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ORIGINAL RESEARCH ARTICLE  
Year : 2017  |  Volume : 20  |  Issue : 6  |  Page : 439-444
Comparison of different agitation methods for the removal of calcium hydroxide from the root canal: Scanning electron microscopy study


Department of Endodontics, Dental School, Aristotle University of Thessaloniki, Thessaloniki, Greece

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Date of Submission29-Sep-2017
Date of Decision15-Nov-2017
Date of Acceptance28-Nov-2017
Date of Web Publication15-Jan-2018
 

   Abstract 


Aim: This ex vivo study compared the efficiency of different irrigations systems to remove calcium hydroxide from root canal walls, especially from the apical third by using scanning electron microscopy (SEM).
Materials and Methods: Eighty-four single-rooted teeth were divided into 4 groups of 20 teeth each, according to different irrigation protocols using a 30-gauge slot-tipped needle, ultrasonic irrigation system, erbium-doped yttrium aluminum garnet laser (Er: YAG) laser, and EndoVac system. The rest 4 teeth were used as control groups (2 positive and 2 negative control groups). After coronal access, all teeth were instrumented by Protaper Next rotary files (Dentsply-Maillefer, Ballaigues, Switzerland) up to size X3, followed an irrigation protocol and filled with pure calcium hydroxide powder mixed with saline. Teeth were stored in an incubator for 7 days, and then, calcium hydroxide was removed using 3 techniques: Manually (Group 1), by ultrasonic irrigation (Group 2), by laser Er: YAG and x-pulse tip (Group 3), and by EndoVac system (Group 4). The teeth of control groups were instrumented as the experimental groups; no removal technique was applied in positive group, whereas in negative one, the root canals were left empty. Teeth were sectioned longitudinally and observed under SEM Results were statistically analyzed with the Kruskal–Wallis Test and Mann–Whitney Test.
Results: The results showed a significant difference between laser and the other three groups in coronal and middle root third, but no statistic difference in apical third.
Conclusion: Laser improved the removal of calcium hydroxide in comparison with conventional techniques.

Keywords: Calcium hydroxide; erbium-doped yttrium aluminum garnet laser laser; removal techniques

How to cite this article:
Kourti E, Pantelidou O. Comparison of different agitation methods for the removal of calcium hydroxide from the root canal: Scanning electron microscopy study. J Conserv Dent 2017;20:439-44

How to cite this URL:
Kourti E, Pantelidou O. Comparison of different agitation methods for the removal of calcium hydroxide from the root canal: Scanning electron microscopy study. J Conserv Dent [serial online] 2017 [cited 2020 Sep 26];20:439-44. Available from: http://www.jcd.org.in/text.asp?2017/20/6/439/223195



   Introduction Top


Calcium hydroxide is the most common antimicrobial intracanal dressing used between the sessions of endodontic therapy, due to its antibacterial action and organic tissue dissolution capacity.[1] Despite the unique properties, studies have advocated that calcium hydroxide should be removed totally before dentinal tubules obturation.[2] To date, there is no consensus on which method is the best for calcium hydroxide removal. Several techniques have been described to remove calcium hydroxide from root canals.[2],[3],[4],[5],[6],[7] The most popular technique is instrumentation with the use of master apical file (MAF) at working length, in combination with copious irrigation.[3]

Conventional irrigation with syringes has been considered as an efficient method of irrigant delivery, using syringe with agents, such as NaOCl and ethylenediaminetetraacetic acid (EDTA) in different combination. This technique is still widely accepted by both general practitioners and endodontists. However, when conventional irrigation is used, stream action is relatively weak because of complex root canal anatomy.[8],[9] It is supported that effectiveness of irrigation depends importantly on stream action[10] and not on the volume of irrigant.[11] Therefore, the current endodontic techniques fall short of the goal to remove all calcium hydroxide dressing consistently. To overcome the previous problem, different irrigation techniques have been proposed to improve the efficiency of irrigation, including the use of sonic and ultrasonic agitation,[12] which generates continuous irrigant movement.[5]

The recent years, dental laser (light amplification by stimulated emission of radiation) has established the acceptance of the scientific community due to its unique properties. Results suggest that erbium-doped yttrium aluminum garnet laser (Er: YAG) laser is an effective tool for disinfection thanks to its highest absorption in water and consequently, in dental tissues without significant thermal effects.[13],[14] On the other hand, there is little evidence of the Er: YAG laser concerning its capacity to remove calcium hydroxide.

