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ORIGINAL RESEARCH ARTICLE  
Year : 2016  |  Volume : 19  |  Issue : 5  |  Page : 434-439
A comparative evaluation of the increase in root canal surface area and canal transportation in curved root canals by three rotary systems: A cone-beam computed tomographic study


Department of Conservative Dentistry and Endodontics, Vishnu Dental College, West Godavari, Andhra Pradesh, India

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Date of Submission04-May-2016
Date of Decision16-Jul-2016
Date of Acceptance22-Aug-2016
Date of Web Publication7-Sep-2016
 

   Abstract 


Aim: The aim of this study was to measure the increase in root canal surface area and canal transportation after biomechanical preparation at 1, 3, and 5 mm short of the apex with three different rotary systems in both continuous rotary and reciprocating rotary motions.
Materials and Methods: Sixty freshly extracted human mandibular molars with mesial root canal curvatures between 20° and 30° were included in the study. Teeth were randomly distributed into three groups (n = 20). Biomechanical preparations were done in all the mesial canals. In Group 1, instrumentation was done with ProTaper universal rotary files, Group 2, with K3XF rotary files, and Group 3, with LSX rotary files. Each group was further subdivided into subgroups A and B (n = 10) where instrumentation was done by continuous rotary and reciprocating rotary techniques, respectively. Increase in root canal surface area and canal transportation was measured using the preoperative and postoperative cone-beam computed tomography scans.
Statistical Analysis : The data were analyzed by one-way ANOVA followed by Tukey pairwise multiple comparison tests.
Results: Increase in root canal surface area was significantly more (P < 0.05) in ProTaper and K3XF groups when compared to LSX group. Canal transportation was significantly more (P < 0.05) in ProTaper group when compared to K3XF and LSX groups. There was no significant difference (P > 0.05) in increase of root canal surface area and canal transportation between continuous rotary and reciprocating rotary techniques for ProTaper Universal, K3XF and LSX groups.
Conclusion: LSX rotary system showed minimal increase of root canal surface area and minimal canal transportation when compared to ProTaper and K3XF rotary systems.

Keywords: Canal transportation; cone-beam computed tomography; Ni-Ti; root canal surface area

How to cite this article:
Prasanthi NN, Rambabu T, Sajjan GS, Varma K M, Satish R K, Padmaja M. A comparative evaluation of the increase in root canal surface area and canal transportation in curved root canals by three rotary systems: A cone-beam computed tomographic study. J Conserv Dent 2016;19:434-9

How to cite this URL:
Prasanthi NN, Rambabu T, Sajjan GS, Varma K M, Satish R K, Padmaja M. A comparative evaluation of the increase in root canal surface area and canal transportation in curved root canals by three rotary systems: A cone-beam computed tomographic study. J Conserv Dent [serial online] 2016 [cited 2022 Aug 13];19:434-9. Available from: https://www.jcd.org.in/text.asp?2016/19/5/434/190003



   Introduction Top


The main drawback with the traditional stainless steel files is their inability to follow the canal curvature with a tendency to straighten, particularly at the start of the curvature.[1],[2]

Ni-Ti instruments introduced in 1988 to endodontics showed super-elasticity and shape memory.[3] The main problems with instruments used in continuous rotary motion are the instrument separation caused by cyclic fatigue and inability of the instrument to maintain canal curvature. An alternative for continuous rotary is a reciprocating rotary instrument that travels shorter angular distance in one direction and reverses its direction before completing a full rotation, thereby subjecting the instrument to lower stress values. As a result, an instrument has an extended fatigue life when used in reciprocation as opposed to rotary motion.[4],[5],[6],[7],[8]

Cone beam computed tomography (CBCT) is a recent advancement with advantages of image accuracy, acquisition of images in three planes (coronal, sagittal and axial) and reduced image artifacts.[9],[10],[11]

The ProTaper rotary system has an active file design without radial lands. The K3XF system has an active file design with radial lands. The LightSpeed system has a passive file design with radial lands. These rotary systems were selected because of their versatility in designs.

The null hypothesis tested was that increase in root canal surface area and canal transportation may not vary between rotary systems with different designs in either continuous rotary or reciprocating rotary motions.


   Materials and Methods Top


Sixty freshly extracted human mandibular molars from patients of age group 40 to 50 years with fully formed apices, absence of root caries, cracks, and structural defects with mesial root canal curvatures in distal direction between 20° and 30° (Schneider's method) and those with initial minimum working width of 0.1mm were selected for analysis so that apical enlargement can be done uniformly to the same size in all the teeth. Teeth with minimum working width of >0.15 mm were excluded from the study. Modeling wax was manipulated and adapted into a stock tray. Into each wax mounting, the radicular portions of five teeth were embedded, leaving the crowns oriented upward so that they are accessible for the endodontic procedure.

