SCANNING VOL. 36, 411–418 (2014) © Wiley Periodicals, Inc.
SEM Analysis of Defects and Wear on Ni–Ti Rotary Instruments WERINGTON BORGES ARANTES,1 CELSO MONTEIRO DA SILVA,2 JOSE´ LUIZ LAGE-MARQUES,3 SANDRAMARCIA HABITANTE,2 LUIZ CARLOS LAUREANO DA ROSA,4,5 AND JOA˜O MARCELO FERREIRA DE MEDEIROS2 1
Department of Dentistry, Program Graduate Masters, Taubate´ University, Taubate´, Brazil Department of Dentistry, Taubate´ University, Taubate´, Brazil 3 Department Dentistry, Sa˜o Paulo University, Sa˜o Paulo, Brazil 4 Department of Biostatistics, Institute of Basic Mathematical Sciences, University Taubate´, Taubate´, Brazil 5 Center for Economic and Social Research, University Taubate´, Taubate´, Brazil 2
Summary: SEM analysis of endodontic instruments from a Ni–Ti rotary system was assessed, before and after using them, considering their defects and deformations. Twenty Twisted File1, BioRa˛Ce1, Mtwo1, and EndoWave1 instruments were micrographed at 190 magnification. The files were washed and micrographed again to view alterations as to the presence or absence of irregular edges, grooves, microcavities, and scraping. Simulated root canal preparations were performed using these instruments. The instruments were cleaned and received a microscopic analysis after being used five times. After analysis tests were tested using Fisher’s exact test and Kappa to evaluate the concordance among examiners. There was a statistically significant difference with respect to deformations between Twisted File1 and other instruments (p < 0.05). There was no statistically significant difference in strains between the other groups (p > 0.05). All Twisted File1 instruments showed the same defects; however damage were lower than those found in BioRace1 and Mtwo1. The Endowave1 did not show the same defects. In accordance with the data we conclude that the presence of defects was higher in Twisted File1 instruments as the instruments and BioRace1 Mtwo1 brand, the defect rate was smaller and Endowave1 instruments had no defects. Regarding the presence of wear after five uses among the groups all instruments showed changes in their cutting blades. SCANNING 36:411–418, 2014. © 2014 Wiley Periodicals, Inc.
Address for reprints: Joa˜o Marcelo Ferreira de Medeiros, Av. Dr. Guilherme Dumont Villares, 3333, apto. 94A, Jardim Londrina, 05640004 Sa˜o Paulo, SP, Brazil E-mail: [email protected] Received 26 May 2013; Accepted with revision 4 December 2013 DOI: 10.1002/sca.21134 Published online 3 January 2014 in Wiley Online Library (wileyonlinelibrary.com).
Key words: dentistry, image analysis, SEM, surface analysis, microanalysis
Introduction Endodontic instruments, in association with chemical cleaning substances, promote disinfection and formation of the canal. With the advent of rotary files of nickel–titanium, there was an inversion in the sequence of instrumentation whose priority is the initial preparation of the cervical third followed by the medial and apical thirds. This procedure has diminished the contact of the file with the walls of the canal, avoiding the risk of fracture during use and allowing better removal of the contents of the root canal. Any previous enlargement of the canal is therefore a consequent benefit of the rotary instrument, which allows a better determination of the apical diameter of the instrument, shaping it in the apical third of the canal (Walia et al., ’88; Murgel et al., ’90). The presence of defects before the use of the instruments is a reality, as is even the presence of dirt on the surface of the active part of endodontic instruments. Rotary instruments of nickel–titanium of the brands EndoWave1, RaCe1, and ProFile1 were evaluated using torsion and flexion fatigue in SEM as a reference, since they were all size 30, standard ISO, and taper of 0.04. It was observed that the instruments that did not receive any electrochemical polishing had a greater number of defects in fabrication such as grooves, cracks, and cavitations and consequently did not perform as well as those instruments that did receive such electrochemical polishing (Anderson et al., 2007). Scanning electron microscopy was performed on rotary nickel–titanium instruments by EndoWave1, ProTaper1, and RaCe1 concerning cleaning in a sodium hypochlorite solution and repeated sterilization as well as concerning instrument wear, and it was observed that all of them showed some signs of
412
SCANNING VOL. 36, 4 (2014)
