The main goal of endodontic therapy is to eradicate all vital and necrotic tissue, microorganisms,

Efficacy and Safety of Various Active Irrigation Devices When Used with Either Positive or Negative Pressure: An In Vitro Study Augusto Malentacca, MD, DDS,* Umberto Uccioli, DDS, Dario Zangari, DDS,* Carlo Lajolo, MD, DDS, PhD, and Cristiano Fabiani, DDS, CAGS, MSD* Abstract Introduction: The purpose of this in vitro study was to evaluate and compare the efficacy and safety of different devices available for canal cleansing. Methods: The following systems were tested: passive ultrasonic irrigation, EndoVac (Discus Dental, Culver City, CA), and the irrigation ultrasonic needle (ProUltra PiezoFlow Irrigation Ultrasonic Needle; Dentsply Tulsa Dental Specialties, Tulsa, OK) used in both the injection mode (IUNI) and the aspiration mode (IUNA). In the control group, traditional irrigation with a syringe and side-vented needle was used. A resin model was used with 4 lateral canals (respectively at 2, 5, 8, and 11 mm from the apical foramen) filled with bovine pulp stained with fuchsin. The model also included a 2- mm chamber in communication with the apex, again filled with bovine pulp, which enabled the measurement of the extrusion of NaOCl beyond the apex. Results: With regard to efficacy, the most effective systems were found to be those using the ultrasonic needle, either in aspiration or injection modes; Endo- Vac was the least effective. Conversely, IUNI was found to bring the highest risk with regard to the extrusion of sodium hypochlorite beyond the apex. EndoVac was the safest but only by a slight margin compared with IUNA and passive ultrasonic irrigation. Conclusions: Based on this study, the system that best reconciles efficacy and safety appears to be IUNA. (J Endod 2012;38:1622 1626) Key Words Passive ultrasonic irrigation, sodium hypochlorite, ultrasonic needle From the *Private Practice, Rome Italy; Private Practice, Ferentino, Italy; and School of Dentistry, Catholic University, Rome, Italy. Address requests for reprints to Dr Cristiano Fabiani, Largo Belloni, 4, 00191 Rome, Italy. E-mail address: criendo@mac. com 0099-2399/$ - see front matter Copyright ª 2012 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2012.09.009 The main goal of endodontic therapy is to eradicate all vital and necrotic tissue, microorganisms, and products of microbial degradation from the canal system. The irrigation of root canals with an antibacterial solution is considered an essential phase of chemical/mechanical canal preparation (1); irrigation with a syringe and needle remains the most commonly used procedure (2, 3). Mechanical preparation, combined with the usual irrigation methods, is not capable of guaranteeing optimal cleansing of the endodontic system (4). The intricate nature of the root canal anatomy, with isthmi, fins, webs, anastomoses, and other irregularities, makes complete cleansing of all areas of the root canal a complex procedure because it hinders the irrigant from dissolving the organic tissues within the canal and destroying the bacterial biofilm (5, 6). The use of ultrasonic systems has been proposed as a possible solution to the problem of canal cleansing; their use after complete mechanical or manual instrumentation has been found to reduce the number of bacteria (7, 8). A marked efficacy in cleansing after the passive use of ultrasound has been reported (9 12). This technique using a file freely oscillating at ultrasonic frequencies in a root canal filled with sodium hypochlorite is known as passive ultrasonic irrigation (PUI) (9). In vivo histologic studies on the mesial roots of mandibular molars by Haidet et al (12) and by Archer et al (13) analyzed the removal of organic tissue with or without the use of ultrasound. These 2 studies reported that both canals and isthmi were significantly cleaner with the ultrasound method. Recent in vitro studies have confirmed the efficacy of PUI in removing pulp tissue from lateral canals (14 16) in straight canals and curved canals (17, 18). Also with this technique, the complete penetration of the irrigant cannot be achieved in all the phases of the root