanical debridement with active scrubbing of the walls during up and down motion might have resulted in better cleaning in this group. The design of the NaviTip FX allows it to reach up to the apex and at the same time can be used to actively scrub the canal wall while concomitantly delivering the irrigant. This mechanical activation would have enhanced the chemical action of irrigant in removing the smear layer and debris and might have a similar cleansing effect as a bottle brush. These results are supported by a study by Batista et al.,27 who proposed that neither time of application nor concentration of the irrigant was responsible for removal of smear layer; it was the method of application that was more important. They found that active application of EDTA by means of brush was more effective than passive application using soaked cotton pellets in removing smear layer from root surface. Similar findings indicating improved canal debridement were reported by Keir et al.,22 who used the
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endobrush with an attached handle and actively brushed the root canal with a 90-degree rotary motion combined with 2-3 mm up and down motion for 1 minute. However, those results are contrary to the study of AlHadlaq et al.,24 who did not find significantly better debris removal in the apical and middle thirds with NaviTip FX. However, in that study the NaviTip FX was used in a passive manner without scrubbing along the canal walls, which might have resulted in inefficient cleaning. CONCLUSION Within the limits of this in vitro study, it can be postulated that both brush and intermittent ultrasonic are effective in the removal of smear layer from the apical third. However the NaviTip FX, being easy to handle, might be a good alternative to ultrasonic and various other methods in cleaning the root canal, with minimal chances of temperature rise as in PUI. Although intermittent ultrasonic irrigation was found to be a better alternative to continuous PUI in removal of smear layer and debris, it might not be an acceptable technique in clinical practice and requires further research on its effectiveness. Although NaviTip FX showed better results, further clinical study with a greater number of samples and on posterior teeth with curved root canals is required before this technique can be recommended for routine use during root canal treatment. REFERENCES 1. Haapasalo M, Endal U, Zandi H, Coil JM. Eradication of endodontic infection by instrumentation and irrigation solutions. Endod Top 2005;10:77-102. 2. Baugh D, Wallace J. The role of apical instrumentation in root canal treatment: a review of literature. J Endod 2005;31:333-40. 3. McComb D, Smith DC. A preliminary scanning electron and microscopic study of root canals after endodontic procedures. J Endod 1975;1:238-42. 4. Brannstrom M, Nyborg H. Cavity treatment with a microbicidal fluoride solutions growth of bacteria and effect on pulp. J Prosthet Dent 1973;30:303-10. 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. Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9. 7. White RR, Goldman M, Lin PS. The influence of smeared layer upon dentinal tubule penetration by endodontic filling materials. Part II. J Endod 1987;13:369-74. 8. Oksan T, Aktener BO, Sen BH, Tezel H. The penetration of root canal sealers into dentinal tubules. A scanning electron microscope study. Int Endod J 1993;26:301-5. 9. Cheung GSP, Stock CJR. In vitro cleaning ability of root canal irrigants with and without endosonics. Int Endod J 1993;26:334-43. 10. Lee SJ, Wu MK, Wesselink PR. The efficacy of ultrasonic irrigation to remove artificially placed dentine debris from different-sized simulated plastic root canals. Int Endod J 2004;37:607-12.