Cone-beam computed tomography scanning procedure

Pre- and post-instrumentation scans were performed using CBCT (Kodak 9000, Kodak Carestream Health, Trophy, France) and all the scans were conducted with a 4 cm field of view, at 0.125 mm voxel resolution with 60 kV and 2.5 mA.

Endodontic procedure

After preoperative scanning, access cavities were prepared and working length (WL) was established 0.5 mm short of the apex. Teeth were randomly divided into three groups (n = 20). Glide path was established with #10K-file in all the samples. Manual instrumentation was not done prior to the use of mechanical instrumentation as the purpose of this study was to measure the canal transportation with different rotary systems. Recapitulation was done with one size smaller hand K-file corresponding to the rotary file.

Irrigation protocol

During instrumentation, 17% ethylenediaminetetraacetic acid (Prime Dental Products Pvt. Ltd., India) was used as a lubricant and, after every instrumentation, irrigation was done with 2 ml of 3% NaOCl (Prime Dental Products Pvt Ltd, India) in all groups.

Biomechanical preparation

Instrumentation was started with SX file upto half of the working length (WL) and proceeded with S1 file upto two thirds the working length, and S2 file to the complete WL. The SX and S1 instruments were used at 300 rpm and 3 Ncm torque, followed by instruments S2, F1, and F2 upto the working length, at 250 rpm and 2 Ncm torque, avoiding apical pressure and applying gentle strokes against the canal walls.

  1. Group 1: ProTaper group, 20 teeth were made into two subgroups (n = 10)

    • Subgroup A: Instrumentation of mesial canals was done by continuous rotary technique with ProTaper Universal rotary files (Dentsply Maillefer, Ballaigues, Switzerland) connected to X-Smart endomotor (Dentsply Maillefer, Switzerland) according to the manufacturer's instructions
    • Subgroup B: Instrumentation was done by reciprocating rotary technique with ProTaper rotary files connected to Waveone endomotor (Dentsply Maillefer, Switzerland) according to the manufacturer's instructions following the same irrigation protocol as in subgroup A.


  2. Group 2: K3XF group, 20 teeth were made into two subgroups (n = 10)

    • Subgroup A: Instrumentation was done by continuous rotary technique with K3XF rotary files (SybronEndo, Glendora, CA, USA) connected to X-Smart endomotor according to the manufacturer's instructions up to ISO size 25 and 06% taper
    • Subgroup B: Instrumentation was done by reciprocating rotary technique with K3XF rotary files connected to Waveone endomotor following the manufacturer's instructions up to ISO size 25 and 06% taper.


  3. Group 3: LSX group, 20 teeth were made into two subgroups (n = 10)

    • Subgroup A: Instrumentation was done in crown down method by continuous rotary technique with LSX rotary files (LightSpeed Technology Inc., San Antonio, TX, USA) connected to TCM Endo V endomotor (Nouvag). The speed was set at 2000 rpm. Initially, #15, #20 LSX files were used, and then #25 LSX file was used up to the WL. All the teeth were selected with initial minimum working width of 0.1mm and apical enlargement was done upto three sizes larger than the initial apical file i.e., upto ISO size 25[12]
    • Subgroup B: Instrumentation was done by reciprocating rotary technique with LSX rotary files connected to Waveone endomotor following the same protocol as in subgroup A.




Assessment of the increase in root canal surface area

Adobe Photoshop software [Figure 1]a was used to export and evaluate the preoperative [Figure 1]b and postoperative CBCT images [Figure 1]c (axial sections). The surface area of root canals at three different levels, i.e., at 1, 3, and 5 mm cross-sections was measured according to the protocol given by Özer.[13] The difference between the post- and pre-operative values represented the increase in root canal surface area at that cross-section [Figure 1]d.
Figure 1: (a) Preoperative marking of root canal outline using magic wand tool of Adobe Photoshop software to measure the root canal surface area; (b) preoperative root canal outline to measure the root canal surface area; (c) postoperative root canal outline to measure the root canal surface area; (d) diagrammatic representation of increase in root canal surface area for mesiobuccal canal at 5 mm; (e) diagrammatic representation of root canal transportation for mesiobuccal canal at 5 mm; and (f) preoperative distance measurements for mesiobuccal canal of a sample from root canal wall to external root surface using cone-beam computed tomography software

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Assessment of apical transportation

The distances from the root canal outline to the external surface of root were measured in all the four directions, both preoperatively and postoperatively as per the method suggested by Gambill et al.[14] [Figure 1]e and [Figure 1]f. To standardize the procedure and avoid variations in results, a single operator conducted the study. The data obtained were subjected to statistical analysis.

Differences in increase of root canal surface area and canal transportation between groups were analyzed by one-way analysis of variance, followed by Tukey pairwise multiple comparison tests.


