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 Table of Contents  
Year : 2017  |  Volume : 29  |  Issue : 1  |  Page : 3-6

Effect of different rotary instruments on crack formation after coronal preflaring of root dentin

Department of Conservative Dentistry and Endodontics, Maitri College of Dentistry and Research Centre, Durg, Chhattisgarh, India

Date of Web Publication25-May-2017

Correspondence Address:
Shanin Farista
Tyre House, G.E. Road, Rajnandgaon - 491 441, Chhattisgarh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_112_16

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Introduction: The aim of the present study was to investigate the incidence of cracks in root dentin after coronal flaring using various coronal preflaring instruments such as Gates Glidden drills (Mani, Japan), ProTaper Universal SX (Dentsply, Switzerland), K3 (Sybron Endo, USA), Endoflare (MicroMega, France).
Materials and Methods: Fifty freshly extracted single-rooted teeth with single canal were collected. All the teeth were randomly divided into five groups of ten each, of which one group served as Control and rest of the four groups were instrumented with Gates Glidden drills, ProTaper Universal (SX), K3 instrument, and Endoflare, respectively. All roots were then sectioned perpendicular to the long axis at 1, 2, 3, 4, and 5 mm from the cementoenamel junction and examined under a stereomicroscope at 10 magnification. Any crack formations were recorded. The data were analyzed using Chi-square test.
Results: The Gates Glidden drills resulted in a higher rate of crack formation in root dentin (P < 0.05) than the ProTaper Universal, Endoflare, and K3 instruments (P > 0.05) while preflaring of canal orifices.
Conclusions: The use of the Gates Glidden drills resulted in more crack formation. However, the results for the ProTaper Universal, Endoflare, and K3 flaring instruments were less in terms of crack formation.

Keywords: Coronal preflaring; Endoflare; Gates Glidden drills; K3 system; ProTaper Universal; stereomicroscope; vertical root fracture.

How to cite this article:
Dash AK, Farista S, Dash A, Farista S. Effect of different rotary instruments on crack formation after coronal preflaring of root dentin. Endodontology 2017;29:3-6

How to cite this URL:
Dash AK, Farista S, Dash A, Farista S. Effect of different rotary instruments on crack formation after coronal preflaring of root dentin. Endodontology [serial online] 2017 [cited 2022 Jul 5];29:3-6. Available from: https://www.endodontologyonweb.org/text.asp?2017/29/1/3/206995

  Introduction Top

Proper access opening with a proper coronal preflaring is one of the important factor responsible for a successful endodontic treatment outcome.[1] Early coronal flaring provides a number of advantages to the clinician.[2],[3],[4] Several coronal flaring instruments are available for use in root canal preparation. The coronal flaring instruments have greater volume, and they require more contact with root canal dentin thus creating momentary stress concentration, leading to dentinal defects which may propagate to form root fractures.[5] Dentinal crack formation has been shown to originate from several factors, including root canal preparation,[6] obturation techniques, and retreatment procedures.[7]

Vertical root fracture is an untoward complication to root canal therapy that often calls for tooth extraction.[8] To our knowledge, there are only a few studies related to the effect of coronal flaring instruments on crack formation.[1],[4] Therefore, the aim of the present study was to evaluate crack formation after flaring root canals with Gates Glidden drills (Mani Inc., Japan), ProTaper Universal (SX instrument; Dentsply Maillefer, Ballaigues, Switzerland), Endoflare (MicroMega, France), K3 (Sybron Endo, USA).

  Materials and Methods Top

Selection of specimens

Freshly extracted single-rooted second mandibular premolars were collected, cleaned with hand scalers, and stored in normal saline until use. All the teeth were decoronated 2 mm above the cementoenamel junction with slow-speed diamond disc using water as coolant and observed under a stereomicroscope to exclude any external defects or cracks [Figure 1].
Figure 1: Stereomicroscope

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Distribution of the specimens

The buccolingual thickness of each root was measured using a Digital Vernier Caliper and fifty roots with buccolingual width ranging from 7.22 cm to 7.27 cm were selected for the study. After selection, individual tooth were embedded in modeling wax.

