Saudi Endodontic Journal

ORIGINAL ARTICLE
Year
: 2019  |  Volume : 9  |  Issue : 1  |  Page : 8--13

Removal ability of MTA-, bioceramic-, and resin-based sealers from obturated root canals, following XP-endo® Finisher R file: An ex vivo study


Taxiarchis G Kontogiannis, Nikolaos P Kerezoudis, Konstantinos Kozyrakis, Elefterios Terry. R. Farmakis 
 Department of Endodontics, Dental School, National and Kapodistrian University of Athens, Athens, Greece

Correspondence Address:
Dr. Taxiarchis G Kontogiannis
Department of Endodontics, Dental School, University of Athens, 2 Thivon Str., 115 27 Athens
Greece

Abstract

Aim: Removability assessment of mineral trioxide aggregate (MTA)-, bioceramic-, and epoxy resin-based sealers, with or without XP-endo® Finisher R file, was achieved. Materials and Methods: One hundred and twenty extracted single-rooted premolars were randomly organized into three equal groups, instrumented up to #40.04 and obturated with single-cone technique by gutta-percha and one of the following sealers: MTA Fillapex, TotalFill BC Sealer, or AH Plus. Following setting of the sealer, D-RaCe instruments were used in retreating all specimens. In half of the specimens, XP-endo® Finisher R file was additionally applied following D-RaCe, as a final step in retreatment. Working length (WL) following the procedure and patency were recorded. All specimens were split and observed for residuals under optical microscopy. Images were acquired, placed adjacent to each other forming continuous strips, and focus stacked with Helicon Focus software. A blinded observer evaluated all photographs. Analysis included Chi-square tests and one-way ANOVA. Results: WL was fully regained in all cases. Patency regaining (in terms of canal cleanness) was easier in AH Plus groups. Residuals were significantly more in TotalFill groups (P < 0.0001). XP-endo® Finisher R file improved removal only in the AH Plus subgroup. Conclusions: TotalFill residuals were harder to remove than those from MTA Fillapex or AH Plus groups. Patency is also harder to regain. XP-endo® Finisher R file had a positive removal influence only in the AH Plus subgroup.



How to cite this article:
Kontogiannis TG, Kerezoudis NP, Kozyrakis K, Farmakis ET. Removal ability of MTA-, bioceramic-, and resin-based sealers from obturated root canals, following XP-endo® Finisher R file: An ex vivo study.Saudi Endod J 2019;9:8-13


How to cite this URL:
Kontogiannis TG, Kerezoudis NP, Kozyrakis K, Farmakis ET. Removal ability of MTA-, bioceramic-, and resin-based sealers from obturated root canals, following XP-endo® Finisher R file: An ex vivo study. Saudi Endod J [serial online] 2019 [cited 2019 Apr 20 ];9:8-13
Available from: http://www.saudiendodj.com/text.asp?2019/9/1/8/249598


Full Text

 Introduction



The success of orthograde endodontic retreatment depends on the complete removal of root-filling material and the adequate cleaning and shaping of the previously untouched areas of the root canal system.[1],[2] Apart from the retreatment modality, the filling technique, type of used filling material, and sealer can affect its removability.[3] Furthermore, sealers are used to obturate any canal irregularities and fill the voids between root canal filling and canal walls.[4],[5],[6] Calcium silicate-based sealers have been recently introduced for obturation because of their excellent biocompatibility and bioactivity.[7],[8],[9] TotalFill BC Sealer is a bioceramic sealer (BCS) composed of biocompatible nanosphere components such as tricalcium silicate, dicalcium silicate, calcium phosphate monobasic, amorphous silicon dioxide, and tantalum pentoxide.[10] Literature data indicated excellent physical and antimicrobial properties.[7],[11] Mineral trioxide aggregate (MTA)-based sealers have been introduced to take advantage of the biological and sealing properties of MTA. MTA Fillapex is a sealer that contains MTA, resins, radiopaque bismuth, nanoparticulated silica, and pigments. The setting of this sealer is based on hydration from surrounding moist dentin.[9]

