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Year : 2021  |  Volume : 11  |  Issue : 2  |  Page : 240-245

Effect of three glass fiber post removal techniques on the amount of removed root dentin ''An in vitro study

1 Department of Endodontic and Restorative Dentistry, Faculty of Dentistry, Damascus University, Damascus, Syria
2 Department of Endodontic and Restorative Dentistry, Faculty of Dentistry, Qasyoun Private University, Damascus, Syria

Date of Submission13-Jul-2020
Date of Decision12-Aug-2020
Date of Acceptance03-Sep-2020
Date of Web Publication8-May-2021

Correspondence Address:
Dr. Samia Alsafra
Faculty of Dentistry, Damascus University, Damascus
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sej.sej_187_20

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Introduction: Glass fiber posts removal is a major obstacle in nonsurgical endodontic retreatment. The currently used removal techniques cause tooth structure loss in different amount. The aim of this study was to evaluate three glass fiber post removal techniques according to their effect on the amount of removed root dentin.
Materials and Methods: Endodontic treatment was accomplished for 45 extracted single-rooted teeth. The teeth were decoronated and roots were cut apically at (11 mm) then fiber post spaces were prepared. Photographs of the apical cross-section for post space were taken using a camera at a magnification of 40. Fiber posts were cemented with dual cure resin cement. Then, the samples were divided into three groups (n = 15) depending on the fiber post removal technique: Group (I) DT post removal Kit, Group (II) ultrasonic tips E4D and Group (III) diamond bur and Peeso reamer. Posts were removed and images of the previous section were taken under the same magnification. AutoCAD program was used to compare the spaces difference between before and after removal images. Data were subjected to statistical analysis.
Results: The average percentage of removed dentin was (1.89, 0.48, 0.09) cm2 in Groups I, II, and III, respectively. Group I showed the highest amount of removed dentin comparing to other groups, but no significant difference between Group II and Group III was recorded (P = 0.000).
Conclusion: DT post removal kit group was the most aggressive technique for removing glass fiber.

Keywords: DT post removal kit, fiber post, post removal, removed root dentin, ultrasonic

How to cite this article:
Alsafra S, Yassin O, Mohammad Y. Effect of three glass fiber post removal techniques on the amount of removed root dentin ''An in vitro study. Saudi Endod J 2021;11:240-5

How to cite this URL:
Alsafra S, Yassin O, Mohammad Y. Effect of three glass fiber post removal techniques on the amount of removed root dentin ''An in vitro study. Saudi Endod J [serial online] 2021 [cited 2021 Jun 16];11:240-5. Available from: https://www.saudiendodj.com/text.asp?2021/11/2/240/315643

  Introduction Top

Restoration of endodontically treated teeth is an important stage of the whole treatment plan and treatment success and restorations of such weakened teeth can be accomplished using various intra-radicular posts.[1],[2] The main function of the post is to anchor the core within the radicular part of the remaining tooth and help in replacing missing tooth structure to provide sufficient retention and resistance for the final restoration or crown.[2],[3] Recently, various types of fiber posts have been introduced to offer excellent esthetic properties and most of them show good physical properties and acceptable radiographic appearance.[4],[5] They have suitable elastic modulus and good bonding ability to cement, in addition to the relatively easy removal.[6] Forces placed on a tooth restored with a fiber post would be absorbed by the post and core and not transferred to the root structure, so that failure modes with fiber posts is more favorable than metal posts.[7],[8],[9],[10] Nowadays, the removal of fiber posts has become an increasingly frequent procedure in daily dental practice especially when nonsurgical retreatment is needed due to endodontic treatment failure caused by coronal micro-leakage or poor disinfection of the root canal system and even post fracture.[10],[11]

Many techniques and bur kits have been advocated for fiber post removal. The ability to remove an existing post depends on its fabricated material, but in most situations, the dentist is confronted with a fiber post of unknown origin. Hence, most removal kits would be ineffective because they are specifically designed by manufacturers for their respective post system.[12] A universal fiber post removal system was designed to allow removal of any fiber post system.[13],[14]

Techniques that use ultrasonic vibration to remove posts have shown efficiency in fragmenting different kind of cement layer and facilitating post removal.[15] However, resin cements used to fix fiber posts are more resistant and can absorb the ultrasonic energy, thus hindering its fragmentation.[16],[17]

Different amount of root dentin can be lost during retreatment especially when the tooth restored with fiber post.[11] Fiber post removal techniques may also cause more dentin loss, so the aim of this study was to compare among three glass fiber post removal techniques according to their effect on the amount of removed root dentin.

  Materials and Methods Top

The protocol of this study was approved by the Research Ethics Committee of Damascus University. The number of the ethical approval is (3731, date: 5/2015).

G power program was used to measure sample size. Forty-five mandibular premolars were extracted for orthodontic reasons and randomly divided into three groups (n = 15) depending on fiber post removal technique.

Sample's teeth were single-rooted, had complete radicular formation, and free of caries and cracks when evaluated radiographically and under microscope. Teeth with radicular caries, internal resorption, and curved root were excluded.

