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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 32  |  Issue : 2  |  Page : 81-85

Influence of working length determined by three different apex locators on the apical extrusion of debris following the instrumentation with rotary Ni–Ti instrumentation system


Department of Conservative Dentistry and Endodontics, I.T.S. Dental College and Hospital, Ghaziabad, Uttar Pradesh, India

Date of Submission23-Aug-2019
Date of Decision12-Jan-2020
Date of Acceptance01-Feb-2020
Date of Web Publication18-Jun-2020

Correspondence Address:
Pragya Kumar
Department of Conservative Dentistry and Endodontics, I. T. S. Dental College and Research, Muradnagar, Ghaziabad, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_60_19

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  Abstract 


Aim: This study aimed to comparatively evaluate the influence of working length (WL) determined by three different electronic apex locators (EALs) on the apical extrusion of debris following the instrumentation with a rotary NiTi instrumentation system.
Methodology: Forty extracted human maxillary or mandibular premolar teeth with single root and canal were selected. Standardized access cavities were prepared, and the samples were divided into four groups according to the method used to determine the WL: Group I (n = 10) – actual working length (AL), Group II (n = 10) – Root ZX mini, Group III (n = 10) – CanalPro™, and Group IV (n = 10) – Propex Pixi™. Each specimen was held in a test apparatus to evaluate the apical extrusion of debris during instrumentation. Instrumentation of all the specimens was done using ProTaper Next till the size X3. The apically extruded debris was collected and calculated by subtracting the initial weight of the tube from the weight of the tube containing dried debris. The apically extruded debris weight score was calculated and tabulated and was subjected to statistical analysis using one-way ANOVA and post hoc Tukey test.
Results: Group II and Group III exhibited similar results and exhibited significantly less apical extrusion of debris compared to Groups I and IV.
Conclusion: WL determined by EAL (Root ZX mini and CanalPro) showed lesser apical extrusion of debris than AL determination.

Keywords: Apex locators, CanalPro™, Propex Pixi™, Protaper next, Root ZX mini


How to cite this article:
Chand A, Kumar P, Taneja S. Influence of working length determined by three different apex locators on the apical extrusion of debris following the instrumentation with rotary Ni–Ti instrumentation system. Endodontology 2020;32:81-5

How to cite this URL:
Chand A, Kumar P, Taneja S. Influence of working length determined by three different apex locators on the apical extrusion of debris following the instrumentation with rotary Ni–Ti instrumentation system. Endodontology [serial online] 2020 [cited 2020 Jul 13];32:81-5. Available from: http://www.endodontologyonweb.org/text.asp?2020/32/2/81/287069




  Introduction Top


The major prerequisite for successful root canal treatment is thorough debridement of root canals and three dimensionally sealing the root canal system. The complete disinfection is achieved by chemomechanical preparation and intracanal medication. However, during root canal treatment, dentine chips and pulp tissue, which contain microorganisms, may be extruded into the periapical tissues. As a result of this periapical extrusion of debris, postoperative complications such as pain or flareups may occur, which, in turn, leads to delayed periapical healing.[1],[2]

Ideally, root canal preparation and filling should not extend beyond the tooth root nor leave uninstrumented areas inside the root canal.[3] Apical constriction (AC) (the minor apical diameter or minor diameter) is the end reference point or termination of the working length (WL), as it often coincides with the narrowest diameter of the root canal.[4] The cementodentinal junction has also been suggested as the termination point for WL as it represents the transition between pulpal and periodontal tissues.[5]

Traditional methods used for establishing root canal length include the use of radiography, knowledge of anatomy, anatomical averages, tactile sensation, and presence of moisture on paper points. All these methods have certain limitations such as more radiation exposure and lengthy time consumption and provide false readings in case of narrow canals and open immature apex.

Therefore, the search for a more accurate and predictable method of determining WL has led to the invention of the electrical method.

Root ZX mini (J. Morita, Kyoto, Japan) is the most recent version of Root ZX, which uses multiple frequencies and can be classified as a fourth-generation electronic apex locator (EAL) (Kobayashi, Suda, 1994). It measures just over 4” × 2 1/3.” The liquid crystal display screen maintains an excellent readability with a progressive display and a high contrast. CanalPro™ (Coltene, Whaledent, Germany) is characterized by its brilliant, colored, three-dimensional (3D) panel and its accuracy of measurement. It has an ergonomic design and provides the ease of operation. CanalPro apex locator provides accuracy of measurement, is user friendly, and has an intelligent interface (colored 3D panel). Propex Pixi™ (Densply, Maillefer, USA) is a fifth-generation EAL. The fifth generation of EAL uses multiple frequencies, in addition to calculating the root mean square values of the electric signals.

