| Abstract|| |
Aim: The aim was to evaluate and compare a novel polyamide polymer based obturating system and Gutta-percha and sealer in filling simulated lateral canals and their homogeneity when used for obturating the root canals.
Materials and Methods: A total of 60 freshly extracted human single rooted teeth with fully formed apices were selected for this study. Teeth were de-coronated, and roots were standardized to a working length of 15 mm. Root canal preparation was carried out with rotary Protaper file system in all groups. The specimens were then randomly divided into three groups A, B, and C (n = 20). Ten samples from each group were decalcified and simulated lateral canals were made at 2, 4, and 6 mm from the root apex. Remaining ten samples from each group were maintained calcified. Group A was obturated with SmartSeal system (Prosmart-DRFP Ltd., Stamford, UK). Group B was obturated with sectional backfill method. Group C was obutrated with cold lateral compaction method (control). Decalcified samples from the respective groups were analyzed with digital radiography and photography and the measurement of the linear extension and area of lateral canal filling was done using UTHSCSA (UTHSCSA Image Tool for Windows version 3.0, San Antonio, TX, USA) software. Calcified samples were subjected to cone beam computed tomography image analysis sectioned axially.
Results: Group A 92.46 ± 19.45 showed greatest extent of filling in lateral canals and denser homogeneity of oburation, followed by Group B 78.43 ± 26.45 and Group C 52.12 ± 36.67.
Conclusions: Polyamide polymer obturation proved to have greater efficiency when compared with Gutta-percha system, when used for obturation with regards to adaptation of the sealer and penetration into the simulated lateral canals.
Keywords: Cone beam computed tomography; Gutta-percha; polyamide polymer; SmartSeal system
|How to cite this article:|
Arora S, Hegde V. Comparative evaluation of a novel smart-seal obturating system and its homogeneity of using cone beam computed tomography: In vitro simulated lateral canal study. J Conserv Dent 2014;17:364-8
|How to cite this URL:|
Arora S, Hegde V. Comparative evaluation of a novel smart-seal obturating system and its homogeneity of using cone beam computed tomography: In vitro simulated lateral canal study. J Conserv Dent [serial online] 2014 [cited 2019 Sep 15];17:364-8. Available from: http://www.jcd.org.in/text.asp?2014/17/4/364/136512
| Introduction|| |
The main aim of an endodontic obturation is to obtain a fluid tight hermetic seal of the entire root canal system (RCS).  The presence of great anatomic complexity of the RCS, , has advocated the evolution of different materials and techniques to achieve the desired fluid tight hermetic seal. , Gutta-percha, in combination with sealer, is the most widely used solid material for endodontic root canal obturation. Cold lateral condensation as an obturation technique is widely practiced throughout because of its advantages of controlled placement of Gutta-percha in the root canal and low cost. ,, The final filling is composed of a large number of Gutta-percha cones tightly compressed together and joined by frictional grip and root canal sealer, rather than a homogeneous mass of Gutta-percha.  There is usually presence of voids because of spaces between individual Gutta-percha cones and the root canal walls. This can be seen with poor root canal preparations, curved canals, inadequate lateral pressure during condensation or mismatch between Gutta-percha cones and the prepared root canals. Such obturations would lack homogeneity and have to depend on sealer to fill the voids and thus would have a poor prognosis. , Because Gutta-percha obturation techniques generally require some type of condensation (lateral, vertical) their final radiographic appearance may or may not be as expected due to variations in appearance such as sealer voids, spreader tracks, condenser voids and material welds (in the case of heated techniques). While various studies have attempted to relate these aberrancies with case unacceptability and failure, little correlation exist at present; except for the standard that a dense, well-adapted root-filling is clinically and radio graphically acceptable.  Since the introduction of thermoplastic obturation techniques in 1967 by Schilder,  new devices and systems using thermoplasticized Gutta-percha as root canal filling material have been developed. The sectional backfill technique with thermoplastic Gutta-percha is one of these options, consisting of an apparatus for heating and injecting thermoplasticized Gutta-percha into the root canal. This technique has shown better adaptation to the root canal walls in comparison to lateral condensation, and also result in successful filling of simulated lateral canals. ,, The most recent advancement in endodontic obturating materials uses a hydrophilic polymer in the root canal, The SmartSeal system (Prosmart - DRFP Ltd., Stamford, UK). The system consists of obturation points (Pro-points) containing a polyamide core with an outer bonded hydrophilic polymer coating and an accompanying sealer which is further provided with polymer powder to be incorporated during the manipulation of the sealer. The endodontic points are designed to expand laterally without expanding axially by absorbing residual water from the instrumented root canal space and the naturally present moisture in the dentinal tubules.  The inner core of Pro-points is a mix of two proprietary nylon polymers: Trogamid T and Trogamid CX. The polymer coating is a cross-linked copolymer of acrylonitrile and vinylpyrrolidone which has been polymerised and cross-linked using allyl methacrylate and a thermal initiator. The lateral expansion of Pro-points is claimed to occur nonuniformly with the expand-ability depending on the extent to which the hydrophilic polymer is prestressed (i.e., contact with a canal wall will reduce the rate or extent of polymer expansion). 