Tooth crown was removed by a diamond disk® (Horico, Berlin, Germany), canal was prepared using ProTaper®files (Dentsply-Maillefer, Ballaigues, Switzerland), starting with shaping files (S1, Sx, S2) fallowed by finishing files (F1, F2, F3), irrigated with 2.5% NaOCl and smear layer was removed with17%EDTA. The prepared canal was coated with root canal sealer AH plus ®sealer (Dentsply-Maillefer, Ballaigues, Switzerland) then filled with #F3 gutta-percha cone as a master cone and 0.02 cones as accessory cones (Meta. Korea) using lateral condensation technique. The samples were temporized with temporary filling MD-Temp® (Meta. Korea).

The samples were incubated directly in 100% humidity in vial contained 0.9% saline solution at room temperature for 7 days.

Intra-radicular gutta-percha was removed using a Largo reamer no. 2 with a rubber stopper to 11 mm of canal space, then prepared to receive No. 3 fiber (1.6 mm) using the corresponding drill (Deukega, Germany).

Root apex was cut apically in a way to maintain 11 mm root length [Figure 1]. Root parts were attached and stored in additional silicon mold (Elite®-HD +, Zhermack, Italy) to resemble clinical situation before starting fiber post removal.
Figure 1: Study stages applied to the sample

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Photographs of the apical cross-section area were taken by a Nikon® Coolpix S2900 digital camera (Nikon, Tokyo, Japan), which was mounted on a stereomicroscope ocular eye (stereomicroscope, Japan. MEIJI) at a magnification of 40 [Figure 2]a, [Figure 2]c and [Figure 2]e. The distance between lens and root section was 20 mm for both stages of photographing (after post space preparation and after post removal). Photographs were coded and saved for later matching.
Figure 2: Photograph of stereomicroscope view after post space preparing (a, c and e) Photograph of stereomicroscope view after fiber post removal (b, d and f)

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Fiber posts were cut at 11 mm and conditioned with alcohol according to manufacturer recommendations. Prosil coupling agent (FGM, Brazil) was applied with a special brush to cover all surfaces of the post for 60 s and was exposed to a slight current air stream for 5 s. All posts were treated without touching the activated area followed by applying the bond agent on the fiber post.

Canals were etched 37% phosphoric acid (Eco-Etch®, ivoclar vivadent®, Schaan, Liechtenstein) for 15 s and rinsed with water, then the canals were blotted dry with paper points making sure not to desiccate the dentin, after that one-step dental bond (TetricN-bond®, ivoclar vivadent®, Liechtenstien) was applied to the canal walls lightly blown with air, and light cured for 20 s each cut section to ensure a complete bond curing.

Dual cure resin cement variolink-N® (ivoclar vivadent®, Liechtenstien) was injected into the canal space using a syringe with a spiral lentulo. Fiber posts were inserted into the full depth of the post space to ensure the best adaptation and maximum bonding to the canal.[6],[18] Light curing for 60 s was done after removal of excess cement. The samples were stored at 37°C for 30 days to allow cement curing before post removal, then randomly distributed to three groups (n = 15) depending on fiber post removal technique, using a software-generated random numbers.

Group I: D. T Removal® Kit (VDW. Germany).

The D. T. Light-Post removal kit was used according to the manufacturer's recommendations. This kit consists of a low-speed short pilot drill that prepares a pilot hole in the center of the fiber post, then it is followed by another low-speed latch D. T. Removal carbide drill to a depth of 11 mm.

Group II: Ultrasonic tip E4D (Woodpecker, China).

The post was worn down at the center with brushing movement using power mode E and dry working mode to allow postvisualization and disarrangement of post fibers caused by the generated heat.

Group III: Combination of diamond bur and Peeso reamer.

The center of post was worn down until about half of the space using a spherical long neck (0.6 mm) water cooled bur at high speed followed by Largo Peeso reamer no. 3 at low speed and without cooling to the full length of the post until its complete removal. Post removal procedure was considered complete when;

  1. Preparation depth for the post removal tool reached (11 mm)
  2. Resin cement and/or fiber post remainder was not seen on the canal walls or in the apical region under the stereomicroscope.

After complete postremoval, the debris was cleaned and photograph was captured of the previous cross section [Figure 2]b, [Figure 2]d and [Figure 2]f.

The amount of removed root dentin was analyzed using the photographs transferred to a specific computer software (AutoCAD Architecture2014 Autodex, USA). AutoCAD calculated the total area of space resulting from fiber post removal depending on uncountable references points around the space and subtracted the prepared canal area to obtain the amount of removed root dentin [Figure 3].
Figure 3: Matching the area of canal after canal preparation with the resulted area after fiber post removal using AUTOCAD program Yellow circle: Prepared canal area. Red area: The space resulting from fiber post removal

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Statistical analysis

Data were subjected to Statistical Package for the Social Sciences (SPSS®) version 21(IBM® SPSS, USA). A one-way ANOVA test was used to detect significant differences between the compared groups (P < 0.05), and Bonferroni analysis was used to investigate binary comparisons between the study groups.