canal treatment (19). Gutarts et al (6) proposed the use of an ultrasonically-activated needle placed in the canal through which the sodium hypochlorite would flow, enabling the irrigant to be continually replaced. Studies by these researchers in vivo have shown this method to be remarkably effective at cleansing inaccessible zones of the endodontic system (20, 21). Conversely, it has been found that this method may push the action of irrigants beyond the distance at which the frontal pressure of a syringe normally operates when used for canal cleansing (22). Clearly, this might compromise the safety of the cleansing procedure because the severe consequences of the extrusion of sodium hypochlorite into the periapical tissue are well known (23). Different recent studies (22, 24) have shown the absolute safety of using negative-pressure cleansing systems compared with manual and ultrasonic irrigation with particular reference to the ultrasonic needle; however, no clear superiority of this latter system in terms of penetrating and cleansing the endodontic space has been reported. The dilemma remains that there is a need for an effective irrigation system that is able to penetrate in depth into the apical endodontic system but at the same time does not cause extrusion of irrigants beyond the apex. The aim of this study was to evaluate the efficacy and safety of an ultrasonic needle operating by aspirating sodium hypochlorite from the canal and to compare this with recently developed systems, namely PUI, EndoVac (Discus Dental, Culver City, CA), and the ultrasonic needle operating in injection mode. 1622 Malentacca et al. JOE Volume 38, Number 12, December 2012

Materials and Methods Model Fabrication A customized transparent epoxy resin model was used, modifying a model developed by Al-Jadaa et al (15). Our model had lateral canals placed at different distances from the apex (ie, 11, 8, 5, and 2 mm); we added a cylindrical chamber of 0.3 ml to simulate an apical lesion. Once the model had been constructed, the main canal was instrumented with an F5 ProTaper file (Dentsply Maillefer, Ballaigues, Switzerland). To gain access to the lateral canals and the simulated lesion at the end of the main canal, external perforations were made with a calibrated tip from the MetaLift Kit (Classic Practice Resources Inc, Metalift, LLC, Baton Rouge, LA); these access holes could be sealed with corresponding screws from the same kit, thus creating a closed system. The assembled model is shown in Figure 1A. The same model could be used for the whole series of tests involved in this study because the canal system could be emptied, cleaned, and reused simply by unscrewing the calibrated screws. In order to verify any alterations that the model would undergo in repetitive trials, the model was tested in a pilot study. No alterations were observed in the 100-trial test. Bovine Pulp Tissue Preparation In order to simulate in vivo conditions, an artificial pulp tissue was prepared using pulp taken from bovine teeth as described by Al- Jadaa et al (15). Once a sufficient quantity of pulp had been obtained, it was stained with fuchsin and put into a syringe. The artificial pulp was injected into the lateral canals and into the apical cavity with a 22-G needle, leaving the main canal empty. After having sealed the access holes with the calibrated screws, the model was ready for the different systems to be tested. Main Experiment Five groups were set up (ie, irrigation ultrasonic needle in injection mode [IUNI], irrigation ultrasonic needle in aspiration mode [IUNA], PUI, EndoVac, and the control group). For the IUNI group, we used a ProUltra PiezoFlow Ultrasonic Irrigation 25-gauge Needle (Dentsply Tulsa Dental Specialties, Tulsa, OK) in the injection mode. For the IUNA group, the same needle as in group IUNI was used but in an off-label way (ie, in aspiration mode [the chair-side suction tube was attached to the Luer-Lock connection on the ProUltra Piezo- Flow Ultrasonic Irrigation Needle). For the PUI group, a passive ultrasonic ESI File (EMS, Nyon, Switzerland) was used. In the EndoVac group, the EndoVac irrigation system was used; in the negative