MICROSCOPY RESEARCH AND TECHNIQUE 00:00–00 (2015)
Evaluation of Surface Alterations in Different Retreatment Nickel-Titanium Files: AFM and SEM Study 1 € € € 2 BARAN CAN SAGLAM, * AND GULIZ GORG UL 1 2
Department of Endodontics, Faculty of Dentistry, B€ ulent Ecevit University, Zonguldak, Turkey Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey
KEY WORDS
endodontics; root canal instrument; atomic force microscopy
ABSTRACT The aim of this study was to evaluate the surface changes of nickel titanium (Ni-Ti) rotary retreatment files after three and five uses. Furthermore, the effects of 2% sodium hypochlorite and chloroform solutions and sterilization procedures on the NiTi rotary retreatment surfaces were investigated. ProTaper Retreatment files, R-endo files, and Mtwo retreatment files were used for this study. The palatinal roots of maxillary molar teeth were obturated with gutta percha and Ah26. Retreatment procedures were performed with these retreatment file systems. The surface changes of untreated NiTi rotary files that were used three and five times, immersed in NaOCl and chloroform and subjected to sterilization procedures were investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The RMS values, three dimensional images and SEM images at various magnifications were obtained. RMS values showed that all three NiTi rotary retreatment file systems showed significant deteriorations after three and five uses. Cracks, damages and spiral construction deteriorations were detected in the SEM images after three and five uses. Furthermore, the Mtwo 15 file was broken off after five uses. AFM data indicated that 2% NaOCl caused significant surface deteriorations on NiTi rotary files and both AFM and SEM evaluation showed that chloroform solution and sterilization procedures did not cause significant surface deteriorations. In conclusion, ProTaper retreatment, R-endo, and Mtwo retreatment files showed surface damages depending on retreatment procedures. Clinicians have to consider that retreatment files always have a tendency to break off after the third time they have been used. Microsc. Res. Tech. 00:000–000, 2015. V 2015 C
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INTRODUCTION The failure of endodontically treated tooth is associated with the persistence of microorganisms in the root canal system after cleaning and shaping or removing of bacteria from the root canal space (Nair et al., 1990). The primary goal of root canal retreatment is to reduce the microbial load from the root canal through the removal of filling material, debris, and microorganisms then effectively cleaning, shaping and refilling the root canal system (Hussne et al., 2011; Saad et al., 2007; Stabholz and Friedman, 1988). Gutta-percha is the most commonly used root canal filling material and it should be removed during retreatment (Friedman et al., 1989). Many techniques have been recommended including rotary instruments, ultrasonic instruments, heat, hand files combined with heat or chemicals such as solvents for the removal of filling materials from the root canal system (Fenoul et al., 2010). Studies have shown that none of the retreatment procedures is able to clean the root canal walls completely (Ferreira et al., 2001; Gu et al., 2008; _ Imura et al., 2000; Inan and Aydın, 2012; Mollo et al., 2012; Wilcox et al., 1987). Nickel titanium (NiTi) systems have been suggested for removing gutta-percha from the root canal and studies demonstrated that they could be both effective C V
2015 WILEY PERIODICALS, INC.
and safe (Bramante and Betti, 2000; H€ ulsmann and Bluhm, 2004; Masiero and Barletta, 2005; Mollo et al., 2012). Some advantages such as reducing time consumed and diminishing operator and patient fatigue were reported, in addition to being more efficient than other techniques (Somma et al., 2008). However, none of these techniques, including NiTi systems is effective in removing filling material (Hammad et al., 2008; Pirani et al., 2009). Various NiTi rotary instrument systems have been specifically developed to remove filling material from the root canal walls, and their efficacy, cleaning ability and safety have been studied (Gu et al., 2008; Fenoul et al., 2010; Hussne et al., 2011; Tasdemir et al., 2008). The ProTaper retreatment, Rendo, and Mtwo retreatment instruments, specifically designed for removal of root canal filling material in retreatment procedures. The ProTaper retreatment instruments, the D1, D2, and D3, are manufactured in three sizes, 30, 25, and 20, respectively, with 0.09, 0.08, and 0.07 tapers; these instruments are designed *Correspondence to: Baran Can Sa glam, B€ ulent Ecevit University, Faculty of Dentistry, Department of Endodontics, Kozlu, Zonguldak, Turkey. E-mail: [email protected] Received 17 November 2014; accepted in revised form 10 February 2015 DOI 10.1002/jemt.22481 Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
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for the removal of filling materials from the coronal, middle and apical portions of root canals (Gu et al., 2008; Hussne et al., 2011). The R-Endo system (MicroMega, Besanc¸on, France) is comprised of four instruments: Re (size 25, 0.12 taper) to flare the first few millimetres of the canal, and three files (R1, R2, and R3) with a size of 25 are dedicated to each one -third part of the canal, with 0.08, 0.06, or 0.04 tapers respectively. The files have a triangular cross-section with three equal spaced cutting edges and no radial surface; the tip of the files is claimed to be inactive (Fenoul et al., 2010). The Mtwo-R file comes in sizes 15 and 25, both with 0.05 taper, and was designed with two blades, a tighter pitch that increases in the distal direction and an active point for easy penetration (Hussne et al., 2011; Somma et al., 2008). Although having several advantages such as flexibility, the risk of fracture during clinical use is a major problem with the rotary NiTi instruments. Many studies compared the efficacy of different rotary NiTi instruments in retreatment and they reported a high risk of instrument fracture (Giuliani et al., 2008; Inan and Gonulol, 2009; Schirrmeister et al., 2006). The fracture can occur with no preliminary visible defects on the instrument, so it is difficult to decide when the clinician will stop using the instrument. Retreatment procedures include mechanical removal of root canal material and root canal disinfection. Thus, a NiTi instrument is in contact with filling material and dentin while working in the root canal and is also in contact with a solvent and irrigation solution. No study investigated the effects of retreatment and the other factors associated with retreatment protocols, such as irrigation solution, solvent or sterilization of instrument, on NiTi retreatment file surfaces. The aim of this study was to evaluate the efficacy of the main retreatment procedures on the different NiTi retreatment instrument surfaces after using multiple times by atomic force microscopy (AFM) and scanning electron microscopy (SEM). A secondary goal of the study was to evaluate the efficacy of 2% NaOCl, chloroform and sterilization procedures, particularly on the different NiTi retreatment instrument surfaces in this study. MATERIAL AND METHODS A total of nine retreatment systems, three sets from each of the ProTaper retreatment, R-endo and Mtwo retreatment systems, and a total of nine retreatment instruments—three files each of ProTaper retreatment D1, R-endo R1, and Mtwo retreatment size 25/.05 taper files—were used in this study. One of each retreatment system was used as the control group and the other systems were used for three and five times for the removal of root canal filling material. Retreatment Procedures A total of 24 maxillary first molar teeth with straight palatinal root canals with no caries were selected and crowns were separated to standardize the samples with the working length established at 13 mm. To estimate the working length a size 10 stainless steel K-file (VDW Antaeos, Munich, Germany) was passively introduced into the root canal until the tip of the file was seen at the level of the major foramen on
