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ORIGINAL RESEARCH ARTICLE  
Year : 2017  |  Volume : 20  |  Issue : 6  |  Page : 445-450
Comparative evaluation of fracture resistance of root canals obturated with four different obturating systems


Department of Conservative Dentistry and Endodontics, ITS Dental College and Hospital, Greater Noida, Uttar Pradesh, India

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Date of Submission26-Jul-2017
Date of Decision10-Oct-2017
Date of Acceptance28-Nov-2017
Date of Web Publication15-Jan-2018
 

   Abstract 


Aim and Objectives: The aim of this study is to evaluate and compare the fracture resistance of root canals obturated with four different obturating systems in endodontically treated teeth.
Materials and Methods: One hundred and twenty single-rooted teeth were selected and decoronated at cementoenamel junction. Instrumentation of teeth (except control group) was done with Mtwo rotary files up to size 25/0.06 using a step-back technique. All teeth were divided into four experimental groups (n = 25) and two control groups (n = 10). In Group I (negative control), teeth were neither instrumented nor obturated, in Group II (positive control), instrumentation was done, but no obturation was performed, in Group III, obturation was done with cold lateral compaction technique, in Group IV, obturation was done with cold free-flow compaction technique, in Group V, obturation was done with warm vertical compaction technique, and in Group VI, obturation was done with injection-molded thermoplasticized technique. All prepared teeth were embedded in an acrylic resin block, and their fracture strength was measured using Universal Testing Machine. Statistical data were analyzed using one-way analysis of variance and Tukey's honestly significant difference test.
Results: Negative control Group I showed highest fracture resistance and positive control Group II had lowest fracture resistance. Among experimental groups, cold free-flow compaction technique with GuttaFlow2 (Group IV) showed higher fracture resistance as compared to the Group III, Group V, and Group VI.
Conclusion: GuttaFlow2 has the potential to strengthen the endodontically treated roots to a level that is similar to that of intact teeth.

Keywords: Fracture resistance; GuttaFlow2; gutta-percha; RoekoSeal Automix; Universal Testing Machine

How to cite this article:
Punjabi M, Dewan RG, Kochhar R. Comparative evaluation of fracture resistance of root canals obturated with four different obturating systems. J Conserv Dent 2017;20:445-50

How to cite this URL:
Punjabi M, Dewan RG, Kochhar R. Comparative evaluation of fracture resistance of root canals obturated with four different obturating systems. J Conserv Dent [serial online] 2017 [cited 2020 Sep 27];20:445-50. Available from: http://www.jcd.org.in/text.asp?2017/20/6/445/223191



   Introduction Top


The aim of root canal treatment is proper cleaning and shaping of the canal, obturation, preventing reinfection, maintaining the integrity of periodontium and achieving healing.

Endodontically treated teeth are weak and more susceptible to fracture than vital teeth because there is dehydration and loss of dentin during chemomechanical preparation, prolonged use of chemical agent during disinfection, and exertion of excessive pressure during obturation.[1] The goal of root canal obturation, therefore, is to increase the strength of the root canal and increase root fracture resistance by adhesion and mechanically interlocking root canal filling material with radicular dentin.[2] Root canal sealers bind gutta-percha to canal walls and fill up the voids, accessory canals, and irregularities within the canal and help in achieving three-dimensional sealing of the root canal system.[3]

Gutta-percha in combination with root canal sealers is the gold standard of root canal fillings because of its biological compatibility, lack of toxicity or allergic effects, and easy removal from the root canal, but it has some drawbacks such as its inability to strengthen root canal as it does not bond to dentin and leads to an incomplete obliteration of root canal space.[4],[5]

One of the most commonly used techniques of obturation of root canal system is the cold lateral compaction of gutta-percha. In 2004, a self-cure shrinkage-free material, GuttaFlow (Coltene/Whaledent, Switzerland) was introduced. It is the first nonheated, flowable gutta-percha which has both properties of sealer and gutta-percha and advantages of thermoplasticized gutta-percha systems such as homogeneous mass and reduced stresses on roots.[6]

In 2012, Coltene introduced a new GuttaFlow2 filling system for root canals which is delivered in two different ways: a capsule that is to be triturated for 30 s and in a convenient 5 ml automix syringe delivery system. This filling system works with cold free-flow gutta-percha. The syringe provides easy handling and ready to use, dispenses just the quantity required, mixes the material homogeneously, hygienically and free of air bubbles, working time is 10–15 min, and curing time is 25–30 min.

