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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 3  |  Page : 475-480
Effect of different intraradicular posts in the dimensions of root canal computed tomography images


1 Departament of Oral Rehabilitation, Brazilian Dental Association, Goiânia, Goiás, Brazil
2 Department of Oral Science, Dental School, Federal University of Goiás, Goiânia, Goiás, Brazil
3 Department of Oral Radiology, Dental School, Paulista University, Goiânia, Goiás, Brazil

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Date of Submission27-Nov-2018
Date of Acceptance20-Aug-2019
Date of Web Publication06-Aug-2020
 

   Abstract 


Objectives: To evaluate the effect of different intraradicular posts on the dimensions of computed tomography (CT) images in cone-beam and fan-beam equipment. Materials and Methods: A total of 15 root canals of bovine teeth were instrumented up to a file #50 and root-filled by the active lateral condensation technique. The teeth were randomly divided into three groups, according to the type of intraradicular post: 1) tight fiberglass post; 2) anatomical fiberglass post; and 3) metal post. The root canals were desobturated in 10 mm and tomographic images were acquired in two devices, a cone-beam and fan-beam equipment. Then, the intraradicular posts were cemented using an automix self-conditioning and self-adhesive resin cement, and the final acquisitions of the CT images were performed for analysis. The diameter of the canal was compared before and after cementation of the intraradicular posts. The t-test was used between the initial and final measurements of each tomograph and also between the cone-beam and fan-beam tomographs (α = 0.05). Results: The anatomical fiberglass post presented the smallest dimensional change among the initial and final measurements, followed by the tight fiberglass post, with the metal post being the material that showed the most considerable dimensional difference in the cone-beam. Conclusion: All of the intraradicular posts used promoted a change in the size of the CT image. The fan-beam scanner promoted greater dimensional change in the images.

Keywords: Cone-beam computed tomography, intra-radicular posts, multislice computed tomography

How to cite this article:
Vasconcelos CC, Loureiro MA, Elias MR, Botelho TL, Magalhães AP, Decurcio DA. Effect of different intraradicular posts in the dimensions of root canal computed tomography images. Indian J Dent Res 2020;31:475-80

How to cite this URL:
Vasconcelos CC, Loureiro MA, Elias MR, Botelho TL, Magalhães AP, Decurcio DA. Effect of different intraradicular posts in the dimensions of root canal computed tomography images. Indian J Dent Res [serial online] 2020 [cited 2020 Sep 23];31:475-80. Available from: http://www.ijdr.in/text.asp?2020/31/3/475/291502



   Introduction Top


The advent of computed tomography (CT) has initiated an information revolution in health studies and has contributed to the planning, diagnosis, treatment, and prognosis of several pathological alterations.[1],[2] Cone-beam computed tomography (CBCT) is a technology developed[3],[4] with potential for application in different areas of dentistry research and clinical practice.[5],[6],[7],[8] Conventional radiographs promote a two-dimensional analysis of a three-dimensional structure, which can result in misinterpretation. Periapical lesions of endodontic origin may be present and not visible on conventional radiographs.[9] New methods using CBCT to investigate apical periodontitis and root resorption have been proposed,[9],[10],[11] and new imaging tools have been used in several studies in dentistry.[7],[8],[12],[13]

However, CT images are affected by the presence of imaging artefacts that can result in a loss of diagnostic quality, leading to a limited interpretation of the three-dimensional image.[7],[14],[15] Artefacts can be defined as a structure visualized next to the image formed through the data used in the reconstruction that is not present in the object from which the tomographic image was created.[7],[14],[15] Different types of artefacts may be present in tomographic images, each of which has a determining factor for its appearance.[7],[14],[15] Materials with a high atomic number, such as those used in intra-radicular posts, generate beam hardening artefacts which have been the focus of several studies.[16],[17],[18]

Alterations in the image size of root canal diameter may induce errors in interpretation of the condition of the dentinal remnant, leading to the false diagnosis of root perforations and nonconservative treatments. In this way, the present study aimed to evaluate the effect of different intra-radicular posts on root canal dimensions in cone-beam and fan-beam CT images.


   Material and Methods Top


Teeth selection

Fifteen bovine teeth were obtained from Frigorífico Friboi, Goiânia, Brazil. This study was approved by the Animal Ethics Committee of the Federal University of Goiás, Brazil. Preoperative periapical radiographs of each tooth were performed to verify the absence of calcifications, internal or external resorptions, and the presence of complete rhizogenesis.

