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  • 1. Basic Research—TechnologyGlide Path Preparation in S-shaped Canals with RotaryPathfinding Nickel-Titanium InstrumentsNatasha C.C. Ajuz, DDS,* Luciana Armada, PhD,* Lucio S. Goncalves, PhD,* ¸Gilberto Debelian, PhD,† and Jos F. Siqueira, Jr, PhD* eAbstractIntroduction: This study compared the incidence ofdeviation along S-shaped (double-curved) canals afterglide path preparation with 2 nickel-titanium (NiTi) N egotiation and glide path preparation are the initial phases of chemomechanical procedures and can be regarded as crucial steps for assessment of the root canal anatomy and establishment of unimpeded access to the apical part of the canal (1, 2).rotary pathfinding instruments and hand K-files. These approaches may be especially challenging in curved and narrow canals;Methods: S-shaped canals from 60 training blocks consequently, procedural difficulties or errors are not uncommon (3). Instrumentswere filled with ink, and preinstrumentation images used for canal negotiation should ideally be of small size and flexible to permit theirwere obtained by using a stereomicroscope. Glide progression in apical direction with safety and efficiency (2, 4–7). Also, they shouldpath preparation was performed by an endodontist produce an initial enlargement of the canal that is smooth and centered from itswho used hand stainless steel K-files (up to size 20), orifice to the physiologic terminus, the so-called glide path (8), which is very importantrotary NiTi PathFile instruments (up to size 19), or rotary for further adequate shaping of the root canal, especially when using rotary nickel-NiTi Scout RaCe instruments (up to size 20). Postinstru- titanium (NiTi) instrumentation (9).mentation images were taken by using exactly the same Hand-operated and engine-driven instruments have been recently introducedconditions as for the preinstrumentation images, and with the specific recommendation for root canal negotiation. There are not manyboth pictures were superimposed. Differences along studies evaluating the mechanical features and performance of these instrumentsthe S-shaped canal for the mesial and distal aspects (4–6). A recent study by Lopes et al (10) compared the mechanical properties ofwere measured to evaluate the occurrence of deviation. the pathfinding instruments C-Pilot (hand-operated; VDW, Munich, Germany), PathFileResults: Intragroup analysis showed that all instru- (engine-driven; Dentsply Maillefer, Ballaigues, Switzerland), and Scout RaCe (engine-ments promoted some deviation in virtually all levels. driven; FKG Dentaire, La Chaux-de-Fonds, Switzerland). They found that the resultsOverall, regardless of the group, deviations were varied according to the mechanical property tested. The C-Pilot instrument showedobserved in the mesial wall at the canal terminus and increased resistance to buckling but decreased flexibility when compared with NiTiat levels 4, 5, 6 and 7 mm and in the distal wall at levels pathfinding instruments; PathFile instruments showed the highest resistance to cyclic1, 2, and 3 mm. These levels corresponded to the inner fatigue, and Scout RaCe files exhibited the highest angular deflection to fracture. Inwalls of each curvature. Both rotary NiTi instruments terms of performance in simulated canals, Berutti et al (7) compared changes to canalperformed significantly better than hand K-files at all curvature and incidence of canal aberrations after glide path preparation with hand K-levels (P < .05), except for PathFiles at the 0-mm level. files or PathFile in S-shaped canals in resin blocks. PathFile instruments generated lessScoutRaCe instruments showed significantly better modification of curvature and fewer canal aberrations. So far, no study has comparedresults than PathFiles at levels 0, 2, 3, 5, and 6 mm the performance of the newly introduced Scout RaCe instruments with hand files and(P < .05). Conclusions: Findings suggest that rotary the rotary PathFile instruments. Therefore, this study was intended to compare the inci-NiTi instruments are suitable for adequate glide path dence of deviation along S-shaped (double-curved) canals after negotiation and glidepreparation because they promoted less deviation path preparation with 2 NiTi rotary pathfinding instruments (PathFile and Scout RaCe)from the original canal anatomy when compared with and hand K-files.hand-operated instruments. Of the 2 rotary pathfindinginstruments, Scout RaCe showed an overall significantly Materials and Methodsbetter performance. (J Endod 2013;39:534–537) Sixty ISO #15, 0.02-tapered, S-shaped Endo Training