Introduction: Manufacturers offer gutta-percha (GP) cones matched with different sizes of endodontic files as an attempt to simplify the obturation process and create a tight seal in the canal. The purpose of this study was to evaluate whether intra-manufacture GP diameters matched the diameters of their corresponding files at different levels using laser micrometre. Methods and Materials: Twenty files and corresponding GP master cones of Reciproc R40 (40/0.06) (VDW, Munich, Germany), WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo 40/0.06 (VDW, Munich, Germany) were examined using laser micrometre (LSM 6000 by Mitutoyo, Japan) with accuracy of 1 nm to establish their actual diameter at D0, D1, D3 and D6. The data was analysed using the independent t-test. The differences were considered at 0.05. Results: The diameter of GP master cones was significantly larger than that of the corresponding files at all levels in all brands. ProTaper GP diameter was closest to the file diameter at D1 (GP=0.35, File=0.35 mm), and D3 (GP=0.48, File=0.49). Conclusion: Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip so as to appropriate the diameter from a smaller sized GP cone.Keywords: Diameter; Gutta-Percha; Root Canal; Rotary File; Size 

Mirmohammadi, Hesam

Shemesh, Hagay

Sitarz, Monika

English

Introduction: Manufacturers offer gutta-percha (GP) cones matched with different sizes of endodontic files as an attempt to simplify the obturation process and create a tight seal in the canal. The purpose of this study was to evaluate whether intra-manufacture GP diameters matched the diameters of their corresponding files at different levels using laser micrometre. Methods and Materials: Twenty files and corresponding GP master cones of Reciproc R40 (40/0.06) (VDW, Munich, Germany), WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo 40/0.06 (VDW, Munich, Germany) were examined using laser micrometre (LSM 6000 by Mitutoyo, Japan) with accuracy of 1 nm to establish their actual diameter at D0, D1, D3and D6. The data was analysed using the independent t-test. The differences were considered at 0.05. Results: The diameter of GP master cones was significantly larger than that of the corresponding files at all levels in all brands. ProTaper GP diameter was closest to the file diameter at D1 (GP=0.35, File=0.35 mm), and D3 (GP=0.48, File=0.49). Conclusion: Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip so as to appropriate the diameter from a smaller sized GP cone

Mirmohammadi, H.

Sitarz, M.

Shemesh, H.

VU Research Portal

Diameter variability of rotary files and their corresponding gutta-percha cones using laser scan micrometre