Sample preparation

The teeth were stored in 0.2% thymol solution after being immersed in 5% sodium hypochlorite (Fitofarma, Goiânia, Brazil) for 30 min to remove remaining organic tissue. The dental faces (buccal, palatal, mesial, and distal) were identified, followed by sectioned crowns using steel discs (KG Sorensen, Cotia, Brazil), to standardize a root length of 16 mm. This length was determined by a calibrated digital calliper of 0.01 mm (Fowler/Sylvac Ultra-Cal Mark IV Electronic Caliper, Crissier, Switzerland), measured from the root apex.

After the initial radiographs and coronary removal, the cervical third of the root canal of each tooth was prepared using Gates-Glidden ISO No. 1 through 3 (Dentsply/Maillefer). Odontometry was performed by viewing the K-file in the apical foramen followed by a 1 mm return (visual method). The apical thirds of the root canals were enlarged to ISO K-File No. 50 (Dentsply/Maillefer). During root canal preparation, they were irrigated with 3 ml of 1% sodium hypochlorite (Fitofarma) at each instrument change. The root canals were dried and filled with 17% ethylenediamine tetraacetic acid (EDTA) (pH 7.2) (Biodynamic, Ibiporã, Brazil) for 3 min to remove the smear layer. After that, the canals were again irrigated with 3 ml of 1% sodium hypochlorite and dried with No. 50 absorbent paper cones (Dents er). The teeth were root-filled with the AH Plus sealer (Dentsply/Maillefer) and gutta-percha cones using the conventional active lateral condensation technique.

The teeth were randomly divided into three experimental groups (each containing five specimens), according to the type of posts used: Group 1 - Tight fiberglass post; Group 2 - fiberglass posts plus composite resin - anatomical; and Group 3 - Fused metallic post.

All teeth were desobturated in 10 mm using a Gates-Glidden n. 2 and 3 (Dentsply/Maillefer), in a low rotation. After the removal of gutta-percha, the root canals were prepared for the intraradicular posts with Glassix extension drills (Nordin, Chailly/Montreux, Switzerland) n. 1 for group 1, and n. 4 for groups 2 and 3.

The buccal faces of the specimens were marked at a distance of 4 mm from the cervical using a steel disk (KG Sorensen), and the measurement was done through a digital calliper (Fowler/Sylvac Ultra-Cal Mark IV Electronic Calliper, Crissier, Switzerland). This marking, in a cross form, served as a guide for the orientation and standardization of the determined plans for the measurements made on tomographic images [Figure 1].
Figure 1: Sample standardization sequence. (a) - section of the roots; (b) - numbering of samples; (c) - marking on the buccal face; (d) - groove confection with steel disc; (e) - samples with finished marking; (f) - addition silicone fixture

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Acquisition of images

Tomographic images were acquired from each specimen at two different moments: 1) After root canal desobturation; and 2) After cementing the intra-radicular post.

To obtain the tomographic images, a prefabricated form of silicone was used containing five equidistant individualized compartments measuring approximately 20 mm in its largest diameter and 10 mm in depth. These were filled with high precision silicone impression material (Express XT, 3M ESPE, Sumaré, Brazil); the teeth were introduced to this material individually, with a coronary portion facing up, perpendicular to the vertical plane, all with the buccal face fronting anteriorly to the correct repositioning and standardization when obtaining the images after desobturation, and after cementation of the intraradicular posts.

CT images were acquired by two different equipments: cone-beam and fan-beam. The cone-beam CT was Eagle 3D (Dabi Atlante, Ribeirão Preto, Brazil) with an isometric voxel of 0.13 mm and FOV of 6 × 8 cm. The fan-beam computed tomography was Aquilion 64 (Toshiba Medical System, Tokyo, Japan) with a 0.5 mm isometric voxel and 64 detector channels.

Cementation of the intraradicular posts

For the cementation of intraradicular posts, three different procedures were performed, according to the group tested. For the cementation of the tight posts, it was positioned to prove the stability inside the root canal. After the test and confirmation of the Glassix post + Plus (Nordin) n. 1, it was immersed in 24% H2O2(Fitofarma, Goiânia, Brazil) for 60 s, washed abundantly with air and a water jet for 20 s and dried with an air jet. After that, the Monobond silane (Ivoclar Vivadent, Schaan, Liechtenstein) was applied to the entire post structure and then left for 60 s. The root canal was irrigated abundantly with saline solution and then dried with n. 50 absorbent paper cones (Dentsply/Maillefer, Ballaigues, Switzerland). After preparation of the root canal and post, RelyX U200 automix self-conditioning and self-adhesive resin cement (3M ESPE, Sumaré, Brazil) was inserted into the root canal with an intracanal mixing tip. The post was positioned inside the root canal, removing excess cement and photoactivating for 60 s (Valo Cordless, Ultradent, Utah, USA).

