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Aust Endod J 2014; 40: 12–16
ORIGINAL RESEARCH
Comparative micro-computed tomography evaluation of apical root canal transportation with the use of ProTaper, RaCe and Safesider systems in human teeth Kadir T. Ceyhanli, DDS, PhD1; Necdet Erdilek, DDS, PhD2; I˙lkan Tatar, DDS, PhD3; and Bekir Çetintav, DDS, PhD4 1 2 3 4
Department of Endodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey Department of Endodontics, Faculty of Dentistry, Ege University, I˙zmir, Turkey Department of Anatomy, Faculty of Medicine, Hacettepe University, Ankara, Turkey Department of Statistics, Faculty of Science and Art, Dokuz Eylül University, I˙zmir, Turkey
Keywords apical transportation, micro-CT, Safesider, RaCe, ProTaper. Correspondence Dr Kadir Tolga Ceyhanli, Endodonti Anabilim Dali, Dis Hekimligi Fakultesi, Karadeniz Teknik Universitesi, Trabzon 61080, Türkiye. Email: [email protected] doi:10.1111/aej.12014
Abstract The aim of this study was to compare apical centring ability of nickel titanium (NiTi) ProTaper, RaCe and mainly stainless steel Safesider systems using microcomputed tomography. Thirty freshly extracted mandibular molars with two separate mesial canals and separate foramina were used for the study. Mesial roots were embedded in acrylic resin and instrumented with the ProTaper, RaCe or Safesider systems. Root canal transportation and centring ability of the instruments were evaluated using superimposed micro-computed tomography images of the apical 4 mm of the roots taken at 1 mm intervals. One-way analysis of variance and post hoc Tukey’s tests were performed to compare apical transportations. Significant differences were observed between groups at the apical 1, 2 and 3 mm levels (P < 0.05). The reciprocating Safesider system transported root canals significantly more than the other two NiTi systems in the apical 1 mm level (P = 0.001) and more than RaCe system in the apical 2 mm level (P = 0.003). The ProTaper instruments caused more apical root canal transportation than did RaCe instruments at apical 3 mm (P = 0.045). NiTi instrumentation systems showed better centring ability than the mainly stainless steel Safesider system because of the flexible structure of the NiTi alloy.
Introduction Instrumentation is an effective approach to the elimination of bacteria. The aims of endodontic instrumentation are to remove all pulp tissue remnants and infected radicular dentine and to shape root canals for improved irrigation and placement of intracanal medicaments and filling materials (1). The main advantages of nickel titanium (NiTi) instruments are their flexibility and capacity for maintaining the original canal curvature. NiTi rotary instruments have also reduced working time, operator fatigue and procedural errors associated with root canal instrumentation (2). However, the use of these instruments may cause torsional and cyclic fatigue fractures, especially in narrow and curved root canals (3,4). 12
Recent research focusing on the development of new instrumentation techniques to overcome the disadvantages of NiTi systems has suggested the use of reciprocating techniques to reduce the incidence of fracture (5,6). However, limited information is available regarding the shaping ability of such reciprocating motion preparation techniques (7–9). ProTaper NiTi rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) have a convex, triangular crosssectional design and a non-cutting safety tip. These instruments incorporate a shallow U-shaped groove in each convex triangular side, which the manufacturer claims improves the flexibility of larger instruments. ProTaper system has a multi-tapered instrument design; the shaping instruments (SX, S1 and S2) have increasingly larger percentage tapers over the length of their cutting
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
K. T. Ceyhanli et al.
blades. Three finishing instruments (F1, F2 and F3) have decreasing percentage taper (10). RaCe instruments (FKG Dentaire, La-Chauxde-Fonds, Switzerland) have a triangular cross-sectional design, except for the smaller instruments (15/0.02 and 20/0.02), which have a square cross-sectional design. According to the manufacturer, the combination of the triangular cross section with sharp edges and alternating cutting edges enhances cutting efficiency and ensures efficient debris evacuation. The EZ-Fill Safesider system (Essential Dental Systems, Hackensack, NJ, USA) has an uninterrupted flat-sided design that reduces dentinal engagement and improves fracture resistance during canal instrumentation. The reduced cross-sectional diameter with flat sides makes the instrument thinner and more flexible (11). There are eight stainless steel and three NiTi instruments in the system. The system’s Endo-Express handpiece provides 1500–2000 reciprocating motion per minute. The apical portion of the root canal is an area of interest because it may harbour a critical level of microorganisms (12). Increased apical debridement reduces microbial levels, but root canal instrumentation with increasing apical sizes can lead to procedural errors, such as, root canal transportation, ledge, zip, elbow and crack formation (13,14). Different shaping systems face the challenge of making more centred preparations and minimising apical root canal transportation. Micro-computed tomography (micro-CT) is a noninvasive method that has enabled the three-dimensional analysis of instrumentation effects and has provided highresolution horizontal section images (15). Many investigations have used micro-CT to evaluate the effects of different instrumentation techniques on root canal anatomy (8,16,17), but no study has directly compared the NiTi rotary ProTaper and RaCe systems with the mainly stainless steel reciprocating Safesider system. Therefore, the purpose of the present study was to use micro-CT to compare apical transportation and apical centring ability in the use of ProTaper, RaCe and Safesider instruments.