corrosion, with the Endowave1 instruments suffering the least—a fact possibly attributable to surface treatments of electrochemical polishing included in the fabrication process of these instruments (Kuber et al., 2006). The quality of the surface finish of the rotary instruments at the time of purchase was examined using a scanning electron microscope. Instruments under the names ProFile1, ProTaper1, RaCe1, HERO1, and K3 Endo1 were examined via a sample of fifty instruments chosen at random, the final 3 mm of whose tips were then photomicrographed at an enlargement of 190. Chianello et al. (2008), concluded that all instruments showed defects of manufacturing flaws in the surface finish, and that none presented zero defects. Rotary nickel–titanium instruments with and without electrochemical polishing were chemically analyzed concerning the effect of using a 5.25% solution of sodium hypochlorite; the instruments used were of the RaCe1 brand. The instruments were analyzed before and after cleaning with sodium hypochlorite on a scanning electron microscope, and it was concluded that those that did not receive electrochemical finishing suffered more corrosion than those that did receive the cited finishing (Bonaccorso et al., 2008). Over a period of 2 years, 414 RaCe1 instruments that received an electrochemically polished finish were judged after being discarded from clinical use. These instruments were observed under a scanning electron microscope and evaluated on their defects. From these, 388 showed structural changes and 26 were fractured. It was concluded that there had been a significant increase in defects after the seventh use of the instruments, therefore there was a statistically significant increase in the failure rate since it exceeded 45% of instrument defect cases (Shen et al., 2009). Scanning electron microscopy was used on 593 nickel–titanium rotary instruments of the brand Mtwo1 (VDW1-Germany) discarded over a 12-month period of clinical practice considering the rate of deformation and fracturing of these instruments. It was observed that the greatest cause of fractures was cyclic fatigue and the instrument with the highest incidence of this was the No. 10, the finest and first in each series. Therefore the authors (Inan and Gonulol, 2009) recommend that the instruments not be used beyond the maker’s recommendation and that the cited instrument be used only once. The efficacy of the different production procedures and the cross-sectional area was examined as regards resistance to cyclic fatigue of four different brands of NiTi rotary instruments (K3, ProFile, RaCe, and Twisted File) used in simulated root canals with a pecking movement until they fracture, and analyzed under a scanning electron microscope. In analyzing the surface of the instruments, the RaCe appeared to be free of defects, whereas the ProFile and K3 showed machining grooves. The surface treatment reduces
residual machining defects from the fabrication process, increasing the resistance to cyclic fatigue (Oh et al., 2010). With the objective of evaluating the deformation of rotary files in vitro as a function of the number of uses. Ten F2 files from the ProTaper Universal System (not electro-polished) and ten 25/0.06 files from the EndoSequence System (electro-polished) were used. The files were cleaned and brought to the scanning electron microscope for viewing before use and after five uses. The conclusion was that there was no significant statistical difference between the ProTaper and the EndoSequence files as to deformation despite the EndoSequence instruments having been electrochemically polished (Reis et al., 2011). The resistance to cyclic fatigue of nickel–titanium files of three different brands was compared: ProTaper, Waveone, and Twisted File. Cyclic fatigue tests were run on an operational instrument starting with the ProTaper F2 file, the Waveone No. 25 with a 0.08 conicity, and the Twisted File size 25 with a 0.08 conicity. A total of 184 instruments were used in four artificial canals curved at different angles and radii of curvature. The time and the cycles until fracture were calculated and the data were compared for differences using variance analysis (p < 0.05). Most of the time the Waveone file was the most resistant to fatigue fractures among the instruments tested; the Twisted File completed more cycles before fracturing than the ProTaper file did. The pecking movement of the Waveone file showed a longer life before cyclic fatigue than the conventional continuous rotating movement of the files from Twisted File and ProTaper. The new torsion process of fabrication by Twisted File produced NiTi rotary instruments more resistant to fatigue than the NiTi instruments from ProTaper produced by the traditional machining method (Castello´Escriva´ et al., 2012). Due to the presence of imperfections of the cutting blades and deformations before and after five uses, the goal of this research was to MEV evaluate, in vitro, the effect of root canal preparation on the cut surface of the active part endodontic instruments of the system nickel–titanium rotary four different brands.