11. Passarinho-Neto JG, Marchesan MA, Ferreira RB, Silva RG, Silva-Sousas YTC, Sousa-Neto MD. In vitro evaluation of endodontic debris removal as obtained by rotary instrumentation coupled with ultrasonic irrigation. Aust Endod J 2006;32:123-8. 12. Gutarts R, Nusstein J, Reader A, Beck M. In vivo debridement efficacy of ultrasonic irrigation following hand-rotary instrumentation in human mandibular molars. J Endod 2005;31:166-70. 13. Baumgartner JC, Madear CL. A scanning electron microscopic study of four root canal irrigations regimes. J Endod 1987;3:147-57. 14. Ciucchi B, Khettabi M, Holz J. The effectiveness of different endodontic irrigation procedures on the removal of the smear layer: a scanning electron microscopic study. Int Endod J 1989; 22:21-8. 15. Abbott PV, Heijkoop PS, Cardaci SC, Hume WR, Heithersay GS. An SEM study of the effects of different irrigation sequences and ultrasonics. Int Endod J 1991;24:308-16. 16. Mayer BE, Peters OA, Barbakow F. Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: a scanning electron microscopic study. Int Endod J 2002;35:582-9. 17. Guerisoli DM, Merchesan MA, Walmsley AD, Lumley PJ, Pecora JD. Evaluation of smear layer removal by EDTAC and sodium hypochlorite with ultrasonic agitation. Int Endod J 2002;35:418-21. 18. Cameron JA. The synergistic relationship between ultrasound and sodium hypochlorite: a scanning electron microscope evaluation. J Endod 1987;13:541-5. 19. Cameron JA. Factors affecting the clinical efficiency of ultrasonic endodontics: a scanning electron microscopy study. Int Endod J 1995;28:47-53. 20. Van der Sluis LWM, Gambarini G, Wu KW, Wesselink PR. The influence of volume, type of irrigant and flushing method on removing artificially placed dentine debris from the apical root canal during passive ultrasonic irrigation. Int Endod J 2006;39:472-6. 21. The SD. The use of cotton-wrapped file to evacuate necrotic pulp tissue. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1979;48:77-88. 22. Keir DM, Senia ES, Montgomery S. Effectiveness of a brush in removing post-instrumentation canal debris. J Endod 1990;16: 323-7. 23. Ruddle CJ. Cleaning and shaping the root canal system. In: Cohen S, Burns RC, editors. Pathways of the pulp. 8th ed. St. Louis: Mosby; 2002:231-91. 24. Al-Haddlaq SM, Al-Turaiki SA, Al-Sulami U, Saad AY. Efficacy of a new brush covered irrigation needle in removing root canal debris: a scanning electron microscopic study. J Endod 2006;32:1181-4. 25. Lui JN, Kuahb HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonics on removal of smear layer. J Endod 2007;33:472-5. 26. Wu MK, Wesselink PR. Efficacy of three techniques cleaning the apical portion of curved root canals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:492-6. 27. Batista LHC, Sampalo CEJ, Pilatti LG, Shibii AJ. Efficacy of EDTA-T gel for smear layer removal at root surfaces. Quintessence Int 2005;36:551-8. Reprint requests: Dr. Sanjay Tewari Professor and Head Department of Conservative Dentistry and Endodontics Principal Government Dental College Postgraduate Institute of Medical Sciences Rohtak, Haryana India [email protected]
Objective. The aim of this study was to compare the effect of continuous, intermittent passive ultrasonic irrigation (PUI) and active scrubbing of irrigants with NaviTip FX (Ultradent, South Jordan, UT) in removing smear layer. Study design. Forty single-rooted teeth were randomly divided into 5 test groups and subjected to final irrigation with 17% EDTA followed by 2.5% NaOCl for 1 minute each using different activation methods: no activation (control), brushing with NaviTip FX, continuous PUI with irrigant delivered at pulp chamber, continuous PUI with irrigant delivered through the ultrasonic unit, and intermittent PUI. Specimens were examined under scanning electron microscope, and the data were analyzed using Friedman 2-way analysis of variance, Kruskal-Wallis, and Mann-Whitney U tests. Results. NaviTip FX and intermittent PUI showed significantly lower smear score than other groups at the 3 mm level (P ⬍ .05). Conclusions. Both brush and intermittent ultrasonic activation were effective in the removal of smear layer from the apical third. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:465-470)
Removal of pulp tissue and elimination of microorganisms and their toxins from the root canal system is one of the most important objectives of root canal therapy.1 This is usually achieved by a combination of mechanical instrumentation and irrigation. The efficacy of irrigation depends on its ability to remove dentin debris and smear layer that occur following instrumentation of root canal.2 McComb and Smith3 were the first to describe the smear layer in instrumented root canals through the use of scanning electron microscopy (SEM). Possible deleterious effect may occur if the smear layer and debris are not removed during root canal treatment. Microorganisms remaining in the smear layer after the instrumentation of an infected root canal space can survive and reinfect the canal.4,5 The smear layer has also been shown to hinder the penetration of intracanal disinfectants6 and sealers7,8 into dentinal tubules. Although not substantiated in clinical trials, it would appear to be prudent to remove the smear layer before filling an instrumented root canal. The effectiveness of irrigation relies on both the mechanical flushing action and the chemical ability of irrigants to dissolve the tissue. The flushing action from the syringe irrigation is relatively weak, and passive a