Blocks (Dentsply Maillefer) were used in this study. Each simulated canal was filled with ink by using an insulinKey Words syringe. To facilitate superimposition of preinstrumentation and postinstrumentationDouble-curved canal, pathfinding instruments, root images, 4 landmarks were placed in each resin block. Specimens were randomly as-canal deviation, rotary nickel-titanium instruments signed to 3 different groups of 20 blocks each. Each specimen was mounted on From the *Department of Endodontics, Faculty of Dentistry, Estcio de S University, Rio de Janeiro, Rio de Janeiro, Brazil; and †Department of Endodontics, a aUniversity of Oslo, Oslo, and endodontic private practice, Bekkestua, Norway. Supported by grants from Conselho Nacional de Desenvolvimento Cient ıfico e Tecnolgico (CNPq) and Fundac~o Carlos Chagas Filho de Amparo  Pesquisa do o ¸a aEstado do Rio de Janeiro (FAPERJ), Brazilian governmental institutions. Address requests for reprints to Dr Jos F. Siqueira Jr, Faculty of Dentistry, Estcio de S University, Av. Alfredo Baltazar da Silveira, 580/cobertura, Recreio, Rio de e a aJaneiro, RJ, Brazil 22790-710. E-mail address: jose.siqueira@estacio.br0099-2399/$ - see front matter Copyright ª 2013 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2012.12.025534 Ajuz et al. JOE — Volume 39, Number 4, April 2013
  • 2. Basic Research—Technologya customized stable support apparatus, which consisted of a rectangular 1-mm scale generated by the stereomicroscope image capture system.slot of the size of the block and adapted to the base of a Leica S8 APO The first measuring point was at the WL, ie, the apical terminus of thestereomicroscope (Leica, Wetzlar, Germany), so that the specimen was canal (0 mm), and the last measuring point was 7 mm from the WL,positioned at 90 to the objective lens. A digital image was captured of which resulted in 8 measuring points for both the mesial and distal sideseach specimen before instrumentation by using the software Leica of the canal, a total of 16 measuring points per specimen. All measure-Application Suite 3.6 (Leica), under magnification of Â10, and saved ments were made at right angles to the surface of the canal. If the differ-as TIFF format file. ence between the mesial and distal measures at a given point was equal All instruments were used up to the working length (WL), which to 0, the canal was considered nondeviated and uniformly enlarged, atwas established at the terminus of the artificial canal (0 limit). All canals least in the plane (mesiodistal) analyzed.were initially irrigated with 2 mL tap water to remove the excess dye. Inone group, negotiation and glide path preparation of the S-shaped Statistical Analysescanals were performed with stainless steel K-files (Dentsply Maillefer) Data were analyzed by using the Statistical Package for the Socialsizes 08, 10, 15, and 20; all were used with circumferential filing Sciences (SPSS) software, version 17.0 (IBM, Chicago, IL). Intragroupmotions. In another group, a stainless steel K-file size 08 (Dentsply Mail- analysis evaluated the isolate performance of the 3 systems. The differ-lefer) was used to negotiate the canal up to the WL. Mechanical prep- ence of material removal from the mesial and distal walls of the canals ataration was performed with PathFile rotary instruments (Dentsply the 8 measuring points was compared by using repeated-measuresMaillefer) sizes 13, 16, and 19 coupled to an endodontic motor (X- analysis of variance (ANOVA). This initial analysis permitted to identifySmart Easy; Dentsply Maillefer) at the setting suggested by the manufac- the points where significant deviation occurred. Then, mesial and distalturer (300 rpm, 1.0 Ncm). In the third group, a stainless steel K-file size values for each level were compared by using the paired t test to assess08 was also used to scout the canal up to the WL, and then preparation to which side deviation occurred. Intergroup analysis was performed byof the glide path was carried out with Scout RaCe files (FKG Dentaire) using the one-way ANOVA for each level. For multiple comparisons, thesizes 10, 15, and 20 by using the same motor and settings as for the Tukey post hoc test was used for one-way ANOVA and the least signifi-PathFile instruments. Irrigation was performed with tap water, 2 mL cant difference test for repeated-measures ANOVA. Data were tested forafter each instrument size, totaling 10 mL per canal for all groups. normality before applying the parametric tests. The statistical signifi- After instrumentation, all specimens in each group were reposi- cance level of 5% (P < .05) was established for all