control group, the irrigant was delivered with a 25-G side-vented needle. In all 4 groups, the irrigant solution used was 5.25% sodium hypochlorite at room temperature. In the IUNI group, the ultrasound source was activated for 3 minutes, with an irrigant flow of 10 ml solution every minute. In the IUNA group, the ultrasound source was activated for 3 minutes with an aspiration flow of 3 ml solution every minute. In the PUI group, the ultrasound source was activated in 3 steps of 1 minute each with irrigation of 10 ml with a 25-G side-vented needle after every activation. In the EndoVac group, the system was active for 3 minutes with an aspiration flow of 1.5 ml every minute. In the negative control group, the irrigant was left in place for 3 minutes, replacing 10 ml solution every minute. To replace the irrigant solution, the VATEA system (Re- Dent-Nova Ltd, Ra anana, Israel) was used. The ultrasound source (Suprasson PMax; Satelec Acteon, Merignac, France) was used at a power setting just sufficient to cause a drop of irrigant on the needle tip to be nebulized. In the case of the PUI group, the yellow 4 level of the Suprasson PMax device was used. For all the groups, the tip of the cleansing system was taken to a distance of 5, 3, or 1 mm from the apical foramen. During the experiment, the IUNI needle, the IUNA needle, and the ESI file (the PUI group) were moved back and forth within the canal, stopping at the predetermined distance from the apex, whereas in the case of the EndoVac group, the system was activated while keeping the tip stationery at the reference distance. There were no cases of breakage of any device during any of the tests. Photographs were taken with a 22-megapixel digital camera (5D; Canon, Tokyo, Japan) and macrolens (Canon 100 f2.8) at the beginning and 5 seconds after the end of each experiment. The photographs, bearing a digital code number, were analyzed randomly and blindly by 1 operator tested for his accuracy by analyzing the same images 5 times after different intervals. Both the penetration of the irrigant into the simulated lateral canals and the extrusion of sodium hypochlorite beyond the apex were measured. Thirty trials were recorded for each test group for a total of 150 trials. The mean value of extrusion beyond the apex in each group was calculated when the tip of the instrument was brought to 5, 3, or 1 mm from the apex. Tissue dissolution was measured from the Figure 1. (A) The assembled epoxy resin model used in the current study with tissue injected into the lateral canals and into the apical cavity, leaving the main canal empty. (B) A close up of a lateral canal with the artificial pulp partially dissolved. (C) A close up of the simulated apical lesion with the pulp partially dissolved. JOE Volume 38, Number 12, December 2012 Various Active Irrigation Devices 1623

canal entrance to the closest tissue-irrigant interface (Fig. 1B) for each of the 4 simulated lateral canals placed at 2, 5, 8, and 11 mm from the apex. The maximum value taken into consideration was 4 mm. The extrusion of sodium hypochlorite beyond the apex was analyzed on the photograph by calculating the area of the dissolved tissue (Fig. 1C). All images were analyzed using Adobe Photoshop CS5 software (Adobe Systems Inc, San Jose, CA), setting the same reference scale for all images. Statistical Analysis Quantitative variables were tested for normal distribution by a Shapiro-Wilk test. Because variables did not show a normal distribution, the Kruskal-Wallis nonparametric test was used to detect differences among devices and within the same device among lateral canals. Significance at the P #.01 level was used to determine statistical significance. Statistical analysis was performed using the software Intercooled Stata 8.0 (Stata Corp, College Station, TX). Results Apical Extrusion The mean values of extrusion (the area of dissolved tissue) beyond the apex when the tip of the different devices was placed at 5, 3, or 1 mm from the apex are shown in Table 1. Significant differences in the amount of extruded irrigant beyond the apex were observed among the different devices when placed at the same distance