One of the basic properties of an ideal root canal-filling material is to be easily removed for retreatment purposes.[12] For proper removal, many techniques and materials have been proposed including hand files, heat-carrying instruments, chemical solvents, ultrasonic devices, lasers, and engine-driven instruments such as Gates-Glidden drills, nickel-titanium (NiTi) rotary instruments, and rotary instruments.[13],[14],[15],[16] Dedicated rotary retreatment kits have been developed to facilitate this procedure. One of them, the D-RaCe retreatment system, includes two instruments, 25.08 and 30.04. Despite clinical manipulations, it has been shown[13],[17] that residuals of the filling materials upon canal walls are always present after retreatment. To remove them as satisfactorily as possible, instruments that can come in contact with the canal walls as much as possible have been developed. One of them is XP-endo Finisher R. Although the philosophy of this type of instrument has recently been studied in primary root canal treatments,[18] to the best of our knowledge, there are no respective data about the use of XP-endo Finisher R in retreatments.

The aim of the present study was to evaluate the removability of root canals obturated with gutta-percha (GP) and three different sealers (MTA Fillapex, TotalFill BC Sealer, and AH Plus), using the rotary system D-RaCe with or without the XP-endo Finisher R.

 Materials and Methods



This study was approved by the Ethics Committee of the Dental School of the National and Kapodistrian University of Athens (protocol number 233a, 10/04/2014). One hundred and twenty extracted straight- and single-rooted mandibular premolars with single canals (verified radiographically) and mature apices, stored in 0.1% thymol, were used in the present study. After access cavity preparation, patency was confirmed by extending a #10 hand Flexofile (Dentsply Maillefer, Tulsa, OK, USA) 1 mm past the apical foramen, and working length (WL) of each canal was established 1 mm short of where the file tip exits onto the root surface.[19],[20] All teeth selected presented an initial apical gauge size of #25 or less. If a tooth had presented an initial size smaller or larger than that, it was discarded immediately and replaced by an appropriate one.

Further root canal instrumentation was carried out using BTRaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) to a major apical file of 40.04 for all teeth. 3 mL of 2.5% NaOCl was used in between each rotary file, and apical patency was verified before each succeeding instrument. A final irrigation with 5 mL of 2.5% NaOCl was performed.[19] The smear layer was removed with 5 mL of 17% ethylenediaminetetraacetic acid for 3 min[21] followed by 5 mL of 2.5% NaOCl, passive ultrasonic activation was applied for a minute, and final rinse with sterile saline and drying with paper points.

Obturation in all teeth was carried out with a single cone of 40.04 GP and sealer. Three groups of teeth (n = 40) were formed according to the sealer used: MTA Fillapex (Angelus, Londrina, PR, Brazil) (group A), TotalFill BC Sealer (FKG Dentaire, La Chaux-de-Fonds, Switzerland) (group B), and AH Plus (Dentsply International, Addlestone, UK) (group C). After obturation, all canals were temporarily sealed with Cavit-G (ESPE-Premier, Norristown, PA, USA) and the teeth were stored in a humidified chamber (100% humidity and 37°C) for 2 weeks to allow the sealers to set.[19]

Retreatment was carried out in all teeth with D-RaCe rotary instruments (FKG Dentaire, La Chaux-de-Fonds, Switzerland), with or without the use of XP-endo® Finisher R file (FKG Dentaire, La Chaux-de-Fonds, Switzerland). All instruments were used according to the manufacturer's instructions. No solvent was applied. The number of teeth in which the WL and patency were reestablished, defined as frequency of reestablishment of the WL and patency respectively, was recorded. When the WL was reached, complementary preparation with BTRaCe instruments up to 40.04 was carried out in all groups. The irrigation protocol was the same as mentioned above during primary treatment. The teeth were subdivided into six groups (n = 20) according to the use (or not) of XP-endo® Finisher R file during retreatment. In the XP-endo® Finisher R file subgroups, the irrigating solution (2.5% NaOCl) was preheated at 37°C corresponding to human body temperature.

