Saudi Endodontic Journal

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 2  |  Page : 126--130

Comparative evaluation of porosity distribution in root canals obturated with gutta-percha using single-cone technique and thermoplasticized technique


Tanya Sawhney1, Ansu Ann Abraham1, Karuna Y Mahabala2, Madhura Sen2, Srikant Natarajan3, Nithin Thilak4, Ashwin Rao2, Anupama Nayak2,  
1 Under Graduate Student, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
2 Department of Pediatric and Preventive Dentistry, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
3 Department of Oral Pathology, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India
4 Department of Oral Medicine and Radiology, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka, India

Correspondence Address:
Dr. Karuna Y Mahabala
Department of Pediatric and Preventive Dentistry, Manipal College of Dental Sciences, Mangalore, Manipal Academy of Higher Education, Manipal, Karnataka
India

Abstract

Introduction: The objective of the study was to comparatively evaluate the porosity distribution in the root canals obturated using the single-cone technique and thermoplasticized technique. Materials and Methods: A total of 42 permanent single-rooted human extracted teeth were divided equally into two groups based on the technique employed: single-cone technique and thermoplasticized technique. Following postobturation restoration, void volume was analyzed by cone-beam computed tomography (CBCT) and void location was evaluated by microscopic method at three levels: coronal, middle, and apical. Independent Student't-test and Chi-square test were used for analyzing the obtained results. Results: On comparing the void volumes as seen in CBCT images between the two groups, the thermoplasticized technique showed greater but insignificant void volume (P = 0.18). When the association of the location of the void with the void area percentage was analyzed between the two techniques, significant associations were seen in the middle (P = 0.016) and the apical levels (P = 0.031). Conclusion: The single-cone technique showed a comparable seal with the thermoplasticized technique. Voids were predominantly seen at the sealer–cone interface and sealer–root canal wall interface for single-cone technique and in between the condensed gutta-percha for thermoplasticized technique.



How to cite this article:
Sawhney T, Abraham AA, Mahabala KY, Sen M, Natarajan S, Thilak N, Rao A, Nayak A. Comparative evaluation of porosity distribution in root canals obturated with gutta-percha using single-cone technique and thermoplasticized technique.Saudi Endod J 2020;10:126-130


How to cite this URL:
Sawhney T, Abraham AA, Mahabala KY, Sen M, Natarajan S, Thilak N, Rao A, Nayak A. Comparative evaluation of porosity distribution in root canals obturated with gutta-percha using single-cone technique and thermoplasticized technique. Saudi Endod J [serial online] 2020 [cited 2020 Jul 12 ];10:126-130
Available from: http://www.saudiendodj.com/text.asp?2020/10/2/126/283133


Full Text

 Introduction



Achieving a hermetic seal while performing obturation of the root canal during an endodontic treatment procedure is of utmost importance to prevent the recolonization of microorganisms in the empty root canal space.[1] The impervious sealing of the root canals is also important to facilitate the healing of the periapical tissues.[2] Among the obturation techniques available, the superior sealing ability of the different thermoplasticized gutta-percha-based obturation techniques has been well established in the literature.[3],[4],[5]

Warm/thermoplastisized obturation techniques use an alpha form of gutta-percha, which is pliable and tacky, and when heated, it gets molded into the intricacies of the root canal anatomy, providing a more homogeneous filling.[6],[7],[8] Various systems of warm/thermoplasticized gutta-percha techniques include Thermafil, System B technique, Obtura II, and E and Q plus system. The E and Q plus system comprises a control unit which has a pen-grip device holding a heating tip and a gutta-percha injection gun similar to that in Obtura II system.[6]

An emerging simple approach for obturation is a single-cone technique, which uses a beta form (rigid in nature) of gutta-percha.[7] In this technique, the gutta-percha cones are manufactured to match the taper of the rotary files.[9] The procedure involves the insertion of a properly matched single cone along with a root canal sealer to completely fill the entire canal.[10] This obturation technique saves time for clinician.[11]

Both the aforementioned techniques crucially require good adaptation of the gutta-percha to the root canal walls as well as proper wetting of the cones and the dentinal walls with the sealer to prevent entrapment of air during obturation.[10] The air entrapment can occur anywhere within the root canal filling and is greatly dependent on the technique of obturation used. The created porosities are of great clinical significance as they present as foci for microbial colonization eventually causing reinfection and treatment failure.[12] Thus, keeping in mind to provide an improved quality of the root canal filling and a tight seal, it is important to study the porosity distribution while using different techniques of obturation.

In a study by Moinzadeh et al.,[10] it was found that the porosity associated with single-cone technique was significantly less than that with lateral condensation technique. However, there exists no literature comparing the porosity distribution in the root canal filling while using single-cone and thermoplasticized techniques of obturation. Thus, the present study was conducted to comparatively evaluate the porosity distribution in the root canals obturated with gutta-percha and mineral trioxide aggregate (MTA) sealer using the single-cone technique and thermoplasticized technique.

 Materials and Methods



The study was initiated after obtaining approval from the Institutional Ethics Committee of Manipal College of Dental Sciences, Mangalore (protocol reference number: 18097). This study was anin vitro intergroup comparative study.