Materials and Methods Twenty rotary instruments of different brands were used in this investigation, namely: five by Twisted File (Group A) from SybronEndo, Sybron Dental Specialties, Orange, CA/USA, and all of size 25 and taper 0.12, 0.10, 0.08, 0.06, 0.04; six by BioRaCe (Group B) FKG DENTAIRE Swiss Dental Products LA CHAUX-DEFONDS-SWISS (25/0.08, 15/0.05, 25/0.04, 25/0.06, 35/ 0.04, and 40/0.04); four by Mtwo (Group C) from VDW GmbH Munich/Germany (10/0.04, 15/0.05, 20/0.06,
Arantes et al.: WITHOUT Analysis of Defects
and 25/0.06); and five by EndoWave (Group D) from J Morita Coorporation Osaka Japan (35/0.08, 30/0.06, 25/0.06, 20/0.06, and 15/0.02). The instruments went through a rigorous cleaning process using cleaning methods such as thermochemistry and washing in an ultrasonic bath. For the cleaning ´ S1) was process, an ultrasonic bath (ODONTOBRA used for 10 min with a heating system using an enzymatic detergent diluted in water to 5 mL per liter (Murgel et al., ’90; Linsuwanont et al., 2004; Aasim et al., 2006).
Scanning Electron Microscope (SEM) Analysis
After the cleaning process was complete, the instruments were dried and analyzed under the scanning electron microscope (MEV-JEOL1 JSM 5900 LV from LME-LNLS—Laborato´rio Nacional de Luz Sı´ncrotron, Campinas, SP); photomicrographs were taken of the leading edge of the cutting blades considering the last 5 mm of the tip at a standard enlargement at magnification 190 (Chianello et al., 2008). The images were recorded digitally viewing two points on the cutting edge as a standard: one at the tip of the instrument and the other, 5 mm down. Then, the images were examined by three evaluators with an eye towards analyzing alterations and manufacturing defects of the files; their criteria for such evaluation were the presence of: irregular edges, grooves, microcavities, and burrs. After a new cleaning in 20 block in phenolic resin simulated canals (Bakelite1) with 75˚ of curvature (Medeiros et al., 2009) were prepared with instruments being the brands of instruments were randomly divided into four groups A–D. In group A, the files from Twisted File1 had the following instrumentation sequence: 0.12 (#25), 0.10 (#25), 0.08 (#25), 0.06 (#25), and 0.04 (#25). For group B, the BioRaCe1 files were: 0.08 (#25), 0.05 (#15), 0.04 (#25), 0.06 (#25), 0.04 (#35), and BioRaCe1 0.04 (#40). In group C, the Mtwo1 was 0.04 (#10) followed by 0.05 (#15), 0.06 (#20), and 0.06 (#25). In group D, the EndoWave files were sequenced: 0.08 (#35), 0.06 (#30), 0.06 (#25), 0.06 (#20), and 0.02(#15). Each instrument was used five times for 10 s in the blocks with simulated canals, after which cleaning and sterilization procedures were followed in an autoclave (KAVOKLAVE 21001; Kavo Dental Ltd, Blackburn, UK) up to 121˚C. The maneuvers were made with an X-Smart1 motor (Dentsply/Maillefer, Baillagues, Switzerland), a machine that, according to the manufacturer, allows torque control, 1.6 N of force, and a speed of 300 rpm, of course in addition to an automatic autoreverse system. The same instruments previously analyzed under the scanning electron microscope at the same sites previously
413
examined at magnification 190 enlargement were viewed again, and again the images were digitally photographed and labelled (Chianello et al., 2008).
Statistical Analysis
Next was the scoring by the three evaluators of the standard viewing area of the cutting edge at the two points previously analyzed: one at the tip of the instrument, and the other, 5 mm down from there. To establish the scores, the evaluators observed and analyzed the images of the files on a computer screen before and after being used five times, considering four discrete criteria, namely: (1) the long axis of the file has undistorted spirals—in other words, without any stretching or compressing and without any wear on the examined surface; (2) the long axis of the file has a distorted spiral—in other words, stretched or shortened and with one to three defective or worn areas on the examined surface; (3) the long axis of the file has more than one distorted spiral—in other words, stretched or shortened and with four or five worn areas on the examined surface; (4) severe wear on the spiral and more than five worn areas on the examined surface (Troian et al., 2006). The program BioEstat version 5.0 (Program by Professor Manuel Ayres, Universidade Federal do Para´, Bele´m-PA) was used for statistical analysis. After the analyses by scanning electron microscopy, the data was tabulated and submitted to analysis where the Intraclass Correlation Coefficient (ICC) was applied using the Kappa test. To analyze the deformations, a descriptive statistic was used with minimum, average, and maximum values, SD, and coefficient of variation. For statistical inference with a significance level of 5%, the Fisher’s exact test, the Mann–Whitney “U” test, and the Kolmogorov–Smirnov Test were used.