analyses.tioned in the slot of the support apparatus and photographed asdescribed above. Preinstrumentation and postinstrumentation imageswere used to evaluate the occurrence of deviation in the canal shape. ResultsPhotoshop software (CS5 Extended, version 12.0.4; Adobe Systems Intragroup analysis showed that all instruments promoted someInc, San Jose, CA) was used to automatically superimpose the images deviation in virtually all levels (Table 1). This was evaluated byby using the ‘‘Scripts/Load Files into Stack’’ tool. Whenever necessary, comparing material removed from the mesial and distal walls of themanual adjustments for alignment were done. The figure on top of canal at the 8 measuring points. There was a significant difference atthe stack was placed in ‘‘multiply’’ blend mode, and opacity was all levels for all groups (P < .01), except for the 1-mm level of the Path-adjusted to permit proper visualization of the 2 images for measure- File group (P = .11) and the 7-mm level of the Scout RaCe group (P =ments. Measurements of the effects of the different instruments on .39). Overall, regardless of the group, deviations were observed in thethe canal walls were performed according to modifications from mesial wall at the canal terminus and at levels 4, 5, 6, and 7 mm andprevious studies (11, 12). Two evaluators working together and in the distal wall at levels 1, 2, and 3 mm (Table 1). These levels corre-blinded to the groups performed all measurements. The amount of spond to the inner walls of each curvature (Fig. 1). In the manual group,resin removed, ie, the difference between the canal configuration the 4 levels with the greatest deviation were the following: 6 mm >5 mmbefore and after preparation, was determined for both the mesial and >0 mm >2 mm. A significantly higher deviation occurred at 6 mm whendistal sides of the S-shaped canal in 1-mm increments under high compared with all levels, except 5, 2, and 0 mm. In the PathFile group,magnification and by using the ruler tool of the Photoshop software. the 4 levels with the greatest deviation were the following: 0 mm >2 mmFigure 1 shows what were considered as mesial and distal walls of >6 mm >5 mm. A significantly higher deviation occurred in the 0-mmthe block. The values obtained were corrected on the basis of the level when compared with all other 7 levels. In the Scout RaCe group, theFigure 1. Superimposed preinstrumentation and postinstrumentation images of representative specimens of the groups that used hand stainless steel files (A),PathFile instruments (B), and ScoutRaCe instruments (C). D, distal; M, mesial.JOE — Volume 39, Number 4, April 2013 Pathfinding Instruments and Canal Deviation 535
  • 3. Basic Research—TechnologyTABLE 1. Mean Material Removed (mm) at Different Levels from the Apical Terminus of Simulated S-shaped Canals after Glide Path Preparation with 3 DifferentInstrument Systems Instruments Hand K-files PathFiles Scout RaCe Level Mesial Distal Difference* Mesial Distal Difference* Mesial Distal Difference* †,‡ 0 0.427 0.004 0.419 Æ 0.05 0.415 0.018 0.398 Æ 0.06 0.145 0.012 0.151 Æ 0.06 1†,§ 0.003 0.282 0.280 Æ 0.06 0.066k 0.118k 0.130 Æ 0.07 0.023 0.123 0.107 Æ 0.04 2†,‡,§ 0 0.412 0.412 Æ 0.06 0 0.285 0.285 Æ 0.05 0.007 0.156 0.147 Æ 0.04 3†,‡,§ 0 0.295 0.295 Æ 0.04 0.007 0.211 0.204 Æ 0.06 0.023 0.126 0.130 Æ 0.04 4†,§ 0.231 0.037 0.191 Æ 0.05 0.128 0.064 0.109 Æ 0.06 0.119 0.072 0.064 Æ 0.05 5†,‡,§ 0.434 0.005 0.429 Æ 0.05 0.269 0.013 0.256 Æ 0.07 0.171 0.072 0.109 Æ 0.08 6†,‡,§ 0.437 0.003 0.433 Æ 0.07 0.298 0.019 0.279 Æ 0.07 0.186 0.082 0.130 Æ 0.09 7†,§ 0.275 0.020 0.281 Æ 0.05 0.182 0.079 0.120 Æ 0.09 0.136k 0.109k 0.116 Æ 0.07*Mean of the differences between the amount of material removed in mesial and distal walls. Zero (0) in the difference value means no deviation.Statistically significant differences for deviation (‘‘difference’’ data): †between K-file and Scout RaCe; ‡between PathFile and Scout RaCe; §between K-file and PathFile.k Lack of statistically significant difference when comparing material removed in mesial and distal walls. For all the other levels and instruments, significant differences were observed.4 levels with greater deviation were the following: 0 mm >2 mm >6 mm Two rotary systems were tested. One of them, the PathFile system,>3 mm. Although the highest deviation occurred at 0 mm, it was only has been the subject of previous investigations, which showed a similarlystatistically significant when compared with levels 1 and 4 mm. Compar- good (22) or even better performance for these instruments whenisons between deviations at all measuring points are