Till date, all the preparation and instrumentation techniques have been reported to be associated with the extrusion of the infected debris into the periradicular tissue during chemomechanical preparation, even if the preparation is short of the apical terminus.[6],[7] Vande Visse and Brilliant [8] first quantified the amount of debris extruded apically during instrumentation using hand files.

Although all preparation techniques and instruments are related with some sort of debris extruding through the apical foramen, less dentine debris extrusion has been associated with the use of motor-driven rotary instruments when compared to hand-file techniques, as demonstrated in laboratory studies.[9],[10]

Till date, no study has compared the influence of WL using various apex locators on the apical extrusion of debris.

Hence, this study comparatively evaluated the influence of WL determined by three different apex locators (Root ZX mini, CanalPro, and Propex Pixi) on the apical extrusion of debris following the instrumentation with a rotary Ni–Ti instrumentation system (ProTaper Next [PTN]).

The null hypothesis tested was that there was no difference in the amount of apically extruded debris when WL was determined actually and with apex locators (Root ZX mini, CanalPro, and Propex Pixi).


  Methodology Top


Selection of sample and preparation of sample

Forty extracted human maxillary or mandibular premolar teeth freshly extracted for orthodontic purpose with single root, mature apices, similar length, and straight root canal (curvature 0°–10°) were selected for the study. These specimens were stored in 1% thymol until used. The sample size was decided on a previously done pilot study with ten samples in each group using software Open Epi, version 3, Atlanta, GA, USA. The sample used in the pilot study was discarded.

The cuspal tips of each tooth were flattened to achieve a reproducible stable reference point, and standard oval-shaped access cavities were prepared using a high-speed air rotor hand piece and Endo access bur under water cooling. The pulp chamber was flared and redefined using Endo Z bur, and the root canal orifice was located. The apical patency of all the teeth was checked using a 10-k file.

The coronal portion of the canal was flared using sequential Gates Glidden burs #4 and #3 and #2 in a crown-down manner.

Grouping of samples

The samples were randomly divided into four groups of ten samples each according to the method used for the determination of WL.

  • Group I (n = 10) – Actual working length (AL)
  • Group II (n = 10) – Root ZX mini Apex locator (J. Morita, Kyoto, Japan)
  • Group III (n = 10) – CanalPro Apex locator (Coltene, Whaledent, Germany)
  • Group IV (n = 10) – Propex Pixi Apex locator (Densply Maillefer, USA).


Group I: To obtain the AL, a size 15 K-type stainless steel file was inserted into the canal until the file tip became just visible at the root apex under ×2.5 magnification loops. The file was then withdrawn until its tip was tangential to the apical foramen followed by adjusting the silicon stopper. The file was withdrawn from the canal, and the distance between the file tip and the stopper was measured using a digital caliper. AL was recorded by subtracting 0.5 mm of this WL and was measured to the nearest 10th of a millimeter.

In Groups II, III, and IV, to simulate the periodontium, anin vitro alginate model was prepared to determine the WL. The samples of these groups were embedded up to the cementoenamel junction in a container containing freshly mixed alginate which simulated the periodontium. To complete the circuit, a labial clip was placed in contact with the alginate. All measurements were made within 30 min with the alginate model kept sufficiently humid. In Groups II, III, and IV, all the WL measurements were done according to the manufacturer's instruction. Measurements done with different apex locators were considered valid if the reading remained stable for at least 5 s, measurements were repeated three times, and the mean values were calculated and recorded for every sample and for every EAL.

Preparation of the test apparatus

Myers and Montgomery's [11] experimental model was used to record the apical extrusion of debris. Eppendorf tubes were separated, and an analytical balance was used to determine the initial weight with an accuracy of 5–10 g. The mean value was calculated by weighing each tube three times. Specimens were placed through the stopper up to the cementoenamel junction. A 27G- needle was also placed in the stopper to balance air pressure inside and outside the tubes. The tubes were fitted into the vials after the attachment of the stoppers. The specimens were then placed in the test apparatus.

Biomechanical preparations of samples

PTN system was used in gentle inward and outward motions to prepare the samples at 300 rpm and 2 Ncm torque with a torque-controlled endodontic motor. All instruments were used at a predetermined WL. During the instrumentation, the PTN was used according to the manufacturer's instructions from X1 (17/0.04) to X2 (25/0.06) followed by an apical enlargement of X3 (30/0.07). A total volume of 3 mL of distilled water was used as irrigation solution.