Materials and methods The mesial roots of 30 extracted mandibular molars, with curvatures of 20–40 degrees and curvature radius of 6–13 mL according to the method of Pruett et al. (3), were used in this study. Mesiodistal and buccolingual radiographs were taken to ensure that all teeth had two separate mesial root canals. Distal roots and crowns were removed with diamond burs (Mani, Inc., TochigiKen, Japan). The angles and radii of canal curvature were measured on standard radiographs using the
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
Evaluation of Effects of Different Instruments
AutoCAD 2006 program (Mechanical Desktop Power Pack, Microsoft Corporation, Redmond, WA, USA). Three groups of teeth (10 teeth, 20 canals per group) with similar canal length, angle and radius of canal curvature were designated for instrumentation with the ProTaper, RaCe or Safesider system. Coronal root sections were embedded in resin discs 2 mm from the coronal part and micro-CT scans (SkyScan 1174, SkyScan bvba, Aartselaar, Belgium) were obtained before and after instrumentation at 50 kV and 800 mA with each specimen in the same sagittal position, with the long axis of the root perpendicular to the beam. Typically 700–900 slices (pixel size 18 mm) were scanned per tooth. Root canals were prepared using the ProTaper, RaCe or Safesider system in accordance with the manufacturer’s instructions. Before instrumentations, root canals were explored with a no. 10 K-file (Mani, Inc.) to determine the working length (WL) as 1 mm short of the apical foramen and to confirm a glide path reaching to the WL. Apical enlargements were made with instrument sizes up to no. 30 for all systems. The X-Smart endodontic motor (Dentsply Maillefer) was used with the speed and torque recommended by the manufacturer of each rotary instrumentation system. The Safesider system was used with the Endo-Express reciprocating handpiece. All canals were prepared by one experienced operator. Each rotary instrument was discarded after the enlargement of three canals. In the ProTaper rotary system, the S1, S2, F1, F2 and F3 instruments were used to WL. In the RaCe system, instrument sequence nos. 15 and 20 (2% taper) and nos. 25 and 30 (4% taper) were used to the WL. The following instrument sequence was used to WL in the Safesider system: nos. 08, 10, 15, 20, 25, 30 and 35 (2% taper, stainless steel), followed by no. 30 (4% taper, NiTi). Following instrumentation, each root specimen was inserted into the micro-CT scanner in the same sagittal position and scanned using the same parameters as in the initial scan. All CT scans were recorded on a computer in bitmap image format. Root canal transportation and instrument centring ratios were evaluated on apical sections (4 mm) of the root specimens at 1 mm intervals. Pre- and post-instrumentation micro-CT images were superimposed at the same level on 4 mm apical root sections at 1 mm intervals to determine the direction and quantity of root canal transportation. The Adobe Photoshop CS2 image program (v 9.0, Adobe Systems Incorporated, San Jose, CA, USA) was used for this analysis. The colours of the micro-CT images were shifted to red for pre-instrumentation and green for post-instrumentation to facilitate image contrast (Fig. 1). Root canal transportation was evaluated in the buccolingual and mesiodistal directions using the 13