Flaring of the root canals

A 10 K-file (Mani) was used to establish the canal patency. The root canals (n = 10) were then flared as follows:

  • Group 1 - Control group: In this group, the specimens were left unflared
  • Group 2 - Gates Glidden drills: For each Gates Glidden drill, the rotational speed (800 rpm) and the torque suggested by the manufacturer were used.

The sequence was as follows:

  • Size #3 (3 N/cm torque) with a working length of 3 mm
  • Size #2 (1 N/cm torque) with a working length of 5 mm
  • Size #1 (0.8 N/cm torque) with a working length of 8 mm
  • Group 3 - ProTaper Universal: The SX instrument was used with a rotational speed of 300 rpm and 3 N/cm torque at a working length of 8 mm
  • Group 4 - Endoflare: The Endoflare file was used with a rotational speed of 300 rpm and 3 N/cm torque at a working length of 3 mm
  • Group 5 - K3: K3 shaper (10% taper, 25 tip size, 17 mm) was used with a rotational speed of 300 rpm and 5 N/cm torque at a working length of 5 mm.

The rotational speed, torque limits, and depth of insertion for each system were determined as suggested by the manufacturer. The files and drills were used with a gentle brushing motion. Each instrument was used for preparing five canals using X-Smart Endo Motor (Dentsply-Maillefer, Ballaigues, Switzerland). All root canals were irrigated with 2 ml 3% NaOCl between each instrument. Final rinse was done using 5 ml of normal saline.


From each sample, slices were obtained at 1, 2, 3, 4 and 5 mm from the cementoenamel junction using a low-speed, water-cooled saw (Diamond disc and Mandrel - Axiss Dental, Indore, Madhya Pradesh, India). Both sides of each section were then examined under a stereomicroscope (SMZ-168, Motic Asia, Hong Kong, China) at ×10 magnification. To prevent dehydration, all of the sections were kept in saline between the procedures.

Definition of crack

“No crack” was defined as root dentin without cracks or craze lines either at the internal surface of the root canal wall or at the external surface of the root.

“Crack” was defined as all lines observed on the slice that either extended from the root canal lumen to the dentin or from the outer root surface into the dentin [Figure 2].[1]
Figure 2: Crack formation

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Statistical analysis

The differences in crack formation among the groups were analyzed with the Chi-square test. All statistical analyses were performed using IBM Statistics 20.0 software (IBM Analytical, Armonk, NY).

  Results Top

A total of 250 slices were examined. The numbers of roots with cracks for all groups are shown in [Table 1]. The Gates Glidden drills caused a higher rate of crack formation than that found in the control group (P < 0.05). Flaring of the root canals using the ProTaper Universal, Endoflare, and K3 instruments resulted in crack formation, but they were not statistically significant to that found in the control group (P > 0.05). Number of slices with cracks at each millimeter section for all the groups is given in [Table 2]. Comparison between the groups is shown in [Table 3].
Table 1: Number of roots with crack and crack percentage

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Table 2: Number of sections with cracks at each level

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Table 3: Table of comparison

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  Discussion Top

It is a well-known fact that coronal flaring provides many advantages, but the use of coronal flaring instruments leads to crack formation in root dentine and eventually compromises the pericerival dentin which acts as neck of tooth prevents the fracture of tooth. The microcracks and craze lines so formed by the use of coronal flaring instruments can lead to weakened pericervical dentin with reduced resistance to fracture.[9] Therefore, the aim of this study was to evaluate and compare the crack formation after use of Gates Glidden drills, ProTaper Universal SX, K3, and Endoflare.

The results of the present study revealed that after coronal flaring with the Gates Glidden drills, ProTaper Universal (SX), Endoflare, K3 instruments, the incidence of cracks in the roots was 50%, 20%, 30%, and 20%, respectively.

In this study, up to a size #3 Gates Glidden drill was used for coronal flaring and cracks were found. Similar to our findings, Arslan et al. 2014[1] and Shemesh et al. 2009[10] reported that the use of Gates Glidden drills resulted in dentinal defects. Liu et al. 2013[11] found no cracks in apical root dentin after coronal flaring of the mandibular incisors using size #2 and size #1 Gates Glidden drills.