the root surface and the working length was recorded as being 1 mm shorter. All palatinal canals were instrumented by the same operator using a series of ProTaper NiTi rotary instruments (Dentsply Maillefer, Ballai- gues, Switzerland) in an electric motor (VDW, M€ unchen, Germany) rotating at 300 rpm. The preparation of the root canals was completed when a ProTaper F3 reached the working length. Irrigation was performed with 3 mL 2% NaOCl between each instrument. After the biomechanical preparation, a final rinse with 3 mL 2% NaOCl and 17% EDTA was used for 1 min, followed by distilled water. Each canal was dried using paper points. Root canals were filled with gutta percha and AH-26 (Dentsply DeTrey, Konstanz, Germany) root canal sealer using cold lateral condensation technique. The coronal aspect of the roots were sealed with composite resin filling material and stored in 100% humidity at 37 C in a drying oven for 2 months to allow for complete setting of the sealers. The teeth were randomly divided in two retreatment groups for three-time and five-time use of the retreatment kits; in the first group, one set from the each of ProTaper retreatment, R-endo, and Mtwo retreatment files was used to remove the root canal filling material three times in total nine palatal roots. For the fivetime use, one set from each of these retreatment kits was used five times for retreatment of the other fifteen teeth. Retreatment instruments were used according to the manufacturer’s instructions. D1 (size 30/.09 taper), D2 (size 25/.08 taper), and D3 (size 20/.07 taper) ProTaper retreatment instruments were used sequentially until the working length was reached. R1 (size 25/.08 taper), R2 instrument (size 25/.06 taper), and R3 (size 25/.04 taper) were used sequentially to reach the working length. Two Mtwo retreatment instruments, size 25/.05 taper and size 15/.05 taper, were used sequentially until the working length was reached. Two drops of chloroform were used as a solvent in all root canals. The irrigation was performed with 3 mL 2% NaOCl between each instrument during the retreatment. After every retreatment procedure instruments were ultrasonically cleaned and autoclaved at 121 C for 20 min. The apical 3 mm of the control group instruments, the retreatment instruments that were used three times used and those that were used five times were separated for surface alteration examination. NaOCl Experiment One new ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment instruments were used for the NaOCl experiment. The apical 3 mm of the instruments were separated and immersed into 2% NaOCl for 5 min. Then the samples were rinsed with 5 mL of distilled water and dried with filter papers. Chloroform Experiment The apical 3mm of new three retreatment instruments (ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment) were separated and immersed into a chloroform solution for 5 min. Then, the samples were dried with filter papers and the samples were rinsed with 5 mL of distilled water and dried with filter papers. Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
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TABLE 1. The mean RMS values of the control, three time uses and five time uses of retreatment instruments
ProTaper retreatmentfiles
File
Groups
N
Mean
Std. Dev.
D1
Control 3-time use 5-time use Control 3-time use 5-time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use
11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
1.33 4.41 11.63 1.32 4.50 13.30 1.58 4.28 14.21 8.32 17.54 20.42 9.00 18.13 20.26 10.50 17.15 22.36 11.83 16.89 19.73 11.65 16.36 21.17
0.558 2.529 4.299 0.699 2.545 5.208 0.550 2.260 4.224 2.379 3.916 7.286 2.545 4.554 6.271 2.212 4.119 8.832 2.138 5.097 5.586 2.389 5.043 5.487
D2 D3 R-Endo retreatment files
R1 R2 R3
Mtwo retreatment files
Mtwo25 Mtwo15
P
Significant differences
0.000*
C-3 C-5 3-5 C-3 C-5 3-5 C-3 C-5 3-5 C-3 C-5
0.000*
C-3 C-5
0.006*
C-3 C-5
0.000* 0.000* 0.000*
C-3 C-5 3-5 C-3 C-5 3-5
0.000* 0.000*
* Significant difference.
Sterilization Experiment The apical 3 mm of new three retreatment instruments (ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment) were separated and autoclaved five times at 121 C and 20 min. Atomic Force Microscopy Examination All unused (control) and treated specimens obtained from retreatment procedures and NaOCl, solvent and sterilization tests, were attached to a metal base with double sided tape for AFM evaluation (Veeco Instrument Nanoscope 4A). AFM images were recorded on a multimode SPM Nanoscope IVa (Veeco, Santa Barbara, CA). The AFM analyses were performed on 11 different regions located between the first and second millimeters from the tip with 2 mm 3 2 mm uniform scanned areas. Three-dimensional images of the NiTi specimens were taken and the root mean square (RMS), which provides quantitative data for the instrument surface, was chosen to investigate the structure of the NiTi specimens. All RMS values were evaluated statistically by one way ANOVA and MannWhitney U test. Scanning Electron Microscope Evaluation The specimens used for AFM analysis were planted into SEM (Quanta400F Field Emission SEM) and the images were taken under 800, 1,200, 1,500, and 10,000 magnification from different regions of all samples. RESULTS Table 1 presents the mean RMS values of the control, three uses and five uses of the retreatment instruments. There were significant differences between the control, three uses, and five uses in all ProTaper retreatment instruments. Significant differences were found between the control, three uses and five uses in the R1 and R3 instrument. However, there were no Microscopy Research and Technique
TABLE 2. The mean RMS values of retreatment files after the immersion in 2% NaOCl and chloroform and after the five-time sterilization process Files NaOCl
D1
Groups
Control NaOCl R1 Control NaOCl Mtwo 25 Control NaOCl Chloroform D1 Control Chloroform R1 Control Chloroform Mtwo 25 Control Chloroform Sterilization D1 Control Sterilization R1 Control Sterilization Mtwo 25 Control Sterilization
N
Mean Std. Dev.