from the apex (P <.001). IUNI caused the most extrusion and EndoVac the least. EndoVac (same as the control) did not cause extrusion when placed at any distance from the apex, whereas IUNI, PUI, and IUNA caused some extrusion. When the tips were placed at varying depths of insertion, there were significant differences of extrusion within the same device (except EndoVac), with 5 mm from the apex being the safest (ie, the least amount of extrusion) and 1 mm from the apex being more dangerous (P <.001). IUNI showed extrusion of 0.5 mm 2 even when placed at 5 mm; when placed at 1 mm, it caused complete extrusion in all the samples. IUNA, among the devices that caused extrusion, was the safest at any working length. Even when the device was placed 1 mm from the apex, it showed extrusion of the irrigant for less than 1 mm 2. PUI showed extrusion of the irrigant for less than 1 mm 2 at 3 and 5 mm from the apex, whereas at 1 mm it showed extrusion of 2.04 mm 2. Accessory Canal Tissue Dissolution The values relating to the dissolution of tissue in the lateral canals are graphically presented in Figure 2. IUNI effectively dissolved tissue in all of the lateral canals regardless of its distance from the apex. IUNA was most effective when placed 1 mm from the apex with its effectiveness decreasing as it is moved coronally. PUI had similar results. EndoVac was almost ineffective at all depths. When the device tips were placed at 3 different working lengths, significant differences in lateral canal tissue dissolution were observed. At 1 mm from the apex, the IUNA group had the best results, and EndoVac was the least efficient device in dissolving lateral canal tissue (P <.001). At 3 and 5 mm from the apex, IUNI was the more efficient device. The control group had the worst results (P <.001). Within the same device, there were statistically significant differences in tissue dissolution when the tip of the device was placed at different depths. IUNI and IUNA were the most efficient devices at any depth, and the mean amount of dissolved tissue was more than 3 mm for both devices. PUI had a range between 1.5 and 1.8 mm, whereas EndoVac and the control group showed dissolution lower than 1 mm. Discussion Within the limitations of this in vitro study conducted on resin models, it can be stated that the ultrasonic systems based on the agitation of the irrigant are more effective in dissolving necrotic pulp than systems merely based on the replacement of the irrigant. The model used in this study was similar to the model used by Al-Jadaa et al (15) to assess the dissolution of artificial necrotic pulp tissue. However, their model was an open system. To simulate more accurately the conditions encountered in vivo, the resin model used here was hermetically sealed with screws inserted into the resin, ensuring a perfect seal of the system. However, in vivo it is not known whether at high pressures the biological system maintains a perfect hermetic seal because, unlike resin, the biological tissues are not rigid. Furthermore, dentin is markedly different from the material used to make the endoblocks used in most studies. The mechanisms of action of ultrasound (ie, cavitation, acoustic streaming, and so on) might be influenced by the different characteristics and hardness of the walls on which they act. The artificial pulp used in this study, lacking an intact fabric of collagen fibers holding it together, is easier to dissolve than natural pulp tissue either through chemical or mechanical action of the irrigant. Apart from these intrinsic limitations, the current model system allowed TABLE 1. Mean Values of Extrusion beyond the Apex When the Tip of the Different Devices Was Placed at 5, 3, or 1 mm from the Apex Distance from apex Device No. of samples Mean Standard deviation Minimum Maximum 1mm* IUNI A 10 8.28 0 8.28 8.28 IUNA B 10 0.78 0.56 0.01 1.72 PUI C 10 2.04 0.78 0.92 3.44 3mm* IUNI a 10 1.47 0.58 0.60 2.21 IUNA b 10 0.02 0.03 0.01 0.1 PUI c 10 0.95 0.8 0.20 3.00 5mm* IUNI a 10 0.57 0.32 0.18 1.10 IUNA b 10 0.01 0.01 0 0.02 PUI c 10 0.04 0.06 0 0.20 Data are expressed in mm 2. Statistically significant differences were observed in IUNI ( a ), IUNA ( b ), and PUI ( c ) when irrigation was performed at different working lengths (1 mm vs 3 mm vs 5 mm) (Kruskal- Wallis test, P <.001). *Statistically significant differences in the amount of extruded irrigant beyond the apex were observed among the different devices when placed at the same distance from the apex (Kruskal-Wallis test, P <.001). 1624 Malentacca et al. JOE Volume 38, Number 12, December 2012