Control group and SX group showed cracks when examined, but there is no statistically significant difference between SX and the control group in the present study. On the contrary in a study by Bier et al. 2009,[6] the ProTaper Universal (SX) reported cracks which were statistically significant when compared with the control group. The decreased crack formation with use of SX in our study when compared to Bier's study might be caused by the use of more files in Bier's study.

In the present study, coronal flaring was done using ProTaper Universal, Endoflare, K3, and Gates Glidden drills; Gates Glidden drills caused more dentinal cracks than the others. Several possible factors attributed to the mentioned results are the larger number of instruments used than in the other procedures, different rotational speeds of the instruments, different instrument designs, and different instrument alloys.

The incidence of cracks in the control group was 20% in the present study, which was higher than in previous reports.[6],[10] The contradictory results of these studies could be caused by the use of different tooth types. Barreto et al.[12] and Arslan et al.[1] found the incidence of crack formation in control groups to be 20% and 16.6%, respectively. This result was harmonious with the results of the present study. Furthermore, Barreto et al.[12] used ×10 magnification stereomicroscope to examine the cracks and the craze lines similar to our study.

The use of different speed and torque settings for each file system could be a limitation of the present study. In addition, each instrument was used for five canals. However, the dulling of the instrument would tend to induce more stress/crack. Further studies should be conducted to evaluate the effect of the dulling of the instruments on crack formation.

  Conclusions Top

The use of Gates Glidden drills resulted in the more crack formation. The ProTaper Universal, Endoflare, and K3 instruments have a tendency to cause less crack formation compared with the Gates Glidden drills.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Arslan H, Karatas E, Capar ID, Ozsu D, Doganay E. Effect of ProTaper Universal, Endoflare, Revo-S, HyFlex coronal flaring instruments, and gates glidden drills on crack formation. J Endod 2014;40:1681-3.  Back to cited text no. 1
Cohen S, Hargreaves K, Cohen M. Pathways of Pulp. 9th ed. Missouri: Elsevier Publication; 2006. p. 327-8.  Back to cited text no. 2
Shivanna V, Agarwal D. Influence of cervical preflaring on apical file size determination-An in vitro study. Endodontology 2010;1:73-7.  Back to cited text no. 3
Tennert C, Herbert J, Altenburger MJ, Wrbas KT. The effect of cervical preflaring using different rotary nickel-titanium systems on the accuracy of apical file size determination. J Endod 2010;36:1669-72.  Back to cited text no. 4
Kim HC, Lee MH, Yum J, Versluis A, Lee CJ, Kim BM. Potential relationship between design of nickel-titanium rotary instruments and vertical root fracture. J Endod 2010;36:1195-9.  Back to cited text no. 5
Bier CA, Shemesh H, Tanomaru-Filho M, Wesselink PR, Wu MK. The ability of different nickel-titanium rotary instruments to induce dentinal damage during canal preparation. J Endod 2009;35:236-8.  Back to cited text no. 6
Topçuoglu HS, Demirbuga S, Tuncay Ö, Pala K, Arslan H, Karatas E. The effects of Mtwo, R-Endo, and D-RaCe retreatment instruments on the incidence of dentinal defects during the removal of root canal filling material. J Endod 2014;40:266-70.  Back to cited text no. 7
Tamse A. Vertical root fractures in endodontically treated teeth: Diagnostic signs and clinical management. Endod Topics 2006;13:84-94.  Back to cited text no. 8
Arora V, Yadav MP, Singh SP. Peri-cervical dentin (PCD): A new paradigm for endodontic success. Glob J Res Anal 2015;4:490-3.  Back to cited text no. 9
Shemesh H, Bier CA, Wu MK, Tanomaru-Filho M, Wesselink PR. The effects of canal preparation and filling on the incidence of dentinal defects. Int Endod J 2009;42:208-13.  Back to cited text no. 10
Liu R, Kaiwar A, Shemesh H, Wesselink PR, Hou B, Wu MK. Incidence of apical root cracks and apical dentinal detachments after canal preparation with hand and rotary files at different instrumentation lengths. J Endod 2013;39:129-32.  Back to cited text no. 11
Barreto MS, Moraes Rdo A, Rosa RA, Moreira CH, Só MV, Bier CA. Vertical root fractures and dentin defects: Effects of root canal preparation, filling, and mechanical cycling. J Endod 2012;38:1135-9.  Back to cited text no. 12


  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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