11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
1.33 2.24 8.32 14.48 11.83 17.67 1.33 1.73 8.32 7.64 11.83 12.44 1.33 1.75 8.32 11.01 11.83 12.57
0.558 0.555 2.379 5.380 2.138 8.391 0.558 0.897 2.379 4.106 2.138 6.062 0.558 0.940 2.379 3.867 2.138 3.839
P 0.003* 0.004* 0.061 0.218 0.718 0.818 0.224 0.061 0.577
* Significant difference.
significant differences between three uses and five uses in the R2 instrument. There were significant differences among the control, three uses and five uses in both of the Mtwo retreatment instruments. The mean RMS values of the retreatment files after immersion in 2% NaOCl and chloroform and after sterilization are presented in Table 2. D1 and R1 instruments showed significant differences after immersion in 2%NaOCl, but no significant differences in Mtwo retreatment instrument according to the RMS values. No significant differences were obtained in all instruments after immersion in chloroform. There were no significant differences in all instruments after a five-time sterilization process. Three dimensional images of AFM evaluation are shown in Figure 1. SEM images of control and tested NiTi files were presented in Figure 2. Microcracks and
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Fig. 1. Three dimensional AFM images of different retreatment files. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
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Fig. 2. SEM images of differrent retreatment files.
deformations on the cutting edge of the instruments were observed in SEM images after all retreatment instruments were used three and five times. The Mtwo 25 file fractured at the apical part during the fifth use. Microscopy Research and Technique
DISCUSSION The NiTi rotary retreatment instruments were used in this study and their surface morphologies were evaluated. Many studies have investigated and compared
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the surface alterations of different NiTi rotary instruments; however no study evaluated the alterations on the surface of instruments after retreatment (Ametrano et al., 2011; Cavalleriet al., 2009; Inan et al., 2007; Torian et al., 2006; Valois et al., 2008). A previous study evaluating instrument surfaces after root canal preparation by SEM stated that, after canal shaping, all instruments had microcracks and widening of machine grooves and blunting of the cutting edges (Vieira et al., 2009). Furthermore, in another study, Inan et al. (2007) evaluated the topography of new and used ProTaper rotary NiTi instruments by using AFM and reported that ProTaper instruments demonstrated more surface deformation and wear. Although using retreatment file systems for the removal of gutta-percha was performed in this study, similarly, physical surfaces defects including microcracks and blunting of the cutting edges were obtained as a result, considering the previous studies. Both AFM and SEM analyses were used in this study to observe and measure the alterations on the instrument surface. AFM analysis has become popular among the microscope evaluation such as stereo microscope and SEM. AFM is used to examine the surface properties of various materials that can provide threedimensional images and numerical data for the surface properties (Braga and Ricci, 2004). Many studies have used this analysis in endodontic researches to adress the issues of bleaching, disinfection of gutta-percha cones or surface properties of NiTi instrument after root canal preparation (Forner et al., 2009; Topuz et al., 2008; Valois et al., 2005). The RMS values obtained from AFM examination were used as quantitative data to compare the groups statistically, similar to previous studies (Inan et al., 2007; Topuz et al., 2008; Valois et al., 2005). Moreover, SEM analysis was performed in this study to observe the deteriorations under high magnifications. AFM and SEM evaluations were used together in this study for both the description and measuring the surface alterations occured after the retreatment. All instruments in the three retreatment systems were used a maximum of five times in the present study. Similarly, Inan et al. (2007) used the ProTaper Universal rotary files five times and evaluated the surface alterations by AFM. However, this study demonstrated the examination of retreatment instruments distinctively. In another study, Unal et al. (2009) compared the efficacy of conventional and new retreatment instruments when removing gutta-percha root fillings in curved root canals, and each instrument was used for a maximum of five canals. Somma et al. (2008) used each Mtwo retreatment and ProTaper retreatment instrument five times to compare their effectiveness in the removal of different root canal filling materials, and they reported that NiTi rotary systems proved to be safe and fast devices for the removal of endodontic filling material. The manufacturer indicated that each R-endo file can be used for 5 to 8 root canals, but working with the same file should be finished under high-stress conditions. A molar tooth commonly has three or four root canals; so, during the retreatment of a molar tooth each file has to be used at least three times. For that reason, each file was used three or five times in this study.
The RMS values of all ProTaper retreatment and Mtwo retreatment instruments increased significantly with use count. Moreover, a fracture occurred during the fifth use of a Mtwo retreatment 15.05 file. A significant increase was not seen in the R1, R2, and R3 instruments of the R-endo system between three and five uses. These results showed that the surface deteriorations occured in the first three uses and then it slowed down. Inan et al. (2012) evaluated the cyclic fatigue resistance of ProTaper retreatment D3, R-endo R1, and Mtwo retreatment 25.05 instruments and it was reported that the R-endo R3 instruments were more resistant to fatigue failure than the ProTaper retreatment D3 and Mtwo 25.05 instruments.The SEM images showed that micro cracks and blunting of cutting edges occured after three uses of all instruments in all three systems. These deformations increased in the five-use groups. Moreover, the spiral distortions were observed after five uses caused by the embedding of the apical part of the file into guttapercha when rotation was resumed. Efficacy of 2% NaOCl solution, chloroform and sterilization process on the instrument surface were tested in this study because retreatment protocol includes irrigation, softening of filling material and sterilization of the instrument for multiple uses. Topuz et al. (2008) investigated the effect of sodium hypochlorite immersion on the surface of RaCe rotary nickel2titanium instruments using AFM and reported that deteriorations occured on the surface of RaCe instruments after the immersion in 5.25% NaOCl for 5 min. Additionally, in another AFM study, Ametrano et al. (2011) reported that 5.25% NaOCl caused surface alterations on the surface of the ProTaper instruments. ProTaper retreatment and R-endo instruments showed compatible results with previous studies. The RMS values of the Mtwo retreatment group showed increases without significant differences. This result could be caused by the concentration of the NaOCl, and 2% NaOCl was used in this study. According to the SEM examination, no changes were observed after immersion in 2% NaOCl