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Year : 2019  |  Volume : 31  |  Issue : 1  |  Page : 78-83

Comparative evaluation of apical extrusion of intracanal bacteria using four single-file NiTi instruments: An in vitro study

Department of Conservative Dentistry and Endodontics, Rajas Dental College and Hospital, The Tamil Nadu Dr. M. G. R. Medical University, Chennai, Tamil Nadu, India

Date of Web Publication19-Jun-2019

Correspondence Address:
Dr. A Sheerin Sarthaj
Department of Conservative Dentistry and Endodontics, Rajas Dental College and Hospital, The Tamil Nadu Dr. M. G. R. Medical University, Chennai, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_30_18

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Introduction: A major objective in root canal treatment is to clean the root canal system. During the process, dentine chips, pulp tissue fragments, necrotic tissue, microorganisms, and intracanal irrigants may be extruded through the apical foramen. This in vitro study was conducted to evaluate the apical extrusion of Enterococcus faecalis with One Shape, F360, WaveOne, and Reciproc endodontic single-file systems.
Materials and Methods: Seventy-five human single-rooted mandibular premolar teeth were selected. Endodontic access cavities were prepared. Pulp chamber was accessed, and a pure culture of E. faecalis was used to infect the root canals. Vials with rubber stoppers were selected as the test apparatus. Then, the samples were broadly divided into four main groups with a sample size of 15 teeth. Fifteen previously infected teeth were used as controls. All the root canals were instrumented with the size 25 instruments. A total volume of 2 ml of saline was used for each root canal as irrigant. After 24 h, colonies of bacteria were counted using classical bacterial counting technique as colony-forming units.
Statistical Analysis: Data were analyzed statistically using Statistical Package for the Social Sciences, version – 21 (IBM Corp., NY) Software for Windows. Data were expressed in its mean and standard deviation.
Results: The results indicated that all the four single-file systems tested caused a measurable apical extrusion of debris. Statistically, significant difference was observed between One Shape, F360, WaveOne, and Reciproc in terms of E. faecalis extrusion, P < 0.05. The highest mean value was with One Shape rotary single-file system and the lowest mean value was with WaveOne reciprocating single-file systems.
Conclusion: Within the limitations of the present study, it can be concluded that the reciprocating single-file systems extruded less amount of E. faecalis than compared to rotary single-file systems.

Keywords: Apical extrusion, Enterococcus faecalis, WaveOne, Reciproc, One Shape, F360, engine-driven techniques, rotary instruments

How to cite this article:
Sarthaj A S, Gopal V R, Kumar A A, Paulaian B, Raveendran LK, DeviPrasad C S. Comparative evaluation of apical extrusion of intracanal bacteria using four single-file NiTi instruments: An in vitro study. Endodontology 2019;31:78-83

How to cite this URL:
Sarthaj A S, Gopal V R, Kumar A A, Paulaian B, Raveendran LK, DeviPrasad C S. Comparative evaluation of apical extrusion of intracanal bacteria using four single-file NiTi instruments: An in vitro study. Endodontology [serial online] 2019 [cited 2020 Feb 23];31:78-83. Available from: http://www.endodontologyonweb.org/text.asp?2019/31/1/78/260525

  Introduction Top

Endodontics is not an uncomplicated term.[1] The reality is that the further we know about the innovation and curvatures of the root canal systems, the more that we are attentive to nature's anatomic complications.[2] Complete debridement and reduction of the bacterial infection from the root canal space are necessary for long-term success of endodontic treatment.[3],[4] However, these materials may be extruded through the apical foramen into the periapical tissues during root canal preparation.[5] This results in postoperative complications such as a flare-up, which is described by periapical inflammation, pain, and swelling.[6],[7] Advancements in rotary instruments have facilitated and fastened the root canal procedures and resulted in less iatrogenic errors.[8]

One Shape file was introduced by Micro-Mega. Directed down the glide path by three cutting edges, its flexibility assures adaptation to the new canal path and curvature. The antibreakage organize of One Shape file is a protection bonus, i.e., the instrument will slow down to avoid division.