In this ex vivo study, scanning electron microscopy (SEM) was used to compare the efficiency of different irrigation techniques in removing calcium hydroxide from root canal walls.


   Materials and Methods Top


Specimen preparation

The protocol of this study was accepted by the Research Ethics Committee of Dental School of Aristotle University of Thessaloniki (Greece). After approval, 84 permanent single-rooted human teeth extracted were selected and radiographed in the buccal-lingual and mesial-distal direction. Criteria for tooth selection included a single root canal, no visible root caries, no fractures, cracks, internal and external resorption, calcification, completely formed apex, and no former root canal therapy.

Teeth were stored in a 5% NaOCl solution for 2 days to remove organic residues and then in a 0, 1% thymol solution until they were used. Root canal length was standardized to a length of 14 mm [Table 1]. Teeth were set in acrylic blocks and were de-crowned with a double-sided diamond disc using a low-speed handpiece. Apical patency was obtained by K-file size #15 (Sybron Endo, Kerr, USA). The files were introduced further into the root canal until just the tip was visible at the apical foramen. Root canals were instrumented using ProTaper Next (Dentsply-Maillefer, Ballaigues, Switzerland) upsize χ3 and irrigated with 1 ml 5% NaOCl between the instruments. Canal preparation was performed using an electric engine (X-Smart, Dentsply Maillefer) with contact speed of 300 rpm and rotational force (torque) of 1, 6 N. cm, at the working length. At the end of instrumentation, root canals were irrigated by 5 ml 5% NaOCl followed by 5 ml 17% EDTA for smear layer removal and distilled water.
Table 1: Laser parameters

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Root canals were dried with absorbent paper points and filled with pure powder calcium hydroxide mixed with barium sulfate (8:1) and distilled water using the Lentulo spiral No 35 and under the magnification of an operative microscope. The coronal orifices were sealed with cotton pellets and temporary restorative material Coltosol (Coltene, WholeDent, Switzerland). Teeth were incubated for 7 days in a thermostatic incubator at 37°C temperature and 100% humidity (Memmert, Schwabach Germany).

Experimental procedure

Teeth were then randomly assigned into 4 groups, according to the protocol used to remove the calcium hydroxide dressing:

  • 1st Group (n = 20): Manual. Calcium hydroxide was removed by manual technique, with the use of MAF (size of #35 K-file) and syringe irrigation for 60 s
  • 2nd Group (n = 20): Ultrasonic (P5 Newtron, Satelec, Acteon, UK). Calcium hydroxide was removed by ultrasonic technique. The solution was delivered using a master delivery tip which was located at the root canal orifice. Continuous irrigant supply was ensured for 60 s
  • 3rd Group (n = 20): EndoVac system (Sybron Endo). Root canals were rinsed according to manufacturer's recommendations with macro and micro irrigations: The macro cannula was inserted into the root canal 4 mm less from the working length, and NaOCl was delivered for 30 sec into the pulp chamber. The microcannula was placed to working length. Each of irrigant (5% NaOCl, 17% EDTA, distilled water) was delivered for 60 sec
  • 4th Group (n = 20): Er: YAG Laser (Fotona, Ljubljana, Slovenia). Root canals were irradiated at pulse duration of 50 μsec, pulse energy of 20 mJ (10−3 Joule) and pulse frequency of 15 Hz, according to manufacturer's parameters. The tip, called x-pulse (600 μm, diameter, 14 mm length) was inserted into the canal and held stationary, parallel to the canal wall, at the first 1 mm of the coronal third. It was followed the same irrigation protocol (5% NaOCl and 5 ml 17% EDTA, distilled water for 60 sec each one)


    • Positive control (n = 2): The teeth were instrumented as the experimental groups. The root canals were filled with calcium hydroxide, but none of the removal technique was applied
    • Negative control (n = 2): The teeth were instrumented as the experimental groups, but the root canals were left empty.