compared with the control. A search of the literature revealed that there has been no study about the effects of solvent upon the retreatment instrument surface. Chloroform is an effective and widely used solvent for gutta-percha and preferred for this study. AFM results showed that chloroform has no effect on the instrument surface. The effects of multiple sterilization cycles on the instrument surface were demonstrated previously (Valois et al., 2008). It was reported that after 5 and 10 repeated autoclave cycles, RMS values increased significantly. In contrast to the previous study, no significant differences were observed in the present study. Valois et al. (2008) indicated that the number of autoclave cycles needed to cause surface alterations changed between different types of rotary NiTi files. This difference could be caused by using different files. CONCLUSIONS All three retreatment systems showed surface alterations after multiple uses. R-endo instruments demonstrated resistance to deformation after three uses. NaOCl solution caused deteriorations on the NiTi rotary instruments without visible defects. Chloroform Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
and sterilization process did not affect the NiTi rotary instruments. AFM examination is a more detailed and sensitive method than SEM for examination of NiTi rotary instrument surfaces. Clinicians have to consider that retreatment files always have a tendency to break off after the third time they have been used. REFERENCES Ametrano G, D’Ant o V, Di Caprio MP, Simeone M, Rengo S, Spagnuolo G. 2011. Effects of sodium hypochlorite and ethylenediaminetetraacetic acid on rotary nickel-titanium instruments evaluated using atomic force microscopy. Int Endod J 44:203–209. Braga PC, Ricci D. 2004. Methods in molecular biology. New Jersey: Humana Press. 3 pp. Bramante CM, Betti LV. 2000. Efficacy of Quantec rotary instruments for gutta-percha removal. Int Endod J 33:463–467. Cavalleri G, Cantatore G, Costa A, Grillenzoni M, Comin Chiaramonti L, Gerosa R. 2009. The corrosive effects of sodium hypochlorite on nickel-titanium endodontic instruments: Assessment by digital scanning microscope. Minerva Stomatol 58:225– 231. Fenoul G, Meless GD, P erez F. 2010. The efficacy of R-Endo rotary NiTi and stainless-steel hand instruments to remove gutta-percha and Resilon. Int Endod J 43:135–141. Ferreira JJ, Rhodes JS, Ford TR. 2001. The efficacy of gutta-percha removal using ProFiles. Int Endod J 34:267–274. Friedman S, Rotstein I, Shar-Lev S. 1989. Bypassing gutta-percha root fillings with an automated device. J Endod 15:432–437. Forner L, Salmeron-S anchez M, Palomares M, Llena C, Amengual J. 2009. The use of atomic force microscopy in determining the stiffness and adhesion force of human dentin after exposure to bleaching agents. J Endod 35:1384–1386. Giuliani V, Cocchetti R, Pagavino G. 2008. Efficacy of ProTaper Universal retreatment files in removing filling materials during root canal retreatment. J Endod 34:1381–1384. Gu LS, Ling JQ, Wei X, Huang XY. 2008. Efficacy of ProTaper Universal rotary retreatment system for gutta-percha removal from root canals. Int Endod J 41:288–295. Hammad M, Qualtrough A, Silikas N. 2008. Three-dimensional evaluation of effectiveness of hand and rotary instrumentation for retreatment of canals filled with different materials. J Endod 34: 1370–1373. Hussne RP, Braga LC, Berbert FL, Buono VT, Bahia MG. 2011. Flexibility and torsional resistance of three nickel-titanium retreatment instrument systems. Int Endod J 44:731–738. H€ ulsmann M, Bluhm V. 2004. Efficacy, cleaning ability and safety of different rotary NiTi instruments in root canal retreatment. Int Endod J 37:468–476. Imura N, Kato AS, Hata GI, Uemura M, Toda T, Weine F. 2000. A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment. Int Endod J 33:361–366. Inan U, Gonulol N. 2009. Deformation and fracture of Mtwo rotary nickel-titanium instruments after clinical use. J Endod 35:1396– 1399.
Microscopy Research and Technique
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Inan U, Aydin C. 2012. Comparison of cyclic fatigue resistance of three different rotary nickel-titanium instruments designed for retreatment. J Endod 38:108–111. Inan U, Aydin C, Uzun O, Topuz O, Alacam T. 2007. Evaluation of the surface characteristics of used and new ProTaper Instruments: an atomic force microscopy study. J Endod 33:1334–1337. Masiero AV, Barletta FB. 2005. Effectiveness of different techniques for removing gutta-percha during retreatment. Int Endod J 38:2–7. Mollo A, Botti G, Prinicipi Goldoni N, Randellini E, Paragliola R, Chazine M, Ounsi HF, Grandini S. 2012. Efficacy of two Ni-Ti systems and hand files for removing gutta-percha from root canals. Int Endod J 45:1–6. Nair PN, Sjogren U, Krey G, Kahnberg KE, Sundqvist G. 1990. Intraradicular bacteria and fungi in root-filled, asymptomatichuman teeth with therapy-resistant periapical lesions: Along-term light and electron microscopic follow-up study. J Endod 16:580–588. Pirani C, Pelliccioni GA, Marchionni S, Montebugnoli L, Piana G, Prati C. 2009. Effectiveness of three different retreatment techniques in canals filled with compacted gutta-percha or Thermafil: A scanning electron microscope study. J Endod 35:1433–1440. Saad AY, Al-Hadlaq SM, Al-Katheeri NH. 2007. Efficacy of two rotary NiTi instruments in the removal of Gutta-Percha during root canal retreatment. J Endod 33:38–41. Schirrmeister JF, Wrbas KT, Schneider FH, Altenburger MJ, Hellwig E. 2006. Effectiveness of a hand file and three nickel-titanium rotary instruments for removing guttapercha in curved root canals during retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:542–547. Somma F, Cammarota G, Plotino G, Grande NM, Pameijer CH. 2008. The effectiveness of manual and mechanical instrumentation for the retreatment of three different root canal filling materials. J Endod 34:466–469. Stabholz A, Friedman S. 1988. Endodontic retreatment–case selection and technique. Part 2: Treatment planning for retreatment. J Endod 14:607–614. Topuz O, Aydin C, Uzun O, Inan U, Alacam T, Tunca YM. 2008. Structural effects of sodium hypochlorite solution on RaCe rotary nickeltitanium instruments: An atomic force microscopy study.Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105:661–665. Troian CH, S o MV, Figueiredo JA, Oliveira EP. 2006. Deformation and fracture of RaCe and K3 endodontic instruments according to the number of uses. Int Endod J 39:616–625. Unal GC, Kaya BU, Tac¸ AG, Kec¸eci AD. 2009. A comparison of the efficacy of conventional and new retreatment instruments to remove gutta-percha in curved root canals: An ex vivo study. Int Endod J 42:344–350. Valois CR, Silva LP, Azevedo RB. 2005. Effects of 2% chlorhexidine and 5.25% sodium hypochlorite on gutta-percha cones studied by atomic force microscopy. Int Endod J 38:425–429. Valois CR, Silva LP, Azevedo RB. 2008. Multiple autoclave cycles affect the surface of rotary nickel-titanium files: an atomic force microscopy study. J Endod 34:859–862. Vieira EP, Nakagawa RK, Buono VT, Bahia MG. 2009. Torsional behaviour of rotary NiTi ProTaper Universal instruments after multiple clinical use. Int Endod J. 42:947–953. Wilcox LR, Krell KV, Madison S, Rittman B. 1987. Endodontic retreatment: Evaluation of gutta-percha and sealer removal and canal reinstrumentation. J Endod 13:453–457.