Evaluation of Effects of Different Instruments
K. T. Ceyhanli et al.
Figure 1 Superimpositioning of apical image sections using Adobe Photoshop. Table 1 Mean apical vectorial transportations, centring ratios, and ⫾standard deviations of the systems for apical 4 mm at 1 mm intervals in millimetre for 20 canals of each system
ProTaper RaCe Safesiders P-value
Apical 1 (mm)
Apical 2 (mm)
Apical 3 (mm)
Apical 4 (mm)
CR
0.07 ⫾ 0.04* 0.08 ⫾ 0.06* 0.14 ⫾ 0.1# 0.001
0.15 ⫾ 0.06*# 0.09 ⫾ 0.05# 0.16 ⫾ 0.09* 0.003
0.14 ⫾ 0.08# 0.09 ⫾ 0.05* 0.13 ⫾ 0.1*# 0.045
0.14 ⫾ 0.09* 0.09 ⫾ 0.04* 0.14 ⫾ 0.07* 0.066
0.58 ⫾ 0.11* 0.58 ⫾ 0.04* 0.48 ⫾ 0.08# 0.027
* and # symbols indicate significant differences between groups (P < 0.05). CR, centring ratio, mean of apical 4 mm of 20 canals for each instrumentation system.
AutoCAD 2006 program (Mechanical Desktop Power Pack, Microsoft Corporation). The mean of three measurements was used for each direction. In these measurements, A1 = amount of mesial transportation, A2 = amount of distal transportation, B1 = amount of buccal transportation, B2 = amount of lingual transportation, |A1 - A2| = amount of mesiodistal transportation (a) and |B1 - B2| = amount of buccolingual transportation (b). The cumulative vectorial transportation value (c) was calculated using the Pythagorean formula (a2 + b2 = c2; Fig. 1). The instrument centring ratio was calculated as A1/A2 or A2/A1, using the lower value as the numerator, with a ratio of 1 indicating perfect centring (18). One-way analysis of variance was used to compare differences in apical transportation and instrument cen14
tring ratio among groups. If a significant difference was found among groups, Tukey’s multiple comparison test was performed. The level of significance was set at P < 0.05.
Results Table 1 shows mean apical transportation values and mean centring ratios resulting from the use of the three systems. Significant differences in apical transportation were observed among groups at the apical 1, 2 and 3 mm levels (P < 0.05). The Safesider system transported root canals to a significantly greater extent than did the ProTaper and RaCe systems at the apical 1 mm level (P = 0.001), but no significant difference was found between the ProTaper and RaCe systems at this level. The
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
Evaluation of Effects of Different Instruments
K. T. Ceyhanli et al.
Safesider system transported canals significantly further than did the RaCe system at the apical 2 mm level (P = 0.003), but no significant difference was observed between the ProTaper and RaCe or Safesider system. The ProTaper system transported canals further than did the RaCe and Safesider systems at the apical 3 mm level (P = 0.045), but only the difference between ProTaper and RaCe was significant. No significant difference was observed among systems at the apical 4 mm level. Mean centring ratio of apical 4 mm is shown in Table 1. No significant difference in centring ratio was found between the ProTaper and RaCe systems, but this ratio was significantly lower for the Safesider system than for the other two systems (P = 0.027).
Discussion Various methods have been used to assess apical transportation and centring ability, including radiographs (19), the Bramante method (20), Kuttler’s endodontic cube (21), CT (2,22) and micro-CT (9,15,16). Micro-CT is a quick, reliable and repeatable non-invasive method. CT and micro-CT enable the comparison of highresolution pre- and post-instrumentation images (16,23). In this study, apical transportation was evaluated using micro-CT. Schneider’s canal curvature measurement is used most commonly to identify potential canal deviation difficulty (24). However, the curvature radius is an effective parameter for the evaluation of such potential; a small radius indicates abrupt canal deviation with acute curvature and a greater risk of instrument deviation from the original canal trajectory. Therefore, in this study, root canal curvatures and radii were determined according to the method of Pruett et al. (3). Apical enlargement using ProTaper rotary instruments up to F1 is usually sufficient in narrow and curved canals (17). However, in comparison of RaCe and ProTaper instruments, some authors shaped root canals using instruments up to no. 30 to obtain equivalent apical diameters (25,26). In the present study, instrumentation in all groups used instruments up to ISO 30 to create similar apical enlargements. The flattened sides of Safesider instruments improve the elasticity of stainless steel instruments. In addition, the reciprocating motion provides a balanced force for movement into the root canal (11). However, many research groups have reported significant transportation after the use of reciprocating stainless steel instruments (8,27). In a comparison of Vortex 06 and Safesider instruments, Rhodes et al. (7) reported that the use of Safesider instruments resulted in significantly greater deviations in root canals, especially with instruments larger than ISO
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
20. Many earlier studies revealed the superiority of NiTi instruments in maintaining root canal curvature, even in severely curved canals (8,28). In agreement with these findings, the results of our study indicate the superiority of RaCe and ProTaper instrumentation systems to the Safesider system in terms of apical transportation. The method of Uyanik et al. (23) was used to determine the direction and quantity of vectorial transportation. Uyanik et al. (23) found no significant difference in apical transportation among the ProTaper, RaCe and Hero Shaper systems. In the current study, apical transportation was greater with the ProTaper system than with the RaCe system at the apical 3 mm level, and showed no significant difference between the two NiTi systems at the apical 1, 2 and 4 mm levels. ProTaper instruments have a multi-tapered design and finishing instruments extend further than RaCe instruments at the apical 1–4 mm levels (10), presumably resulting in higher transportation values. These results are in accordance with those of Yun and Kim (29), who reported that more centred preparations were achieved with the ProFile than with ProTaper system. Inferior molars demonstrate some variations of root canal morphologies (30). Although similar root specimens were chosen for the study, some root canals demonstrated excessively larger buccolingual extensions resulting in untouched buccal or lingual walls that may affected the measurements. This may be the reason for relatively higher standard deviation values. Recently, root canal shaping with reciprocating NiTi instruments has become popular in Endodontics. Comparison of stainless steel Safesider system with these innovative NiTi reciprocating systems may give some supportive results to the current study. Therefore, further investigations may be useful to assess this aspect in further detail.