GuttaFlow2 is an advancement of the existing GuttaFlow material and has the same excellent material properties. It does not shrink but expands slightly by 0.2% and has a very good adhesion to gutta-percha points and dentin walls. This combination of expansion and adhesion creates an excellent seal. The solubility of GuttaFlow2 is zero. GuttaFlow2 contains microsilver particles that provide protection against reinfection of the root canal and does not lead to any corrosion or discoloration of GuttaFlow2 under clinical conditions.

GuttaFlow2 is thixotropic, the viscosity diminishes under pressure, and therefore, it flows into the smallest canals during placement of master point and optional auxiliary points. This feature allows for a three-dimensional obturation without condensation.

The BeeFill system (BeeFill 2in1) (VDW, Munich Germany) is a new thermoplasticized injection device and was developed to simplify obturation after canal preparation by the Mtwo rotary system.[7] BeeFill system (BeeFill 2in1) is a warm vertical compaction system which consists of downpack and backfilling device.[8] Silicone-based sealer, RoekoSeal Automix (RSA, Roeko, Langenau, Germany) contains polydimethylsiloxane, silicone oil, paraffin-based oil, hexachloroplatinic acid (catalyst), and zirconium dioxide for the radiopacity, has been used for the study.[9]

The aim of this study was to evaluate and compare the fracture resistance of root canals obturated with four different obturation systems (cold lateral compaction technique, cold free-flow compaction technique, warm vertical compaction technique, and injection-molded thermoplasticized technique) in endodontically treated teeth.

The null hypothesis was that there is no significant difference of fracture resistance of root canals obturated with four different obturating system in endodontically treated teeth.


   Materials and Methods Top


One hundred and twenty freshly extracted single-rooted anterior (central incisors) teeth with single canal of similar root sizes, root curvature, free from caries, cracks, restoration, fracture, dilacerations, root resorption, or open apices were selected. All debris and remaining tissues were removed from the teeth, and the teeth were disinfected with 5% sodium hypochlorite solution and then kept in normal saline solution.

Teeth were decoronated at the level of cementoenamel junction (CEJ) using a diamond disc and obtained a standardized root length of 14 mm [Figure 1]. Root length was established with size #15 K-files (VDW GmbH, Munich Germany). Working length was determined 1.0 mm shorter than the actual root canal length using digital radiography. All teeth, except those in control group, were instrumented using Mtwo rotary files (VDW) up to size #25/0.06 using a step-back technique. Root Canals were irrigated with 10 ml of 5% NaOCl and then with 3 ml of 17% Ethylenediaminetetraacetic acid (RC Help) (Prime Dental) to remove the smear layer. Then, a final flush with 1 ml of 5% NaOCl followed by 5 ml of normal saline was done. The biomechanical preparation was done under constant irrigation. Samples were then dried with sterile paper points of size #25/0.06. All specimen were randomly divided into four experimental groups (n = 25) and two control groups (n = 10).
Figure 1: Decoronated Samples

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  • Group I (n = 10): Negative control group – teeth were neither instrumented nor obturated
  • Group II (n = 10): Positive control group – instrumentation was done, but no obturation was performed
  • Group III (n = 25): Obturation was done using cold lateral compaction technique
  • Group IV (n = 25): Obturation was done using cold free flow compaction technique with GuttaFlow2 (Coltene/Whaledent GmbH Co. KG, Langenau, Germany)
  • Group V (n = 25): Obturation was done using warm vertical compaction technique with BeeFill (2 in1) (VDW, Munich Germany).


In all the groups, a master gutta-percha cone size #25/0.06 taper (METABIOMED Co., LTD, Korea) was selected and adjusted to fit with tug back at working length. The master gutta-percha cone was coated with RSA (Coltene/Whaledent GmbH Co.) and inserted into the canal, and a RVG (Kodak RVG5100) for each sample was taken. Accessory cones (0.02 taper) were coated with sealer and placed in the canal. The excess gutta-percha cone was seared off at the canal orifice with heated instrument 1 mm below the CEJ. The access opening was then sealed with Cavit (3M ESPE).

Group VI (n = 25): Obturation was done using injection-molded thermoplasticized technique with C-fill system ([COXO] Guangdong China [Mainland]). The C-fill obturation system consists of cordless obturation pen and cordless obturation gun. Gutta-percha pellet (METABIOMED Co., LTD, Korea) was inserted into the gutta-percha slot of the cordless obturation gun by pulling out the plunger. Turn on the power button and adjusted the temperature at 200°C. After 3 min, the warm gutta-percha flow out. The master gutta-percha cone (size #25/0.06 taper) that matched with prepared root canal and confirmed the tug back was coated with RoekoSeal sealer and inserted into the canal.