Results The results of the instrument defects (irregular edge, grooves, microcavity, and burrs) after cleaning are available in Table 1as well as Figures 1A–H and 2A and H. The scores for the presence of the type of defects at the tip and at 5 mm down for the different instruments are shown in Table 1. The files from Twisted File1 had different defects from the others such as ragged edge, groove, and microcavity with statistical significance (p < 0.05), while there were no statistically significant differences among the others (p > 0.05). The files from group A showed a significant difference of the microcavity item between BioRaCe1, Mtwo1, and EndoWave1 (p < 0.05) and no statistically significant difference among the other three (p > 0.05). As to the
SCANNING VOL. 36, 4 (2014)
414
TABLE 1 Presence of the type of defects at the tip and at 5 mm from the tip of the groups A (Twisted File), B (BioRace), C (Mtwo), and D (EndoWave) Irregular edge Group A B C D
Grooves
Microcavity
Burrs
Tip
5 mm
Tip
5 mm
Tip
5 mm
Tip
5 mm
5 1 0 0
5 1 0 0
5 1 0 0
5 0 0 0
5 0 0 0
5 0 0 0
0 0 1 0
0 0 1 0
“burrs” parameter, there was no statistically significant difference between the groups (p > 0.05). The Twisted File1 file showed a statistical significance with instruments with ragged edges in relation to the other brands (p < 0.05), while comparing the other brands to each other there was no significant difference (p > 0.05). The number of grooves and microcavities present in the files from Twisted File1 compared to the other brands showed a statistical significance (p < 0.05) and by
contrast, among the other brands there was no statistical significance (p > 0.05). The Figure 1A–H are the photomicrographs (at 190) of the presence or absence of defects in the cutting edges at the tip and at 5 mm down from the tip of the instruments in the groups studied. Tables 2–4 detail the wear on the cutting surface of the instruments obtained from the images after five uses and from the scores given by the evaluators, as well as
Fig 1. A: Presence of defects at the tip of the instrument Twisted File (25/06) unused (microcavity, groove, and irregular edge). B: Presence of more than five areas with wear on the tip of the instrument Twisted File (25/06) used five times. C: Absence of defects at the tip of the instrument BioRaCe (25/04) unused. D: Presence of more than three areas of wear on the tip of the instrument BioRaCe (25/04) used five times. E: Absence of defects at the tip of the instrument Mtwo (20/06) unused. F: Presence of wear on the tip of the instrument Mtwo (20/06) used five times. G: Absence of defects at the tip of the instrument EndoWave (15/02) unused. H: Presence over five areas in the wear tip of the instrument EndoWave (15/02) used five times. 190 magnification micrographs.
Fig 2. A: Presence of defects at 5 mm of the tip of the instrument Twisted File (25/04) unused (microcavity and groove). B: Presence of three-wear areas to 5 mm instrument tip Twisted File (25/04) used five times. C: Absence of defects at 5 mm from the tip of the instrument BioRaCe (15/05) unused. D: Presence of five areas of wear to 5 mm instrument tip BioRaCe (15/05) used five times. E: Presence of defects at 5 mm from the tip of the instrument Mtwo (20/06) unused (Burr). F: Presence of more than five areas wear a 5 mm instrument tip Mtwo (20/06) used five times. G: Absence of defects at 5 mm from the tip of the instrument EndoWave (30/06) unused. H: Presence of more than five areas of wear at 5 mm from the tip of the instrument EndoWave (30/06) used five times. 190 magnification micrographs.
Arantes et al.: WITHOUT Analysis of Defects TABLE 2
Statistics on deformation of the cutting edge Instrument tip
Group A B C D
5 mm down from tip
X
s
CV (%)
K–S
X
s
CV (%)
K–S
1.53 1.56 1.00 1.20
0.7432 0.6157 0 0.4140
48.47 39.58 0 34.50
p < 0.05 p < 0.05 p < 0.05 p < 0.05
1.93 1.44 1.25 1.47
0.5936 0.6157 0.4523 0.5164
30.70 42.63 36.18 35.21
p < 0.05 p < 0.05 p < 0.05 p < 0.05
TABLE 3 Comparison among the groups analyzed. Mann– Whitney “U” test Instrument tip
5 mm down from tip
Groups
“U” test
p-Value
“U” test
p-Value
AB AC AD BC BD CD
0.2712 1.7566 1.0577 2.2860 1.5185 0.8783
0.7863 0.0790 0.2902 0.0223 0.1289 0.3798
2.0428 2.617 1.8458 0.6985 0.2531 0.9515
0.0411 0.0104 0.0649 0.4849 0.8002 0.3413
415
Significant.