shown in compared with hand instruments (7, 23). The latter was confirmed inSupplemental Table S1 (available online at www.jendodon.com). the present study. The other system was the Scout RaCe instruments, Data from intergroup analysis are also shown in Table 1. When the for which so far there is no previous study of its performance. The3 groups were compared for the ability of enlarging the canal with present investigation showed that Scout RaCe instruments causedminimal deviation, the Scout RaCe instruments were significantly better significantly less modifications in the canal anatomy than PathFilethan the hand K-files at all levels. PathFiles showed also significantly instruments, in spite of the fact that the last instrument of the Scoutbetter results than the hand files, except for the 0-mm level. ScoutRaCe RaCe series has a nominal diameter at D0 that is a little larger thaninstruments showed significantly better results than PathFiles at levels 0, the last PathFile instrument (#20 versus #19). The reasons for2, 3, 5, and 6 mm, with no significant differences for the other levels. superior performance might be related to an increased flexibility of the Scout RaCe files, which, however, has not been demonstrated in comparisons involving the first instrument in each series (10). Whether Discussion a significant difference exists between the other instruments in the series, Natural teeth are the best specimens to evaluate the shaping effects especially the last (and largest) ones, remains to be determined. Oneof instrumentation, but they are very difficult to standardize because of major difference between these files is the flute design. PathFile instru-different curvatures, initial canal diameter, and dentin hardness. For the ments have a square cross section, constant pitch between the flutes, andsake of better standardization of experimental conditions, simulated a tip that has a short transition angle that could be considered an activecanals in resin blocks have been widely used in investigations of tip. Scout RaCe files have a square cross section, an alternating pitchthe shaping ability of instruments and instrumentation techniques. between the flutes, and a rounded tip with a long transition angle. InS-shaped canals were used because of the inherent difficulties in fact, the flute of these files will start 0.5 mm from the base of the tip.preparing canals with this shape without causing deformations as On the basis of flute design, the tip of the Scout RaCe files seems to bea consequence of the presence of the 2 curvatures (4, 7, 13, 14). In less aggressive than the PathFile’s and will serve as a guiding tip. Theaddition, S-shaped canals also influence the cyclic fatigue of rotary differences of the tip design of these files might be the main reasonNiTi instruments, with the number of cycles to fracture being for the differences in the results presented in this study. This shouldstatistically lower in double-curved canals when compared with be further tested in a separate study.single-curved canals (15). It becomes apparently clear from this study that the use of stainless A very important recommendation for safe and effective rotary NiTi steel hand instruments of size larger than 10 should be reduced wheninstrumentation of curved canals is to create a smooth glide path first. a predictable and repeatable scouting can be obtained by using smallSuch previous enlargement should be performed with fine hand instru- stainless steel hand files (sizes 06, 08, and 10), and a predictable glidements, which creates a smooth glide path for subsequent use of the path can be obtained safely and effectively with NiTi instruments, whichlarger rotary instruments (9, 16). Occurrence of canal modifications avoids the increased transportation reported for bigger and less flexibleand aberrations seems to be significantly reduced when previous stainless steel instruments. Furthermore, because some root canalglide path is performed (17–19). The present findings are in transportation has been reported for the tested NiTi rotary glide pathagreement with previous studies showing that rotary NiTi instruments instruments to a last size of 19 and 20, further studies should evaluatecause less deviation of the canal walls when compared with hand the possible influence of the use of smaller size for glide path instrumentstainless steel files (20, 21). Modifications in the canal shape (ie, #10 or #15) before starting with the preferred preparationinduced during glide path preparation have the potential to become technique.still more accentuated during the further use of larger instruments, In conclusion, our findings demonstrated that rotary NiTi instru-predisposing to procedural errors or accidents. Therefore, rotary ments appear to be suitable for adequate preparation of the glide pathNiTi instruments seem to be more appropriate for glide path before rotary NiTi instrumentation because they promoted significantlypreparation. less deviation from the original canal anatomy when compared with536 Ajuz et al. JOE — Volume 39, Number 4, April 2013