During instrumentation, the glass vial was covered with a tin foil to shield the view of root apex during instrumentation.

Collection of debris

After the instrumentation was completed, the stopper, needle, and tooth were separated from the Eppendorf tube, and debris adhered to the root surface were collected by washing the root with 1 mL of distilled water while in the tube. The tubes were stored in an incubator at 68°C for 5 days to evaporate the distilled water.

Each of the tubes was weighed in triplicate, and the mean value was calculated. The amount of extruded debris was calculated by subtracting the initial weight of the tube from the weight of the tube containing dried debris.

The apically extruded debris weight score was calculated, was tabulated, and was subjected to statistical analysis using SPSS version 20 (IBM SPSS Statistics for Windows, IBM Corp, Armonk, NY, USA) The changes in different groups were quantified using one way ANOVA followed by post hoc comparision by least significant difference method.


  Results Top


Group II (Root ZX mini) showed minimum extrusion of debris and Group I (actual length) showed maximum. The intergroup comparison between Group II and Group III showed no significant difference and was significantly less than Group I and Group IV. The intergroup comparison between Group I and Group IV showed no significant difference [Table 1].
Table 1: Mean of apically extruded debris after working length determination by different methods

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  Discussion Top


EALs are one of the mainstays to determine the WL. Many studies have evaluated the accuracy of WL determination using EALs, and it has been reported that EALs have great accuracy and also reduce the incidence of overinstrumentation.[12]

Several studies have been carried out to compare the accuracy of different apex locators, but till date, no study has been done to evaluate the influence of these apex locators – Root ZX mini (J. Morita), CanalPro (Coltene), and Propex Pixi (Dentsply) on the apical extrusion of debris.

In this study, forty single-rooted premolars were used to ensure the standardization of selected specimens. The teeth with similar canal size at the WL and canal curvature were used since it decreases the number of variables and ensure that the amount of apically extruded debris caused due to the instrumentation techniques and not due to the tooth morphology.

The AL was taken using a size 15 K-type stainless steel file which was inserted into the canal until the file tip became just visible at the level of the major apical foramen under ×2.5 magnification loops. The file was then withdrawn until its tip was tangential to the apical foramen, as reported by earlier studies in literature.[13],[14]

In this study, to evaluate the apical extrusion of debris, Mayer and Montgomery's (1991) apparatus was used. In this apparatus, the apical extrusion is not limited, due to the absence of the physical back pressure provided by periapical tissues as each tooth specimen was held in a preweighed Eppendorf tube which was then fixed inside the glass vial through a rubber stopper.[11] The vial was obscured with a foil so that the operator was not able to see the root apex during instrumentation. Many studies in literature have used the same Mayer and Montgomery model to study the apical extrusion of debris as it quantifies the amount of extruded debris.[15],[16]

The importance of weighing the apically extruded debris is that, if large amount of debris is extruded during root canal instrumentation, a higher incidence of postoperative pain might be anticipated. In addition, it is well documented in literature that extruded microorganisms and debris can cause an inflammatory reaction when it was forced apically during root canal preparation.

The result of the current study showed that none of the WL determination method completely avoided the apical extrusion of debris, with Group II (Root ZX mini) showing minimum extrusion of debris followed by Group III (CanalPro), Group IV (Propex Pixi), and Group I (Actual length) [Table 1]. Thus, the null hypothesis was rejected.

AL determination showed more amount of extruded debris as compared to apex locator groups. This might be because AL was determined manually by visualizing the tip of the file at the root apex using loop and then calculating it by subtracting 0.5 mm from the whole length. This might have decreased the precision of calculating the WL or even precision of locating the AC, thus increasing the chances of overestimation of the WL, leading to overinstrumentation in turn increasing the apical extrusion of debris. In a study done by Arora and Tewari on the morphology of the apical foramen in posterior teeth in a North Indian population, it was seen that the distance (in mm) and % age deviation of minor apical foramina from the apex for the mandibular first premolar range from 0.112 to 2.18 mm with an average of 0.79 mm. This signifies that the distance between anatomic apex and AC is not constant, and 0.5 mm short of anatomic apex might lead to overestimation of the WL.[17]