The F360 (KOMET, Brasseler GmBH & Co., Lemgo, Germany) has a cross-section which resembles a double S. The file features a unique S-curve design and a thin instrument core to deliver outstanding cutting efficiency.

Dr. Yared has introduced the Reciproc (VDW, Munich Germany) system. The single-file NiTi system consists of three files, including the R25 (ISO 25; 8%), R40 (ISO 40; 6%), and R50 (ISO 50; 5%).[9]

WaveOne (Dentsply, Maillefer, Ballaigues, Switzerland) designated as a single file system is used to shape the root canal from start to end. The files run in a “balanced force” action.

Among the varied microflora of the root canal system, Enterococcus faecalis has been reported to be the frequently isolated microorganism in obturated root canals exhibiting chronic periapical pathology.[10] Its role in endodontic treatment failure is attributed to its ability to invade dentinal tubules and to persist any depriving conditions and its resistance to intracanal medicaments.[11]

In microbiology, a colony-forming unit (CFU, cfu, Cfu) is a unit used to estimate the number of viable bacteria or fungal cells in a sample.[12]

With the advent of such improved technology, the efficacy of various single-file systems can be studied and the amount of apical extrusion of intracanal bacteria can be quantified with precision. Hence, this study aimed at comprehending the apical extrusion of intracanal bacteria using four different single-file systems with the use of bacterial colony counting.

  Materials and Methods Top

Collection of study samples

Seventy-five freshly extracted human mandibular single-rooted premolar teeth were collected from the Department of Oral and Maxillofacial Surgery, Raja's Dental College, Tirunelveli, from patients who had undergone therapeutic extraction. All teeth were analyzed with digital radiographs (Satelec, Acteon, France) in buccal and proximal directions to check for a single canal.

All the collected teeth were then washed thoroughly in running water. Any debris, calculus, and soft-tissue remnants on the root surfaces were removed using a Gracey curette (Hu-Friedy Mfg. Co., LLC Chicago) and an ultrasonic scaler (Woodpecker, China). The organic and inorganic debris were removed by treating the teeth with 17% ethylene diamine tetraacetic acid (Nice chemicals Pvt. Ltd., Delhi, India) for 5 min, followed by 3% sodium hypochlorite (Nice chemicals Pvt. Ltd., Delhi, India) for 5 min and then placed in hydrogen peroxide (Nice chemicals Pvt. Ltd., Delhi, India) for 1 h. The cleaned teeth were then stored in normal saline (Nice chemicals Pvt. Ltd., Delhi, India) 0.9%, until use.

Canal preparation

The buccal cusp edge of each tooth was then flattened as a reference point. Conventional access to the root canals was obtained using access preparation bur (Dentsply Maillefer, Ballaigues, Switzerland) with a high-speed handpiece (NSK, Corporation, Japan). A 15 K-file (Mani Inc., India) was introduced till the tip emerges at the apex, and the length of the root canal space was estimated. The working length was fixed at 0.5 mm short of this estimated value. The remnant pulpal tissue from the canal was removed using a 15H file (Mani Inc., India).

Sterilization of the test samples and glass vials

Subsequently, all the teeth and glass vials were sterilized by autoclaving at the recommended 121°C, 15 lbs for 15 min using a digital autoclave in a self-sealable autoclave pouch (Inlab Equipment, Chennai, India).

Test apparatus

Holes were created in the stoppers of vials, and the teeth were inserted under pressure through the stoppers, which were fixed to the cementoenamel junction by means cyanoacrylate. A bent 27-gauge needle was also forced alongside the stopper to use as a drainage cannula, balance between the air pressure inside and outside the vials. The vials were filled with 27 ml of 0.9% NaCl till the apex of the tooth mounted in the vial through the rubber stopper.

Bacterial growth and teeth contamination

The test organism that was used in this study was E faecalis. Twenty-four-hour colonies of a pure culture of E. faecalis (MTCC 439) were obtained. E. faecalis was grown in nutrient agar (HiMedia, Mumbai, India). Then, it was suspended in 5 ml of nutrient broth and incubated for 24 h at 37°C. The density of E. faecalis was adjusted to the turbidity of 0.5 McFarland standard against a ruled paper, which can be comparable with a bacterial suspension of 1.5 × 108 CFU/ml. All the 75 teeth were contaminated with the E. faecalis organism.