Conclusions NiTi instrumentation systems showed better centring ability than the mainly stainless steel Safesider system because of the flexible structure of the NiTi alloy. The extended design of the F3 ProTaper instrument caused more apical root canal transportation than did the no. 30 (6% taper) RaCe instrument in this study.
Acknowledgements The authors thank Brian Rasimick from Edsdental Inc, Is¸ıl Kayahan from Denstply Tulsa Dental Specialties and Sevgi Bas¸türk from FKG Dentaire for the donation of instruments used in this research project. The authors deny any conflict of interest related to this study. 15
Evaluation of Effects of Different Instruments
References 1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974; 18: 269–96. 2. Gluskin AH, Brown DC, Buchanan LS. A reconstructed computerized tomographic comparison of Ni-Ti rotary GT files versus traditional instruments in canals shaped by novice operators. Int Endod J 2001; 34: 476–84. 3. Pruett JP, Clement DJ, Carnes DL, Jr. Cyclic fatigue testing of nickel-titanium endodontic instruments. J Endod 1997; 23: 77–85. 4. Haikel Y, Serfaty R, Bateman G et al. Dynamic and cyclic fatigue of engine-driven rotary nickel-titanium endodontic instruments. J Endod 1999; 25: 434–40. 5. You SY, Bae KS, Baek SH et al. Lifespan of one nickeltitanium rotary file with reciprocating motion in curved root canals. J Endod 2010; 36: 1991–4. 6. De-Deus G, Moreira EJ, Lopes HP, Elias CN. Extended cyclic fatigue life of F2 ProTaper instruments used in reciprocating movement. Int Endod J 2010; 43: 1063–8. 7. Rhodes SC, Hulsmann M, McNeal SF et al. Comparison of root canal preparation using reciprocating Safesiders stainless steel and Vortex nickel-titanium instruments. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011; 111: 659–67. 8. Paque F, Barbakow F, Peters OA. Root canal preparation with Endo-Eze AET: changes in root canal shape assessed by micro-computed tomography. Int Endod J 2005; 38: 456–64. 9. You SY, Kim HC, Bae KS et al. Shaping ability of reciprocating motion in curved root canals: a comparative study with micro-computed tomography. J Endod 2011; 37: 1296–300. 10. Ruddle CJ. The ProTaper technique: endodontics made easier. Dent Today 2001; 20: 6–8, 58–64. 11. Musikant BL, Cohen BI, Deutsch AS. Comparison instrumentation reamers and files versus a flat-sided design of conventional noninterrupted, flat-sided design. J Endod 2004; 30: 107–9. 12. Nair PN, Sjogren U, Krey G et al. Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: a long-term light and electron microscopic follow-up study. J Endod 1990; 16: 580–8. 13. Allison DA, Weber CR, Walton RE. The influence of the method of canal preparation on the quality of apical and coronal obturation. J Endod 1979; 5: 298–304. 14. Alodeh MH, Doller R, Dummer PM. Shaping of simulated root canals in resin blocks using the step-back technique with K-files manipulated in a simple in/out filling motion. Int Endod J 1989; 22: 107–17. 15. Nielsen RB, Alyassin AM, Peters DD et al. Microcomputed tomography: an advanced system for detailed endodontic research. J Endod 1995; 21: 561–8.