Evaluation of Surface Alterations in Different Retreatment Nickel-Titanium Files: AFM and SEM Study 1 € € € 2 BARAN CAN SAGLAM, * AND GULIZ GORG UL 1 2
Department of Endodontics, Faculty of Dentistry, B€ ulent Ecevit University, Zonguldak, Turkey Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey
KEY WORDS
endodontics; root canal instrument; atomic force microscopy
ABSTRACT The aim of this study was to evaluate the surface changes of nickel titanium (Ni-Ti) rotary retreatment files after three and five uses. Furthermore, the effects of 2% sodium hypochlorite and chloroform solutions and sterilization procedures on the NiTi rotary retreatment surfaces were investigated. ProTaper Retreatment files, R-endo files, and Mtwo retreatment files were used for this study. The palatinal roots of maxillary molar teeth were obturated with gutta percha and Ah26. Retreatment procedures were performed with these retreatment file systems. The surface changes of untreated NiTi rotary files that were used three and five times, immersed in NaOCl and chloroform and subjected to sterilization procedures were investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The RMS values, three dimensional images and SEM images at various magnifications were obtained. RMS values showed that all three NiTi rotary retreatment file systems showed significant deteriorations after three and five uses. Cracks, damages and spiral construction deteriorations were detected in the SEM images after three and five uses. Furthermore, the Mtwo 15 file was broken off after five uses. AFM data indicated that 2% NaOCl caused significant surface deteriorations on NiTi rotary files and both AFM and SEM evaluation showed that chloroform solution and sterilization procedures did not cause significant surface deteriorations. In conclusion, ProTaper retreatment, R-endo, and Mtwo retreatment files showed surface damages depending on retreatment procedures. Clinicians have to consider that retreatment files always have a tendency to break off after the third time they have been used. Microsc. Res. Tech. 00:000–000, 2015. V 2015 C
Wiley Periodicals, Inc.
INTRODUCTION The failure of endodontically treated tooth is associated with the persistence of microorganisms in the root canal system after cleaning and shaping or removing of bacteria from the root canal space (Nair et al., 1990). The primary goal of root canal retreatment is to reduce the microbial load from the root canal through the removal of filling material, debris, and microorganisms then effectively cleaning, shaping and refilling the root canal system (Hussne et al., 2011; Saad et al., 2007; Stabholz and Friedman, 1988). Gutta-percha is the most commonly used root canal filling material and it should be removed during retreatment (Friedman et al., 1989). Many techniques have been recommended including rotary instruments, ultrasonic instruments, heat, hand files combined with heat or chemicals such as solvents for the removal of filling materials from the root canal system (Fenoul et al., 2010). Studies have shown that none of the retreatment procedures is able to clean the root canal walls completely (Ferreira et al., 2001; Gu et al., 2008; _ Imura et al., 2000; Inan and Aydın, 2012; Mollo et al., 2012; Wilcox et al., 1987). Nickel titanium (NiTi) systems have been suggested for removing gutta-percha from the root canal and studies demonstrated that they could be both effective C V
2015 WILEY PERIODICALS, INC.
and safe (Bramante and Betti, 2000; H€ ulsmann and Bluhm, 2004; Masiero and Barletta, 2005; Mollo et al., 2012). Some advantages such as reducing time consumed and diminishing operator and patient fatigue were reported, in addition to being more efficient than other techniques (Somma et al., 2008). However, none of these techniques, including NiTi systems is effective in removing filling material (Hammad et al., 2008; Pirani et al., 2009). Various NiTi rotary instrument systems have been specifically developed to remove filling material from the root canal walls, and their efficacy, cleaning ability and safety have been studied (Gu et al., 2008; Fenoul et al., 2010; Hussne et al., 2011; Tasdemir et al., 2008). The ProTaper retreatment, Rendo, and Mtwo retreatment instruments, specifically designed for removal of root canal filling material in retreatment procedures. The ProTaper retreatment instruments, the D1, D2, and D3, are manufactured in three sizes, 30, 25, and 20, respectively, with 0.09, 0.08, and 0.07 tapers; these instruments are designed *Correspondence to: Baran Can Sa glam, B€ ulent Ecevit University, Faculty of Dentistry, Department of Endodontics, Kozlu, Zonguldak, Turkey. E-mail: [email protected] Received 17 November 2014; accepted in revised form 10 February 2015 DOI 10.1002/jemt.22481 Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
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for the removal of filling materials from the coronal, middle and apical portions of root canals (Gu et al., 2008; Hussne et al., 2011). The R-Endo system (MicroMega, Besanc¸on, France) is comprised of four instruments: Re (size 25, 0.12 taper) to flare the first few millimetres of the canal, and three files (R1, R2, and R3) with a size of 25 are dedicated to each one -third part of the canal, with 0.08, 0.06, or 0.04 tapers respectively. The files have a triangular cross-section with three equal spaced cutting edges and no radial surface; the tip of the files is claimed to be inactive (Fenoul et al., 2010). The Mtwo-R file comes in sizes 15 and 25, both with 0.05 taper, and was designed with two blades, a tighter pitch that increases in the distal direction and an active point for easy penetration (Hussne et al., 2011; Somma et al., 2008). Although having several advantages such as flexibility, the risk of fracture during clinical use is a major problem with the rotary NiTi instruments. Many studies compared the efficacy of different rotary NiTi instruments in retreatment and they reported a high risk of instrument fracture (Giuliani et al., 2008; Inan and Gonulol, 2009; Schirrmeister et al., 2006). The fracture can occur with no preliminary visible defects on the instrument, so it is difficult to decide when the clinician will stop using the instrument. Retreatment procedures include mechanical removal of root canal material and root canal disinfection. Thus, a NiTi instrument is in contact with filling material and dentin while working in the root canal and is also in contact with a solvent and irrigation solution. No study investigated the effects of retreatment and the other factors associated with retreatment protocols, such as irrigation solution, solvent or sterilization of instrument, on NiTi retreatment file surfaces. The aim of this study was to evaluate the efficacy of the main retreatment procedures on the different NiTi retreatment instrument surfaces after using multiple times by atomic force microscopy (AFM) and scanning electron microscopy (SEM). A secondary goal of the study was to evaluate the efficacy of 2% NaOCl, chloroform and sterilization procedures, particularly on the different NiTi retreatment instrument surfaces in this study. MATERIAL AND METHODS A total of nine retreatment systems, three sets from each of the ProTaper retreatment, R-endo and Mtwo retreatment systems, and a total of nine retreatment instruments—three files each of ProTaper retreatment D1, R-endo R1, and Mtwo retreatment size 25/.05 taper files—were used in this study. One of each retreatment system was used as the control group and the other systems were used for three and five times for the removal of root canal filling material. Retreatment Procedures A total of 24 maxillary first molar teeth with straight palatinal root canals with no caries were selected and crowns were separated to standardize the samples with the working length established at 13 mm. To estimate the working length a size 10 stainless steel K-file (VDW Antaeos, Munich, Germany) was passively introduced into the root canal until the tip of the file was seen at the level of the major foramen on