   Results Top


In both mesiobuccal and mesiolingual canals, increase in root canal surface area was significantly more between ProTaper Universal and LSX groups, K3XF, and LSX groups. There was no significant difference between ProTaper Universal and K3XF groups at 1, 3, and 5 mm cross-sections at 1 mm, 3 mm and 5 mm cross-sections in both continuous rotary and reciprocating rotary techniques.

Increase of root canal surface area was not significant (P = 1.000) for any given rotary system in this study when used in either continuous rotary or reciprocating rotary techniques at all the three levels [Table 1].
Table 1: Tukey pairwise multiple comparison tests to determine the significant increase in root canal surface area between the groups at 5, 3, and 1 mm for mesiolingual canal

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Mesio-buccal and mesio-lingual canals were analysed independently in all the samples. Individual canals vary both in angle of curvature and radius of curvature but were not measured as it was not the aim in the present study. However measurement of canal curvature and radius of curvature in all the three dimensions is possible only with µ-CT. Increase in root canal surface area and canal transportation in both the mesial canals was clinically significant but was not statistically significant. In both of the mesial canals, canal transportation was significantly more between ProTaper Universal and K3XF groups, K3XF and LSX groups, and ProTaper Universal and LSX at all the three cross-sections both in continuous rotary and reciprocating rotary techniques.

Canal transportation was seen in mesial direction in all the samples, i.e., opposite to the direction of canal curvatures for all the rotary systems used. Canal transportation was clinically as well as statistically significant. Canal transportation is inversely related to the remaining dentin thickness. More the canal transportation less will be the remaining dentin thickness. This parameter was not measured as it was not the aim in the present study.

Increase in canal transportation was not significant (P = 0.986) for any given rotary system in this study when used in either continuous rotary or reciprocating rotary techniques at all the three levels [Table 2].
Table 2: Tukey pairwise multiple comparison tests to determine the significant increase in root canal transportation between the groups at 5, 3 and 1 mm for mesiolingual canal

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   Discussion Top


Increase in root canal surface area and canal transportation was measured at 1 mm, 3 mm and 5 mm short of the apex as this was the region most crucial with respect to canal aberrations.

Transportation of the root canal is considered to be an important parameter to assess the root canal preparation, particularly in curved root canals. Severe canal transportation associated with an over reduction of sound dentin along the inner aspect in the middle part and along the outer aspect in the apical part of the root canal may result in a marked reduction of the fracture resistance of enlarged root canals.[15]

The effect of reciprocating rotary technique on increase of root canal surface area and canal transportation has not been well investigated, and very few studies compared the canal transportation in continuous rotary and reciprocating rotary techniques.[16] Hence, the present study was aimed at determining the increase in root canal surface area and canal transportation in both continuous rotary and reciprocating rotary techniques.

On comparison of the increase in root surface area between ProTaper Universal and K3XF groups, there was no significant difference (P > 0.05) at all the three cross-sections. This might be because both groups were enlarged to the same apical diameter (0.25 mm) and both of them had a positive rake angle for efficient cutting.

While comparing increase in root canal surface area between ProTaper Universal, K3XF, and LSX groups, it showed that there was a significant increase in root canal surface area (P < 0.05) for ProTaper Universal and K3XF groups when compared to LSX group. This might be because the length of cutting portion of LSX files was greatly reduced (0.5–2 mm) with no taper, presence of small radial lands, and noncutting tip whereas ProTaper and K3XF systems had positive rake angle that led to increased cutting of dentin. Similar results were reported by Rao et al.[17] where they found that least amount of dentin was removed with LSX files when compared to K3 and Mtwo groups.

On comparison of the increase in root canal surface area between two subgroups, i.e. in continuous rotary and reciprocating rotary techniques, of a given group, there was no significant difference (P > 0.05) between each other. This was common for all groups. This might be because the reciprocating rotary technique increases the cyclic fatigue resistance of the instrument but had no extra beneficial effects in the enlargement of the root canal.

Significantly more apical transportation in mesial direction in ProTaper Universal group (P < 0.05) when compared to K3XF and LSX groups might be because of the variable taper along the length of cutting portion, positive rake angle without radial lands, and the triangular cross-section of ProTaper rotary system. Similar results were reported by Sonntag et al.[18] and Schäfer and Vlassis [19] where they concluded that ProTaper group showed maximum canal transportation (P < 0.05) when compared to K3, Mtwo, and RaCe systems.

In the present study, canal transportation was significantly less in K3XF group (P < 0.05) when compared to ProTaper Universal group. This might be because of the variable core diameter along the length of cutting portion of K3XF that led to maintenance of canal curvature.

