|Year : 2014 | Volume
| Issue : 5 | Page : 576-579
|Efficiency and effectiveness evaluation of three glass fiber post removal techniques using dental structure wear assessment method
Flávia Casale Abe1, Carlos Eduardo da Silveira Bueno1, Alexandre Sigrist De Martin1, Felipe Davini1, Rodrigo Sanches Cunha2
1 Department of Restorative Dentistry, Faculty of Dentistry São Leopoldo Mandic, SP, Brazil
2 Department of Restorative Dentistry, University of Manitoba, Winnipeg, MB, Canada
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|Date of Submission||14-Jan-2010|
|Date of Decision||07-Apr-2010|
|Date of Acceptance||28-Jul-2010|
|Date of Web Publication||16-Dec-2014|
| Abstract|| |
Aim: This study evaluated the efficiency and effectiveness of three glass fiber post removal techniques.
Materials and Methods: Forty-five extracted maxillary teeth were endodontically treated and cross-sectioned in thirds. Presence of cementing agent and dental structure wear were assessed by analyzing images taken before luting of glass fiber post and after removal procedure. Teeth were divided into 3 groups: Group 1 - diamond bur + Largo reamer; Group 2 - ultrasonic insert; Group 3 - carbide bur + ultrasonic insert. Time spent on removal procedures, dental structure wear and amount of remaining cement agent were recorded and results submitted to ANOVA, Kruskal Wallis and Tukey-Kramer tests.
Results: Group 1 - 16'46", 33.33% and 6.99%; Group 2 - 12'31", 40% and 7.86%; and Group 3 - 10'24", 80% and 8.14%. Group 3 presented the most effective removal of glass fiber posts. Conclusion: There was no significant difference in efficiency among the evaluated techniques.
Keywords: Pre-fabricated post, retreatment, ultrasonics
|How to cite this article:|
Abe FC, Bueno Cd, De Martin AS, Davini F, Cunha RS. Efficiency and effectiveness evaluation of three glass fiber post removal techniques using dental structure wear assessment method. Indian J Dent Res 2014;25:576-9
As esthetic dentistry gains headway, the removal of fiber posts has become an increasingly frequent procedure in the endodontic clinical practice, since intraradicular retainers must occasionally be removed due to endodontic treatment failure caused by coronal microleakage or poor sanitation of the root canal system and even retainer fracture. ,
|How to cite this URL:|
Abe FC, Bueno Cd, De Martin AS, Davini F, Cunha RS. Efficiency and effectiveness evaluation of three glass fiber post removal techniques using dental structure wear assessment method. Indian J Dent Res [serial online] 2014 [cited 2019 Oct 14];25:576-9. Available from: http://www.ijdr.in/text.asp?2014/25/5/576/147091
Techniques that use ultrasonic vibration to remove metal posts have proven efficient in fragmenting the zinc phosphate cement layer, facilitating post removal.  However, the resinous cements used to fix esthetic posts are more resistant and absorb the ultrasonic energy better than zinc phosphate cement does, besides presenting components that promote bonding to root dentin, thus hindering its fragmentation. ,
The aim of this study was to assess the effectiveness and efficiency of three glass fiber post removal techniques.
| Materials and methods|| |
(This paper was submitted to the Ethical Research Committee - protocol no. 06/108, according to resolution 196/1996 of CNS - Ministry of Health).
Forty-five single-rooted and complete radicular formation maxillary canine teeth extracted for different reasons, (obtained from the Teeth Bank at São Leopoldo Mandic Center for Dental Research - Campinas, SP, Brazil) had their crowns cut with a carborundum disc and root length standardized at 16 mm, measured from the root apex towards the crown. Samples were stored in 0.9% saline solution.
Root canals were endodontically treated using a crown-down technique. After confirmation of foraminal patency, Gates-Glidden burs nos. 5, 4, and 3 were used in decreasing order. K-type files were used to establish the final diameter at caliber 40. Root canals were irrigated with 20 mL of 2.5% sodium hypochlorite (NaOCl). Root canals were filled with large size gutta percha TP Cones (Dentsply Indústria e Comércio Ltda., Petrópolis, RJ, Brazil) calibrated at 40 and endodontic cement Sealer-26 (Dentsply Indústria e Comércio Ltda., Petrópolis, RJ, Brazil). Filling was finalized through the Tagger hybrid technique.  Next, a 10 mm prosthetic space established with the help of a rubber stop was prepared using a Largo reamer no. 4 (as suggested by the post manufacturer).
In this experiment glass fiber posts Reforpost (Angelus Indústria de Produtos Odontológicos S/A, Londrina, PR, Brazil) no. 2, with a diameter of 1.3 mm were used. X-rays were taken to confirm adaptation of post to roots. After confirmation, root entries were sealed with Cavit. To allow cement hardening, samples were stored in a kiln at 37ºC and relative air humidity for 48 hours.