Different techniques and root canal materials have been used for evaluating obturation in a simulated lateral canal. Both natural and artificial teeth have been used for in order to simulate the lateral canals. ,, Natural teeth have been more commonly used as evaluation can be done by radiographic methods, decalcification, clearing methods or a combination of both.  To the best of our knowledge, there is no reported study comparing novel SmartSeal system and Gutta-percha system using simulated lateral canals using decalcification methods and cone beam computed tomography (CBCT) image analysis. The homogeneity of the materials has been evaluated using CBCT with axial sections obtained at coronal, middle and apical levels. Because we were evaluating a new material, a three-dimensional (3D) evaluation by CBCT was advised to further substantiate the results. 
| Materials and methods|| |
Preparation of the specimens
A total of 60 freshly extracted human single rooted teeth with fully formed apices were selected for this study. Teeth were de-coronated and roots were standardized to a working length (WL) of 15 mm. Root canal preparation was subjected to crown down technique with rotary Protaper files until file size F2 with full sequence. After each file 1 ml of 3% sodium hypochlorite was used as an irrigating solution delivered with 27-gauge side venting needles inserted 3 mm from the apex. Ethylenediaminetetraacetic acid (EDTA) gel (RC help) was used as a lubricant. This was followed by a rinse of 3 ml of 17% EDTA for 1 min. After completion of instrumentation, the canals were dried using sterile absorbent points.
After completion of root canal preparation ten specimens from each group were subjected to a tooth decalcification and clearing protocol previously described by Venturi et al.  Specimens were decalcified in a solution of 5% hydrochloric acid (Hexis Cientύfica S/A, Jundia, SP, Brazil) which was changed every 24 h for 5 days. Teeth were de-mineralized until they achieved a rubber-like consistency. Later, #8 and #10 K-files were inserted through the buccal and lingual root surfaces at 2, 4, and 6 mm from the WL until they reached the main root canal, creating the simulated lateral canals. The patency and standardization of lateral canals were tested with #8 or #10 K-file. In order to eliminate the acid, teeth were washed in running tap water for 4 h and dehydrated using increasingly concentrated serial dilutions of alcohol, which reverted the specimens back to its hard consistency. Finally, specimens were immersed in ethyl salicylate (Vetec Quύmica Fina Ltda, Rio de Janeiro, RJ, Brazil) in order to render the tissues transparent., Remaining ten specimens from each group were mounted on modeling wax for CBCT analysis.
Obturation and distribution of the specimens
- Group A: SmartSeal system
- Group B: Sectional backfill technique
- Group C: Cold lateral condensation technique
Group A: Teeth were obturated with 6 taper master polyamide polymer cone using single-cone technique with no accessory cones being used. The sealer used in this group was SmartPaste sealer (Prosmart-DRFP Ltd.Stamford, UK) an epoxy amine resin-based sealer with active polymer powder. Group B: Teeth were obturated using sectional backfill technique with 6 taper Gutta-percha cone seared off 4 mm from the apex and the remaining canal backfilled with warmed Gutta-percha. Group C: Teeth were obturated using cold lateral compaction technique. A F 2 0.06 taper GP cone (DiaDent, Vancover, BC, Canada) was placed to WL. A fine size finger spreader was advanced to within 1 mm of the WL or to resistance, rotated and removed. A size #25 0.02 taper accessory GP cone (Tulsa Dental) was placed into the prepared space. This was repeated until no more than 2 mm of the spreader could be advanced into the canal. Excess GP was removed with a #15 scalpel blade at the coronal root surface. Sealer used in Groups B and C was AH Plus (Dentsply Maillefer); an epoxy amine resin-based sealer. After obturation, all the specimens were stored at a temperature 37°C for duration of 24 h to allow complete setting of the sealer.