NARCIS 

Journals Portal, Shahid Beheshti University of Medical Sciences

 IEJ Iranian Endodontic Journal 2018;13(2): 159-162 Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometre Hesam Mirmohammadi a, b*, Monika Sitarz a, c, Hagay Shemesh a a Department of Cariology Endodontology Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, the Netherlands; b Department of Endodontics, Shahid Beheshti University of Medical Sciences, Tehran, Iran; c Department of Conservative Dentistry and Endodontics, Medical University of Lublin, Lublin, Poland ARTICLE INFO  ABSTRACT Article Type: Original Article  Introduction: Manufacturers offer gutta-percha (GP) cones matched with different sizes of endodontic files as an attempt to simplify the obturation process and create a tight seal in the canal. The purpose of this study was to evaluate whether intra-manufacture GP diameters matched the diameters of their corresponding files at different levels using laser micrometre. Methods and Materials: Twenty files and corresponding GP master cones of Reciproc R40 (40/0.06) (VDW, Munich, Germany), WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo 40/0.06 (VDW, Munich, Germany) were examined using laser micrometre (LSM 6000 by Mitutoyo, Japan) with accuracy of 1 nm to establish their actual diameter at D0, D1, D3 and D6. The data was analysed using the independent t-test. The differences were considered at 0.05. Results: The diameter of GP master cones was significantly larger than that of the corresponding files at all levels in all brands. ProTaper GP diameter was closest to the file diameter at D1 (GP=0.35, File=0.35 mm), and D3 (GP=0.48, File=0.49). Conclusion: Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip so as to appropriate the diameter from a smaller sized GP cone. Keywords: Diameter; Gutta-Percha; Root Canal; Rotary File; Size  Received: 20 Sep 2017 Revised: 04 Jan 2018 Accepted: 17 Jan 2018 Doi: 10.22037/iej.v13i2.14710  *Corresponding author: Hesam Mirmohammadi, ACTA, Department of Cariology Endodontology Pedodontology, Gustav Mahlerlaan 3004 1081 LA Amsterdam, the Netherlands. Tel: +31-020 5980770 E-mail: hmirmoha@acta.nl           Introduction uccessful endodontic treatment is based on correct diagnosis, canal debridement and disinfection, obturation and coronal restoration [1]. Good sealing reduces coronal leakage and bacterial contamination, stops influx of periapical tissue fluids and entombs the remaining irritants and surviving bacteria in the canal [2-6]. The most common method to fill the prepared canal space is the obturation of the root canal system (RCS) with gutta-percha (GP) and sealer [7, 8]. Nickel-titanium rotary files were introduced to endodontics more than two decades ago [9]. These files usually have greater tapers than hand instruments [10]. Nowadays, manufactures offer a plethora of nickel-titanium rotary systems classified by different features (e.g. tip-design, cross-section, cutting edge, tapers, diameter, composition, movement). The preferred filling method is the subject of much debate and research. The single cone technique attracted the attention of many investigators owing to its speed and effectiveness [11]. Although a perfect match between instrumented canal and GP cone is impossible, if the size and taper of the master cone differs significantly from the prepared area by the master file, insufficient obturation may result. Ideally, GP cones should closely match the diameter and taper of the last instrument used to the working length [12].  Previous studies reported variability in actual sizes of GP [13] and files [10, 14] amongst different endodontic systems. Chesler et al. [15] evaluated the diameter and taper of rotary instruments and their corresponding GP cones within the same manufacturer using scanning electron microscopy (SEM). They observed significant S IEJ Iranian Endodontic Journal 2018;13(2): 159-162 160 Mirmohammadi et al. differences between the file and the corresponding GP cone regarding to tapers and diameters. However, the use of SEM to evaluate the dimensional change, especially for a thermoplastic material like GP, had its drawbacks. These problems are due to the special thermal and pressure conditions in the SEM chamber that could influence the dimension of GP cones. A laser-scan micrometer (LSM) system