The organism with the broth was then coated along the canal walls. Ten microliters of the inoculums was then injected into the canal with the help of a micropipette. The excess broth was decanted and drained off. The teeth were then incubated at 37°C for 1 day. Bacterial viability and purity were checked in three randomly picked samples. The samples were incubated for 21 days at 37°C. During the incubation period, to prevent dehydration of the samples, the nutrient broth was replenished every 3 days.

Sample grouping

Seventy-five teeth were grouped into four main groups of 15 teeth each and one control group of 15 teeth.

Canal preparation

All root canal preparations were completed in the laminar flow chamber according to the manufacturers' suggestions. Instruments were used only for preparation of three canals, after which they were discarded. In each sample, 2 mL 0.9% saline was used as an irrigating solution with a 31-gauge side-vented needle (NaviTip Sideport; Ultradent, USA) between files in the One Shape and F360 groups and between pecking sequences in the Reciproc and WaveOne groups. Apical patency was maintained by passing a size 10 K file to working length after the use of each file.

  • Group 1 (One Shape): Instrumentation was carried out using One Shape Rotary Ni-Ti technique. The canals were prepared with a 25 / 0.06 taper at a rotational speed of 400 rpm, and torque of 4 Ncm
  • Group 1I (F360): Instrumentation was carried out using F 360 Rotary Ni-Ti technique. The canals were prepared with a 25 / 0.04 taper at a rotational speed of 300 rpm, and torque of 1.8 Ncm
  • Group 1II (Reciproc): Instrumentation was carried out using Reciproc Reciprocating Ni-Ti technique. The canals were prepared with a 25 / 0.08 taper. The flutes of the instrument were cleaned after three in-and-out-movements (pecks)
  • Group IV (WaveOne): The root canals were instrumented using a WaveOne reciprocating single-file (25/0.06) with a gently in-and out-pecking motion
  • Group V (Control Group): No instrumentation was done in this group.

At the end of the preparation, 0.01 ml of NaCl solution was taken from the experimental vials to count the bacteria; the suspension was plated on brain–heart agar and incubated at 37°C for 24 h. [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5] represent the bacterial colonies formed for individual groups. Colonies of bacteria were counted using the classical counting technique in the colony counter, and the results were given as a number of CFU.
Figure 1: Colony-forming units for control group (Group 1) original image

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Figure 2: Colony-forming units for One Shape Group (Group 2) original image

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Figure 3: Colony-forming units for F360 Group (Group 3) original image

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Figure 4: Colony-forming units for Reciproc Group (Group 4) original image

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Figure 5: Colony-forming units for WaveOne Group (Group 5)

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Statistical analysis

The data entry was done with Microsoft Office Excel Spreadsheet. Data were analyzed using Statistical Package for the Social Sciences (SPSS) Software version 21 (IBM Statistics IBM Corp., NY). Descriptive statistics include mean and standard deviation for all the parameters. Statistical tests used were Kruskal–Wallis test to find out the significance among the four different groups and multiple comparisons using Mann–Whitney U-test was done. A P < 0.05 was considered statistically significant.

  Results Top

[Table 1] shows the comparison of the four groups of single-file systems on the apical extrusion of E. faecalis, which was done using Kruskal–Wallis test. The mean value of CFUs for One Shape group was 39.46, F360 group was 27.83, Reciproc group was 18.29, and WaveOne group was 12.42. This shows statistically significant difference (P = 0.001) in the mean of the CFUs among the four groups. The graphical representation of the same is given in [Graph 1].
Table 1: Testing the significance effects of file systems on the apical extrusion of Enterococcus faecalis

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[Table 2] shows the intergroup comparison rotary single-file systems and reciprocating single-file systems on the apical extrusion of E. faecalis, which was done using Mann–Whitney test. The mean value of CFUs for rotary single-file systems was 33.65 and the reciprocating file systems was 15.35. This shows statistically significant differences in the mean of the CFUs among the rotary single-file systems and the reciprocating file systems. The graphical representation of the same is given in [Graph 2].
Table 2: Testing the significance effects of rotary and reciprocating file systems on the apical extrusion of Enterococcus faecalis