For the cementation of anatomical posts, the same technical sequence was obeyed until silane application. After this step, the root canal was lubricated with a water-soluble gel, placing an increment of composite resin Z350 XT (3M ESPE, Sumaré, Brazil) on the post, and then the postresin assembly was inserted inside the root canal and photoactivated for 2 s with a high power photopolymerizer (Valo). The assembly was removed and repositioned inside the root canal by repeating the photopolymerization with 2 s periods. After anatomization, external photopolymerization was performed for 60 s. The canal was irrigated abundantly with saline solution and dried with n. 50 absorbent paper cones. The postresin assembly was flushed with air and water, and the silane was applied. The anatomical post was cemented as previously described [Figure 2].
Figure 2: Cementation sequence of fiberglass post anatomized by composite resin. (a) - Immersion of the post in hydrogen peroxide; (b) - silanization; (c) - lubrication of the root canal with water-soluble gel; (d) - anatomization of the post with composite resin; (e) - silanization of the anatomical post; (f) - insertion of the U200 cement into the root canal; (g) - postcementation

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For the metallic posts, the fabrication of the patterns of the molten metal cores was done using the direct technique with chemically activated acrylic resin (Duralay, São Paulo, Brazil). Subsequently, they were cast with an alternative seminoble metal alloy (Ag 43; Sn 24; and Cu 33). After disinfection of the metal post with 70% alcohol and gauze rubbing, the canals were irrigated with saline solution and dried with absorbent paper tips. The Single bond Universal Adhesive (3M ESPE, Sumaré, Brazil) was applied to the metal post, and the canal was filled with RelyX U200 automix (3M ESPE). The metal post was cemented as previously described.

Measurement of CT images

Measurements of CT images were made by two assessors, previously calibrated, using the original Dicom obtained by the different tomographers using the same program, OnDemand3D® software (Cybermed, Seoul, Korea). There was a previous adjustment to the density of the images, standardizing brightness in WW (Windows Wide) to 4000, the contrast in WL (Windows Level) to 900, the 3.5 × Zoom and the 2 × Filter to obtain the best image quality. Adjustment of the long axis of each tooth was performed with the coronal and sagittal planes as a reference, guided by the previously performed cross-marking, to obtain the standardized axial cut selected for the measurements. The root canal diameter was measured both before (after the preparation for the posts) and after the cementation of the posts. The distance in the axial plane of the root canal was measured in the buccal--lingual and mesiodistal directions, employing the software tool itself. These measurements were obtained to evaluate the dimensional alteration of these materials in the images of different tomographs and the influence of the beam hardening artefacts in the images [Figure 3] and [Figure 4].
Figure 3: Measurement of the root canal diameter of a post just in the MD and BL direction before and after the cementation of the intraradicular posts on the cone-beam tomograph

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Figure 4: Measurement of the root canal diameter of a post just in the MD and BL direction before and after the cementation of the intraradicular posts on the fan-beam tomograph

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Statistical analysis

The data obtained were tabulated and analyzed in the program Stat Plus: Mac v. 6.2.21 (Analysoft Inc., Atlanta, USA). Initially, the data were tested for their homogeneity (Levene test) and normality (Shapiro--Wilk test). Due to its parametric and homogeneous distribution, the T-test was used between the initial and final measurements of each tomograph and also between the cone-beam and fan-beam tomographs in the same measurement (α = 0.05).


   Results Top


The mean and standard deviations of the M-D measurements obtained for each tomograph are shown in [Table 1], and those for the B-L measurements are in [Table 2].
Table 1: Means and standard deviations of the M-D measures of each group

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Table 2: Means and standard deviations of the B-L measurements of each group

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Comparing the groups for both final measurements (B-L and M-D), there was a statistically significant difference in both tomographs for both posts, tight and anatomical fiberglass (P < 0.05). The anatomical fiberglass post presented the smallest dimensional change among the initial and final measurements, after the cementation of the posts, followed by the tight post, with metal being the material that presented the most massive dimensional change in the cone-beam. It was not possible to verify this difference for the fan-beam tomography after cementation of the metallic post, due to the number of artefacts observed, making it impossible to adjust the images following the reference to obtain the final measurements.