The excess gutta-percha was cut by heated obturating pen tip. The heated pen tip with gutta-percha was inserted to 4 mm short of the working length. The warmed gutta-percha was compacted with hand plugger (Dentsply Maillefer, Switzerland). Again obturating pen tip was heated and inserted gutta-percha to half of the working length of the root canal. Compaction was done with bigger plugger (Dentsply Maillefer, Switzerland). Rest of the canal was filled with obturating gun and compacted with bigger plugger, and canal opening was sealed with Cavit (3M ESPE). All teeth were then stored at 37°C in 100% humidity for 1 week.

Measurement of fracture resistance

All prepared teeth were vertically set in self-cure acrylic resin (Pyrax) blocks with a dimension of 20 mm in height and 40 mm in diameter) [Figure 2]. The apical 8 mm of each root was kept exposed. After 24 h, the acrylic resin was set and the blocks were stored in 100% humidity before mechanical tests.
Figure 2: Samples embedded in Acrylic Moulds

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Fracture resistance was evaluated in a Universal Testing Machine (Model No. WDW-5, Taiwan) [Figure 3]. A cross-head speed of 1 mm/min at an angle of 90° was set, and the compressive load was applied perpendicular to the long axis of the tooth at the canal orifice until fracture occurred. The force necessary to fracture each tooth was recorded in Newtons (N).
Figure 3: Universal Testing Machine with sample placed in position

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   Results Top


The results were calculated, tabulated, and subjected to statistical analysis [Table 1] and [Graph 1]. The statistical analysis was performed using the Statistical Package for the Social Sciences program (SPSS, Chicago, illinois, USA)for Windows, version 17.0. One-way analysis of variance with post hoc analysis (Tukey HSD) was applied to find the significant difference among the various groups. P < 0.001 was considered as statistically significant. The data after statistical evaluation were tabulated.
Table 1: Descriptive statistics of fracture resistance of the groups (Newton)

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Tukey's post hoc analysis [Table 2] shows that:
Table 2: Between-group comparison of fracture resistance (Tukey's honestly significant difference test)

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  1. No statistically significant difference was found between Group I and Group IV (P = 0.209) whereas all other groups were significantly lower than the Group I
  2. Mean difference of fracture resistance in Group II (+ve control) was statistically significantly lower than all other groups. There was no significant difference between Group II and Group V (P = 0.858) and between Group II and Group VI (P = 1.000) (P > 0.05)
  3. Mean difference between Group III and Group IV (P = 0.960) and Group III and Group V (P = 0.104) is not statistically significant whereas Group III and Group VI shows highly significant mean difference (P < 0.001)
  4. Mean difference between Group IV and Group V (P = 0.009) and Group IV and Group VI (P < 0.001) is highly statistically significant (P < 0.05)
  5. Group V and Group VI show no statistically significant mean difference (P = 0.730).


On the basis of the above assessment, the following order of fracture resistance was observed in the different groups:

Group I > Group IV > Group III > Group V > Group VI > Group II.


   Discussion Top


The following order of fracture resistance was observed in different groups in descending order:

Group I > Group IV > Group III > Group V > Group VI > Group II (−ve) control > GuttaFlow2 > lateral compaction > BeeFill > C-fill > (+ve) control.

The results of the study showed that all experimental groups had difference in their fracture resistance and reject the null hypothesis.

The highest fracture resistance was observed in Group I (−ve control) followed by Group IV (GuttaFlow2). This is because in unprepared roots, no force was imparted in the teeth, and there was no loss of dentin because no instrumentation was done resulting in an increased amount of intact tooth structure. Many studies have suggested that during instrumentation phase, removal of tooth structure decreases the fracture resistance and create a weakening effect on root (Teixeira et al., 2004).[10]

Group IV showed the highest fracture resistance when compared to all other groups which was statistically significant with a P < 0.001. However, no significant difference was found between Group I (−ve control) and Group IV (GuttaFlow2) with a P = 0.209 while all other groups were significantly lower than Group I. This could be due to the reason that the GuttaFlow2 obturating material has a strong sealing ability and has a homogeneous structure with particles of gutta-percha. It appears to fill the dentinal tubules well with extremely good adhesion to gutta-percha cones.[11] GuttaFlow2 is a first sealer/gutta-percha combination which is flowable at room temperature that can be used as sealer as well as an obturating paste without a solid master cone.[12]

The mean difference of fracture resistance in Group II (+ve control) was lower than all other groups and statistically significant. This could be because there is excessive loss of dentin during the instrumentation phase resulting in weakening of the root which is inevitable.[10] It was expressed in studies (Lertchirakarn et al., 1999;[13] Lindauer et al.,[14] 1989; and Murgel et al., 1990[15]) that the fracture resistance of the roots reduced due to excessive removal of dentin to facilitate the usage of pluggers in heat condensation technique with vertical compaction and with spreaders in cold lateral condensation technique.