Radiographic and photographic analysis of the cleared specimens
Proximal radiographs of each specimen (Kodak RVG 6100; Kodak Dental Systems, Atlanta, GA, USA) were taken using the Spectro ×70 Electronic X-ray unit after standardizing the positioning of the roots and the focus-film distance. Then, specimens were soaked once again in methyl salicylate, and standardized digital photographs were taken (Nikon D80; Nikon, Tokyo, Japan). The radiographic and photographic images showing the root canal fillings in each specimen were imported into the Image Tool software (UTHSCSA Image Tool for Windows version 3.0, San Antonio, TX, USA). The amount of filling material observed in each lateral canal at the level of 2, 4 and 6 mm was calculated by single calibrated examiner. The data were expressed as linear extension (length in mm of the lateral canal that was filled in relation to its entire length) and of the area filled (area in millimeter square occupied by the filling material inside the lateral canal in relation to its entire area). Results were subjected to statistical analysis using the Kruskal-Wallis test at 5% significance using SPSS software version 16.
Cone beam computed tomography analysis
An attempt was made to assess homogeneity of the obturation using CBCT. The CBCT scans were done using Promax 3D Mid (Planmeca OY Helsinki, Finland). The samples were mounted on wax block for stabilizing them and were exposed to the CBCT scans with 90 kV and 8 mA with field of view of 4.5 cm × 4.5 cm and an isotropic resolution of 2 mm resulting in 400-450 slices per tooth with exposure time of 12.28 s.
| Results|| |
Kruskal-Wallis test was performed using SPSS version 16. [Table 1] shows the radiographic analysis of each material of filled the simulated lateral canals (measured in linear and area percentages). SmartSeal system of obturation when evaluated, presented a high mean (89.45 ± 16.21) in linear extension of root canal and high mean of (92.46 ± 19.45) in area filled. Pro-points demonstrated a greater filling ability (P < 0.05) than Gutta-percha in all thirds of canal, as shown by the radiographic analysis (extension and area), and as by the analysis of cleared specimens (extension). [Figure 1] shows the radiograph and photograph of a decalcified and cleared specimen. [Figure 2] shows the CBCT analysis (axial sections) of all groups, in coronal (a), middle (b) and apical (c) sections. Polyamide polymer reveals minimum voids in all sections indicating an obturation of greater homogeneity in comparison to Gutta-percha system.
|Figure 1: Photographic and radiographic analysis. (a) Polyamide polymer obturation. (b) Sectional backfi lled obturation. (c) Cold lateral condensation (control)|
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|Table 1: Mean percentage of linear extension and area extended in coronal, middle and apical root canal|
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|Figure 2: Cone beam computed tomography analysis (axial sections). (a) Coronal section. (b) Middle section. (c) Apical section — (A) Polyamide polymer obturation, (B) Sectional backfi lled obturation, (C) Cold lateral obturation (control)|
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| Discussion|| |
The ultimate goal of obturation is to prevent the re-infection of root canals that have been biomechanically cleaned, shaped and disinfected by instrumentation and irrigation. Successful obturation requires the use of materials and techniques capable of densely filling the entire RCS and providing a fluid tight seal from the apical segment of the canal to the canal orifice in order to prevent re-infection.  Therefore, the goal of 3D obturation is to achieve an impermeable fluid tight seal within the entire RCS which will further help in preventing oral and apical microleakage.  Gutta-percha along with root canal sealers is the worldwide accepted combination available till date and is considered as the gold standard. Despite its many advantages and having achieved the status of a high quality material, Gutta-percha still has its limitations like its inability to strengthen root as it does not bond to dentin. Although few materials have seriously challenged Gutta-percha in the majority of aspects associated with Gutta-percha, research continues to find alternatives that may seal better and mechanically reinforce compromised roots. 
The major demerit seen with Gutta-percha is its inability to reinforce endodontically treated tooth.  Gutta-percha does not chemically bond to the dentin wall, that is, does not form the monoblock system. According to Teixeira and Trope.  Gutta-percha does not from a monoblock even with the use of a resin-based sealer such as AH Plus because the sealer does not bind to Gutta-percha. Moreover, the sealer tends to pull away from the Gutta-percha on setting. 
