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 Table of Contents  
ORIGINAL RESEARCH
Year : 2020  |  Volume : 12  |  Issue : 1  |  Page : 41-45

Micro-computed tomographic evaluation of the apical seal of endodontically treated teeth by two obturating techniques and two post space preparation techniques


1 Restorative and Dental Materials Department, National Research Centre, Cairo, Egypt
2 Head of Endodontic Department, Faculty of Dentistry, The British University in Egypt, Cairo, Egypt

Date of Submission25-Jun-2019
Date of Decision07-Sep-2019
Date of Acceptance09-Sep-2019
Date of Web Publication25-Feb-2020

Correspondence Address:
Prof. Engy M Kataia
Restorative and Dental Materials Department, National Research Centre, Cairo.
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jioh.jioh_168_19

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  Abstract 

Aim: This study evaluated apical seal of teeth obturated by two techniques and gutta-percha (GP) removed by two methods for post space preparation, using micro-computed tomography (micro-CT). Materials and Methods: Fifty-six single rooted teeth were decapitated at 15mm from the apex and prepared using ProTaper Universal System. Specimens were divided into two main groups of 28 each according to technique of GP Removal and post space preparation: Group A1, GP removed by a penetrating drill and Group A2, GP removed by hot plugger. Each main group was divided into two subgroups according to obturation technique: single cone (SC) and System B. Each subgroup was further divided into two minor subgroups according to storage time—immediately and one-week post-obturation. Approximately 9mm of GP was removed for post space preparation. All specimens were scanned three times by micro-CT: post-preparation, post-obturation, and after post space preparation. Total mean percentage of voids/gaps in the apical portion was calculated at 1, 3, and 5mm from the apex. Data were explored for normality using Kolmogorov–Smirnov and Shapiro–Wilk tests. Paired sample t-test was used to compare between two groups. Independent sample t-test was used to compare between two groups in non-related samples (significant P ≤ 0.05). Results: It showed that group A2 recorded significantly lower voids than group A1 at the two investigation periods. Voids associated with System B technique were lower than those with SC. Conclusion: An immediate removal of GP by hot plugger would not affect the apical seal.

Keywords: Gutta-Percha Removal, Micro-Computed Tomography, Post Space Preparation, Single Cone, System B


How to cite this article:
Kataia EM, Kataia MM. Micro-computed tomographic evaluation of the apical seal of endodontically treated teeth by two obturating techniques and two post space preparation techniques. J Int Oral Health 2020;12:41-5

How to cite this URL:
Kataia EM, Kataia MM. Micro-computed tomographic evaluation of the apical seal of endodontically treated teeth by two obturating techniques and two post space preparation techniques. J Int Oral Health [serial online] 2020 [cited 2020 Apr 3];12:41-5. Available from: http://www.jioh.org/text.asp?2020/12/1/41/279215




  Introduction Top


The ultimate target of endodontic treatment is to produce a tight seal, contributing in periapical tissues healing, preventing apical periodontitis, and restraining root canal infections.[1],[2]

Lateral compaction technique is the most commonly utilized obturating technique and has been used as the standard against which the sealing ability of new obturating materials or techniques is compared.[3],[4]

Its disadvantages include absence of homogeneity, high percentage of sealer in the apical portion of the canal, and incomplete adaptation to canal walls.[4] To beat these drawbacks, warm vertical compaction has been imported, resulting in a more homogeneous mass of gutta-percha.[5] Single cone (SC) obturation has become more popular now and is considered less damaging to the dentin than warm vertical compaction techniques and is also less operator dependent.[6]

Several techniques have been advocated to evaluate the sealing ability of root canal fillings.[7]

The recently introduced three-dimensional (3D) computed tomography (CT) imaging techniques helped to overcome some of the drawbacks of the conventional methods. It is a definite, non-damaging method for evaluating root canal fillings and provides 3D volume measurements of root canal spaces without sectioning specimens, avoiding material loss.[8]

Root canal treated teeth usually have little remaining tooth structure to retain the final restoration. Moreover, the loss of radicular dentin increases susceptibility to fracture.[9] Posts are usually the solution to restoring such teeth, and they also provide retention to the coronal core material.[10],[11] However, this requires removing part of the filling material from the canal so that we can proceed with post space preparation. This procedure can affect the apical seal. Around 5mm of obturating material is considered a safe margin but reducing the filling to 3mm might produce an unpredictable seal.[12],[13]

The technique of obturation, sealer type, GP removal instruments and techniques, the amount of filling remaining in the canals, and the post space preparation timing are all factors that may contribute to leakage.[14] Thus, it is important to evaluate the seal of remaining obturation materials after post space preparation.[15]

Hence, apical seal of endodontically treated teeth by two obturating techniques and subjected to two different techniques of GP removal for post space preparation was evaluated in this study.