The entire experimental part of the study was carried out by one operator. Grooves were prepared on the buccal and lingual surfaces with a diamond bur used with a high-speed handpiece. Teeth were split along their long axis in a buccolingual direction using a hammer and chapel. They were set suitably in round bases and were carbon coated, to be observed under the scanning electronic microscope at 3 levels of magnification (×100, ×500, and ×2000). Digital images were taken at the center of coronal (9 mm from apex), middle (6 mm from apex), and apical (3 mm from apex) thirds [Figure 1].
Figure 1: Scanning electron image of the root canal: C (coronal), M (middle), A (apical)

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All samples were analyzed using energy dispersive spectrometry (EDS) (Inca software, Oxford, UK) at ×2000 magnification within an area (30 μm) at every third. The identification of the calcium was achieved usingNORAN System Six X-ray (Microanalysis System from Thermo Fisher) [Figure 2].
Figure 2: Scanning electron microscopy/energy dispersive spectrometry analysis (×2000)

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To estimate the percentage of calcium hydroxide residues, it was followed a specific rating system [Figure 3]:
Figure 3: Scanning electron microscopy images representative of scores attribution. (a) Score 0: Absence of residues; (b) Score 1: Small amount of residues; (c) Score 2: Moderate amount of residues; (d) Score 3: Large amount of residues

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The evaluation was performed by two calibrated examiners independently and in a blind manner. If the examiners could not reach an agreement, a third examiner would assist in the scoring of the sample.

The Cohen's kappa coefficient was calculated to analyze inter-rater agreement. Results were statistically analyzed with Kruskal–Wallis and Mann–Whitney test. Kruskal–Wallis test was used to compare the percentage of calcium hydroxide remaining among groups, for each third and considering the canal as a whole. Mann–Whitney test was performed as the post hoc multiple comparison method. Statistical analysis was performed with IBM SPSS Statistics Software 20 and the significance level was set at 1% (P < 0. 01).


   Results Top


The Cohen's kappa coefficient of inter-rater reliability was 0.81, while the intra-rater reliability scores were 94% and 96%. Positive control specimens showed densely packed remnants in all thirds as opposed to the negative controls. Residual calcium hydroxide was found in specimens of all experimental groups.

When examining the efficacy of calcium hydroxide removal from all thirds, Kruskal–Wallis test revealed that laser group was more efficient than other groups [Table 2]. Representatives SEM images are shown in [Figure 4]. More specifically:
Table 2: Percentage of residual Ca(OH)2 residues at every canal third

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Figure 4: Scanning electron microscopy images representative of three groups. Group 1 (A = Coronal third; B = Middle third; C = Apical third), Group 2 (D = Coronal third; E = Middle third; F = Apical third), Group 3 (G = Coronal third; H = Middle third; I = Apical third), Group 4 (J = Coronal third; K = Middle third; L = Apical third)

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  • Group 1: The root canal walls in this group are moderate clean in coronal part. It is possible to see some open tubule orifice in the middle third. However, in apical third, all the magnification images show the presence of intact calcium hydroxide and debris
  • Group 2: The root canal walls in this group are not cleaner that in 1st group but it is possible to see a less percentage of remnants in apical third
  • Group 3: The root canal walls appeared cleaner from group in apical third from Group 1 and 2
  • Group 4: In all thirds, dentin surfaces appeared 50% less calcium hydroxide residues than other groups.



   Discussion Top


Strict criteria were applied in sample selection to standardize the specimens, and to avoid sample-related bias. Likewise, irrigation protocol (irrigants, volume, and activation time) was common in all experimental groups. This reduced the amount of variables and allowed the evaluation of the contribution of removal techniques.

Er: YAG laser is the most investigated wavelength in endodontics and has proven to have many advantages over conventional methods. Laser-activated irrigation using Er: YAG laser is an irrigants agitation technique with great potential for improved cleaning of the root canal system.[10] This could be attributed to the photoacoustic streaming effect seen when light energy is pulsed in liquid. Laser emits photons to generate photoacoustic shockwaves into root canals. With the irrigant continuously delivered by means of a syringe into the pulp chamber during the laser process, the resultant shock wave is directed 3-dimensionally in the fluid and effectively removes both vital and necrotic tissue remnants.[15] We speculate that this phenomenon was responsible for the lowest percentage of calcium hydroxide residues among the other experimental groups, in coronal and middle root third-the results of SEM observations showed that the biggest number of teeth with 0 score belongs to Group 4.