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  Discussion Top

One of the most significant complications that occur as a result of apical extrusion during root canal procedures is inter-appointment flare-ups, due to the release of histamines which is an undesirable occurrence both for the patient and the practitioner.[13] The effects of apical extrusion may be related to the quantitative as well as qualitative factors. Even though the former can be controlled effectively by instrumentation techniques, the latter can never be controlled.[14] Hence, the present study was done to assess the apical extrusion of intracanal bacteria using two rotary single-file systems and two reciprocating single-file systems.

Single-rooted mandibular premolar with straight canals and closed mature apex was preferred in this study as curved root canals are associated with a more complicated curvature determination. Strict adherence to the selection of teeth was done to decrease the number of variables which makes it reliable that the extrusion was done by instrumentation only.

In the present study, E. faecalis was chosen because of its implication as the possible microbial factor in therapy-resistant apical periodontitis.[10] The apical extrusion of E. faecalis is calculated using CFUs. The CFU/ml can be calculated using the formula:

cfu/ml = (Number of colonies × dilution factor)/volume of culture plate.

In the present study, the CFUs were evaluated 21 days after instrumentation. This was done to facilitate evaluation of bacterial regrowth within the samples after the instrumentation.

Saline was used as an irrigant in this study to maintain the vitality of the bacteria to determine the amount of apically extruded E. faecalis.

The results of this study demonstrated that One Shape and F360 rotary single-file NiTi instruments extruded more intracanal bacteria than Reciproc and WaveOne reciprocating single-file NiTi instruments.

However, various studies conducted by various authors have concluded that there is no correlation between apical size and the extrusion of intracanal bacteria.[15],[16] The present study did not control apical size after instrumentation. The entire root canal instrumentation was done according to the manufacturer's instructions.

The results of this study may also be related to the movement, cross-sectional design, and thread pitch of the instruments. The movement of rotary file systems is a linear filing motion, which usually creates a greater mass of debris. The bacteria that were accumulated in the apical third due to repeated instrumentation are pushed as debris through the apical foramen because the apical one-third of the file acts as a piston. The greatest number of microorganisms in the root canal lie in the coronal because of the linear filing motion there is a tendency of the debris being pushed apically rather than coronally.[17]

Reciprocating single-file systems are gaining popularity in the recent years due to their advantage of time-saving and working safety and also less debris extrusion compared with multifile systems.[18] The cross-sectional geometry of double “S” shaped have a two-point contact to the canal walls rather than a complete contact. The S-shaped cross section gives a point contact to the root canal while the remaining acts as a flute space which packs the debris into the flutes and directs them to the canal orifice, thereby avoiding large amounts of bacterial extrusion.

WaveOne reciprocating single-file systems use a triangular or improved cross-section design. The tip of the WaveOne has a debris diversion trench on each cutting edge, which reduces the tendency for debris extrusion into periradicular tissues.

The “in-and-out pecking motion” adopted by the reciprocating file systems promotes the preflaring of the coronal portion of the canal, which reduces the amount of apically extruded bacteria.

A study conducted earlier[19] had concluded that there was a significant reduction in CFU when the taper was increased from 4% to 8%. The higher reduction of the microbial load extruded in the present study was associated with the greater taper of 8% in reciprocating single-file systems. The present study supports the concept that the degree of the taper preparation is important for the reduction of intracanal bacterial load.[20],[21],[22]

In the future, studies should be designed in an in vivo situation to validate the results obtained in this study and proving the efficacy of these single-file NiTi instruments.