Assistant Professor. Senior Professor and Head. Received for publication Feb 5, 2009; returned for revision Apr 2, 2009; accepted for publication Apr 17, 2009. 1079-2104/$ - see front matter © 2009 Published by Mosby, Inc. doi:10.1016/j.tripleo.2009.04.023 b
ultrasonic irrigation (PUI) has recently been reported to increase the flushing action and improve the efficacy of irrigants in removing remnants of pulp tissue and debris.9-12 Studies on smear layer removal by PUI are inconclusive. Smear layer removal is less predictable in the apical third as compared with the coronal and middle third of the root.13-16 This could be attributed to comparatively smaller apical canal dimensions hindering the penetration of irrigants and resulting in limited contact between canal walls and irrigants.17 Two flushing methods can be used during PUI, namely, a continuous flush of irrigant from the ultrasonic handpiece10,17 or an intermittent flush method using syringe delivery.18,19 Abbott et al.15 reported that intermittent PUI did not enhance the removal of smear layer, and Cameron19 found that intermittent flush irrigation with EDTAC followed with 4% sodium hypochlorite left a minimum smear layer restricted to the apical seat. Van der Sluis et al.20 found both continuous and intermittent flushing equally effective in debris removal from artificially prepared grooves in the apical third; however, no study has compared the effect of continuous and intermittent flushing in the removal of smear layer with EDTA. To aid in root canal debris and smear layer removal, a few attempts have been described that use cotton wrapped around an endodontic file or a broach,21 or an endobrush.22,23 Recently a 30-gauge irrigation needle covered with a brush (NaviTip FX, Ultradent, South Jordan, UT) was introduced into the market. A review of the literature revealed that only 1 study reported the 465
466
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use of these tips in the removal of debris and reported significantly better debris removal in the coronal third but not in the middle and apical thirds.24 However, their effect on smear layer removal was not studied. The purpose of the present study was to evaluate and compare the effect of intermittent and continuous passive ultrasonic irrigation with syringe irrigation in removing smear layer from the root canal wall. In addition, the effects of these methods were compared with the new cotton-coated irrigation needle NaviTip FX. MATERIALS AND METHODS Forty single-rooted noncarious extracted human premolars and canines with single root canals, fully developed apices, and straight roots were included in this study. The teeth selected ranged from 21 to 24 mm in length and were randomly and equally distributed over the different groups. The specimens were stored in 0.1% thymol solution throughout the experiment, and root surfaces were thoroughly cleaned of soft tissue and calculus using ultrasonic scaler. All root surfaces were examined at ⫻20 magnification in a stereomicroscope (RSM-9; Radical, Ambala, Haryana, India) for location of apical foramina, cracks, or resorption. Root surfaces having cracks, fracture, resorption, and apical foramina ⬎0.5 mm from the anatomic apex were discarded. Access cavities were prepared using diamond burs (Mani, Tochigiken, Japan), and Gates-Glidden burs (Mani) were used for the stepback preparation. Working lengths were set by deducting 1 mm from lengths of the files when they extruded just beyond the apical foramina. All preparations were carried out by the principal author. The preparation was begun with size 25 K-files (Dentsply Maillefer, Ballaigues, Switzerland) which bound in the canal at working length, and roots with wider apical foramina were discarded. The middle and coronal thirds of the canals were flared before apical preparation, with Gates-Glidden burs of numbers 2, 3, and 4 with stepbacks of 3, 5, and 7 mm, respectively, relative to the length of last instrument used. Instrumentation of the apical third was continued through 3 sequentially larger K-files, and thus the master apical file was size 40 in all roots. The stepback phase of the apical third begin with the size 45 K-file and 5 larger K-files up to 70. Patency of the apical foramen was maintained throughout preparation with a size 15 K-file. Root canals were thoroughly irrigated with 2 mL freshly prepared 2.5% NaOCl solution between each instrument using a 30-gauge needle which was inserted as far into the prepared root as possible without binding. Final irrigation in all of the groups was carried out with 10 mL 17% EDTA and 10 mL 2.5% NaOCl for 1 minute each. Samples were divided into 5 groups of 8
Fig. 1. 30-gauge NaviTip FX.