  Materials and Methods Top


This in vitro randomized control study was conducted on 56 maxillary anterior teeth extracted for periodontal problems. Teeth with single root, no sign of caries, no cracks or fractures, and without any structural anomalies or resorption or defects were included. Inclusion criteria were analyzed under light microscope in this study. More than one root was excluded from the study. The study started on January 15, 2018 and ended by February 7, 2018, and the teeth preparation was carried out in our private dental clinic.

A solution of 5.25% sodium hypochlorite (Egyptian Detergent Company, 10th of ramadan, Egypt) soaked into gauze was used to remove any soft tissue covering the root surface, and any calculus was removed by the aid of an ultrasonic scaler (Woodpecker, Guiling, Guangxi, China). Teeth were decapitated 15mm from the root apex[16] using a tapered diamond stone mounted on a high-speed handpiece (W&H, Burmoos, Austria) with water spray. Flattening of the coronal portion of the roots was carried out with wheel stone.

k-File no. 10 (Dentsply Maillefer, Tulsa, OK) was introduced into the canal till the tip of the file was seen from the apex to ensure patency. The teeth were stored in distilled water at room temperature till the time of use.

Working length was 14mm for all teeth. All root canals were then prepared using ProTaper Rotary System (Dentsply Maillefer, Ballaigues, Switzerland). The sequence used was ProTaper S1, S2, F1, F2, F3, F4, and F5. Preparation was accomplished using DentaPort ZX (MORITA, Kyoto, Japan) torque control motor at rotational speed 250rpm. One milliliter NaOCl of 2.6% concentration was the irrigant solution used after each file. The specimens received a final rinse with 17% ethylene diamine tetraacetic acid (EDTA) solution (Dentsply, Latin America, São Paulo, Brazil), in order to remove the smear layer, then they were rinsed with sterile water.

Specimens’ grouping: The prepared specimens were divided randomly into two main groups of 28 specimens each according to the technique of GP removal and post space preparation: In Group A1, GP was removed by a penetrating drill, equivalent to titanium post size 308 S, and in Group A2, GP was removed using a hot endodontic plugger, followed by post space preparation using a calibrated drill (EXACTO bur). Each main group was divided into two subgroups with 14 specimens each according to the obturation techniques: SC technique and System-B. Each subgroup was further divided into two minor subgroups with seven specimens each according to the time at which the post space preparation will be conducted: immediate and one week.

Obturation was carried out using AH Plus sealer (DENTSPLY Maillefer-USA 5100 E. Skelly Drive, Suite 300 Tulsa, Oklahoma 74135). Each main group contained 28 specimens, half of the specimens in each main group were obturated by SC: F5 points, ProTaper GP cones, and the other half of the specimens were obturated by vertical condensation technique using Sybron Endo System-B (Kerr Endodontics, KerrHawe SA, Via Strecce 4, 6934 Bioggio, Switzerland).

Post space preparation was carried out by removing 9mm[17] of the GP in each specimen leaving only 5mm[18] of the apical filling at the following times: immediately after obturation (S1) and one-week post obturation (S2), where the specimens were stored in distilled water at 37°C, 95% relative humidity.

Group A1: GP was removed and post space was prepared by a penetrating drill (Dentsply) of the same size as the post of size (308 S), working at low speed (800–1200rpm) with micro motor (W&H). Standardization of the length of GP removal was achieved with the help of rubber stoppers placed on the drill.

Group A2: GP removal was carried out using a hot endodontic plugger, and post space was prepared using a calibrated drill (EXACTO bur).

Light-cured composite Filtek Z-250 (Shade A1) was used to seal the canal orifice after post space preparation.