the root surface and the working length was recorded as being 1 mm shorter. All palatinal canals were instrumented by the same operator using a series of ProTaper NiTi rotary instruments (Dentsply Maillefer, Ballai- gues, Switzerland) in an electric motor (VDW, M€ unchen, Germany) rotating at 300 rpm. The preparation of the root canals was completed when a ProTaper F3 reached the working length. Irrigation was performed with 3 mL 2% NaOCl between each instrument. After the biomechanical preparation, a final rinse with 3 mL 2% NaOCl and 17% EDTA was used for 1 min, followed by distilled water. Each canal was dried using paper points. Root canals were filled with gutta percha and AH-26 (Dentsply DeTrey, Konstanz, Germany) root canal sealer using cold lateral condensation technique. The coronal aspect of the roots were sealed with composite resin filling material and stored in 100% humidity at 37 C in a drying oven for 2 months to allow for complete setting of the sealers. The teeth were randomly divided in two retreatment groups for three-time and five-time use of the retreatment kits; in the first group, one set from the each of ProTaper retreatment, R-endo, and Mtwo retreatment files was used to remove the root canal filling material three times in total nine palatal roots. For the fivetime use, one set from each of these retreatment kits was used five times for retreatment of the other fifteen teeth. Retreatment instruments were used according to the manufacturer’s instructions. D1 (size 30/.09 taper), D2 (size 25/.08 taper), and D3 (size 20/.07 taper) ProTaper retreatment instruments were used sequentially until the working length was reached. R1 (size 25/.08 taper), R2 instrument (size 25/.06 taper), and R3 (size 25/.04 taper) were used sequentially to reach the working length. Two Mtwo retreatment instruments, size 25/.05 taper and size 15/.05 taper, were used sequentially until the working length was reached. Two drops of chloroform were used as a solvent in all root canals. The irrigation was performed with 3 mL 2% NaOCl between each instrument during the retreatment. After every retreatment procedure instruments were ultrasonically cleaned and autoclaved at 121 C for 20 min. The apical 3 mm of the control group instruments, the retreatment instruments that were used three times used and those that were used five times were separated for surface alteration examination. NaOCl Experiment One new ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment instruments were used for the NaOCl experiment. The apical 3 mm of the instruments were separated and immersed into 2% NaOCl for 5 min. Then the samples were rinsed with 5 mL of distilled water and dried with filter papers. Chloroform Experiment The apical 3mm of new three retreatment instruments (ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment) were separated and immersed into a chloroform solution for 5 min. Then, the samples were dried with filter papers and the samples were rinsed with 5 mL of distilled water and dried with filter papers. Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
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TABLE 1. The mean RMS values of the control, three time uses and five time uses of retreatment instruments
ProTaper retreatmentfiles
File
Groups
N
Mean
Std. Dev.
D1
Control 3-time use 5-time use Control 3-time use 5-time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use Control 3 time use 5 time use
11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
1.33 4.41 11.63 1.32 4.50 13.30 1.58 4.28 14.21 8.32 17.54 20.42 9.00 18.13 20.26 10.50 17.15 22.36 11.83 16.89 19.73 11.65 16.36 21.17
0.558 2.529 4.299 0.699 2.545 5.208 0.550 2.260 4.224 2.379 3.916 7.286 2.545 4.554 6.271 2.212 4.119 8.832 2.138 5.097 5.586 2.389 5.043 5.487
D2 D3 R-Endo retreatment files
R1 R2 R3
Mtwo retreatment files
Mtwo25 Mtwo15
P
Significant differences
0.000*
C-3 C-5 3-5 C-3 C-5 3-5 C-3 C-5 3-5 C-3 C-5
0.000*
C-3 C-5
0.006*
C-3 C-5
0.000* 0.000* 0.000*
C-3 C-5 3-5 C-3 C-5 3-5
0.000* 0.000*
* Significant difference.
Sterilization Experiment The apical 3 mm of new three retreatment instruments (ProTaper retreatment D1, R-endo R1, and size 25/.05 taper Mtwo retreatment) were separated and autoclaved five times at 121 C and 20 min. Atomic Force Microscopy Examination All unused (control) and treated specimens obtained from retreatment procedures and NaOCl, solvent and sterilization tests, were attached to a metal base with double sided tape for AFM evaluation (Veeco Instrument Nanoscope 4A). AFM images were recorded on a multimode SPM Nanoscope IVa (Veeco, Santa Barbara, CA). The AFM analyses were performed on 11 different regions located between the first and second millimeters from the tip with 2 mm 3 2 mm uniform scanned areas. Three-dimensional images of the NiTi specimens were taken and the root mean square (RMS), which provides quantitative data for the instrument surface, was chosen to investigate the structure of the NiTi specimens. All RMS values were evaluated statistically by one way ANOVA and MannWhitney U test. Scanning Electron Microscope Evaluation The specimens used for AFM analysis were planted into SEM (Quanta400F Field Emission SEM) and the images were taken under 800, 1,200, 1,500, and 10,000 magnification from different regions of all samples. RESULTS Table 1 presents the mean RMS values of the control, three uses and five uses of the retreatment instruments. There were significant differences between the control, three uses, and five uses in all ProTaper retreatment instruments. Significant differences were found between the control, three uses and five uses in the R1 and R3 instrument. However, there were no Microscopy Research and Technique
TABLE 2. The mean RMS values of retreatment files after the immersion in 2% NaOCl and chloroform and after the five-time sterilization process Files NaOCl
D1
Groups
Control NaOCl R1 Control NaOCl Mtwo 25 Control NaOCl Chloroform D1 Control Chloroform R1 Control Chloroform Mtwo 25 Control Chloroform Sterilization D1 Control Sterilization R1 Control Sterilization Mtwo 25 Control Sterilization
N
Mean Std. Dev.