  Results Top

Descriptive statistics of the studied groups are shown in [Table 1].
Table 1: Descriptive statistics of the studied groups (n=45 with 15 teeth each group) and one-way ANOVA result

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The highest mean value of removed root dentin was observed in the Group I followed by Group II, whereas the lowest was in Group III [Figure 4].
Figure 4: Means and statistical differences of the removed root dentin for the study groups (P = 0.000)***

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Two perforation and tow transportation cases were observed in DT removal kit group.

One-way ANOVA observed a statistical significant difference among the study groups (P = 0.000).

According to Bonferroni analysis, D. T Removal Kit gave the highest amount of removed root dentin with statistically significant differences compared to other groups (P = 0.000). No significant difference was observed between Groups II and III (P = 0.023) [Figure 4].

  Discussion Top

Post removal from endodontically treated teeth can be a major obstacle in the tooth retreatment.[19],[20] and when it is indicated, it should be done by a safe and simple procedure.[10],[11]

The most common technique for post removal involves ultrasonic vibration, which provokes fragmentation of the cement layer.[3],[4] Nonetheless, resin cement used in luting fiber posts contains components that promote adhesion to the intra-radicular dentin and make it more resistant and able to absorb the ultrasonic energy creating the need to reinforce ultrasonic vibration using diamond burs first then complete post removal by vibration.[14],[15],[16],[21]

Dental structure loss is unavoidable when the target is to ensure the maximum removal of filling material and presented bacteria or broken fiber post to expose fresh dentin to the adhesive system.[11]

The unique structure of the fiber posts which consists of stretched parallel fibers in a resin matrix, guides the removal drills and burs and keeps them within the structure of the post, eliminating the risk of root perforations.[22]

Teeth sort, canal preparation size, obturation technique, and fiber post (post space preparation, length, conditioning, size, and type) were standardized in this study, to prevent all the effect of differences in content, matrix, and fibers direction on post removal.[23]

The anatomical shape of tooth root makes the apical third highly affected by retreatment procedures, so the apical root section at 11 mm length was selected.

Since the most common cause of glass fiber post failure is its detachment from root canal dentin,[6] it was important to standardize the fiber post bond criteria to obtain a maximum bond with root canal dentin. Therefore, total acid etching technique with the dual cured resin cement was used to ensure the best adhesion according to Goracci and Ferrari's study.[6]

The results of the current study showed that E4D diamond ultrasonic tip caused less amount of removed dentin than DT removal kit system when used to break up the fiber post structure by vibrations. This may be due to the cutting force of the main removal carbide blades of DT system, which seemed to have more influence on the root dentin than on the post fibers.

Study groups displayed different amount of removed dentin, but the great dentin loss was recorded in DT removal kit group, this may be attributed to the fact that this system is prepared to remove fiber posts made from the same company. Unfortunately, it's impossible to determine the type of fiber post contained within the canal and therefore the best solution is to use a universal fiber post removal kit to get safe and fast removal. This is what Lindemann have coincided with when studying the effectiveness and efficiency of several fiber post removal techniques.[12]

Although the mean value of the ultrasonic was slightly higher, no statistically significant difference was recorded between the effect of Peeso and ultrasonic tip, this could be explained by the heat resulting from the ultrasonic vibrations that caused a greater removal of dental tissue and adhesion cement surrounding the fiber post. This result agreed with the study of Abe et al., where efficacy was greater with ultrasonic heads.[21]

The matching stage pictures (before and after posts removal) showed that the frequency of a complete fiber post removal from the root canal was not observed within the studied teeth, whereas all sample teeth showed different amount of removed root dentin. This is consistent with the results of Lindemann et al. and Anderson et al.[12],[22]

Moreover, two perforations and two transportations cases were observed in D. T Removal kit group, and this may be due to the incisive strength of the bur blades. This result was partially consistent with previous studies, while Abe study did not report any perforation case when removing fiber post,[21] Haupt et al.'s study found a high risk of perforations with all removal techniques used.[24]

There were no significant changes in size of the root dentin in ultrasonic removal technique compared with DT removal kit; this is not in agreement with the results of Arukaslan and Aydemir's study.[25] This may be attributed to that Arukaslan and Aydemir's study depended on the micro-computed tomography technique while the technique used in this study was two-dimensional and insufficient to decide the amount of three-dimensional damage that occurred during glass fiber post removal from the root canals.

Safe removal is a very important factor in selecting a post removal system, so further in vitro and in vivo studies may be needed to evaluate other fiber post removal techniques, fiber post types and other ultrasonic tips ability to remove glass fiber posts with a minimum amount of removed root dentin.

  Conclusion Top

According to this study results and under the limitations of the experiment, it was concluded that DT removal Kit group was the most aggressive technique for removing glass fiber posts when compared to ultrasonic tip E4D and combination of diamond bur and Peeso reamer techniques More studies should be carried out to evaluate other techniques able to remove glass fiber posts and preserve the dental structure.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]


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