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16. Peters OA, Schonenberger K, Laib A. Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J 2001; 34: 221–30. 17. Peters OA, Peters CI, Schonenberger K, Barbakow F. ProTaper rotary root canal preparation: effects of canal anatomy on final shape analysed by micro CT. Int Endod J 2003; 36: 86–92. 18. Gambill JM, Alder M, del Rio CE. Comparison of nickeltitanium and stainless steel hand-file instrumentation using computed tomography. J Endod 1996; 22: 369–75. 19. Luiten DJ, Morgan LA, Baugartner JC, Marshall JG. A comparison of four instrumentation techniques on apical canal transportation. J Endod 1995; 21: 26–32. 20. Bramante CM, Berbert A, Borges RP. A methodology for evaluation of root canal instrumentation. J Endod 1987; 13: 243–5. 21. Kuttler S, Garala M, Perez R, Dorn SO. The endodontic cube: a system designed for evaluation of root canal anatomy and canal preparation. J Endod 2001; 27: 533–6. 22. Tasdemir T, Aydemir H, Inan U, Unal O. Canal preparation with Hero 642 rotary Ni-Ti instruments compared with stainless steel hand K-file assessed using computed tomography. Int Endod J 2005; 38: 402–8. 23. Ozgur Uyanik M, Cehreli ZC, Ozgen Mocan B, Tasman Dagli F. Comparative evaluation of three nickel-titanium instrumentation systems in human teeth using computed tomography. J Endod 2006; 32: 668–71. 24. Schneider SW. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol 1971; 32: 271–5. 25. Paque F, Musch U, Hulsmann M. Comparison of root canal preparation using RaCe and ProTaper rotary Ni-Ti instruments. Int Endod J 2005; 38: 8–16. 26. Javaheri HH, Javaheri GH. A comparison of three Ni-Ti rotary instruments in apical transportation. J Endod 2007; 33: 284–6. 27. Frank AL. An evaluation of the Giromatic endodontic handpiece. Oral Surg Oral Med Oral Pathol 1967; 24: 419–21. 28. Hulsmann M, Schade M, Schafers F. A comparative study of root canal preparation with HERO 642 and Quantec SC rotary Ni-Ti instruments. Int Endod J 2001; 34: 538–46. 29. Yun HH, Kim SK. A comparison of the shaping abilities of 4 nickel-titanium rotary instruments in simulated root canals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003; 95: 228–33. 30. Sert S, Bayirli GS. Evaluation of the root canal configurations of the mandibular and maxillary permanent teeth by gender in the Turkish population. J Endod 2004; 30: 391–8.
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
Aust Endod J 2014; 40: 12–16
ORIGINAL RESEARCH
Comparative micro-computed tomography evaluation of apical root canal transportation with the use of ProTaper, RaCe and Safesider systems in human teeth Kadir T. Ceyhanli, DDS, PhD1; Necdet Erdilek, DDS, PhD2; I˙lkan Tatar, DDS, PhD3; and Bekir Çetintav, DDS, PhD4 1 2 3 4
Department of Endodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey Department of Endodontics, Faculty of Dentistry, Ege University, I˙zmir, Turkey Department of Anatomy, Faculty of Medicine, Hacettepe University, Ankara, Turkey Department of Statistics, Faculty of Science and Art, Dokuz Eylül University, I˙zmir, Turkey
Keywords apical transportation, micro-CT, Safesider, RaCe, ProTaper. Correspondence Dr Kadir Tolga Ceyhanli, Endodonti Anabilim Dali, Dis Hekimligi Fakultesi, Karadeniz Teknik Universitesi, Trabzon 61080, Türkiye. Email: [email protected] doi:10.1111/aej.12014
Abstract The aim of this study was to compare apical centring ability of nickel titanium (NiTi) ProTaper, RaCe and mainly stainless steel Safesider systems using microcomputed tomography. Thirty freshly extracted mandibular molars with two separate mesial canals and separate foramina were used for the study. Mesial roots were embedded in acrylic resin and instrumented with the ProTaper, RaCe or Safesider systems. Root canal transportation and centring ability of the instruments were evaluated using superimposed micro-computed tomography images of the apical 4 mm of the roots taken at 1 mm intervals. One-way analysis of variance and post hoc Tukey’s tests were performed to compare apical transportations. Significant differences were observed between groups at the apical 1, 2 and 3 mm levels (P < 0.05). The reciprocating Safesider system transported root canals significantly more than the other two NiTi systems in the apical 1 mm level (P = 0.001) and more than RaCe system in the apical 2 mm level (P = 0.003). The ProTaper instruments caused more apical root canal transportation than did RaCe instruments at apical 3 mm (P = 0.045). NiTi instrumentation systems showed better centring ability than the mainly stainless steel Safesider system because of the flexible structure of the NiTi alloy.