Least canal transportation in LSX group might be because of the short cutting surface (0.5–2 mm) with small radial lands, neutral rake angle, smooth, flexible shaft, and noncutting tip that led to minimum canal deviation. The present study included teeth with moderate root canal curvatures (between 20° and 30°) as most of the mesiobuccal and mesiolingual root canals of mandibular molars were found to have moderate curvatures.[20]

In the present study, all the three groups showed canal transportation toward the outer side of root curvature at all the three apical cross-sections. This might be because of the tendency of these files to straighten. Similar results were reported by Ayar and Love [21] and Bergmans et al.[22],[23] with ProTaper and K3 systems.

In the present study, there was statistically significant difference in increase of root canal surface area and canal transportation for the three rotary systems in either continuous rotary or reciprocating rotary motions. Hence, the null hypothesis was rejected.

Limitations of the present study include only teeth with moderate root canal curvatures were included and usage of manual method to measure the root canal surface area by counting the number of pixels using Adobe Photoshop software. Further research in teeth with severe root curvatures followed by ex vivo and in vivo studies are needed to confirm these results in a clinical scenario.


   Conclusion Top


Increase in root canal surface area was significantly more in ProTaper Universal and K3XF groups when compared to LSX group. Canal transportation was significantly more in ProTaper Universal group when compared to K3XF and LSX groups. Canal transportation was also significantly more in K3XF group when compared to LSX group. There was no significant difference in increase of root canal surface area and canal transportation between the continuous rotary and reciprocating rotary techniques in all the three groups.

Uniformity in the increase of root canal surface area was better in LSX rotary system when compared to ProTaper Universal and K3XF rotary systems. LSX rotary system showed minimal canal transportation when compared to ProTaper Universal and K3XF rotary systems.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

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2.
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4.
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Oliveira CA, Meurer MI, Pascoalato C, Silva SR. Cone-beam computed tomography analysis of the apical third of curved roots after mechanical preparation with different automated systems. Braz Dent J 2009;20:376-81.  Back to cited text no. 5
    
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Prichard J. Rotation or reciprocation: A contemporary look at NiTi instruments? Br Dent J 2012;212:345-6.  Back to cited text no. 7
    
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Madani ZS, Haddadi A, Haghanifar S, Bijani A. Cone-beam computed tomography for evaluation of apical transportation in root canals prepared by two rotary systems. Iran Endod J 2014;9:109-12.  Back to cited text no. 8
    
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Michetti J, Maret D, Mallet JP, Diemer F. Validation of cone beam computed tomography as a tool to explore root canal anatomy. J Endod 2010;36:1187-90.  Back to cited text no. 10
    
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Elsherief SM, Zayet MK, Hamouda IM. Cone-beam computed tomography analysis of curved root canals after mechanical preparation with three nickel-titanium rotary instruments. J Biomed Res 2013;27:326-35.  Back to cited text no. 11
    
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Suresh Chandra B, Gopi Krishna V. Grossman's Endodontic Practice. 12th ed. Gurgaon: Wolter's Kluwer Pvt. Ltd.; 2010. p. 253.  Back to cited text no. 12
    
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Özer SY. Comparison of root canal transportation induced by three rotary systems with noncutting tips using computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:244-50.  Back to cited text no. 13
    
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Gambill JM, Alder M, del Rio CE. Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography. J Endod 1996;22:369-75.  Back to cited text no. 14
    
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Schafer E, Dammaschke T. Development and sequelae of canal transportation. Endod Top 2009;15:75-90.  Back to cited text no. 15
    
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McRay B, Cox TC, Cohenca N, Johnson JD, Paranjpe A. A micro-computed tomography-based comparison of the canal transportation and centering ability of ProTaper Universal rotary and WaveOne reciprocating files. Quintessence Int 2014;45:101-8.  Back to cited text no. 16
    
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Rao MS, Shameem A, Nair R, Ghanta S, Thankachan RP, Issac JK. Comparison of the remaining dentin thickness in the root after hand and four rotary instrumentation techniques: An in vitro study. J Contemp Dent Pract 2013;14:712-7.  Back to cited text no. 17
    
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Sonntag D, Ott M, Kook K, Stachniss V. Root canal preparation with the NiTi systems K3, Mtwo and ProTaper. Aust Endod J 2007;33:73-81.  Back to cited text no. 18
    
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Schäfer E, Vlassis M. Comparative investigation of two rotary nickel-titanium instruments: ProTaper versus RaCe. Part 1. Shaping ability in simulated curved canals. Int Endod J 2004;37:229-38.  Back to cited text no. 19
    
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21.
Ayar LR, Love RM. Shaping ability of ProFile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals. Int Endod J 2004;37:593-601.  Back to cited text no. 21
    
22.
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Correspondence Address:
Tanikonda Rambabu
Department of Conservative Dentistry and Endodontics, Vishnu Dental College, Vishnupur, Bhimavaram - 534 202, West Godavari, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.190003

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