teeth each according to the method of activation of final irrigants: Group A (control): Irrigants were not activated and were delivered with a 30-gauge needle placed 1 mm short of working length without binding. Group B (NaviTip FX): A size 30 NaviTip FX (Fig. 1) was placed 1 mm short of working length, and intracanal push and pull strokes were performed along the canal wall (each with 6 mm amplitude reaching 1 mm short of working length) with concomitant delivery of irrigants, first with 10 mL EDTA then with 10 mL NaOCl for 1 minute. Group C (continuous activation with irrigant supply from needle): In this group passive ultrasonic irrigation was performed, using a size 10 K-file in a modified Suprasson P5 system (Satelec, Merignac, France) without the flow-through irrigation system in the following manner. The canal was filled with EDTA, and the ultrasonic file was placed into the canal 1 mm short of working length without touching the walls, so that it could vibrate freely. The ultrasonic file was activated at a power setting of 4 for 1 minute. During this time, irrigant was delivered continuously with needle near the canal orifice at the rate of 10 mL/min. The procedure was repeated similarly with NaOCl. Group D (continuous activation with irrigant supply from handpiece): In this group also, root canals were passively ultrasonically irrigated for 1 minute similarly to group C, but the irrigants were continuously delivered at a rate of 10 mL/ min through the unit. Group E (intermittent activation): In this group, PUI was done similarly to group C except that the file
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Table I. Mean smear layer scores (⫾SD) for the different groups at various levels Group
3 mm
6 mm
9 mm
A. Control B. Brush C. Continuous ultrasonic D. Continuous ultrasonic E. Intermittent
4.01 ⫾ 0.78* 1.29 ⫾ 0.18† 3.99 ⫾ 0.67*
2.82 ⫾ 0.57§ 1.62 ⫾ 0.63† 2.60 ⫾ 0.42§
1.99 ⫾ 0.75† 1.26 ⫾ 0.17† 1.49 ⫾ 0.40†
3.51 ⫾ 0.33*
2.24 ⫾ 0.45§
1.59 ⫾ 0.28†
2.08 ⫾ 0.51‡
1.78 ⫾ 0.50†
1.25 ⫾ 0.19†
*,†,‡,§Scores with the same letter indicate no statistically significant difference at P ⫽ .05.
Fig. 2. Scanning electron microscopic view at ⫻21 of a sample, showing the location of photographs taken at the 3 mm level along the horizontal line.
was activated only for intervals of 10 seconds. Between each interval, the canals were refilled with irrigant by placing the 30-gauge needle into the canal 1 mm short of working length. This procedure was repeated 6 times, so that total duration of ultrasonic irrigation was 1 minute. A final flush with 2 mL 2.5% NaOCl concluded the preparation in all of the groups, and all specimens were dried with paper points. Immediately after completion of root canal preparation, the samples were coded to allow for blinded evaluation of the samples. Root surfaces were grooved using separation disk to indicate level 3, 6, and 9 mm from the root apices, and specimens were decoronated. Specimens were split longitudinally in the buccolingual plane, taking care not to contaminate the canal with debris. Specimens were dehydrated in ascending grades of alcohol up to 100% and mounted on aluminum stubs. Gold sputter coating was carried out under reduced pressure in an inert argon gas atmosphere in Agar Sputter Coater P 7340 (Agar Scientific, Essex, U.K.) and specimens were examined under scanning electron microscope (Leo 435, VP, Cambridge, U.K.) operated at 15 KV. Serial photomicrographs were taken of the canal walls at ⫻400 magnifications at the 3, 6, and 9 mm levels as shown in Fig. 2. These serial photographs were placed adjacent to each other, forming a continuous horizontal examination strip at 3 levels. A 60-m-square grid was superimposed on the strip, from which smear layer scores were evaluated. The number of assessment units varied from 12 to 48 depending on root canal diameters. Amount of smear layer present in each of the “assessment units” were assessed and recorded using a 5-step scale based on the criteria described by Mayer et al.16:
Score 1: All dentinal tubules were open and no smear layer was present. Score 2: Some dentinal tubules were open and others covered by a thin smear layer. Score 3: Few tubules were open and the rest covered by a thin homogeneous smear layer. Score 4: All dentinal tubules were covered by a homogeneous smear layer without any open tubules visible. Score 5: A thick homogenous smear layer completely covered the canal walls. Two calibrated and blinded evaluators independently scored the samples. The scores were then compared, and if a difference was found the two evaluators jointly examined the sample. For each evaluation strip, average scores for smear layer were calculated from the raw data by dividing the sum of all individual scores by the number of assessment units. The code was then broken and each sample was assigned to its experimental group. Means recorded at the 3, 6, and 9 mm examination levels were statistically analyzed for significance (P ⬍ .05 ) within and between the groups using the Friedman 2-way analysis of variance (ANOVA), Kruskal-Wallis test, and Mann-Whitney U test. RESULTS Mean amounts of smear layer recorded at the 3 mm, 6 mm, and 9 mm levels in the 4 experimental groups and 1 control group are listed in Table I. Of a possible maximum of 5, mean smear layer scores in all 5 groups ranged from 4.01 ⫾ 0.78 to 1.25 ⫾ 0.19 (Table I). Representative SEM photomicrographs at the 3 mm level are shown in Fig. 3. Friedman 2-way ANOVA depicted significant difference between the different groups at different levels (3 mm, 6 mm, and 9 mm levels; P ⬍ .05). Significantly lower smear layer scores (P ⬍ .05) were found at the 3 mm and 6 mm levels in the brush and intermittent ultrasonic groups compared