was previously used to measure the diameter changes of different dental materials [16-19]. The device displayed the specimen dimensional data rapidly and accurately. It used a highly directional parallel-scanning laser beam. LSM was a non-destructive, non-contact measuring system, which combined high rate scanning with a highly accurate measurement (0.00001 mm) [20]. A laser beam was directed at a polygonal mirror rotating at high speed in exact synchronism with highly stable pulses from the system clock. The reflected beam was rotating clockwise as it swept across the input surface of a collimating lens. However, as the beam moved or scanned downwards, it changed its direction to be always horizontal after the lens’ exit surface. This horizontal beam entered the measuring space and, with no work piece present, and via a condensing lens reached a receiver to produce an output signal. When a simple work piece (a GP cone, for example) was put into the measuring space, the beam would be interrupted for a time during its sweep. This time, as indicated by clock pulses when the receiver signal was absent, was proportional to the work piece dimension in the downward direction [21]. To date, there have been no published papers comparing diameters of nickel-titanium rotary files with their matching GP cones using LSM as a non-destructive method. The aim of this study was to evaluate the diameter of four brands of rotary files and their adjusting GP cones by means of LSM. Materials and Methods The following rotary files and their corresponding GP cones were investigated: Reciproc R40 (40/0.06) (VDW, Munich, Germany) WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo (40/0.06) (VDW, Munich, Germany). Based on pilot data and a power analysis, it was determined that 20 specimens from each brand would meet the constraints of α=0.05 and power=0.80. After receiving the materials, they were conditioned at 23±2°C at 50±5% humidity. Specimens were randomly assigned a number, from 1 to 160, in order to keep the operator blind during the measurement process. Specimens were mounted on a special jig using prepared impressions of composite (Z250, 3MSPE, Germany). Jig was settled on a travel crossed roller table connected to a micrometre (Mitutoyo, Japan) with an accuracy of 0.1 µm perpendicular to the scanning laser beam of a laser scan micrometre (LSM 6000, Mitutoyo, Japan) in order to obtain accurate reproducible results (Figure 1). Diameters (D) were measured at four levels, 0 mm, 1 mm, 3 mm and 6 mm from the tip of the files or cones. D0 level was established as a first reading achieved by LSM, where the specimens touched the laser beam. Consequently, specimens were moved manually using micrometre ruler for further measurements (Figure 1). All the measurements were performed at room temperature 23±2 °C and normal humidity (50±5%).  Statistical analysis  Shapiro-Wilk normality test revealed that data was normally distributed. The comparisons between files and GP cones diameters were analysed with the independent t-test using SPSS/PC version 17 (SPSS Inc., Chicago, IL. US). The differences were considered as significant for P<0.05 and highly significant for P<0.01.  Results The diameters of GP cones were significantly larger than the diameters of corresponding files at all levels for all brands (Table 1). For each tested brand, the independent t-test revealed highly significant differences (P<0.0001) between GP cone diameter and corresponding file at all measurement levels. The intra-manufacture mean differences for diameter at D1 were 0.17±0.04, 0.003±0.01, 0.1±0.003, 0.17±0.005 for Mtwo, ProTaper, WaveOne, and Reciproc respectively. WaveOne  Table 1. Diameter measurements of 4 endodontic rotary systems at 4 different levels: 0, 1, 3, and 6 mm Diameter 0 mm 1 mm 3 mm 6 mm File/GP size File (SD) GP (SD)* File (SD)  GP (SD)* File (SD) GP (SD)* File (SD) GP (SD)* Mtwo  0.094 (0.03) 0.286 (0.013) 0.34 (0.073) 0.502 (0.031) 0.47 (0.096) 0.605 (0.03) 0.624 (0,117) 0.79 (0.029) ProTaper X 0.125 (0.016) 0.187 (0.011) 0.349 (0.008) 0.353 (0.022) 0.477 (0.014) 0.488 (0.03) 0.615 (0.018) 0.67 (0.038) WaveOne X 0.093 (0.004) 0.256 (0.009) 0.4 (0.024) 0.498 (0.021) 0.539 (0.02) 0.608 (0.031) 0.665 (0,017) 0.76 (0.037) Reciproc  0.095 (0.003) 0.239 (0.012) 0.304 (0.026) 0.475 (0.021) 