Introduction Instrumentation is an effective approach to the elimination of bacteria. The aims of endodontic instrumentation are to remove all pulp tissue remnants and infected radicular dentine and to shape root canals for improved irrigation and placement of intracanal medicaments and filling materials (1). The main advantages of nickel titanium (NiTi) instruments are their flexibility and capacity for maintaining the original canal curvature. NiTi rotary instruments have also reduced working time, operator fatigue and procedural errors associated with root canal instrumentation (2). However, the use of these instruments may cause torsional and cyclic fatigue fractures, especially in narrow and curved root canals (3,4). 12
Recent research focusing on the development of new instrumentation techniques to overcome the disadvantages of NiTi systems has suggested the use of reciprocating techniques to reduce the incidence of fracture (5,6). However, limited information is available regarding the shaping ability of such reciprocating motion preparation techniques (7–9). ProTaper NiTi rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) have a convex, triangular crosssectional design and a non-cutting safety tip. These instruments incorporate a shallow U-shaped groove in each convex triangular side, which the manufacturer claims improves the flexibility of larger instruments. ProTaper system has a multi-tapered instrument design; the shaping instruments (SX, S1 and S2) have increasingly larger percentage tapers over the length of their cutting
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
K. T. Ceyhanli et al.
blades. Three finishing instruments (F1, F2 and F3) have decreasing percentage taper (10). RaCe instruments (FKG Dentaire, La-Chauxde-Fonds, Switzerland) have a triangular cross-sectional design, except for the smaller instruments (15/0.02 and 20/0.02), which have a square cross-sectional design. According to the manufacturer, the combination of the triangular cross section with sharp edges and alternating cutting edges enhances cutting efficiency and ensures efficient debris evacuation. The EZ-Fill Safesider system (Essential Dental Systems, Hackensack, NJ, USA) has an uninterrupted flat-sided design that reduces dentinal engagement and improves fracture resistance during canal instrumentation. The reduced cross-sectional diameter with flat sides makes the instrument thinner and more flexible (11). There are eight stainless steel and three NiTi instruments in the system. The system’s Endo-Express handpiece provides 1500–2000 reciprocating motion per minute. The apical portion of the root canal is an area of interest because it may harbour a critical level of microorganisms (12). Increased apical debridement reduces microbial levels, but root canal instrumentation with increasing apical sizes can lead to procedural errors, such as, root canal transportation, ledge, zip, elbow and crack formation (13,14). Different shaping systems face the challenge of making more centred preparations and minimising apical root canal transportation. Micro-computed tomography (micro-CT) is a noninvasive method that has enabled the three-dimensional analysis of instrumentation effects and has provided highresolution horizontal section images (15). Many investigations have used micro-CT to evaluate the effects of different instrumentation techniques on root canal anatomy (8,16,17), but no study has directly compared the NiTi rotary ProTaper and RaCe systems with the mainly stainless steel reciprocating Safesider system. Therefore, the purpose of the present study was to use micro-CT to compare apical transportation and apical centring ability in the use of ProTaper, RaCe and Safesider instruments.