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Fig. 3. Scanning electron microscopic view at ⫻400 of the apical portion of the root canal wall with 60-m-square grid used to score the smear score. A, Control: Large amount of debris and smear layer is present. B, Brush: Almost complete removal of smear layer and many dentinal tubule openings are seen. C, Continuous activation with irrigant supply from needle: All dentinal tubules are completely covered by a thick homogeneous smear layer. D, Continuous activation with irrigant supply from handpiece: Large amount of smear layer is present. E, Intermittent activation: small amount of debris and complete removal of smear layer are visible.
with the control and other experimental groups (Fig. 3, B and E). No significant differences in smear layer scores were recorded between the other experimental groups and the control group (Fig. 3, A, C, and D).
Between group B and group E, the brush group was significantly better than intermittent ultrasonic group at the 3 mm level (P ⬍ .05). At the 9 mm level, all of the the groups were equally effective in smear layer re-
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moval; no significant difference was observed between various groups. When comparing the individual levels, in all of the the groups except brush and intermittent ultrasonic groups, lowest smear layer scores were recorded at the 9 mm level, followed by 6 mm and 3 mm level, with significant difference at the 3 levels (P ⬍ .05). In the brush group (group B), all 3 levels were clean with no significant difference in smear layer scores at the 3 levels examined. In the intermittent ultrasonic group (group E), no significant difference in smear layer scores were recorded at the 6 mm and 9 mm levels; however, significantly higher smear layer scores were recorded at the 3 mm level compared to the 6 mm and 9 mm levels. DISCUSSION The aim of the present study was to evaluate the methods to improve the removal of smear layer, particularly from the apical third of root canal. Significantly better smear layer removal with intermittent ultrasonic irrigation in the study could be related to better flushing of apical third. The syringe delivery of irrigant allowed full control of the procedure, because the depth of needle penetration in the canal and volume flushed through the apical region were known. It allowed for the continual deposition and renewal of irrigating solution within the apical third, leading to better flushing. Gutarts et al.12 also found that a passive ultrasonic irrigation resulted in better debris removal from the apical third of molars using the irrigating needle rather than the file for ultrasonic activation and related it to the continuous and better delivery of irrigant from the tip of needle in the apical portion. Our results do not agree with those of Abbott et al.,15 who reported that intermittent activation of EDTA followed by NaOCl was not effective in the removal of smear layer. In that study, they used a power setting of 1 with a size 20 K-file in the ultrasonic unit, and the irrigant was delivered with 25-gauge needle. Lower power settings and larger size of needle and file might have been responsible for the different results in that study. Similarly to previous studies,13,14,16 the present study did not find significantly better smear layer removal in the apical third in group C and group D. In group C, irrigant was delivered at the pulp chamber with needle, and in group D it was delivered through the ultrasonic unit at the rear end of the file rather than the tip. With these methods it is not possible to determine how much irrigant actually enters the root canal and flows through the apical part. Moreover ultrasonic vibration of the file along with narrow apical diameter of the root canal might have prevented flow of irrigating solution from the coronal to apical area. Also in the continuous ul-