Evaluation methods: All specimens were scanned three times using a micro-CT scanner (SkyScan 1072; SkyScan, Aartselaar, Belgium): after preparation, after obturation, and after post space preparation. The mean percentage of voids/gaps in the apical third was calculated in cubic micrometers for the measurements at 1, 3, and 5mm from the apex.[19]

Statistical analysis: Statistical analysis was performed with IBM Statistical Package for the Social Sciences (SPSS) software, version 20 for Windows (IBM, Armonk, New York). Micro-CT results (mean ± standard deviation [SD]) for the total voids and gaps in cubic micrometers for all groups as function of post space preparation technique, obturation technique, and investigation time were calculated. Data were explored for normality using Kolmogorov–Smirnov and Shapiro–Wilk tests, data showed parametric (normal) distribution.

Paired sample t-test was used to compare between two groups in related samples. Independent sample t-test was used to compare between two groups in non-related samples. The significance level was set at P ≤ 0.05.


  Results Top


  1. Effect of technique of obturation [Table 1]: In Groups A1 and A2, a significant difference was found between the two obturation techniques (System B and SC obturation) for both periods of GP removal immediate and after one week, SC group had the highest mean value of voids.


  2. Effect of post space preparation time [Table 2]: A significant difference between both groups, A1 and A2, for the two obturation techniques, was observed for the two post space preparation periods (immediately and after one week), where the highest mean value of voids was found in the groups that had their post space prepared after one week.


  3. Effect of technique of GP removal [Table 3]: There was a significant difference between the two GP removal techniques, with Group A1 (GP was removed and post space was prepared by a penetrating drill of the same size of the post) showing the highest mean value of voids with the two obturation techniques and the two removal periods (immediate and one week).
Table 1: The mean, standard deviation values showing effect of technique of obturation

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,
Table 2: The mean, standard deviation values showing effect of post space preparation time

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,
Table 3: The mean, standard deviation values showing effect of technique of gutta-percha removal

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  Discussion Top


Restoration of root filled teeth with fixed crowns or bridges usually needs core buildups. Buildups include the replacement of lost tooth structure to provide sufficient core for the preparation. If the amount of remaining tooth structure is not enough for retaining a core, a post has to be placed inside the canal to retain it.[20]

Recently, the use of different obturating techniques and materials in relation to post preparation has been investigated. When preparing a post space, root canal filling materials may get displaced, resulting in voids in the obturation.[21]

Although studies may show that immediate or delayed post space preparation in teeth obturated with different techniques have a similar effect on the quality of remaining obturation, clinical research remains necessary to confirm this hypothesis.[22]

This study was carried out to evaluate the apical seal of teeth obturated by SC and System B techniques and post space prepared by two different techniques, using micro-CT, immediately and one week post obturation. Natural teeth were used to simulate clinical conditions.[23]

Natural teeth differ in length, width, and size; therefore, the mesiodistal and buccolingual dimensions of each tooth at the cervical level were documented after preparation to make sure that each experimental group consisted of teeth of similar dimensions. Teeth were cut 15mm from the apex to the amelo-cemental junction to standardize the root length. NaOCl of 2.5% concentration was the irrigant used after each file. EDTA solution (17%) was used as a final rinse for smear layer, followed by rinsing with sterile water.[16]

The two obturating techniques chosen were the SC, as it is being considered less operator dependent and less damaging to the dentin wall[6] (F5 points, size 50, ProTaper GP cones),[16] and System B technique as it provides good sealing for canal irregularities,[24] with AH Plus being the sealer used.[25]

Light-cured composite Filtek Z-250 was used for core buildups as it provides good bond strength, quick and controlled setting, good aesthetics, and acceptable compressive strength. Furthermore, composite core materials have higher fracture resistance.[26]

Light-cured composite Filtek Z-250 (Shade A1) was used to seal the canal orifice after post space preparation.[9]

Micro-CT imaging was used for the apical seal evaluation after post space preparation by measuring the total voids and gaps in cubic micrometers for at 1, 3, and 5mm from the apex for all groups. Micro-CT imaging grants the advantage of 3D reconstructions of samples without sectioning them.[19]

In this study, results of the voids mean values of GP removal and post space preparation technique (by mm) in relation to obturation technique and investigated times showed that in both obturation techniques at the two investigation periods, the group where GP was removed using a hot plugger recorded statistically significant lowest voids mean value.