Figure 2. The mean dissolution of pulp in the lateral canals when the tip of the different devices was placed at 5, 3, or 1 mm from the apex. Brackets represent the standard deviation from the mean. a quantitative comparison of different devices used for cleansing of the endodontic system. The results of this study show that systems using ultrasound cleanse the endodontic space more efficaciously but that this cleansing action is also more difficult to control. There may be a risk of pushing the irrigant beyond the apex. From the resulting data, it emerged quite clearly that the use of an ultrasound needle in the aspiration mode offers an extremely advantageous efficacy-safety ratio. When operating at 5 mm from the apex, the IUNI system was generally the most effective, cleansing the lateral canals even in the most apical part of the root canal system with relative safety. However, this was not true if IUNI was used either at 3 mm or at 1 mm from the apex. At these distances, extrusion was observed in every sample. The PUI system showed absolute safety when used at 5 and at 3 mm, whereas at 1 mm in almost all tests there was some extrusion of sodium hypochlorite. With regard to efficacy, it had a cleansing action of the lateral canals that was less predictable than the other ultrasound systems tested; however, that action extended to all the lateral canals, independent of their position along the principal canal, in agreement with the results of the study by Jiang et al (25). The EndoVac system showed no extrusion of sodium hypochlorite beyond the apex in any of the trials, resulting in the safest system of all tested. However, the system s efficacy on the dissolution of simulated pulp into the lateral canals was only slightly above the values recorded for the control group. These results are in contrast with other studies showing good dissolution of tissue in isthmi of mandibular mesial canals (26). An isthmus is a communication between 2 canals, and so it is an open system within a closed one. Because in this study the lateral canals were closed at their ends, it may be speculated that the EndoVac system is able to promote flow, in a closed system, up to where the tip is placed and no further. When the IUNA system was used at 1 mm from the apex, the efficacy was comparable with that of the IUNI system, working in almost complete safety. In only one of the trials was there slight extrusion of sodium hypochlorite beyond the apex, thus resulting in a better efficacy/safety ratio. Considering that the diameter of the ultrasound needle is 0.51 mm, it is true that with apical preparations of 30 ISO or less it is impossible to reach the apical 2 mm. To get to this depth, the apical preparation should be at least 35 ISO; hence, for future clinical applications, it seems advisable to develop smaller ultrasound needles. Conclusions The present study analyzed 2 aspects of root canal irrigation: the efficacy of irrigation systems by measuring the dissolution of artificial pulp placed in lateral canals and the safety of these systems by measuring the amount of irrigant extruded beyond the apex. The safest system was found to be the EndoVac, which was also the least effective in dissolving tissue placed in lateral canals. The system most effective in dissolving tissue in lateral canals, the ProUltra ultrasound needle (IUNI group), was also the most risky if used at a distance of less than 5 mm from the apex. Within the limitations of this in vitro study, the system that appears to best reconcile efficacy and safety is the ultrasound needle working by aspirating sodium hypochlorite at a distance from the apex of more than 2 mm. Acknowledgments The authors deny any conflicts of interest related to this study. References 1. Haapasalo M, Endal U, Zandi H, Coil JM. Eradication of endodontic infection by instrumentation and irrigation solutions. Endod Topics 2005;10: 77 102. 