11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
1.33 2.24 8.32 14.48 11.83 17.67 1.33 1.73 8.32 7.64 11.83 12.44 1.33 1.75 8.32 11.01 11.83 12.57
0.558 0.555 2.379 5.380 2.138 8.391 0.558 0.897 2.379 4.106 2.138 6.062 0.558 0.940 2.379 3.867 2.138 3.839
P 0.003* 0.004* 0.061 0.218 0.718 0.818 0.224 0.061 0.577
* Significant difference.
significant differences between three uses and five uses in the R2 instrument. There were significant differences among the control, three uses and five uses in both of the Mtwo retreatment instruments. The mean RMS values of the retreatment files after immersion in 2% NaOCl and chloroform and after sterilization are presented in Table 2. D1 and R1 instruments showed significant differences after immersion in 2%NaOCl, but no significant differences in Mtwo retreatment instrument according to the RMS values. No significant differences were obtained in all instruments after immersion in chloroform. There were no significant differences in all instruments after a five-time sterilization process. Three dimensional images of AFM evaluation are shown in Figure 1. SEM images of control and tested NiTi files were presented in Figure 2. Microcracks and
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Fig. 1. Three dimensional AFM images of different retreatment files. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
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Fig. 2. SEM images of differrent retreatment files.
deformations on the cutting edge of the instruments were observed in SEM images after all retreatment instruments were used three and five times. The Mtwo 25 file fractured at the apical part during the fifth use. Microscopy Research and Technique
DISCUSSION The NiTi rotary retreatment instruments were used in this study and their surface morphologies were evaluated. Many studies have investigated and compared
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the surface alterations of different NiTi rotary instruments; however no study evaluated the alterations on the surface of instruments after retreatment (Ametrano et al., 2011; Cavalleriet al., 2009; Inan et al., 2007; Torian et al., 2006; Valois et al., 2008). A previous study evaluating instrument surfaces after root canal preparation by SEM stated that, after canal shaping, all instruments had microcracks and widening of machine grooves and blunting of the cutting edges (Vieira et al., 2009). Furthermore, in another study, Inan et al. (2007) evaluated the topography of new and used ProTaper rotary NiTi instruments by using AFM and reported that ProTaper instruments demonstrated more surface deformation and wear. Although using retreatment file systems for the removal of gutta-percha was performed in this study, similarly, physical surfaces defects including microcracks and blunting of the cutting edges were obtained as a result, considering the previous studies. Both AFM and SEM analyses were used in this study to observe and measure the alterations on the instrument surface. AFM analysis has become popular among the microscope evaluation such as stereo microscope and SEM. AFM is used to examine the surface properties of various materials that can provide threedimensional images and numerical data for the surface properties (Braga and Ricci, 2004). Many studies have used this analysis in endodontic researches to adress the issues of bleaching, disinfection of gutta-percha cones or surface properties of NiTi instrument after root canal preparation (Forner et al., 2009; Topuz et al., 2008; Valois et al., 2005). The RMS values obtained from AFM examination were used as quantitative data to compare the groups statistically, similar to previous studies (Inan et al., 2007; Topuz et al., 2008; Valois et al., 2005). Moreover, SEM analysis was performed in this study to observe the deteriorations under high magnifications. AFM and SEM evaluations were used together in this study for both the description and measuring the surface alterations occured after the retreatment. All instruments in the three retreatment systems were used a maximum of five times in the present study. Similarly, Inan et al. (2007) used the ProTaper Universal rotary files five times and evaluated the surface alterations by AFM. However, this study demonstrated the examination of retreatment instruments distinctively. In another study, Unal et al. (2009) compared the efficacy of conventional and new retreatment instruments when removing gutta-percha root fillings in curved root canals, and each instrument was used for a maximum of five canals. Somma et al. (2008) used each Mtwo retreatment and ProTaper retreatment instrument five times to compare their effectiveness in the removal of different root canal filling materials, and they reported that NiTi rotary systems proved to be safe and fast devices for the removal of endodontic filling material. The manufacturer indicated that each R-endo file can be used for 5 to 8 root canals, but working with the same file should be finished under high-stress conditions. A molar tooth commonly has three or four root canals; so, during the retreatment of a molar tooth each file has to be used at least three times. For that reason, each file was used three or five times in this study.
The RMS values of all ProTaper retreatment and Mtwo retreatment instruments increased significantly with use count. Moreover, a fracture occurred during the fifth use of a Mtwo retreatment 15.05 file. A significant increase was not seen in the R1, R2, and R3 instruments of the R-endo system between three and five uses. These results showed that the surface deteriorations occured in the first three uses and then it slowed down. Inan et al. (2012) evaluated the cyclic fatigue resistance of ProTaper retreatment D3, R-endo R1, and Mtwo retreatment 25.05 instruments and it was reported that the R-endo R3 instruments were more resistant to fatigue failure than the ProTaper retreatment D3 and Mtwo 25.05 instruments.The SEM images showed that micro cracks and blunting of cutting edges occured after three uses of all instruments in all three systems. These deformations increased in the five-use groups. Moreover, the spiral distortions were observed after five uses caused by the embedding of the apical part of the file into guttapercha when rotation was resumed. Efficacy of 2% NaOCl solution, chloroform and sterilization process on the instrument surface were tested in this study because retreatment protocol includes irrigation, softening of filling material and sterilization of the instrument for multiple uses. Topuz et al. (2008) investigated the effect of sodium hypochlorite immersion on the surface of RaCe rotary nickel2titanium instruments using AFM and reported that deteriorations occured on the surface of RaCe instruments after the immersion in 5.25% NaOCl for 5 min. Additionally, in another AFM study, Ametrano et al. (2011) reported that 5.25% NaOCl caused surface alterations on the surface of the ProTaper instruments. ProTaper retreatment and R-endo instruments showed compatible results with previous studies. The RMS values of the Mtwo retreatment group showed increases without significant differences. This result could be caused by the concentration of the NaOCl, and 2% NaOCl was used in this study. According to the SEM examination, no changes were observed after immersion in 2% NaOCl compared with the