TABLE 4 Average scores at the tip of the instrument compared with 5 mm down, for all the groups Test point Tip of Instrument 5mm down from tip
X
s
CV (%)
K–S
1.37 1.56
0.5865 0.5981
42.86 38.31
p-Value
SEM Analysis of Defects and Wear on Ni–Ti Rotary Instruments WERINGTON BORGES ARANTES,1 CELSO MONTEIRO DA SILVA,2 JOSE´ LUIZ LAGE-MARQUES,3 SANDRAMARCIA HABITANTE,2 LUIZ CARLOS LAUREANO DA ROSA,4,5 AND JOA˜O MARCELO FERREIRA DE MEDEIROS2 1
Department of Dentistry, Program Graduate Masters, Taubate´ University, Taubate´, Brazil Department of Dentistry, Taubate´ University, Taubate´, Brazil 3 Department Dentistry, Sa˜o Paulo University, Sa˜o Paulo, Brazil 4 Department of Biostatistics, Institute of Basic Mathematical Sciences, University Taubate´, Taubate´, Brazil 5 Center for Economic and Social Research, University Taubate´, Taubate´, Brazil 2
Summary: SEM analysis of endodontic instruments from a Ni–Ti rotary system was assessed, before and after using them, considering their defects and deformations. Twenty Twisted File1, BioRa˛Ce1, Mtwo1, and EndoWave1 instruments were micrographed at 190 magnification. The files were washed and micrographed again to view alterations as to the presence or absence of irregular edges, grooves, microcavities, and scraping. Simulated root canal preparations were performed using these instruments. The instruments were cleaned and received a microscopic analysis after being used five times. After analysis tests were tested using Fisher’s exact test and Kappa to evaluate the concordance among examiners. There was a statistically significant difference with respect to deformations between Twisted File1 and other instruments (p < 0.05). There was no statistically significant difference in strains between the other groups (p > 0.05). All Twisted File1 instruments showed the same defects; however damage were lower than those found in BioRace1 and Mtwo1. The Endowave1 did not show the same defects. In accordance with the data we conclude that the presence of defects was higher in Twisted File1 instruments as the instruments and BioRace1 Mtwo1 brand, the defect rate was smaller and Endowave1 instruments had no defects. Regarding the presence of wear after five uses among the groups all instruments showed changes in their cutting blades. SCANNING 36:411–418, 2014. © 2014 Wiley Periodicals, Inc.
Address for reprints: Joa˜o Marcelo Ferreira de Medeiros, Av. Dr. Guilherme Dumont Villares, 3333, apto. 94A, Jardim Londrina, 05640004 Sa˜o Paulo, SP, Brazil E-mail: [email protected] Received 26 May 2013; Accepted with revision 4 December 2013 DOI: 10.1002/sca.21134 Published online 3 January 2014 in Wiley Online Library (wileyonlinelibrary.com).
Key words: dentistry, image analysis, SEM, surface analysis, microanalysis
Introduction Endodontic instruments, in association with chemical cleaning substances, promote disinfection and formation of the canal. With the advent of rotary files of nickel–titanium, there was an inversion in the sequence of instrumentation whose priority is the initial preparation of the cervical third followed by the medial and apical thirds. This procedure has diminished the contact of the file with the walls of the canal, avoiding the risk of fracture during use and allowing better removal of the contents of the root canal. Any previous enlargement of the canal is therefore a consequent benefit of the rotary instrument, which allows a better determination of the apical diameter of the instrument, shaping it in the apical third of the canal (Walia et al., ’88; Murgel et al., ’90). The presence of defects before the use of the instruments is a reality, as is even the presence of dirt on the surface of the active part of endodontic instruments. Rotary instruments of nickel–titanium of the brands EndoWave1, RaCe1, and ProFile1 were evaluated using torsion and flexion fatigue in SEM as a reference, since they were all size 30, standard ISO, and taper of 0.04. It was observed that the instruments that did not receive any electrochemical polishing had a greater number of defects in fabrication such as grooves, cracks, and cavitations and consequently did not perform as well as those instruments that did receive such electrochemical polishing (Anderson et al., 2007). Scanning electron microscopy was performed on rotary nickel–titanium instruments by EndoWave1, ProTaper1, and RaCe1 concerning cleaning in a sodium hypochlorite solution and repeated sterilization as well as concerning instrument wear, and it was observed that all of them showed some signs of
412
SCANNING VOL. 36, 4 (2014)