Thus, the ultimate goal of this study was to search an alternative to currently and most widely used Gutta-percha system which would not only have the ideal characteristics of Gutta-percha, but also further new advances installed. SmartSeal system consists of polyamide polymer cones (Propoints) and a resin sealer with additional polymer powder to be mixed during manipulation of the sealer. The white points consist of a radiopaque core coated with a radiopaque hydrophilic polymer, which can expand laterally upon absorbing water from the tooth, adopting the shape of the canal. The points can expand up to around 17% and will still give the same X-ray appearance as with conventional root-filling materials. Leakage studies indicate single-cone obturation methods to be inferior in their ability to achieve a fluid-tight seal.  The use of expandable obturating materials to improve the seal of the root-filled canals have been reported even for Gutta-percha. Gutta-percha expands in the presence of eugenol, which may reduce gaps within the filled canal space. Apart from eugenol-induced expansion, closure of microgaps in Gutta-percha filled root canals by moisture present within the canal space may compensate for leakage that arises from sealer dissolution to certain extent The delayed hygroscopic expansion of Pro-points when latter is coated with a hydrophobic sealer that impedes water sorption may partially compensate for the gaps arising from sealer dissolution.  Farge et al. showed that lateral condensation technique results in more leakage than thermomechanical compaction technique. Brothman et al. reported that the thermoplasticized condensation technique on radiographic examination, shows nearly 2 times more lateral and accessory canals compared with lateral condensation technique.  The amount of filling achieved in the lateral canals of natural teeth has been evaluated by means of radiographs , and visual analysis of decalcified and cleared specimens following a protocol described by Venturi et al.  This protocol allows 3D analysis by rendering the tooth transparent. Venturi et al.  evaluated the diameter and shape of natural lateral canals as well as the ability of different root canal filling materials to fill these root canals using three obturation techniques. In this study, the lateral canal preparation was held after the demineralization of teeth until they achieved a rubber-like consistency. The #8 or #10 K-files were inserted into the softened root creating standardized artificial lateral canals at 2, 4 and 6 mm from the apex. The clearing procedure was then completed by immersion in methyl salicylate to harden the specimens and restore their initial consistency. The radiographic analysis was performed digitally and the specimens had been previously subjected to the decalcification and clearing protocol promoting better image quality.
This study has shown results that polyamide polymer has shown a greater area and linear extension occupied in the root canal space as compared to obturation techniques using Gutta-percha. Such a result can be attributed to the hygroscopic expansion property exhibited by the polyamide polymer system and the shrinkage associated with the Gutta-percha system. Even though, the sealers are mostly responsible for obtaining a proper seal in the lateral canals and attempt was made to show the role of different obturation techniques in filling simulated lateral canals as well as the role of a hydrophobic and a hydrophilic obturating system.
An Outstanding review by Taylor et al. have reported on many possible endodontic application of CBCT, Simon et al. have reported that the CBCT might prove more accurate diagnostic information. One might contradict on the use of CBCT for postobturation analysis pattern. However, for this in vitro study, for the analysis of newer obturating material cross-sectional analysis using CBCT was done to evaluate the homogeneity. As Group A was obturated using a single-cone technique, it can be hypothesized that it would show greater homogeneity as compared to lateral condensation and sectional backfilled methods. As seen in the images lesser number of voids is observed in the cross-section of Group A owing to its greater homogeneity; leading to better adaptation in the root canal space. Even though one can contradict the use of CBCT image analysis for postobturation evaluation as various artifacts like scattering are associated with CBCT image analysis, which can be mistaken for potential voids in the obturation. The only disadvantage of CBCT is its cost. However considering the enormous benefits this cost-effect can be overlooked since the ease of the machine makes it suitable to be used also in minor diagnostic procedures. 
Furthermore, analysis would be required to evaluate the actual expansion shown by the polyamide polymer system; its microleakage properties, fracture toughness, and bond strengths to the dentin.
With the introduction of novel hydrophilic SmartSeal system over the conventional hydrophobic Gutta-percha system, has widened our range of achieving a 3D seal. This study concludes a greater efficiency in filling simulated lateral canals and a comparable homogeneity of obturation using SmartSeal system over Gutta-percha.
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