Based on the technique described by Bramante et al.  samples were embedded in polyester resin using a Nylon 6 muffle. A rectangular compartment with rounded angles was opened in the internal part of the muffle, whose dimensions were: 21 mm long, 16 mm wide and 16 mm deep; base measurements were 17 mm long and 12 mm wide. On the compartment's internal faces, on both sides of the muffle, three 2 mm deep grooves were made to orient positioning of the resin block, promote better tooth bonding and smaller block displacement. Both parts of the muffle were united with the help of two guide posts and fixed with two screws to help keep the block in position.
The muffle walls were lubricated with solid vaseline, and roots positioned until they touched the muffle cavity bottom, and only then was the muffle filled with polyester resin. After total resin polymerization, blocks were removed from the muffle and taken to a water-cooled cutting machine (Isomet Low Speed, Buehler Ltd., Lake Bluff, IL, USA) to be cut transversally into 5 and 10 mm root sections, measured from the crown cut line towards the apex. Samples were divided into cervical, middle and apical thirds. Before cementing the glass fiber posts, the cervical and middle root sections were photographed with a SONY DHC - HC85 camera coupled to an M900 operating microscope (DF Vasconcelos S.A., São Paulo, SP, Brazil) at 12.5× magnification, at a distance of 20 cm from the root section considered. The root thirds were later remounted in the muffle system, temporary cement removed and canal irrigated with saline solution and dried with a Capillary Tip (Ultradent Products Inc. - EUA) and no. 40 absorbent paper tips.
The posts were cut with a tapered trunk diamond tip no. 3071 to a length of 10 mm. The self-etching Clearfil SE Primer (Kuraray Medical Inc., Kurashiki, Okayama, Japan) was used to etch the intraradicular cavity according to the manufacturers' recommendations. The post with the resinous cement Panavia F (Kuraray Medical Inc., Kurashiki, Okayama, Japan) was inserted into the root to ensure a better adaptation.  The excess cement agent was removed with a spatula and photopolymerized for 80 seconds. Samples were stored in a dry light-protected environment for 30 days before removal of posts began. They were randomly divided into 3 groups, each one containing 15 cervical and 15 middle root thirds, totaling 30 samples per group. The operating microscope was used at 8× magnification during the post removal procedure and visual evaluation of any remaining cement and/or any remainder of the post, regardless of the technique employed. An operator acquainted with the three techniques executed them randomly, dividing the thirds into the following groups:
Group 1 - a small cavity was made in the center of the post using a no. 1012 diamond water-cooled bur at high speed to enable Largo reamer no. 4 to be inserted at low speed and without cooling. The bur was placed in the cavity and directed at the center of the post to disintegrate the fibers. As the fibers came loose and the post wore away, the bur scope was increased to wear down the cementing agent.
Group 2 - using an ultrasonic insert ST - 21 (Osada Electric Co. Ltd., Shinagawa-ku, Tokyo, Japan), the post was initially worn down at the center with a brushing movement, until almost complete disintegration of fibers. The procedure was performed without water cooling to allow post visualization and disarrangement of post fibers caused by the generated heat.
Group 3 - The center of post was worn down until about half of the prosthetic space length using a spherical long neck no. 1 carbide bur. From then on, the technique was further applied by using an ultrasonic insert ST - 21 until removal of cement and post was finalized, as described in the technique used in Group 2.
Post removal procedure was considered complete when it met the following parameters: (1) preparation depth for the initial post (10 mm) was reached; (2) visualization of the filling material in the apical region was accomplished; (3) no remaining resinous cement and/or post remainder on the canal walls or in the apical region was observed. From the beginning of removal procedure up to its end, time was recorded with a chronometer, which was paused during instrument change, cavity cleansing or cementing agent and post remainder observation. The following criteria were observed while evaluating effectiveness of glass fiber post removal techniques: length of time for removal, presence of cementing agent in the inside of canal and dental structure wear.
The cervical and middle thirds were photographed after glass fiber post removal. These images were evaluated by two endodontists blind to the research, which observed whether there was presence or absence of cementing agent remaining inside the canal by comparing them with the images obtained before post cementation. When there was discrepancy among the observed results, the sample that presented remaining agent was included.
Dental structure wear was analyzed by using images made before and after post removal, transferred to a specific software: Image Tool for Windows v.3.00 (University of Texas, Health Science Center, San Antonio, TX, USA), used to measure the canal areas and calculate the differences among them. Before removal techniques were carried out, same evaluators measured outer root area and root canal area, obtained in pixels.  Values were transformed into percentages to obtain the ratio between external and internal area of each tooth. Same procedure was done with images obtained after post removal. The percentage value of canal area after removal was subtracted from the percentage value of the canal area before post removal. The result obtained represented the percentage value of increased canal area after post removal (if final area was larger than initial area, this would mean there had been dental structure wear), thus calculating the internal dental structure wear. All values regarding dental structure wear were added and divided by the number of samples in each group, thus reaching the mean wear value of each one.