0.475 (0.028) 0.563 (0.022) 0.633 (0.062) 0.687 (0.023) X: Variable taper with no manufacture data;  *: The intra-manufacture diameters of GP cones were significantly larger than the corresponding files (P<0.0001)  IEJ Iranian Endodontic Journal 2018;13(2): 159-162 161 Variability between nickel-titanium rotary file and GP cone   Figure 1. Travel crossed roller table connected to a micrometre perpendicular to the scanning laser beam of a laser scan micrometer. D0 level was established as a first reading achieved by LSM, where the specimens touched the laser beam; consequently, specimens were moved manually using micrometre ruler for further measurements Large revealed the best match with the manufacture claimed size at D1 (40±0.02). Despite a significant difference between GP cones’ diameters and their corresponding files, ProTaper F3 showed a better match considering the measurements at different levels: D1, D3 and D6. Discussion Previous studies of dimensional variability of GP cones and files used either a measuring microscope, according to the protocol outlined in ANSI/ADA Specifications No. 78, [13, 14] or an SEM according to ANSI/ADA Specifications No. 101. This is the first investigation using LSM to study the diameter variability of rotary systems. LSM could be used under controlled environmental conditions such as temperature, humidity and pressure. GP cones are partially crystalline viscoelastic polymeric materials and thus, an environmental change may cause a dimensional variation. Hence, the use of SEM could bring flaws into the accuracy of the data, as cones should be saturated and later placed in SEM chamber under a high pressure [22]. In the current study, the diameter could be measured at 0 mm level using LSM. In a recent article, Chesler et al. [15] was unable to measure the diameter at the tip of the files or GP cones under SEM and therefore they provided the data from the D1. Two studies reported data for D0 using measuring microscope, which met the ANSI/ADA specifications (Figure 2), although it was not the diameter at the tip [9, 10]. Considering the data from the current study, the manufactures’ provided size would actually corresponded to D1 and not D0.  Figure 2. Diagram representation of the tapered sized cones and measurement sites for diameter (D0) (Adapted from ANSI/ADA specification No. 78) It may not be of clinical importance but could need rethinking on definition of D0, especially for the manufactures’ reported specifications. Previous studies investigated the taper of the files, and found that the most examined files had taper measurement smaller than the nominal taper. However, in the current study, tapering of the specimens was not reported, as ProTaper and WaveOne had a variable taper with no clear industry standard. In this study, at each level, GP cones were always larger than the corresponding file in diameter, which is in agreement with the study by Chesler et al. [15]. Although such findings might not be a significant problem for a skilled endodontist, an inexperienced clinician may find it frustrating and time consuming. This is especially true as larger fitting master cones - in comparison with the master file - would result in premature binding or poor adaptability of GP to the canal walls, and consequently shorter fillings. Since the length of the root canal filling is an outcome predictor for endodontic treatments [1, 23], the importance of a well-fitted master cone is obvious.  The diameter variability of GP cones may be caused by the high plasticity of GP [21-25]. Despite standard procedures throughout manufacturing and packing, mechanical deformation can also occur. Likewise, during transportation and storage due to temperature extremes, shrinkage and/or expansion can result. GP master cones are better kept refrigerated; however, there seems to be a lack of information on the influence of environmental changes such as temperature on GP cones [25]. Variability between nickel-titanium rotary files and GP cone sizes exists within tested manufacturers’ systems. Clinicians  IEJ Iranian Endodontic Journal 2018;13(2): 159-162 162 Mirmohammadi et al. should respect individual root canal anatomy and choose a master cone based on the clinical result of the instrumentation, not on the advertised size. Practitioners are advised to check the Master GP cone fit using radiographs. In case of a mismatch, they can use a smaller size tip diameter and a GP gauge to cut the tip to the needed diameter. Conclusion Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip in order to appropriate the diameter from a smaller-sized GP cone. Conflict of Interest: ‘None declared’. References 1. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature-Part 2. Influence of clinical factors. Int Endod J. 2008;41(1):6-31. 2. Schilder H. Filling root canals in three dimensions. Dent Clin North Am. 1967:723-44. 3. Kerekes K, Tronstad L. Long-term results of endodontic treatment performed with a standardized technique. J Endod. 1979;5(3):83-90. 4. Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod. 1990;16(10):498-504. 5. Sjogren U, Figdor D, Persson S, Sundqvist G. Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis. Int Endod J. 1997;30(5):297-306. 6. Nair PN. On the causes of persistent apical periodontitis: a review. Int Endod J. 2006;39(4):249-81. 7. Godiny M, Hatam R, Khavid A, Khanlari S. Apical Microleakage in Root Canals Containing Broken Rotary Instruments. Iran Endod J. 2017;12(3):360-5. 8. Mozayeni MA, Dianat O, Tahvildari S, Mozayani M, Paymanpour P. Subcutaneous Reaction of Rat Tissues to Nanosilver Coated Gutta-Percha. Iran Endod J. 2017;12(2):157-61. 9. Ng FK, Messer LB. Mineral trioxide aggregate as a pulpotomy medicament: a narrative review. Eur Arch Paediatr Dent. 2008;9(1):4-11. 10. Hatch GW, Roberts S, Joyce AP, Runner R, McPherson JC, 3rd. Comparative study of the variability of 0.06 tapered rotary endodontic files to current taper standards. J Endod. 2008;34(4):463-5. 11. Sadr S, Golmoradizadeh A, Raoof M, Tabanfar MJ. Microleakage of Single-Cone Gutta-Percha Obturation Technique in Combination with Different Types of Sealers. Iran Endod J. 2015;10(3):199-203. 12. Schulte A, Pieper K, Charalabidou O, Stoll R, Stachniss V. Prevalence and quality of root canal fillings in a German adult population. A survey of orthopantomograms taken in 1983 and 1992. Clin Oral Investig. 1998;2(2):67-72. 13. Cunningham KP, Walker MP, Kulild JC, Lask JT. Variability of the diameter and taper of size #30, 0.04 gutta-percha cones. J Endod. 2006;32(11):1081-4. 14. Lask JT, Walker MP, Kulild JC, Cunningham KP, Shull PA. Variability of the diameter and taper of size #30, 0.04 nickel-titanium rotary files. J Endod. 2006;32(12):1171-3. 15. Chesler MB, Tordik PA, Imamura GM, Goodell GG. Intramanufacturer diameter and taper variability of rotary instruments and their corresponding Gutta-percha cones. J Endod. 2013;39(4):538-41. 16. Martin N, Jedynakiewicz N. Measurement of water sorption in dental composites. Biomaterials. 1998;19(1-3):77-83. 17. Jedynakiewicz NM, Martin N. Expansion behaviour of compomer restoratives. Biomaterials. 2001;22(7):743-8. 18. Martin N, Jedynakiewicz NM, Fisher AC. Hygroscopic expansion and solubility of composite restoratives. Dent Mater. 2003;19(2):77-86. 19. Alrahlah A, Silikas N, Watts DC. Hygroscopic expansion kinetics of dental resin-composites. Dent Mater. 2014;30(2):143-8. 20. Fano V, Ma WY, Ortalli I, Pozela K. Study of dental materials by laser beam scanning. Biomaterials. 1998;19(16):1541-5. 21. Wei YJ, Silikas N, Zhang ZT, Watts DC. Hygroscopic dimensional changes of self-adhering and new resin-matrix composites during water sorption/desorption cycles. Dent Mater. 2011;27(3):259-66. 22. Zaslansky P, Fratzl P, Rack A, Wu MK, Wesselink PR, Shemesh H. Identification of root filling interfaces by microscopy and tomography methods. Int Endod J. 2011;44(5):395-401. 23. Abdel-Fatah OM, Hassan MM, Elshafei AM, Haroun BM, Atta HM, Othman AM. Physiological studies on carboxymethyl cellulase formation by Aspergillus terreus DSM 826. Braz J Microbiol. 2012;43(1):1-11. 24. Johansson BI. A methodological study of the mechanical properties of endodontic gutta-percha points. J Endod. 1980;6(10):781-3. 25. Moon HJ, Lee JH, Ahn JH, Song HJ, Park YJ. Temperature-dependent rheological property changes of thermoplastic gutta-percha root filling materials. Int Endod J. 2015;48(6):556-63.   Please cite this paper as: Mirmohammadi H, Sitarz M, Shemesh H. Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometer. Iran Endod J. 2018;13(2):159-62. Doi: 10.22037/iej.v13i2.14710.  

Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometre

International Migration, Integration and Social Cohesion online publications

UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)UvA-DARE (Digital Academic Repository)Diameter variability of rotary files and their corresponding gutta-percha conesusing laser scan micrometreMirmohammadi, H.; Sitarz, M.; Shemesh, H.DOI10.22037/iej.v13i2.14710Publication date2018Document VersionFinal published versionPublished inIranian Endodontic JournalLicenseCC BY-NC-SALink to publicationCitation for published version (APA):Mirmohammadi, H., Sitarz, M., & Shemesh, H. (2018). Diameter variability of rotary files andtheir corresponding gutta-percha cones using laser scan micrometre. Iranian EndodonticJournal, 13(2), 159-162. https://doi.org/10.22037/iej.v13i2.14710General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s)and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an opencontent license (like Creative Commons).Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, pleaselet the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the materialinaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letterto: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. Youwill be contacted as soon as possible.Download date:09 Mar 2023 IEJ Iranian Endodontic Journal 2018;13(2): 159-162 Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometre Hesam Mirmohammadi a, b*, Monika Sitarz a, c, Hagay Shemesh a a Department of Cariology Endodontology Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, the Netherlands; b Department of Endodontics, Shahid Beheshti University of Medical Sciences, Tehran, Iran; c Department of Conservative Dentistry and Endodontics, Medical University of Lublin, Lublin, Poland ARTICLE INFO  ABSTRACT Article Type: Original Article  Introduction: Manufacturers offer gutta-percha (GP) cones matched with different sizes of endodontic files as an attempt to simplify the obturation process and create a tight seal in the canal. The purpose of this study was to evaluate whether intra-manufacture GP diameters matched the diameters of their corresponding files at different levels using laser micrometre. Methods and Materials: Twenty files and corresponding GP master cones of Reciproc R40 (40/0.06) (VDW, Munich, Germany), WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo 40/0.06 (VDW, Munich, Germany) were examined using laser micrometre (LSM 6000 by Mitutoyo, Japan) with accuracy of 1 nm to establish their actual diameter at D0, D1, D3 and D6. The data was analysed using the independent t-test. The differences were considered at 0.05. Results: The diameter of GP master cones was significantly larger than that of the corresponding files at all levels in all brands. ProTaper GP diameter was closest to the file diameter at D1 (GP=0.35, File=0.35 mm), and D3 (GP=0.48, File=0.49). Conclusion: Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip so as to appropriate the diameter from a smaller sized GP cone. Keywords: Diameter; Gutta-Percha; Root Canal; Rotary File; Size  Received: 20 Sep 2017 Revised: 04 Jan 2018 Accepted: 17 Jan 2018 Doi: 10.22037/iej.v13i2.14710  *Corresponding author: Hesam Mirmohammadi, ACTA, Department of Cariology Endodontology Pedodontology, Gustav Mahlerlaan 3004 1081 LA Amsterdam, the Netherlands. Tel: +31-020 5980770 E-mail: hmirmoha@acta.nl           Introduction uccessful endodontic treatment is based on correct diagnosis, canal debridement and disinfection, obturation and coronal restoration [1]. Good sealing reduces coronal leakage and bacterial contamination, stops influx of periapical tissue fluids and entombs the remaining irritants and surviving bacteria in the canal [2-6]. The most common method to fill the prepared canal space is the obturation of the root canal system (RCS) with gutta-percha (GP) and sealer [7, 8]. Nickel-titanium rotary files were introduced to endodontics more than two decades ago [9]. These files usually have greater tapers than hand instruments [10]. Nowadays, manufactures offer a plethora of nickel-titanium rotary systems classified by different features (e.g. tip-design, cross-section, cutting edge, tapers, diameter, composition, movement). The preferred filling method is the subject of much debate and research. The single cone technique attracted the attention of many investigators owing to its speed and effectiveness [11]. Although a perfect match between instrumented canal and GP cone is impossible, if the size and taper of the master cone differs significantly from the prepared area by the master file, insufficient obturation may result. Ideally, GP cones should closely match the diameter and taper of the last instrument used to the working length [12].  