corrosion, with the Endowave1 instruments suffering the least—a fact possibly attributable to surface treatments of electrochemical polishing included in the fabrication process of these instruments (Kuber et al., 2006). The quality of the surface finish of the rotary instruments at the time of purchase was examined using a scanning electron microscope. Instruments under the names ProFile1, ProTaper1, RaCe1, HERO1, and K3 Endo1 were examined via a sample of fifty instruments chosen at random, the final 3 mm of whose tips were then photomicrographed at an enlargement of 190. Chianello et al. (2008), concluded that all instruments showed defects of manufacturing flaws in the surface finish, and that none presented zero defects. Rotary nickel–titanium instruments with and without electrochemical polishing were chemically analyzed concerning the effect of using a 5.25% solution of sodium hypochlorite; the instruments used were of the RaCe1 brand. The instruments were analyzed before and after cleaning with sodium hypochlorite on a scanning electron microscope, and it was concluded that those that did not receive electrochemical finishing suffered more corrosion than those that did receive the cited finishing (Bonaccorso et al., 2008). Over a period of 2 years, 414 RaCe1 instruments that received an electrochemically polished finish were judged after being discarded from clinical use. These instruments were observed under a scanning electron microscope and evaluated on their defects. From these, 388 showed structural changes and 26 were fractured. It was concluded that there had been a significant increase in defects after the seventh use of the instruments, therefore there was a statistically significant increase in the failure rate since it exceeded 45% of instrument defect cases (Shen et al., 2009). Scanning electron microscopy was used on 593 nickel–titanium rotary instruments of the brand Mtwo1 (VDW1-Germany) discarded over a 12-month period of clinical practice considering the rate of deformation and fracturing of these instruments. It was observed that the greatest cause of fractures was cyclic fatigue and the instrument with the highest incidence of this was the No. 10, the finest and first in each series. Therefore the authors (Inan and Gonulol, 2009) recommend that the instruments not be used beyond the maker’s recommendation and that the cited instrument be used only once. The efficacy of the different production procedures and the cross-sectional area was examined as regards resistance to cyclic fatigue of four different brands of NiTi rotary instruments (K3, ProFile, RaCe, and Twisted File) used in simulated root canals with a pecking movement until they fracture, and analyzed under a scanning electron microscope. In analyzing the surface of the instruments, the RaCe appeared to be free of defects, whereas the ProFile and K3 showed machining grooves. The surface treatment reduces
residual machining defects from the fabrication process, increasing the resistance to cyclic fatigue (Oh et al., 2010). With the objective of evaluating the deformation of rotary files in vitro as a function of the number of uses. Ten F2 files from the ProTaper Universal System (not electro-polished) and ten 25/0.06 files from the EndoSequence System (electro-polished) were used. The files were cleaned and brought to the scanning electron microscope for viewing before use and after five uses. The conclusion was that there was no significant statistical difference between the ProTaper and the EndoSequence files as to deformation despite the EndoSequence instruments having been electrochemically polished (Reis et al., 2011). The resistance to cyclic fatigue of nickel–titanium files of three different brands was compared: ProTaper, Waveone, and Twisted File. Cyclic fatigue tests were run on an operational instrument starting with the ProTaper F2 file, the Waveone No. 25 with a 0.08 conicity, and the Twisted File size 25 with a 0.08 conicity. A total of 184 instruments were used in four artificial canals curved at different angles and radii of curvature. The time and the cycles until fracture were calculated and the data were compared for differences using variance analysis (p < 0.05). Most of the time the Waveone file was the most resistant to fatigue fractures among the instruments tested; the Twisted File completed more cycles before fracturing than the ProTaper file did. The pecking movement of the Waveone file showed a longer life before cyclic fatigue than the conventional continuous rotating movement of the files from Twisted File and ProTaper. The new torsion process of fabrication by Twisted File produced NiTi rotary instruments more resistant to fatigue than the NiTi instruments from ProTaper produced by the traditional machining method (Castello´Escriva´ et al., 2012). Due to the presence of imperfections of the cutting blades and deformations before and after five uses, the goal of this research was to MEV evaluate, in vitro, the effect of root canal preparation on the cut surface of the active part endodontic instruments of the system nickel–titanium rotary four different brands.
Materials and Methods Twenty rotary instruments of different brands were used in this investigation, namely: five by Twisted File (Group A) from SybronEndo, Sybron Dental Specialties, Orange, CA/USA, and all of size 25 and taper 0.12, 0.10, 0.08, 0.06, 0.04; six by BioRaCe (Group B) FKG DENTAIRE Swiss Dental Products LA CHAUX-DEFONDS-SWISS (25/0.08, 15/0.05, 25/0.04, 25/0.06, 35/ 0.04, and 40/0.04); four by Mtwo (Group C) from VDW GmbH Munich/Germany (10/0.04, 15/0.05, 20/0.06,
Arantes et al.: WITHOUT Analysis of Defects
and 25/0.06); and five by EndoWave (Group D) from J Morita Coorporation Osaka Japan (35/0.08, 30/0.06, 25/0.06, 20/0.06, and 15/0.02). The instruments went through a rigorous cleaning process using cleaning methods such as thermochemistry and washing in an ultrasonic bath. For the cleaning ´ S1) was process, an ultrasonic bath (ODONTOBRA used for 10 min with a heating system using an enzymatic detergent diluted in water to 5 mL per liter (Murgel et al., ’90; Linsuwanont et al., 2004; Aasim et al., 2006).