A1: Originally obturated with MTA Fillapex and subsequently retreated with D-RaceA2: Originally obturated with MTA Fillapex and subsequently retreated with D-Race + XP-endo® Finisher R fileB1: Originally obturated with TotalFill BC Sealer and subsequently retreated with D-RaceB2: Originally obturated with TotalFill BC Sealer and subsequently retreated with D-Race + XP-endo® Finisher R fileC1: Originally obturated with AH Plus and subsequently retreated with D-RaceC2: Originally obturated with AH Plus and subsequently retreated with D-Race + XP-endo® Finisher R file.

All sample preparation and (re) treatments were performed by a single operator.

Two shallow longitudinal grooves were made on a buccolingual direction (with care not to penetrate into the canal). Each sample was then immersed in liquid nitrogen and split longitudinally resulting in a mesial and distal part.[15] For each specimen, only the half with the most intact canal was kept.[13] During splitting, two specimens (one from B1 and one from B2 group) ended up broken in way too many small pieces; thus, they could not be microscopically examined and were excluded from the study.

Specimens were coded and observed by a blinded operator under an optical microscope (Nikon Eclipse ME600-camera Nikon FDX35). Serial photomicrographs were taken at ×200 magnification at 2, 4, and 6 mm from the apex. The resulting images were then placed adjacent to each other forming a continuous examination strip, with the use of Helicon Focus software (Helicon Soft Inc., Roseau Valley, Dominica). This is a program for focus stacking, which is a post-processing technique that can extend the depth of field beyond what is available in one shot.[15],[22] The final images (that resulted from the focus stacking process [Figure 1]) were evaluated by a blinded observer for residuals of sealers on the canal walls. The evaluation was based on the (rough) calculation of the area of residual per whole area. The following scoring system was used for evaluation:[23]{Figure 1}

“1:” No material present“2:” <25% of the canal covered with material“3:” Up to 50% of the canal covered with material“4:” >50% of the canal covered with material.

Statistical analysis included Chi-square test for correlation between sealer type and reestablishment of patency and one-way ANOVA with Scheffe's post hoc test to investigate any differences between the amounts of residual material among the groups. All analyses were carried out using SPSS Statistics 18.0 software (SPSS, Inc., Chicago, IL, USA) software. The level of significance was set at P < 0.05.

 Results



As mentioned earlier, no mishap (i.e., instrument separation and perforation) took place during canal preparation and removal of GP; however, two specimens were lost during splitting (one from Group B1 and one from Group B2). Thus, 118 teeth were finally included in the statistical analysis.

Reestablishment of the WL was attainable in all teeth. The distribution of patency reestablishment according to the sealer used is displayed in [Table 1]. TotalFill BC Sealer group showed a higher frequency of failure on reestablishment of patency than MTA Fillapex and AH Plus groups. This difference on reestablishment between TotalFill BC Sealer and the other two sealers was statistically significant (Chi-square test, P < 0.0001).{Table 1}

The distribution of samples according to the amount of residual material in the three parts of the canal (apical, middle, and coronal) is displayed in [Table 2]. ANOVA was carried out independently for the results in each third of the canal.{Table 2}

In the apical third, more residuals were recorded in the two TotalFill BC Sealer groups (B1 and B2), followed by the two MTA Fillapex groups (A1 and A2) and last by the two AH Plus groups (C1 and C2). ANOVA showed that this difference in the amount of residuals in the apical third was statistically significant (P < 0.05). Similarly, a statistically significant higher frequency was noted, regarding the amount of residuals in the middle third, for the two TotalFill BC Sealer groups, compared to the other groups (Scheffe's test, P < 0.05). Although there was a tendency for more residuals in the MTA Fillapex groups, no significant difference was found between MTA Fillapex and AH Plus (P > 0.05).

The use of XP-endo® Finisher R file showed a general tendency to reduce the amount of residuals. However, the difference in the amount of residuals was statistically significant only in the AH Plus groups (P < 0.05). No significant difference was observed in the two BCS groups when XP-endo® Finisher R file was applied (P > 0.1). Regarding the coronal third, no significant difference was found (P > 0.1) in none of the groups, with or without the use of XP-endo® Finisher R file.

Removability of AH Plus in the apical and middle third was the easiest of the three sealers, followed by MTA Fillapex and then by TotalFill BC Sealer. No difference was found in the coronal third; the use of XP-endo® Finisher R file significantly improved the removal only of AH Plus.