Previous studies reported variability in actual sizes of GP [13] and files [10, 14] amongst different endodontic systems. Chesler et al. [15] evaluated the diameter and taper of rotary instruments and their corresponding GP cones within the same manufacturer using scanning electron microscopy (SEM). They observed significant S IEJ Iranian Endodontic Journal 2018;13(2): 159-162 160 Mirmohammadi et al. differences between the file and the corresponding GP cone regarding to tapers and diameters. However, the use of SEM to evaluate the dimensional change, especially for a thermoplastic material like GP, had its drawbacks. These problems are due to the special thermal and pressure conditions in the SEM chamber that could influence the dimension of GP cones. A laser-scan micrometer (LSM) system was previously used to measure the diameter changes of different dental materials [16-19]. The device displayed the specimen dimensional data rapidly and accurately. It used a highly directional parallel-scanning laser beam. LSM was a non-destructive, non-contact measuring system, which combined high rate scanning with a highly accurate measurement (0.00001 mm) [20]. A laser beam was directed at a polygonal mirror rotating at high speed in exact synchronism with highly stable pulses from the system clock. The reflected beam was rotating clockwise as it swept across the input surface of a collimating lens. However, as the beam moved or scanned downwards, it changed its direction to be always horizontal after the lens’ exit surface. This horizontal beam entered the measuring space and, with no work piece present, and via a condensing lens reached a receiver to produce an output signal. When a simple work piece (a GP cone, for example) was put into the measuring space, the beam would be interrupted for a time during its sweep. This time, as indicated by clock pulses when the receiver signal was absent, was proportional to the work piece dimension in the downward direction [21]. To date, there have been no published papers comparing diameters of nickel-titanium rotary files with their matching GP cones using LSM as a non-destructive method. The aim of this study was to evaluate the diameter of four brands of rotary files and their adjusting GP cones by means of LSM. Materials and Methods The following rotary files and their corresponding GP cones were investigated: Reciproc R40 (40/0.06) (VDW, Munich, Germany) WaveOne Large (40/0.08) (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper F3 (30/0.09) (Dentsply Maillefer, Ballaigues, Switzerland), and Mtwo (40/0.06) (VDW, Munich, Germany). Based on pilot data and a power analysis, it was determined that 20 specimens from each brand would meet the constraints of α=0.05 and power=0.80. After receiving the materials, they were conditioned at 23±2°C at 50±5% humidity. Specimens were randomly assigned a number, from 1 to 160, in order to keep the operator blind during the measurement process. Specimens were mounted on a special jig using prepared impressions of composite (Z250, 3MSPE, Germany). Jig was settled on a travel crossed roller table connected to a micrometre (Mitutoyo, Japan) with an accuracy of 0.1 µm perpendicular to the scanning laser beam of a laser scan micrometre (LSM 6000, Mitutoyo, Japan) in order to obtain accurate reproducible results (Figure 1). Diameters (D) were measured at four levels, 0 mm, 1 mm, 3 mm and 6 mm from the tip of the files or cones. D0 level was established as a first reading achieved by LSM, where the specimens touched the laser beam. Consequently, specimens were moved manually using micrometre ruler for further measurements (Figure 1). All the measurements were performed at room temperature 23±2 °C and normal humidity (50±5%).  Statistical analysis  Shapiro-Wilk normality test revealed that data was normally distributed. The comparisons between files and GP cones diameters were analysed with the independent t-test using SPSS/PC version 17 (SPSS Inc., Chicago, IL. US). The differences were considered as significant for P<0.05 and highly significant for P<0.01.  Results The diameters of GP cones were significantly larger than the diameters of corresponding files at all levels for all brands (Table 1). For each tested brand, the independent t-test revealed highly significant differences (P<0.0001) between GP cone diameter and corresponding file at all measurement levels. The intra-manufacture mean differences for diameter at D1 were 0.17±0.04, 0.003±0.01, 0.1±0.003, 0.17±0.005 for Mtwo, ProTaper, WaveOne, and Reciproc respectively. WaveOne  Table 1. Diameter measurements of 4 endodontic rotary systems at 4 different levels: 0, 1, 3, and 6 mm Diameter 0 mm 1 mm 3 mm 6 mm File/GP size File (SD) GP (SD)* File (SD)  GP (SD)* File (SD) GP (SD)* File (SD) GP (SD)* Mtwo  0.094 (0.03) 0.286 (0.013) 0.34 (0.073) 0.502 (0.031) 0.47 (0.096) 0.605 (0.03) 0.624 (0,117) 0.79 (0.029) ProTaper X 0.125 (0.016) 0.187 (0.011) 0.349 (0.008) 0.353 (0.022) 0.477 (0.014) 0.488 (0.03) 0.615 (0.018) 0.67 (0.038) WaveOne X 0.093 (0.004) 0.256 (0.009) 0.4 (0.024) 0.498 (0.021) 0.539 (0.02) 0.608 (0.031) 0.665 (0,017) 0.76 (0.037) Reciproc  0.095 (0.003) 0.239 (0.012) 0.304 (0.026) 0.475 (0.021) 0.475 (0.028) 0.563 (0.022) 0.633 (0.062) 0.687 (0.023) X: Variable taper with no manufacture data;  *: The intra-manufacture diameters of GP cones were significantly larger than the corresponding files (P<0.0001)  IEJ Iranian Endodontic Journal 2018;13(2): 159-162 161 Variability between nickel-titanium rotary file and GP cone   Figure 1. Travel crossed roller table connected to a micrometre perpendicular to the scanning laser beam of a laser scan micrometer. D0 level was established as a first reading achieved by LSM, where the specimens touched the laser beam; consequently, specimens were moved manually using micrometre ruler for further measurements Large revealed the best match with the manufacture claimed size at D1 (40±0.02). Despite a significant difference between GP cones’ diameters and their corresponding files, ProTaper F3 showed a better