Scanning Electron Microscope (SEM) Analysis
After the cleaning process was complete, the instruments were dried and analyzed under the scanning electron microscope (MEV-JEOL1 JSM 5900 LV from LME-LNLS—Laborato´rio Nacional de Luz Sı´ncrotron, Campinas, SP); photomicrographs were taken of the leading edge of the cutting blades considering the last 5 mm of the tip at a standard enlargement at magnification 190 (Chianello et al., 2008). The images were recorded digitally viewing two points on the cutting edge as a standard: one at the tip of the instrument and the other, 5 mm down. Then, the images were examined by three evaluators with an eye towards analyzing alterations and manufacturing defects of the files; their criteria for such evaluation were the presence of: irregular edges, grooves, microcavities, and burrs. After a new cleaning in 20 block in phenolic resin simulated canals (Bakelite1) with 75˚ of curvature (Medeiros et al., 2009) were prepared with instruments being the brands of instruments were randomly divided into four groups A–D. In group A, the files from Twisted File1 had the following instrumentation sequence: 0.12 (#25), 0.10 (#25), 0.08 (#25), 0.06 (#25), and 0.04 (#25). For group B, the BioRaCe1 files were: 0.08 (#25), 0.05 (#15), 0.04 (#25), 0.06 (#25), 0.04 (#35), and BioRaCe1 0.04 (#40). In group C, the Mtwo1 was 0.04 (#10) followed by 0.05 (#15), 0.06 (#20), and 0.06 (#25). In group D, the EndoWave files were sequenced: 0.08 (#35), 0.06 (#30), 0.06 (#25), 0.06 (#20), and 0.02(#15). Each instrument was used five times for 10 s in the blocks with simulated canals, after which cleaning and sterilization procedures were followed in an autoclave (KAVOKLAVE 21001; Kavo Dental Ltd, Blackburn, UK) up to 121˚C. The maneuvers were made with an X-Smart1 motor (Dentsply/Maillefer, Baillagues, Switzerland), a machine that, according to the manufacturer, allows torque control, 1.6 N of force, and a speed of 300 rpm, of course in addition to an automatic autoreverse system. The same instruments previously analyzed under the scanning electron microscope at the same sites previously
413
examined at magnification 190 enlargement were viewed again, and again the images were digitally photographed and labelled (Chianello et al., 2008).
Statistical Analysis
Next was the scoring by the three evaluators of the standard viewing area of the cutting edge at the two points previously analyzed: one at the tip of the instrument, and the other, 5 mm down from there. To establish the scores, the evaluators observed and analyzed the images of the files on a computer screen before and after being used five times, considering four discrete criteria, namely: (1) the long axis of the file has undistorted spirals—in other words, without any stretching or compressing and without any wear on the examined surface; (2) the long axis of the file has a distorted spiral—in other words, stretched or shortened and with one to three defective or worn areas on the examined surface; (3) the long axis of the file has more than one distorted spiral—in other words, stretched or shortened and with four or five worn areas on the examined surface; (4) severe wear on the spiral and more than five worn areas on the examined surface (Troian et al., 2006). The program BioEstat version 5.0 (Program by Professor Manuel Ayres, Universidade Federal do Para´, Bele´m-PA) was used for statistical analysis. After the analyses by scanning electron microscopy, the data was tabulated and submitted to analysis where the Intraclass Correlation Coefficient (ICC) was applied using the Kappa test. To analyze the deformations, a descriptive statistic was used with minimum, average, and maximum values, SD, and coefficient of variation. For statistical inference with a significance level of 5%, the Fisher’s exact test, the Mann–Whitney “U” test, and the Kolmogorov–Smirnov Test were used.