Some authors have suggested the need for large canal preparation so as to enable a 27-gauge needle to reach the canal end, resulting in canal transportation or destruction of root anatomy while canal ramifications remain still untouched by any irrigant.[16] In our study, Er: YAG laser was equipped with a newly designed tip of 14 mm long 600-μm diameter, called x-pulse. The tip was placed and held stationary into the coronal access opening of chamber only. The advantage of the tip is that permitted minimal preparation and not over-instrumented root canal to achieve sufficient disinfection.[17]

However, our findings were similar with those of Kaptan et al.[18] who concluded that the calcium hydroxide residues were reduced to 60.58% with Er: YAG laser in comparison to 46.3% by conventional technique. However, the difference between the two groups was not statistically significant. Furthermore, noticing the results of that study, there was no comparison between the three parts of root canals as in our study, in which each third was evaluated concerning the presence or not of remnants.

More recently, the effect of various techniques – including photon-initiated photoacoustic streaming (PIPS), ultrasonic, sonic and conventional irrigation – on the removal of calcium hydroxide from artificial grooves created in root canals was evaluated.[19] It was concluded that PIPS, was superior to other techniques which mentioned, providing complete removal of the intracanal medicament. Other authors concluded that even though none of the techniques removed the calcium hydroxide dressing completely, laser-activated irrigation was significantly more effective than needle irrigation.[20]

In another study, it was showed that pulse energy, pulse length, pulse frequency, irradiation time, and position of the fiber tip all significantly affected the cleaning efficacy of laser. Higher pulse energy, shorter pulse length, longer irradiation time, placement of the fiber tip close to the groove, and to a lesser extent, higher pulse frequency resulted in better debris scores. On the other hand, the shape and diameter of the fiber tip had no statistically significant influence on the results.[17]

Lasing parameters vary considerably, and their influence remains unclear. In the present study, according to manufacturer's parameters, the teeth were irradiated at a wavelength of 2940 nm, with an output of 0.3 Watt, pulse energy of 20 mJ (10 − 3 Joule) and pulse frequency of 15 Hz. We did not investigate the influence of different lasing parameters on the cleaning efficacy of laser-activated irrigation.

Concerning 1st and 2nd group, conventional and ultrasonic technique, there was not statistically significant difference. That comes in disagreement with some authors[21] who compared the efficacy of conventional technique and passive ultrasonic irrigation for the removal of calcium hydroxide. They found that ultrasonic agitation of NaOCl was significantly more effective than irrigant-only techniques. Likewise, it was evaluated that ultrasonic technique removed significantly more residues than conventional technique.[6]

In a study, there was no statistically significant difference between all experimental groups and the negative group in each canal third.[7] However, there was statistic difference between the experimental groups and the positive control. In the present study, only 3rd group – and only in coronal and middle canal part – showed statistically significant difference from negative control.

Some authors found that EndoVac System resulted in significantly cleaner root canal walls compared with conventional irrigation needles.[22] In another study, in which ultrasonic, EndoVac System and needle irrigation are compared, PUI was more effective in removing Ca(OH)2 paste from artificial root canal grooves, but the efficacy of PUI did not differ significantly from that of the EndoVac irrigation system.[23] In the present study, EndoVac System did not present better removal efficiency in comparison with the other groups.

Finally, the data for the present study showed that none of the group removed totally calcium hydroxide from the apical third. This result was similar to the results of the previous study, which showed considerable amounts of calcium hydroxide on the canal walls, regardless of the removal technique used.[5],[6],[7] This drawback could be overcome by some additional interventions and results could be different if the irradiation duration was increased or the tip was located deeper.


   Conclusion Top


Even though none of the techniques achieved complete calcium hydroxide removal from every third of tooth, it is shown that Er: YAG laser improved the removal of calcium hydroxide in comparison to conventional techniques.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Teixeira FB, Levin LG, Trope M. Investigation of pH at different dentinal sites after placement of calcium hydroxide dressing by two methods. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:511-6.  Back to cited text no. 1
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Kuştarcı A, Er K, Siso SH, Aydın H, Harorlı H, Arslan D, et al. Efficacy of laser-activated irrigants in calcium hydroxide removal from the artificial grooves in root canals: An ex vivo study. Photomed Laser Surg 2016;34:205-10.  Back to cited text no. 20
    
21.
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Correspondence Address:
Evriklia Kourti
Department of Endodontics, Dental School, Aristotle University of Thessaloniki, Thessaloniki
Greece
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JCD.JCD_273_17

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