match considering the measurements at different levels: D1, D3 and D6. Discussion Previous studies of dimensional variability of GP cones and files used either a measuring microscope, according to the protocol outlined in ANSI/ADA Specifications No. 78, [13, 14] or an SEM according to ANSI/ADA Specifications No. 101. This is the first investigation using LSM to study the diameter variability of rotary systems. LSM could be used under controlled environmental conditions such as temperature, humidity and pressure. GP cones are partially crystalline viscoelastic polymeric materials and thus, an environmental change may cause a dimensional variation. Hence, the use of SEM could bring flaws into the accuracy of the data, as cones should be saturated and later placed in SEM chamber under a high pressure [22]. In the current study, the diameter could be measured at 0 mm level using LSM. In a recent article, Chesler et al. [15] was unable to measure the diameter at the tip of the files or GP cones under SEM and therefore they provided the data from the D1. Two studies reported data for D0 using measuring microscope, which met the ANSI/ADA specifications (Figure 2), although it was not the diameter at the tip [9, 10]. Considering the data from the current study, the manufactures’ provided size would actually corresponded to D1 and not D0.  Figure 2. Diagram representation of the tapered sized cones and measurement sites for diameter (D0) (Adapted from ANSI/ADA specification No. 78) It may not be of clinical importance but could need rethinking on definition of D0, especially for the manufactures’ reported specifications. Previous studies investigated the taper of the files, and found that the most examined files had taper measurement smaller than the nominal taper. However, in the current study, tapering of the specimens was not reported, as ProTaper and WaveOne had a variable taper with no clear industry standard. In this study, at each level, GP cones were always larger than the corresponding file in diameter, which is in agreement with the study by Chesler et al. [15]. Although such findings might not be a significant problem for a skilled endodontist, an inexperienced clinician may find it frustrating and time consuming. This is especially true as larger fitting master cones - in comparison with the master file - would result in premature binding or poor adaptability of GP to the canal walls, and consequently shorter fillings. Since the length of the root canal filling is an outcome predictor for endodontic treatments [1, 23], the importance of a well-fitted master cone is obvious.  The diameter variability of GP cones may be caused by the high plasticity of GP [21-25]. Despite standard procedures throughout manufacturing and packing, mechanical deformation can also occur. Likewise, during transportation and storage due to temperature extremes, shrinkage and/or expansion can result. GP master cones are better kept refrigerated; however, there seems to be a lack of information on the influence of environmental changes such as temperature on GP cones [25]. Variability between nickel-titanium rotary files and GP cone sizes exists within tested manufacturers’ systems. Clinicians  IEJ Iranian Endodontic Journal 2018;13(2): 159-162 162 Mirmohammadi et al. should respect individual root canal anatomy and choose a master cone based on the clinical result of the instrumentation, not on the advertised size. Practitioners are advised to check the Master GP cone fit using radiographs. In case of a mismatch, they can use a smaller size tip diameter and a GP gauge to cut the tip to the needed diameter. Conclusion Within the same manufacturer, GP cone diameters do not match the diameters of their corresponding files. Clinicians are advised to use a GP gauge to cut the tip in order to appropriate the diameter from a smaller-sized GP cone. Conflict of Interest: ‘None declared’. References 1. Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature-Part 2. Influence of clinical factors. Int Endod J. 2008;41(1):6-31. 2. Schilder H. Filling root canals in three dimensions. 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Hygroscopic dimensional changes of self-adhering and new resin-matrix composites during water sorption/desorption cycles. Dent Mater. 2011;27(3):259-66. 22. Zaslansky P, Fratzl P, Rack A, Wu MK, Wesselink PR, Shemesh H. Identification of root filling interfaces by microscopy and tomography methods. Int Endod J. 2011;44(5):395-401. 23. Abdel-Fatah OM, Hassan MM, Elshafei AM, Haroun BM, Atta HM, Othman AM. Physiological studies on carboxymethyl cellulase formation by Aspergillus terreus DSM 826. Braz J Microbiol. 2012;43(1):1-11. 24. Johansson BI. A methodological study of the mechanical properties of endodontic gutta-percha points. J Endod. 1980;6(10):781-3. 25. Moon HJ, Lee JH, Ahn JH, Song HJ, Park YJ. Temperature-dependent rheological property changes of thermoplastic gutta-percha root filling materials. Int Endod J. 2015;48(6):556-63.   Please cite this paper as: Mirmohammadi H, Sitarz M, Shemesh H. Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometer. Iran Endod J. 2018;13(2):159-62. Doi: 10.22037/iej.v13i2.14710.  

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Diameter Variability of Rotary Files and Their Corresponding Gutta-Percha Cones Using Laser Scan Micrometre

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