There was no statistically significant difference between Group II (+ve control) and Group V (BeeFill) with a P = 0.858 [Table 2]. This could be because the force which was created by the plugger used and the heat applied during obturation caused thermal expansion in the root dentin which affected the fracture resistance adversely.

Similar results were observed by Saw and Messer[16] who compared the forces applied to the roots during the lateral condensation, Obtura and Thermafil techniques and concluded that the maximum force occurred during lateral compaction and minimum with Obtura. They also reported that more thermal intensity occurred in Thermafil and Obtura groups particularly in the coronal region while during cold lateral compaction technique more tension occurred, especially in the apical region.

In this study, there was no statistically significant difference between Group II (+ve control) and Group VI (C-fill) with P = 1.000 [Table 2]. This could be because in an injection-molded thermoplasticized obturating system (C-fill), heating of gutta-percha was done to plasticize the gutta-percha so that it would flow. In this technique, excessive canal enlargement was done to accommodate the injection needles. This excessive loss of tooth structure could have reduced the fracture resistance.

The Group V (BeeFill) and Group VI (C-fill) showed lower fracture resistance and showed no statistically significant mean difference (P = 0.730) [Table 2] between them because these technique have disadvantages such as lack of material control, excessive canal enlargement to accommodate the injection needles, the rapid cooling of the material results in poor condensation, and voids. Furthermore, there are some equipment-related problems such as needle breakage or gutta-percha leakage and presence of under condensed, slender filling in the apical third of the canal.[17]

The fracture resistance of Group III (lateral compaction) was lower than Group IV (GuttaFlow2), but the mean difference between them (P = 0.960) [Table 2] was not statistically significant. This could be because gutta-percha in combination with sealer has good adaptability to root canal wall and master cone and can be comparable to GuttaFlow2.[5] It was however cited by Meister et al. that excessive pressure applied during lateral compaction of gutta-percha is the most common cause of vertical root fractures.

Group III (lateral compaction) and Group V (BeeFill) (P = 0.104) [Table 2] was not statistically significant, and these techniques did not increase the fracture resistance of the teeth because force was created in the root canals by the spreader and plugger during obturation.[18] Saw and Messer suggested that the strains in obturation may be generated by a wedging effect of the spreader within the canal, either by direct contact with the canal walls or transmitted through gutta-percha.

The statistical mean difference between Group III (lateral compaction) and Group VI (C-fill), P< 0.001 and between Group IV (GuttaFlow2) and Group VI (C-fill) (P< 0.001 [Table 2] was highly significant. This could be due to the reason that in an injection-molded GP (C-fill), there is a temperature rise on the external root surface which results in potential damage to root cementum and periodontal ligament. Furthermore, rapid cooling of the material results in poor compaction and voids which might lower the fracture resistance of the roots.[17]

The statistical mean difference between Group IV (GuttaFlow2) and Group V (BeeFill), P = 0.009 [Table 2] was highly significant. This could be because in GuttaFlow2, the gutta-percha flows into lateral canals and completely fills the space between the root canal wall and master cone. In addition, no heat is used with placement of the material thereby no shrinkage occurred, while in BeeFill obturating system, shrinkage of GP occurred and also thermal expansion of root dentin occurred which might decrease the fracture resistance of the roots.[19]


   Conclusion Top


Within the limitations of this present study, the following conclusions were drawn:

  • GuttaFlow2 has the potential to strengthen the endodontically treated roots to a level that is similar to that of intact teeth
  • Warm vertical compaction technique with BeeFill (2 in1) and injection-molded thermoplasticized technique with C-fill system were not superior to the cold free-flow compaction technique with GuttaFlow2 in terms of fracture resistance
  • Cold lateral compaction technique may have the potentiality to strengthen endodontically treated teeth to a level comparable to that of cold free-flow compaction technique with GuttaFlow2.


However, further long-term clinical trials are needed to assess the fracture resistance of the above-mentioned newer obturating systems.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Lertchirakarn V, Palamara JE, Messer HH. Load and strain during lateral condensation and vertical root fracture. J Endod 1999;25:99-104.  Back to cited text no. 13
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Correspondence Address:
Mansi Punjabi
Department of Conservative Dentistry and Endodontics, ITS Dental College and Hospital, Plot No-47, Knowledge Park-III, Greater Noida - 201 307, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JCD.JCD_217_17

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