Comparing the dimensional changes observed in the images obtained in the different tomographies, there was a statistical difference between the tomographs for the tight and anatomical posts (P < 0.05), and it was not possible to evaluate the final measurements of the metallic post. For both the final measurements obtained (B-L and M-D), the images acquired in the cone-beam tomograph showed a smaller dimensional change when compared to the images of the fan-beam tomograph. The anatomical fiberglass post showed less variation in the final images than the post of tight fiberglass, which in turn presented less change in the final images than the metallic post.


   Discussion Top


The presence of different materials with different densities can lead to the formation of beam hardening artefacts, interfering in the size of the obtained images.[16],[17],[18] In restorative dentistry, the use of intraradicular posts has been increasingly used, replacing those made in metal by fiberglass posts, adapted or not to the internal anatomy of the root canals with the association to the composite resins.[19] However, the influence of these materials on the formation of artefacts is not a consensus in the literature.

In this sense, the present study aimed to evaluate the effect of different intraradicular posts on the dimensions of the root canal images in cone-beam and fan-beam CT. The results showed a change in the size of the images in all groups assessed, independent of the material used in both tomographs.

From a clinical perspective, the association of clinical signs and symptoms with imaging should be imperative for correct treatment planning. Variation in the size of the images can lead to errors in the diagnosis, with misinterpretation of possible perforations or root fractures.[6],[7],[8],[12]

The dimensional alteration of nonmetallic root canal sealing materials was also studied by Decurcio et al.[20] The authors evaluated a discrepancy in the measurements of the tomography images and the actual specimens treated endodontically and sealed with different endodontic cements. The measurements ranged from 9% to 100%, depending on the sealing material used. In the present study, this variation was also evident, irrespective of the composite resin added to the fiberglass posts. It was observed that the anatomical posts presented a smaller dimensional change when compared to the tight posts [Table 1] and [Table 2]. The images after metal post cementation in the fan-beam were not measured due to the large number of artefacts, which made it impossible to identify the standardization marking; also, it was not possible to perform measurements in the same region [Figure 5].
Figure 5: Image is illustrating the difficulty of measuring the final dimensions of the metallic posts in the fan-beam CT

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Another critical factor to be observed is the fact that there are several types of tomographs available on the market, so understanding their actual indications becomes fundamental to the clinician. Many advantages and limitations of each tomograph were listed in previously published studies.[5],[6],[7],[8] Scarfe et al.[21] reported that cone-beam CT scans provide sharp images of high-contrast structures and are extremely useful for the evaluation of bone tissue. When compared to the fan-beam CT scans, they have some advantages, such as limitation of x-ray beams, image accuracy, quick time mapping, decreased radiation dose and reduction of technical artefacts.

In the present study, the lower distortion of the image was observed when using the cone-beam CT compared to the fan-beam in all groups evaluated with a statistically significant difference (P < 0.05), which corroborates the findings of other studies; the results obtained in this study are similar to those found in the cone-beam CT scanners when applied to dentistry.[6]

Another important factor in the present study relates to image analysis software since the same program was used to perform the measurements in all of the groups analyzed. In a previous study,[22] the analysis of images was conducted in different software packages, which can lead to bias in the accomplishment of the measures since the tools are different between the software, and can contribute to dimensional variations.

The evolution of new programs, filters and capture techniques will undoubtedly reduce the formation of metallic artefacts and dimensional changes in reconstructions of CT scans.[23] However, with the resources available at present, knowledge of the composition of the intraradicular post and its influence on the formation of image artefacts can also be considered an essential factor in deciding which material to use. The choice of tomograph may also influence the quality of the images obtained and consequently the accuracy of the definitive diagnosis.


   Conclusion Top


All of the intraradicular posts used promoted a change in the size of the root canal in the images obtained through computed tomography. The anatomical post was the one that presented the smallest dimensional alterations, followed by tight and metallic posts. It was not possible to obtain final measurements for the metal group in the fan-beam CT due to the significant presence of artefacts. The fan-beam CT promoted greater dimensional change in the images of the posts when compared to the cone-beam scanner.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Correspondence Address:
Dr. Daniel A Decurcio
Faculdade de Odontologia, Universidade Federal de Goiás, Praça Universitária s/n, Setor Universitário, CEP 74605-020, Goiânia, GO
Brazil
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_866_18

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