 Discussion



The present study revealed that TotalFill BC Sealer showed a higher frequency of failure on reestablishment of patency than MTA Fillapex and AH Plus. Furthermore, significantly more residuals were recorded in TotalFill groups, particularly in the apical and middle third. XP-endo® Finisher R file did not significantly improve removal.

Rotary NiTi files with a similar taper with D-RaCe (.04) have been previously used for retreatment, and it has been shown that the less amount of residuals (especially in the apical part) occur when such files are used without a solvent.[14] Such an approach was also followed in the present study. Rotary retreatment instruments also result in significantly less extrusion of apical debris, compared with hand files.[24] In contrast, when Gates-Glidden burs with hand files are used for retreatment, residuals are more frequently left behind compared with the use of Hedstrom files.[13] However, the argument just mentioned above is based on the observation with a light microscope, in smaller magnification than in the present study, and without focus stacking. Since, in the light microscope, as magnification increases the field of depth decreases, the evaluation of the above study[13] may have significant differences with the present one. Furthermore, no technique managed complete removal of the filling materials. This result should be expected, as shown in the previous studies about canal cleanness in oval canals[15],[25] as those found in mandibular premolars.

AH Plus, an epoxy resin-based root canal sealer, was included in the present study. It is considered to be a “gold standard” sealer,[23] thanks to its excellent physicochemical properties[26] and acceptable biocompatibility.[21]

No solvent was used in the present study, as solvents result in a deposition of a thin layer of filling material on the root canal walls that is difficult to detect and remove.[27] However, it has been reported that the application of chloroform seems to significantly facilitate patency regaining in retreatment of teeth sealed with MTA Fillapex.[28] In contrast, chloroform did not appear to facilitate patency reestablishment when a BCS was used (Brasseler USA, Savannah, GA, USA).[19] In the present study, patency was significantly more easily reestablished in MTA Fillapex groups compared with TotalFill groups despite the absence of solvent in each case. Therefore, the results of the present study are in agreement with the above-mentioned studies.[19],[27],[28]

Complete removal of the filling material from the root canal was not achieved in any of the groups, while TotalFill presented with more residuals. This means that TotalFill presents the most serious difficulty in removing during retreatment; this finding has already shown by previous studies.[19],[20] The combination of ultrasonics, rotary and hand files, and chloroform seems ineffective in sufficiently removing BCSs,[19] despite the fact that ultrasonics have been proposed for the removal of hard paste filling from the root canal.[29]

A new supplementary strategy using a finishing instrument was evaluated for its ability to improve filling material removal. However, the use of XP-endo® Finisher R file did not result in significantly less residuals. To the best of our knowledge, there are no sufficient data for comparisons with similar studies that could have used this instrument. Nevertheless, the results concerning XP-endo® Finisher R file also confirm the inability of most known techniques to fully remove a BCS[19] such as TotalFill BC Sealer.

Scanning electron microscope (SEM) has been used in the literature for the assessment of cleanness of the canals.[19] However, in SEM images, edges and ridges of the specimen emit secondary electrons, which result in a brighter image than reality; this may affect evaluation. A root canal is apparently an uneven surface; thus, this effect is always present with SEM, but does not exist with the optical microscope. On the other hand, the main drawback of the latter is that when magnification increases, the field of depth decreases. This is why focus stacking was chosen and the software of choice was Helicon Focus (Helicon Soft Ltd.). Focus stacking is a postprocessing technique that can extend the depth of field beyond what is available in one shot.[15] Last but not least, liquid nitrogen was crucial in preventing any loss of debris during tooth splitting.[15],[20]

 Conclusions



Within the limitations of this study, it can be concluded that in the TotalFill group, it was more difficult to regain patency compared with the MTA Group, especially in the apical and middle third of the canal. AH Plus was the easiest of the three sealers to remove in the apical and middle third. No difference was found in the coronal third; the use of XP-endo® Finisher R file significantly improved the removal only of AH Plus. The use of XP-endo® Finisher R file significantly improved the removal procedure only in the AH Plus group and did not deliver 100% residual-free canals in any case.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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