Materials and methods The mesial roots of 30 extracted mandibular molars, with curvatures of 20–40 degrees and curvature radius of 6–13 mL according to the method of Pruett et al. (3), were used in this study. Mesiodistal and buccolingual radiographs were taken to ensure that all teeth had two separate mesial root canals. Distal roots and crowns were removed with diamond burs (Mani, Inc., TochigiKen, Japan). The angles and radii of canal curvature were measured on standard radiographs using the
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
Evaluation of Effects of Different Instruments
AutoCAD 2006 program (Mechanical Desktop Power Pack, Microsoft Corporation, Redmond, WA, USA). Three groups of teeth (10 teeth, 20 canals per group) with similar canal length, angle and radius of canal curvature were designated for instrumentation with the ProTaper, RaCe or Safesider system. Coronal root sections were embedded in resin discs 2 mm from the coronal part and micro-CT scans (SkyScan 1174, SkyScan bvba, Aartselaar, Belgium) were obtained before and after instrumentation at 50 kV and 800 mA with each specimen in the same sagittal position, with the long axis of the root perpendicular to the beam. Typically 700–900 slices (pixel size 18 mm) were scanned per tooth. Root canals were prepared using the ProTaper, RaCe or Safesider system in accordance with the manufacturer’s instructions. Before instrumentations, root canals were explored with a no. 10 K-file (Mani, Inc.) to determine the working length (WL) as 1 mm short of the apical foramen and to confirm a glide path reaching to the WL. Apical enlargements were made with instrument sizes up to no. 30 for all systems. The X-Smart endodontic motor (Dentsply Maillefer) was used with the speed and torque recommended by the manufacturer of each rotary instrumentation system. The Safesider system was used with the Endo-Express reciprocating handpiece. All canals were prepared by one experienced operator. Each rotary instrument was discarded after the enlargement of three canals. In the ProTaper rotary system, the S1, S2, F1, F2 and F3 instruments were used to WL. In the RaCe system, instrument sequence nos. 15 and 20 (2% taper) and nos. 25 and 30 (4% taper) were used to the WL. The following instrument sequence was used to WL in the Safesider system: nos. 08, 10, 15, 20, 25, 30 and 35 (2% taper, stainless steel), followed by no. 30 (4% taper, NiTi). Following instrumentation, each root specimen was inserted into the micro-CT scanner in the same sagittal position and scanned using the same parameters as in the initial scan. All CT scans were recorded on a computer in bitmap image format. Root canal transportation and instrument centring ratios were evaluated on apical sections (4 mm) of the root specimens at 1 mm intervals. Pre- and post-instrumentation micro-CT images were superimposed at the same level on 4 mm apical root sections at 1 mm intervals to determine the direction and quantity of root canal transportation. The Adobe Photoshop CS2 image program (v 9.0, Adobe Systems Incorporated, San Jose, CA, USA) was used for this analysis. The colours of the micro-CT images were shifted to red for pre-instrumentation and green for post-instrumentation to facilitate image contrast (Fig. 1). Root canal transportation was evaluated in the buccolingual and mesiodistal directions using the 13
Evaluation of Effects of Different Instruments
K. T. Ceyhanli et al.
Figure 1 Superimpositioning of apical image sections using Adobe Photoshop. Table 1 Mean apical vectorial transportations, centring ratios, and ⫾standard deviations of the systems for apical 4 mm at 1 mm intervals in millimetre for 20 canals of each system
ProTaper RaCe Safesiders P-value
Apical 1 (mm)
Apical 2 (mm)
Apical 3 (mm)
Apical 4 (mm)
CR
0.07 ⫾ 0.04* 0.08 ⫾ 0.06* 0.14 ⫾ 0.1# 0.001
0.15 ⫾ 0.06*# 0.09 ⫾ 0.05# 0.16 ⫾ 0.09* 0.003
0.14 ⫾ 0.08# 0.09 ⫾ 0.05* 0.13 ⫾ 0.1*# 0.045
0.14 ⫾ 0.09* 0.09 ⫾ 0.04* 0.14 ⫾ 0.07* 0.066
0.58 ⫾ 0.11* 0.58 ⫾ 0.04* 0.48 ⫾ 0.08# 0.027
* and # symbols indicate significant differences between groups (P < 0.05). CR, centring ratio, mean of apical 4 mm of 20 canals for each instrumentation system.
AutoCAD 2006 program (Mechanical Desktop Power Pack, Microsoft Corporation). The mean of three measurements was used for each direction. In these measurements, A1 = amount of mesial transportation, A2 = amount of distal transportation, B1 = amount of buccal transportation, B2 = amount of lingual transportation, |A1 - A2| = amount of mesiodistal transportation (a) and |B1 - B2| = amount of buccolingual transportation (b). The cumulative vectorial transportation value (c) was calculated using the Pythagorean formula (a2 + b2 = c2; Fig. 1). The instrument centring ratio was calculated as A1/A2 or A2/A1, using the lower value as the numerator, with a ratio of 1 indicating perfect centring (18). One-way analysis of variance was used to compare differences in apical transportation and instrument cen14
tring ratio among groups. If a significant difference was found among groups, Tukey’s multiple comparison test was performed. The level of significance was set at P < 0.05.