Statistically significant difference in mean values of voids between the two GP removal techniques may be due to the time of sealer setting, the technique of GP removal, instruments used, and the length of the remaining material.[4] During post space mechanical preparation, root canal filling materials may get dislodged, producing voids in the obturation, and the filling material may be twisted or vibrated.[27]

The results of apical leakage related to GP removal technique agreed with that of a study by Haddix et al.,[28] who found that significantly greater leakage was observed after GP was removed using Gates–Glidden drills and GPX instruments than after its removal with heated plugger.

Whereas, these results disagreed with that of a study by Muñoz et al.,[29] where they used Gates–Glidden drills for post space preparation directly after filling, and they found that there was a significantly lower bacterial leakage when using Gates–Glidden or Peeso drills in comparison with heat removal of GP.

The results of the voids mean values of GP removal techniques in relation to obturation techniques and investigation times (immediate and after one week) showed that the voids value, associated with immediate post space preparation, recorded statistically significant lower voids mean value than the leakage value associated with one-week GP removal and post space preparation.

The reason of why more voids was observed with delayed preparation of the post space than with immediate post space preparation may be due to the hypothesis that with immediate preparation, the sealer will still be in its working time, allowing it to set without making microcracks. Whereas in delayed post space preparation, the rotational effect of burs may have caused GP movement, and therefore breaking the bond between the sealer and dentin.[30]

These results were in agreement with a study[30] stating that preparing the post space immediately after obturation was accompanied with less microleakage than delayed preparation of post space, whereas they disagreed with other studies reporting that there was no significant difference between immediate and delayed post space preparation on apical seal.[17],[27]

It was also revealed that the subgroup obturated by System B technique recorded significantly (P ≤ 0.05) lower mean voids value than the one obturated via modified SC technique with the two GP removal methods at the two investigation periods.

This may be attributed to the fact that lateral compaction technique creates many irregularities in the final mass of GP, and it may not fill fins and isthmuses in the canal. Moreover, inadequate sealer dispersion leaves voids in and around GP points.[31]

These results agreed with that of a study by Aydemir et al.,[27] who revealed that warm vertical compaction filling technique was better than cold lateral compaction technique to avoid disruption of apical seal integrity. These results were contradicting to the results by Camp and Todd,[32] who stated that there was no difference between laterally and vertically condensed GP in apical seal after dowel space preparation.

According to the present results, obturation with system B and immediately preparing the post space with a penetrating drill of the same size of the post created less voids. With these findings, it was recommended that GP be removed and post space be prepared immediately after obturation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Abramovitz L, Lev R, Fuss Z, Metzger Z. The unpredictability of seal after post space preparation: A fluid transport study. J Endod 2001;27:292-5.  Back to cited text no. 13
    
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Dhaded N, Dhaded S, Patil C, Patil R, Roshan JM. The effect of time of post space preparation on the seal and adaptation of resilon-epiphany Se and gutta-percha-AH plus sealer—An SEM study. J Clin Diagn Res 2014;8:217-20.  Back to cited text no. 14
    
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20.
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22.
Long W, Li J, Liu Y, Jiang H. Effect of obturation technique with immediate and delayed post space preparation on apical voids and bond strength of apical gutta-percha. J Int Med Res 2019;0:1-11.  Back to cited text no. 22
    
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24.
Schäfer E, Schrenker C, Zupanc J, Bürklein S. Percentage of gutta-percha filled areas in canals obturated with cross-linked gutta-percha core-carrier systems, single-cone and lateral compaction technique. J Endod 2016;42:294-8.  Back to cited text no. 24
    
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28.
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29.
Muñoz HR, Saravia-Lemus GA, Florián WE, Lainfiesta JF. Microbial leakage of Enterococcus faecalis after post space preparation in teeth filled in vivo with realseal versus gutta-percha. J Endod 2007;33:673-5.  Back to cited text no. 29
    
30.
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31.
Kersten HW, Fransman R, Thoden van Velzen SK. Thermomechanical compaction of gutta-percha. II. A comparison with lateral condensation in curved root canals. Int Endod J 1986;19:134-40.  Back to cited text no. 31
    
32.
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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