Results of these evaluations were submitted to statistical analysis. ANOVA was used to evaluate the length of time spent on the procedure and presence of cementing agent in the canals was evaluated by the Kruskal-Wallis test. Tukey scores was the normalization method used. Dental structure wear was analyzed using ANOVA test followed by the Tukey-Kramer non-parametric test.
| Results|| |
The first variable to be analyzed was time spent on procedure, and results are in [Table 1]. The percentages of samples with and without remaining post/cementing agent are presented in [Figure 1]. Presence of remaining cementing agent was observed in 20 samples in Group 1, in 18 samples in Group 2, and in 6 samples in Group 3. Dental structure wear data measured by the difference in area before and after post removal are presented in [Figure 2]. Average increase in canal area after post removal was of 6.99% in Group 1; 7.86% in Group 2; and 8.14% in Group 3, demonstrating that Group 3 presented significant wear difference in relation to Group 1.
|Figure 1: Percentage of samples with and without any remaining post/ cementing agent (P < 0.05). Group 1: diamond bur + Largo reamer; Group 2: ultrasonic insert; Group 3: carbide bur + ultrasonic insert|
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|Figure 2: Percentage of dental structure wear after post removal (area difference). Group 1: diamond bur + Largo reamer; Group 2: ultrasonic insert; Group 3: carbide bur + ultrasonic insert. Bars with the same letters do not differ at P < 0.01 level of significance|
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| Discussion|| |
The most widely used technique for the removal of intraradicular post involves the use of ultrasonic vibration, which provokes fragmentation of the zinc phosphate cement layer. , Nonetheless, the resinous cement used to retain fiber posts has components that promote adhesiveness to the root dentin, is more resistant and absorbs the ultrasonic energy better than the zinc phosphate cement does. For this reason, the ultrasonic vibration technique used for the removal of fiber posts should be modified in relation to the one used to remove metal posts. ,
Gesi et al.  compared a fiber post removal technique using specific removal kits (RTD Fiber Post Removal Kit) for the tested brands (Conic 6%, FRC Poster, Composispost) with a technique using a diamond bur combined with a Largo bur. Results showed that the latter technique was able to remove fiber posts faster. Lindemann et al.  concluded that the removal kits were faster, albeit less effective than the technique, which used a diamond bur associated with an ultrasonic insert. Anderson et al.  also assessed the effectiveness and efficiency of removal kits and compared them to diamond burs associated with Peeso burs for fiber post removal. The authors concluded that although the latter technique was more effective, and there were no statistically significant differences.
In the present study, groups were randomly divided and after application of techniques, it was observed that although results did not present statistically significant differences, the mean times spent on the procedure were similar to those obtained by Lindemann et al.,  whose means ranged from approximately 14 to 18 minutes to remove posts cemented with resin system. However, they differed from the results obtained by Gesi et al.,  whose mean times for fiber post removal ranged from approximately 22 to 34 seconds, regardless of the technique employed, and also from those presented by Anderson et al.,  who used two different removal kits and obtained the following mean times: 136 e 161 seconds for removal kits and 186 seconds when diamond bur was associated with Largo bur.
Radicular and medium thirds were submitted to observation regarding presence/absence of remaining cementing agent on dentinal walls and complemented by analysis of dental structure wear in order to decrease the subjective influence of visual observation. Group 3 presented the largest number of samples with no remaining cementing agent. Unlike Group 1, where the positioning of the counter angle created difficulty in visualizing the bur, microscopic visualization in Group 3 did not suffer interferences. In addition, heating provoked by ultrasonic vibration in Group 3 could make removal of larger amount of cementing agent easier. 
Since the intention was to remove the greatest possible amount of cementing agent, greater wear of remaining dental structure was inevitable. Moreover, in endodontic retreatment when the objective is the complete removal of filling material and bacteria present underneath, dental structure wear is unavoidable,  but necessary once fresh, new dentin is exposed for proper hybridisation by the adhesive system. None of the three techniques perforated the root wall.
The method employed to observe presence/absence of cementing agent and dental structure wear was a modification of the methodology described by Bramante et al.  However, this methodology was considered inadequate as it offered a bi-dimensional view of a tridimensional structure. Besides, making a distinction between dentin and post/cementing agent was a hard task due to their color similarity.
The subject is up-to-date and innovative, especially considering the growing trend of using glass fiber posts to provide retention to cores and prosthetic crowns. The need to remove these posts may pose a major challenge for contemporary endodontics. The present study aimed at contributing to the selection of an intraradicular post removal technique that would be most suitable to the clinical reality faced by endodontists. Further studies should be carried out to reach a consensus on the use of a technique that would be able to remove glass fiber posts and still preserve the remaining dental structure to the most in the shortest possible time.
| Conclusion|| |
According to the results obtained and taking into consideration the limits within which the experiment was conducted, it was concluded that the removal technique used in Group 3 (carbide bur associated with ultrasonic insert) was the most effective for removing glass fiber posts and resinous cement. However, only the presence of remaining cementing agent was statistically significant. From the efficiency point of view, there was no significant difference among the three evaluated removal techniques.
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Flávia Casale Abe
Department of Restorative Dentistry, Faculty of Dentistry São Leopoldo Mandic, SP, Brazil
Source of Support: None, Conflict of Interest: None
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