  Conclusion Top

The present study, with its limitations, concludes that:

  1. All the four single-file NiTi instruments used in this study exhibited significant apical extrusion of intracanal bacteria
  2. There was a significant reduction in the microbial count for all the single-file systems tested when compared with the culture group
  3. Reciprocating single-file NiTi instruments had the least amount of apical extrusion of E. faecalis. Hence, it can be considered as an alternative to other file systems.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Dhingra A, Ruhal N, Bhardwaj N, Rohilla S. Single file systems: A review. Int J Sci Stud 2015;2:169-72.  Back to cited text no. 1
Kuttler S, West J. A single file system: The science of simplicity. Dent Today 2012;94-5.  Back to cited text no. 2
Bystrom A, Sundqvist G. The antibacterial action of sodium hypochlorite and EDTA in 60 cases of endodontic therapy. Int Endod J 1985;18:35-40.  Back to cited text no. 3
Koçak S, Koçak MM, Saǧlam BC, Türker SA, Saǧsen B, Er Ö, et al. Apical extrusion of debris using self-adjusting file, reciprocating single-file, and 2 rotary instrumentation systems. J Endod 2013;39:1278-80.  Back to cited text no. 4
Tambe VH, Nagmode PS, Vishwas JR, PSK, Angadi P, Ali FM, et al. Evaluation of the amount of debris extruded apically by using conventional syringe, endovac and ultrasonic irrigation technique: An in vitro study. J Int Oral Health 2013;5:63-6.  Back to cited text no. 5
Seltzer S, Naidorf IJ. Flare-ups in endodontics: I. Etiological factors. J Endod 1985;11:472-8.  Back to cited text no. 6
Harrington GW, Natkin E. Midtreatment flare-ups. Dent Clin North Am 1992;36:409-23.  Back to cited text no. 7
Capar ID, Ertas H, Ok E, Arslan H, Ertas ET. Comparative study of different novel nickel-titanium rotary systems for root canal preparation in severely curved root canals. J Endod 2014;40:852-6.  Back to cited text no. 8
Yared G. Canal preparation with only one reciprocating instrument without prior hand filing: A new concept. Int Dent 2012;2:78-87.  Back to cited text no. 9
Hancock HH 3rd, Sigurdsson A, Trope M, Moiseiwitsch J. Bacteria isolated after unsuccessful endodontic treatment in a North American population. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:579-86.  Back to cited text no. 10
Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142-9.  Back to cited text no. 11
Goldman E, Green LH. Practical Handbook of Microbiology. 2nd ed. USA: CR Press, Taylor and Francis Group; 2008. p. 864.  Back to cited text no. 12
Siqueira JF Jr. Microbial causes of endodontic flare-ups. Int Endod J 2003;36:453-63.  Back to cited text no. 13
Tanalp J, Kaptan F, Sert S, Kayahan B, Bayirl G. Quantitative evaluation of the amount of apically extruded debris using 3 different rotary instrumentation systems. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:250-7.  Back to cited text no. 14
al-Omari MA, Dummer PM. Canal blockage and debris extrusion with eight preparation techniques. J Endod 1995;21:154-8.  Back to cited text no. 15
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Shovelton DS. The presence and distribution of microorganisms within nonvital teeth. Br Dent J 1964;117:101-7.  Back to cited text no. 17
Türker SA, Uzunoǧlu E, Aslan MH. Evaluation of apically extruded bacteria associated with different nickel-titanium systems. J Endod 2015;41:953-5.  Back to cited text no. 18
Mary Th. Paraskevopoulou, Marouan G. Khabbaz. Influence of Taper of Root Canal Shape on the Intracanal Bacterial Reduction. The Open Dentistry Journal 2016;10:568-74.  Back to cited text no. 19
Siqueira JF Jr, Lima KC, Magalhães FA, Lopes HP, de Uzeda M. Mechanical reduction of the bacterial population in the root canal by three instrumentation techniques. J Endod 1999;25:332-5.   Back to cited text no. 20
Aydin C, Tunca YM, Senses Z, Baysallar M, Kayaoglu G, Ørstavik D. Bacterial reduction by extensive versus conservative root canal instrumentation in vitro. Acta Odontol Scand 2007;65:167-70.  Back to cited text no. 21
Chuste-Guillot MP, Badet C, Peli JF, Perez F. Effect of three nickel-titanium rotary file techniques on infected root dentin reduction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:254-8.  Back to cited text no. 22


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2]


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