Root ZX mini showed the least amount of debris extrusion as compared to AL (Group I), CanalPro (Group III), and Propex Pixi (Group IV). This might be due to the principle of mechanism on which Root ZX mini works. It is a frequency-dependent type of apex locator working on the principle of frequency or comparative impedance. Root ZX mini provides a highly accurate indication of the file's location, which is not affected by the presence or absence of blood, other discharges, electrolytes, saline, tap water, or hydrogen peroxide. Whereas the study done by Rana showed that there was no significant difference between the accuracy of Propex Pixi and Root ZX mini.[18] The results of our study are in accordance with those of Naveed and Pradeep and Ravichandra et al., who showed that the accuracy of Root ZX mini was better than Propex Pixi.[19],[20]

CanalPro (Group III) showed less apically extruded debris than Propex Pixi (Group IV) and AL (Group II). This might be due to the mechanism of CanalPro that measures two frequencies that are alternated and not mixed, thus cancelling the need for signal filtering and eliminating the noise caused by nonideal filters, which makes the measurement much more immune to various kinds of electromagnetic noises. It is based on dual frequencies that are sent from and returned to the unit after traveling along the electric circuit. The results of our study are in accordance with those of Taneja et al., which showed the highest accuracy of CanalPro Apex locator in comparison to Propex Pixi.[21] CanalPro may have shown better results than AL because in AL, the AC was arbitrarily calculated.

Propex Pixi (Group IV) showed less apical extrusion of debris than AL (Group I) because Propex Pixi detects the minor apical foramen based on the analysis of electrical properties of different tissues inside the root canal system. Whereas in the AL, the AC was calculated by subtracting 0.5 mm from the anatomic apex.

Literature have proven that WL determination by all means, either actual or EALs, causes some amount of apical extrusion of debris, although it can be minimized by following all the manufacturer's instructions. Furtherin vitro andin vivo studies are required to justify the influence of WL determination by various apex locators in the apical extrusion of debris.


  Conclusion Top


Within the limitations of the study, it was concluded that EALs were more precise in determining WL in comparison to AL, thus reducing the amount of apically extruded debris. The amount of apically extruded debris was minimum when WL was determined by Root ZX mini in comparison to all the apex locators used in the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Vande Visse JE, Brilliant JD. Effect of irrigation on the production of extruded material at the root apex during instrumentation. J Endod 1975;1:243-6.  Back to cited text no. 8
    
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Paul R, Paul M, Paul G, Mittal A. Comparison of accuracy of root ZX and Propex II apex locator – Anin vitro study. J Endod 2000;24:30-5.  Back to cited text no. 12
    
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Çiçek E, Akkocan O, Furuncuoglu F. Comparison of apically extruded debris associated with several nickel-titanium systems after determining working length by apex locator. J Conserv Dent 2016;19:68-71.  Back to cited text no. 13
    
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Gehlot PM, Manjunath V, Manjunath MK. Anin vitro evaluation of the accuracy of four electronic apex locators using stainless-steel and nickel-titanium hand files. Restor Dent Endod 2016;41:6-11.  Back to cited text no. 14
    
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Çiçek E, Yılmaz N, Furuncuoǧlu F. The influence of determining the working length with an apex locator on the amount of apically extruded debris following instrumentation with ProTaper next and HyFlex CM. Saudi Endod J 2016;6:122-6.  Back to cited text no. 15
    
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Vyavahare NK, Raghavendra SS, Desai NN. Comparative evaluation of apically extruded debris with V-Taper, ProTaper next, and the self-adjusting file systems. J Conserv Dent 2016;19:235-8.  Back to cited text no. 16
[PUBMED]  [Full text]  
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Arora S, Tewari S. The morphology of the apical foramen in posterior teeth in a North Indian population. Int Endod J 2009;42:930-9.  Back to cited text no. 17
    
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Rana A. Comparative evaluation of accuracy of two different electronic apex locators in presence of various herbal irrigating solutions: Anin vitro study. J Dent Med Sci 2017;16:40-4.  Back to cited text no. 18
    
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Naveed N, Pradeep S. Comparative evaluation of the accuracy of two electronic apex locators with CBCT in determining the working length in teeth with simulated apical root resorption: Anin vitro study”. Int J Mult Res Mode Ed 2017;3:2454-9.  Back to cited text no. 19
    
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Ravichandra C, Nimeshika R, Smitha R, Shekar V. The clinical accuracy of 2 electronic apex locators to determine working length in comparison with standard radiographic method in teeth with and without periapical lesion. J. Endod 2015;27:136-41.  Back to cited text no. 20
    
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