Results The results of the instrument defects (irregular edge, grooves, microcavity, and burrs) after cleaning are available in Table 1as well as Figures 1A–H and 2A and H. The scores for the presence of the type of defects at the tip and at 5 mm down for the different instruments are shown in Table 1. The files from Twisted File1 had different defects from the others such as ragged edge, groove, and microcavity with statistical significance (p < 0.05), while there were no statistically significant differences among the others (p > 0.05). The files from group A showed a significant difference of the microcavity item between BioRaCe1, Mtwo1, and EndoWave1 (p < 0.05) and no statistically significant difference among the other three (p > 0.05). As to the
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TABLE 1 Presence of the type of defects at the tip and at 5 mm from the tip of the groups A (Twisted File), B (BioRace), C (Mtwo), and D (EndoWave) Irregular edge Group A B C D
Grooves
Microcavity
Burrs
Tip
5 mm
Tip
5 mm
Tip
5 mm
Tip
5 mm
5 1 0 0
5 1 0 0
5 1 0 0
5 0 0 0
5 0 0 0
5 0 0 0
0 0 1 0
0 0 1 0
“burrs” parameter, there was no statistically significant difference between the groups (p > 0.05). The Twisted File1 file showed a statistical significance with instruments with ragged edges in relation to the other brands (p < 0.05), while comparing the other brands to each other there was no significant difference (p > 0.05). The number of grooves and microcavities present in the files from Twisted File1 compared to the other brands showed a statistical significance (p < 0.05) and by
contrast, among the other brands there was no statistical significance (p > 0.05). The Figure 1A–H are the photomicrographs (at 190) of the presence or absence of defects in the cutting edges at the tip and at 5 mm down from the tip of the instruments in the groups studied. Tables 2–4 detail the wear on the cutting surface of the instruments obtained from the images after five uses and from the scores given by the evaluators, as well as
Fig 1. A: Presence of defects at the tip of the instrument Twisted File (25/06) unused (microcavity, groove, and irregular edge). B: Presence of more than five areas with wear on the tip of the instrument Twisted File (25/06) used five times. C: Absence of defects at the tip of the instrument BioRaCe (25/04) unused. D: Presence of more than three areas of wear on the tip of the instrument BioRaCe (25/04) used five times. E: Absence of defects at the tip of the instrument Mtwo (20/06) unused. F: Presence of wear on the tip of the instrument Mtwo (20/06) used five times. G: Absence of defects at the tip of the instrument EndoWave (15/02) unused. H: Presence over five areas in the wear tip of the instrument EndoWave (15/02) used five times. 190 magnification micrographs.
Fig 2. A: Presence of defects at 5 mm of the tip of the instrument Twisted File (25/04) unused (microcavity and groove). B: Presence of three-wear areas to 5 mm instrument tip Twisted File (25/04) used five times. C: Absence of defects at 5 mm from the tip of the instrument BioRaCe (15/05) unused. D: Presence of five areas of wear to 5 mm instrument tip BioRaCe (15/05) used five times. E: Presence of defects at 5 mm from the tip of the instrument Mtwo (20/06) unused (Burr). F: Presence of more than five areas wear a 5 mm instrument tip Mtwo (20/06) used five times. G: Absence of defects at 5 mm from the tip of the instrument EndoWave (30/06) unused. H: Presence of more than five areas of wear at 5 mm from the tip of the instrument EndoWave (30/06) used five times. 190 magnification micrographs.
Arantes et al.: WITHOUT Analysis of Defects TABLE 2
Statistics on deformation of the cutting edge Instrument tip
Group A B C D
5 mm down from tip
X
s
CV (%)
K–S
X
s
CV (%)
K–S
1.53 1.56 1.00 1.20
0.7432 0.6157 0 0.4140
48.47 39.58 0 34.50
p < 0.05 p < 0.05 p < 0.05 p < 0.05
1.93 1.44 1.25 1.47
0.5936 0.6157 0.4523 0.5164
30.70 42.63 36.18 35.21
p < 0.05 p < 0.05 p < 0.05 p < 0.05
TABLE 3 Comparison among the groups analyzed. Mann– Whitney “U” test Instrument tip
5 mm down from tip
Groups
“U” test
p-Value
“U” test
p-Value
AB AC AD BC BD CD
0.2712 1.7566 1.0577 2.2860 1.5185 0.8783
0.7863 0.0790 0.2902 0.0223 0.1289 0.3798
2.0428 2.617 1.8458 0.6985 0.2531 0.9515
0.0411 0.0104 0.0649 0.4849 0.8002 0.3413
415
Significant.
TABLE 4 Average scores at the tip of the instrument compared with 5 mm down, for all the groups Test point Tip of Instrument 5mm down from tip
X
s
CV (%)
K–S
1.37 1.56
0.5865 0.5981
42.86 38.31
p-Value