2. Gu LS, Kim JR, Ling J, et al. Review of contemporary irrigant agitation techniques and devices. J Endod 2009;35:791 804. 3. Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in endodontics. Dent Clin North Am 2010;54:291 312. 4. Schafer E, Zapke K. A comparative scanning electron microscopic investigation of the efficacy of manual and automated instrumentation of root canals. J Endod 2000;26:660 4. 5. Weller RN, Brady JM, Bernier WE. Efficacy of ultrasonic cleaning. J Endod 1980;6: 740 3. 6. 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. JOE Volume 38, Number 12, December 2012 Various Active Irrigation Devices 1625

7. DeNunzio MS, Hicks ML, Pelleu GB Jr, et al. Bacteriological comparison of ultrasonic and hand instrumentation of root canals in dogs. J Endod 1989; 15:290 3. 8. Spoleti P, Siragusa M, Spoleti MJ. Bacteriological evaluation of passive ultrasonic activation. J Endod 2003;29:12 4. 9. van der Sluis LW, Versluis M, Wu MK, Wesselink PR. Passive ultrasonic irrigation of the root canal: a review of the literature. Int Endod J 2007;40:415 26. 10. Ahmad M, Pitt Ford TJ, Crum LA. Ultrasonic debridement of root canals: acoustic streaming and its possible role. J Endod 1987;13:490 9. 11. Ahmad M, Pitt Ford TR, Crum LA, Walton AJ. Ultrasonic debridement of root canals: acoustic cavitation and its relevance. J Endod 1988;14:486 93. 12. Haidet J, Reader A, Beck M, Meyers W. An in vivo comparison of the step-back technique versus a step-back/ultrasonic technique in human mandibular molars. J Endod 1989;15:195 9. 13. Archer R, Reader A, Nist R, et al. An in vivo evaluation of the efficacy of ultrasound after step-back preparation in mandibular molars. J Endod 1992;18:549 52. 14. van der Sluis LW, Wu MK, Wesselink PR. The efficacy of ultrasonic irrigation to remove artificially placed dentine debris from human root canals prepared using instruments of varying taper. Int Endod J 2005;38:764 8. 15. Al-Jadaa A, Paque F, Attin T, Zehnder M. Necrotic pulp tissue dissolution by passive ultrasonic irrigation in simulated accessory canals: impact of canal location and angulation. Int Endod J 2009;42:59 65. 16. Castelo-Baz P, Martin-Biedma B, Cantatore G, et al. In vitro comparison of passive and continuous ultrasonic irrigation in simulated lateral canals of extracted teeth. J Endod 2012;38:688 91. 17. Al-Jadaa A, Paque F, Attin T, Zehnder M. Acoustic hypochlorite activation in simulated curved canals. J Endod 2009;35:1408 11. 18. Malki M, Verhaagen B, Jiang LM, et al. Irrigant flow beyond the insertion depth of an ultrasonically oscillating file in straight and curved root canals: visualization and cleaning efficacy. J Endod 2012;38:657 61. 19. Vera J, Arias A, Romero M. Effect of maintaining apical patency on irrigant penetration into the apical third of root canals when using passive ultrasonic irrigation: an in vivo study. J Endod 2011;37:1276 8. 20. Carver K, Nusstein J, Reader A, Beck M. In vivo antibacterial efficacy of ultrasound after hand and rotary instrumentation in human mandibular molars. J Endod 2007; 33:1038 43. 21. Burleson A, Nusstein J, Reader A, Beck M. The in vivo evaluation of hand/rotary/ ultrasound instrumentation in necrotic, human mandibular molars. J Endod 2007;33:782 7. 22. Desai P, Himel V. Comparative safety of various intracanal irrigation systems. J Endod 2009;35:545 9. 23. Hulsmann M, Rodig T, Nordmeyer S. Complications during root canal irrigation. Endod Topics 2009;16:27 63. 24. Fukumoto Y, Kikuchi I, Yoshioka T, et al. An ex vivo evaluation of a new root canal irrigation technique with intracanal aspiration. Int Endod J 2006;39:93 9. 25. Jiang LM, Verhaagen B, Versluis M, et al. The influence of the ultrasonic intensity on the cleaning efficacy of passive ultrasonic irrigation. J Endod 2011;37:688 92. 26. Susin L, Liu Y, Yoon JC, et al. Canal and isthmus debridement efficacies of two irrigant agitation techniques in a closed system. Int Endod J 2010;43:1077 90. 1626 Malentacca et al. JOE Volume 38, Number 12, December 2012