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trasonic group, contact of the vibrating file on the EDTA-softened canal wall may have produced a new smear layer during final activation. With intermittent method, the file can better remain centered in the root canal for a smaller period (10 seconds instead of 1 minute), thus minimizing the chances of touching the root canal and creating smear layer again during final irrigation. Findings of the present study are not consistent with the study of Lui et al.,25 who found that 1 minute of continuous ultrasound with EDTA was effective in removing smear layer. The difference could be related to a better scoring method used in the present study. A 60-m-square grid was superimposed over the photomicrographs and the amount of smear layer was evaluated in each assessment unit. A grid scoring method may be more accurate to score smear layer than a single score examined per level, because it is often nonuniformly distributed.26 Also, magnifications of ⫻1,000 and ⫻3,000 used in that study might have resulted in an observational bias, because only a small area of the root canal wall can be observed in higher magnification. Results of the present study are also in contradiction to the study by Van der Sluis et al.,20 reporting that the intermittent ultrasonic method and continuous flow of irrigant through the device were equally effective in the removal of artificial debris from the artificially prepared groves. Removal of debris from the root canal space might be more difficult than the debris removal from artificially created grooves. In the present study, the NaviTip FX brushes showed almost complete removal of the smear layer and debris at the apical third, with no significant difference between the apical, middle, and coronal thirds. Continuous delivery of irrigant at the apical third and better mechanical debridement with active scrubbing of the walls during up and down motion might have resulted in better cleaning in this group. The design of the NaviTip FX allows it to reach up to the apex and at the same time can be used to actively scrub the canal wall while concomitantly delivering the irrigant. This mechanical activation would have enhanced the chemical action of irrigant in removing the smear layer and debris and might have a similar cleansing effect as a bottle brush. These results are supported by a study by Batista et al.,27 who proposed that neither time of application nor concentration of the irrigant was responsible for removal of smear layer; it was the method of application that was more important. They found that active application of EDTA by means of brush was more effective than passive application using soaked cotton pellets in removing smear layer from root surface. Similar findings indicating improved canal debridement were reported by Keir et al.,22 who used the
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endobrush with an attached handle and actively brushed the root canal with a 90-degree rotary motion combined with 2-3 mm up and down motion for 1 minute. However, those results are contrary to the study of AlHadlaq et al.,24 who did not find significantly better debris removal in the apical and middle thirds with NaviTip FX. However, in that study the NaviTip FX was used in a passive manner without scrubbing along the canal walls, which might have resulted in inefficient cleaning. CONCLUSION Within the limits of this in vitro study, it can be postulated that both brush and intermittent ultrasonic are effective in the removal of smear layer from the apical third. However the NaviTip FX, being easy to handle, might be a good alternative to ultrasonic and various other methods in cleaning the root canal, with minimal chances of temperature rise as in PUI. Although intermittent ultrasonic irrigation was found to be a better alternative to continuous PUI in removal of smear layer and debris, it might not be an acceptable technique in clinical practice and requires further research on its effectiveness. Although NaviTip FX showed better results, further clinical study with a greater number of samples and on posterior teeth with curved root canals is required before this technique can be recommended for routine use during root canal treatment. REFERENCES 1. Haapasalo M, Endal U, Zandi H, Coil JM. Eradication of endodontic infection by instrumentation and irrigation solutions. Endod Top 2005;10:77-102. 2. Baugh D, Wallace J. The role of apical instrumentation in root canal treatment: a review of literature. J Endod 2005;31:333-40. 3. McComb D, Smith DC. A preliminary scanning electron and microscopic study of root canals after endodontic procedures. J Endod 1975;1:238-42. 4. Brannstrom M, Nyborg H. Cavity treatment with a microbicidal fluoride solutions growth of bacteria and effect on pulp. J Prosthet Dent 1973;30:303-10. 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. Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9. 7. White RR, Goldman M, Lin PS. The influence of smeared layer upon dentinal tubule penetration by endodontic filling materials. Part II. J Endod 1987;13:369-74. 8. Oksan T, Aktener BO, Sen BH, Tezel H. The penetration of root canal sealers into dentinal tubules. A scanning electron microscope study. Int Endod J 1993;26:301-5. 9. Cheung GSP, Stock CJR. In vitro cleaning ability of root canal irrigants with and without endosonics. Int Endod J 1993;26:334-43. 10. Lee SJ, Wu MK, Wesselink PR. The efficacy of ultrasonic irrigation to remove artificially placed dentine debris from different-sized simulated plastic root canals. Int Endod J 2004;37:607-12.