  • 4. Basic Research—Technologyhand-operated instruments. Of the 2 rotary pathfinding instruments, 8. Peters OA, Koka RS. Preparation of coronal and radicular spaces. In: Ingle JI, ed.Scout RaCe showed significantly better performance in shaping Ingle’s Endodontics, 6th ed. Hamilton, Ontario, Canada: BC Decker; 2008: 877–991.double-curved canals. 9. Di Fiore PM. A dozen ways to prevent nickel-titanium rotary instrument fracture. J Am Dent Assoc 2007;138:196–201. 10. Lopes HP, Elias CN, Siqueira JF Jr, et al. Mechanical behavior of pathfinding Acknowledgments endodontic instruments. J Endod 2012;38:1417–21. 11. Schafer E, Florek H. Efficiency of rotary nickel-titanium K3 instruments compared The authors deny any conflicts of interest related to this study. with stainless steel hand K-Flexofile: part 1—shaping ability in simulated curved canals. Int Endod J 2003;36:199–207. 12. Franco V, Fabiani C, Taschieri S, et al. Investigation on the shaping ability of nickel- Supplementary Material titanium files when used with a reciprocating motion. J Endod 2011;37:1398–401. 13. Bonaccorso A, Cantatore G, Condorelli GG, et al. Shaping ability of four nickel- Supplementary material associated with this article can be titanium rotary instruments in simulated S-shaped canals. J Endod 2009;35:883–6.found in the online version at www.jendodon.com (http://dx.doi. 14. Yoshimine Y, Ono M, Akamine A. The shaping effects of three nickel-titanium rotaryorg/10.1016/j.joen.2012.12.015). instruments in simulated S-shaped canals. J Endod 2005;31:373–5. 15. Al-Sudani D, Grande NM, Plotino G, et al. Cyclic fatigue of nickel-titanium rotary instruments in a double (S-shaped) simulated curvature. J Endod 2012;38:987–9. 16. Ruddle CJ. The ProTaper technique. Endod Topics 2005;10:187–90. References 17. Berutti E, Paolino DS, Chiandussi G, et al. Root canal anatomy preservation of Wave- 1. Peters OA, Peters CI. Cleaning and shaping of the root canal system. In: One reciprocating files with or without glide path. J Endod 2012;38:101–4. Hargreaves KM, Cohen S, eds. Cohen’s Pathways of the Pulp, 10th ed. St Louis, 18. Patino PV, Biedma BM, Liebana CR, et al. The influence of a manual glide path on the MO: Mosby; 2010:283–348. separation rate of NiTi rotary instruments. J Endod 2005;31:114–6. 2. Siqueira JF Jr, Lopes HP. Chemomechanical preparation. In: Siqueira JF Jr, ed. 19. Berutti E, Negro AR, Lendini M, Pasqualini D. Influence of manual preflaring and Treatment of Endodontic Infections. London: Quintessence; 2011:236–84. torque on the failure rate of ProTaper rotary instruments. J Endod 2004;30:228–30. 3. Jafarzadeh H, Abbott PV. Ledge formation: review of a great challenge in endodon- 20. Esposito PT, Cunningham CJ. A comparison of canal preparation with nickel- tics. J Endod 2007;33:1155–62. titanium and stainless steel instruments. J Endod 1995;21:173–6. 4. Allen MJ, Glickman GN, Griggs JA. Comparative analysis of endodontic pathfinders. 21. Gergi R, Rjeily JA, Sader J, Naaman A. Comparison of canal transportation and J Endod 2007;33:723–6. centering ability of twisted files, Pathfile-ProTaper system, and stainless steel 5. Lopes HP, Elias CN, Amaral G, et al. Torsional properties of pathfinding instruments. hand K-files by using computed tomography. J Endod 2010;36:904–7. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:667–70. 22. Alves O, Bueno CE, Cunha RS, et al. Comparison among manual instruments and 6. Lopes HP, Elias CN, Mangelli M, et al. Buckling resistance of pathfinding endodontic PathFile and Mtwo rotary instruments to create a glide path in the root canal prep- instruments. J Endod 2012;38:402–4. aration of curved canals. J Endod 2012;38:117–20. 7. Berutti E, Cantatore G, Castellucci A, et al. Use of nickel-titanium rotary PathFile to 23. Pasqualini D, Bianchi CC, Paolino DS, et al. Computed micro-tomographic evalua- create the glide path: comparison with manual preflaring in simulated root canals. tion of glide path with nickel-titanium rotary PathFile in maxillary first molars curved J Endod 2009;35:408–12. canals. J Endod 2012;38:389–93.JOE — Volume 39, Number 4, April 2013 Pathfinding Instruments and Canal Deviation 537