control. A search of the literature revealed that there has been no study about the effects of solvent upon the retreatment instrument surface. Chloroform is an effective and widely used solvent for gutta-percha and preferred for this study. AFM results showed that chloroform has no effect on the instrument surface. The effects of multiple sterilization cycles on the instrument surface were demonstrated previously (Valois et al., 2008). It was reported that after 5 and 10 repeated autoclave cycles, RMS values increased significantly. In contrast to the previous study, no significant differences were observed in the present study. Valois et al. (2008) indicated that the number of autoclave cycles needed to cause surface alterations changed between different types of rotary NiTi files. This difference could be caused by using different files. CONCLUSIONS All three retreatment systems showed surface alterations after multiple uses. R-endo instruments demonstrated resistance to deformation after three uses. NaOCl solution caused deteriorations on the NiTi rotary instruments without visible defects. Chloroform Microscopy Research and Technique
SURFACE ALTERATIONS IN RETREATMENT FILES
and sterilization process did not affect the NiTi rotary instruments. AFM examination is a more detailed and sensitive method than SEM for examination of NiTi rotary instrument surfaces. Clinicians have to consider that retreatment files always have a tendency to break off after the third time they have been used. REFERENCES Ametrano G, D’Ant o V, Di Caprio MP, Simeone M, Rengo S, Spagnuolo G. 2011. Effects of sodium hypochlorite and ethylenediaminetetraacetic acid on rotary nickel-titanium instruments evaluated using atomic force microscopy. Int Endod J 44:203–209. Braga PC, Ricci D. 2004. Methods in molecular biology. New Jersey: Humana Press. 3 pp. Bramante CM, Betti LV. 2000. Efficacy of Quantec rotary instruments for gutta-percha removal. Int Endod J 33:463–467. Cavalleri G, Cantatore G, Costa A, Grillenzoni M, Comin Chiaramonti L, Gerosa R. 2009. The corrosive effects of sodium hypochlorite on nickel-titanium endodontic instruments: Assessment by digital scanning microscope. Minerva Stomatol 58:225– 231. Fenoul G, Meless GD, P erez F. 2010. The efficacy of R-Endo rotary NiTi and stainless-steel hand instruments to remove gutta-percha and Resilon. Int Endod J 43:135–141. Ferreira JJ, Rhodes JS, Ford TR. 2001. The efficacy of gutta-percha removal using ProFiles. Int Endod J 34:267–274. Friedman S, Rotstein I, Shar-Lev S. 1989. Bypassing gutta-percha root fillings with an automated device. J Endod 15:432–437. Forner L, Salmeron-S anchez M, Palomares M, Llena C, Amengual J. 2009. The use of atomic force microscopy in determining the stiffness and adhesion force of human dentin after exposure to bleaching agents. J Endod 35:1384–1386. Giuliani V, Cocchetti R, Pagavino G. 2008. Efficacy of ProTaper Universal retreatment files in removing filling materials during root canal retreatment. J Endod 34:1381–1384. Gu LS, Ling JQ, Wei X, Huang XY. 2008. Efficacy of ProTaper Universal rotary retreatment system for gutta-percha removal from root canals. Int Endod J 41:288–295. Hammad M, Qualtrough A, Silikas N. 2008. Three-dimensional evaluation of effectiveness of hand and rotary instrumentation for retreatment of canals filled with different materials. J Endod 34: 1370–1373. Hussne RP, Braga LC, Berbert FL, Buono VT, Bahia MG. 2011. Flexibility and torsional resistance of three nickel-titanium retreatment instrument systems. Int Endod J 44:731–738. H€ ulsmann M, Bluhm V. 2004. Efficacy, cleaning ability and safety of different rotary NiTi instruments in root canal retreatment. Int Endod J 37:468–476. Imura N, Kato AS, Hata GI, Uemura M, Toda T, Weine F. 2000. A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment. Int Endod J 33:361–366. Inan U, Gonulol N. 2009. Deformation and fracture of Mtwo rotary nickel-titanium instruments after clinical use. J Endod 35:1396– 1399.
Microscopy Research and Technique
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Inan U, Aydin C. 2012. Comparison of cyclic fatigue resistance of three different rotary nickel-titanium instruments designed for retreatment. J Endod 38:108–111. Inan U, Aydin C, Uzun O, Topuz O, Alacam T. 2007. Evaluation of the surface characteristics of used and new ProTaper Instruments: an atomic force microscopy study. J Endod 33:1334–1337. Masiero AV, Barletta FB. 2005. Effectiveness of different techniques for removing gutta-percha during retreatment. Int Endod J 38:2–7. Mollo A, Botti G, Prinicipi Goldoni N, Randellini E, Paragliola R, Chazine M, Ounsi HF, Grandini S. 2012. Efficacy of two Ni-Ti systems and hand files for removing gutta-percha from root canals. Int Endod J 45:1–6. Nair PN, Sjogren U, Krey G, Kahnberg KE, Sundqvist G. 1990. Intraradicular bacteria and fungi in root-filled, asymptomatichuman teeth with therapy-resistant periapical lesions: Along-term light and electron microscopic follow-up study. J Endod 16:580–588. Pirani C, Pelliccioni GA, Marchionni S, Montebugnoli L, Piana G, Prati C. 2009. Effectiveness of three different retreatment techniques in canals filled with compacted gutta-percha or Thermafil: A scanning electron microscope study. J Endod 35:1433–1440. Saad AY, Al-Hadlaq SM, Al-Katheeri NH. 2007. Efficacy of two rotary NiTi instruments in the removal of Gutta-Percha during root canal retreatment. J Endod 33:38–41. Schirrmeister JF, Wrbas KT, Schneider FH, Altenburger MJ, Hellwig E. 2006. Effectiveness of a hand file and three nickel-titanium rotary instruments for removing guttapercha in curved root canals during retreatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:542–547. Somma F, Cammarota G, Plotino G, Grande NM, Pameijer CH. 2008. The effectiveness of manual and mechanical instrumentation for the retreatment of three different root canal filling materials. J Endod 34:466–469. Stabholz A, Friedman S. 1988. Endodontic retreatment–case selection and technique. Part 2: Treatment planning for retreatment. J Endod 14:607–614. Topuz O, Aydin C, Uzun O, Inan U, Alacam T, Tunca YM. 2008. Structural effects of sodium hypochlorite solution on RaCe rotary nickeltitanium instruments: An atomic force microscopy study.Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105:661–665. Troian CH, S o MV, Figueiredo JA, Oliveira EP. 2006. Deformation and fracture of RaCe and K3 endodontic instruments according to the number of uses. Int Endod J 39:616–625. Unal GC, Kaya BU, Tac¸ AG, Kec¸eci AD. 2009. A comparison of the efficacy of conventional and new retreatment instruments to remove gutta-percha in curved root canals: An ex vivo study. Int Endod J 42:344–350. Valois CR, Silva LP, Azevedo RB. 2005. Effects of 2% chlorhexidine and 5.25% sodium hypochlorite on gutta-percha cones studied by atomic force microscopy. Int Endod J 38:425–429. Valois CR, Silva LP, Azevedo RB. 2008. Multiple autoclave cycles affect the surface of rotary nickel-titanium files: an atomic force microscopy study. J Endod 34:859–862. Vieira EP, Nakagawa RK, Buono VT, Bahia MG. 2009. Torsional behaviour of rotary NiTi ProTaper Universal instruments after multiple clinical use. Int Endod J. 42:947–953. Wilcox LR, Krell KV, Madison S, Rittman B. 1987. Endodontic retreatment: Evaluation of gutta-percha and sealer removal and canal reinstrumentation. J Endod 13:453–457.