11. Passarinho-Neto JG, Marchesan MA, Ferreira RB, Silva RG, Silva-Sousas YTC, Sousa-Neto MD. In vitro evaluation of endodontic debris removal as obtained by rotary instrumentation coupled with ultrasonic irrigation. Aust Endod J 2006;32:123-8. 12. Gutarts R, Nusstein J, Reader A, Beck M. In vivo debridement efficacy of ultrasonic irrigation following hand-rotary instrumentation in human mandibular molars. J Endod 2005;31:166-70. 13. Baumgartner JC, Madear CL. A scanning electron microscopic study of four root canal irrigations regimes. J Endod 1987;3:147-57. 14. Ciucchi B, Khettabi M, Holz J. The effectiveness of different endodontic irrigation procedures on the removal of the smear layer: a scanning electron microscopic study. Int Endod J 1989; 22:21-8. 15. Abbott PV, Heijkoop PS, Cardaci SC, Hume WR, Heithersay GS. An SEM study of the effects of different irrigation sequences and ultrasonics. Int Endod J 1991;24:308-16. 16. Mayer BE, Peters OA, Barbakow F. Effects of rotary instruments and ultrasonic irrigation on debris and smear layer scores: a scanning electron microscopic study. Int Endod J 2002;35:582-9. 17. Guerisoli DM, Merchesan MA, Walmsley AD, Lumley PJ, Pecora JD. Evaluation of smear layer removal by EDTAC and sodium hypochlorite with ultrasonic agitation. Int Endod J 2002;35:418-21. 18. Cameron JA. The synergistic relationship between ultrasound and sodium hypochlorite: a scanning electron microscope evaluation. J Endod 1987;13:541-5. 19. Cameron JA. Factors affecting the clinical efficiency of ultrasonic endodontics: a scanning electron microscopy study. Int Endod J 1995;28:47-53. 20. Van der Sluis LWM, Gambarini G, Wu KW, Wesselink PR. The influence of volume, type of irrigant and flushing method on removing artificially placed dentine debris from the apical root canal during passive ultrasonic irrigation. Int Endod J 2006;39:472-6. 21. The SD. The use of cotton-wrapped file to evacuate necrotic pulp tissue. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1979;48:77-88. 22. Keir DM, Senia ES, Montgomery S. Effectiveness of a brush in removing post-instrumentation canal debris. J Endod 1990;16: 323-7. 23. Ruddle CJ. Cleaning and shaping the root canal system. In: Cohen S, Burns RC, editors. Pathways of the pulp. 8th ed. St. Louis: Mosby; 2002:231-91. 24. Al-Haddlaq SM, Al-Turaiki SA, Al-Sulami U, Saad AY. Efficacy of a new brush covered irrigation needle in removing root canal debris: a scanning electron microscopic study. J Endod 2006;32:1181-4. 25. Lui JN, Kuahb HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonics on removal of smear layer. J Endod 2007;33:472-5. 26. Wu MK, Wesselink PR. Efficacy of three techniques cleaning the apical portion of curved root canals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;79:492-6. 27. Batista LHC, Sampalo CEJ, Pilatti LG, Shibii AJ. Efficacy of EDTA-T gel for smear layer removal at root surfaces. Quintessence Int 2005;36:551-8. Reprint requests: Dr. Sanjay Tewari Professor and Head Department of Conservative Dentistry and Endodontics Principal Government Dental College Postgraduate Institute of Medical Sciences Rohtak, Haryana India [email protected]