Results Table 1 shows mean apical transportation values and mean centring ratios resulting from the use of the three systems. Significant differences in apical transportation were observed among groups at the apical 1, 2 and 3 mm levels (P < 0.05). The Safesider system transported root canals to a significantly greater extent than did the ProTaper and RaCe systems at the apical 1 mm level (P = 0.001), but no significant difference was found between the ProTaper and RaCe systems at this level. The
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
Evaluation of Effects of Different Instruments
K. T. Ceyhanli et al.
Safesider system transported canals significantly further than did the RaCe system at the apical 2 mm level (P = 0.003), but no significant difference was observed between the ProTaper and RaCe or Safesider system. The ProTaper system transported canals further than did the RaCe and Safesider systems at the apical 3 mm level (P = 0.045), but only the difference between ProTaper and RaCe was significant. No significant difference was observed among systems at the apical 4 mm level. Mean centring ratio of apical 4 mm is shown in Table 1. No significant difference in centring ratio was found between the ProTaper and RaCe systems, but this ratio was significantly lower for the Safesider system than for the other two systems (P = 0.027).
Discussion Various methods have been used to assess apical transportation and centring ability, including radiographs (19), the Bramante method (20), Kuttler’s endodontic cube (21), CT (2,22) and micro-CT (9,15,16). Micro-CT is a quick, reliable and repeatable non-invasive method. CT and micro-CT enable the comparison of highresolution pre- and post-instrumentation images (16,23). In this study, apical transportation was evaluated using micro-CT. Schneider’s canal curvature measurement is used most commonly to identify potential canal deviation difficulty (24). However, the curvature radius is an effective parameter for the evaluation of such potential; a small radius indicates abrupt canal deviation with acute curvature and a greater risk of instrument deviation from the original canal trajectory. Therefore, in this study, root canal curvatures and radii were determined according to the method of Pruett et al. (3). Apical enlargement using ProTaper rotary instruments up to F1 is usually sufficient in narrow and curved canals (17). However, in comparison of RaCe and ProTaper instruments, some authors shaped root canals using instruments up to no. 30 to obtain equivalent apical diameters (25,26). In the present study, instrumentation in all groups used instruments up to ISO 30 to create similar apical enlargements. The flattened sides of Safesider instruments improve the elasticity of stainless steel instruments. In addition, the reciprocating motion provides a balanced force for movement into the root canal (11). However, many research groups have reported significant transportation after the use of reciprocating stainless steel instruments (8,27). In a comparison of Vortex 06 and Safesider instruments, Rhodes et al. (7) reported that the use of Safesider instruments resulted in significantly greater deviations in root canals, especially with instruments larger than ISO
© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
20. Many earlier studies revealed the superiority of NiTi instruments in maintaining root canal curvature, even in severely curved canals (8,28). In agreement with these findings, the results of our study indicate the superiority of RaCe and ProTaper instrumentation systems to the Safesider system in terms of apical transportation. The method of Uyanik et al. (23) was used to determine the direction and quantity of vectorial transportation. Uyanik et al. (23) found no significant difference in apical transportation among the ProTaper, RaCe and Hero Shaper systems. In the current study, apical transportation was greater with the ProTaper system than with the RaCe system at the apical 3 mm level, and showed no significant difference between the two NiTi systems at the apical 1, 2 and 4 mm levels. ProTaper instruments have a multi-tapered design and finishing instruments extend further than RaCe instruments at the apical 1–4 mm levels (10), presumably resulting in higher transportation values. These results are in accordance with those of Yun and Kim (29), who reported that more centred preparations were achieved with the ProFile than with ProTaper system. Inferior molars demonstrate some variations of root canal morphologies (30). Although similar root specimens were chosen for the study, some root canals demonstrated excessively larger buccolingual extensions resulting in untouched buccal or lingual walls that may affected the measurements. This may be the reason for relatively higher standard deviation values. Recently, root canal shaping with reciprocating NiTi instruments has become popular in Endodontics. Comparison of stainless steel Safesider system with these innovative NiTi reciprocating systems may give some supportive results to the current study. Therefore, further investigations may be useful to assess this aspect in further detail.
Conclusions NiTi instrumentation systems showed better centring ability than the mainly stainless steel Safesider system because of the flexible structure of the NiTi alloy. The extended design of the F3 ProTaper instrument caused more apical root canal transportation than did the no. 30 (6% taper) RaCe instrument in this study.
Acknowledgements The authors thank Brian Rasimick from Edsdental Inc, Is¸ıl Kayahan from Denstply Tulsa Dental Specialties and Sevgi Bas¸türk from FKG Dentaire for the donation of instruments used in this research project. The authors deny any conflict of interest related to this study. 15
Evaluation of Effects of Different Instruments
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© 2013 The Authors Australian Endodontic Journal © 2013 Australian Society of Endodontology