The sample size for the present study was calculated with an alpha error of 1% and a power of 95%, and the Z values of the given alpha and beta values are 2.58 and 1.64, respectively. With the correlation coefficient derived/reported (0.73) by a study of Moinzadeh et al.[10] and using the above values in the given formula, the required sample size was calculated as 21/group.

[INLINE:1]

Forty-two single-rooted permanent maxillary and mandibular human teeth extracted for therapeutic reasons and stored in 0.1% thymol (Sisco Research Laboratories Pvt., Ltd., India) at room temperature were used in the study. Teeth with complete (fully formed and undamaged) root apex and single straight (curvature <10°) root canals as determined by radiographic examination were included, whereas the ones with root caries, root resorption, and calcified root canals were excluded. The crowns of the selected teeth were removed with a diamond disk (KaVo Kerr, Brea, California) mounted on a high-speed handpiece (NSK, Confident Sales India Pvt., Ltd.) to standardize the root length to 14 mm.

All specimens were prepared by a single operator. An ISO size 10-K file (Mani Inc., Tochigi, Japan) was placed inside the canal to determine the working length (kept 1 mm short of the full root canal length). All root canals were instrumented to F4 instrument (size 40/0.06) taper using a series of nickel–titanium files (ProTaper file system, Dentsply, Johnson City, TN, USA). The root canals were irrigated with 2% NaOCl (Vishal Dentocare Pvt. Ltd., Gujarat, India) after instrumentation with each file. At the end of the preparation, 3 mL of 17% ethylenediaminetetraacetic acid (Anabond Stedman Pharma Research (P) Ltd., Tamil Nadu, India) solution was delivered into the root canal, and the solution was left in place for 3 min before flushing with 2% NaOCl. Finally, the canals were irrigated with distilled water to remove the remnants of the chemicals and were briefly blotted with paper points (DiaDent Group International, Korea).

The prepared specimens were randomly allocated to two groups (21 teeth each) – Group I: single-cone technique and Group II: thermoplastisized gutta-percha technique (E and Q plus system) using the lottery system. An MTA sealer (MTA Fillapex, Angelus, Brazil) was used.

Single-cone technique

The sealer was injected in the root canal to about 4 mm short of the working length using the syringe and the plastic needle supplied by the manufacturer. The plunger of the syringe was pressed while slowly withdrawing the tip. A single F4 gutta-percha cone (size 40/0.06 taper) (Dia-Pro T Plus, DiaDent, Korea) was adjusted to the length of the canal and then seated reaching the full preparation length.

Thermoplastisized gutta-percha technique

E and Q plus system (Meta Dental Corp., Cheongju, Korea) was used for obturation. The fit and tug-back was checked off, with the master apical cone that matches the taper of the canal being obturated. Later, an appropriate pen tip was selected, and the stopper was adjusted to 4 mm short of the working length. The master cone was coated with sealer and inserted into the canal. The excess gutta-percha was cut using the pen. In the next stage, the gun needle was inserted into the root canal, and the trigger was pulled slowly to obtain backfill with warm gutta-percha. Down packing of the warm gutta-percha was done with appropriate cold pluggers to obturate the root canal three-dimensionally (3D).

The root filling was covered with a flowable dental composite resin (3M ESPE, St. Paul, USA) in order to seal the root opening, simulating the conditions of the oral cavity. The roots were stored at 37°C and 100% humidity conditions for 10 days to allow the sealer to set completely before analysis.[10]

The void volume was analyzed by both radiographic methods. Cone-beam computed tomography (CBCT) scan of the mounted teeth was done using Planmeca ProMax 3D Mid unit 9 (Planmeca Oy, Helsinki, Finland) using the exposure parameters of 90 kV and 8 mA for 12 s to obtain a medium field of view (100 mm × 60 mm). Romexis software version 4.1.2 (Planmeca, Helsinki, Finland) was used to assess the scans and void volume in each of the two categories, which was calculated by manual segmentation using “free region grow tool” [Figure 1]a and [Figure 1]b. Later, the sectioning of the tooth was done at three levels, namely apical, middle, and coronal using a diamond disk. The specimens were mounted on a slide and observed under a compound microscope (CH20 Olympus microscope) to check the location of the voids [Figure 2]a and [Figure 2]b. The images taken at every level were analyzed using the program “Image J” where the area percentage of each canal (CA) and the area percentage of each void (VA) were calculated. From these values, the void area percentage was calculated.{Figure 1}{Figure 2}

Statistical analysis

The void volume between the single-cone and thermoplasticized techniques was compared using independent Student's t-test. The association of the void area percentage in relation to the various locations within the root canal was evaluated using the Chi-square test.

 Results



On comparing the void volumes as seen in CBCT images between the two groups, single-cone technique and thermoplasticized technique showed comparable void volume (t = −1.34 and P = 0.18). When the location of the voids as seen microscopically was analyzed between the single-cone and thermoplastisized techniques, significant associations were seen with variations in the middle (P = 0.016) and the apical levels (P = 0.031). In the single-cone technique, the coronal and the middle portions showed predominant voids in between the sealer and the root canal wall, whereas in the apical portion, the voids were predominantly between the sealer and the gutta-percha cone. On the contrary, the thermoplastisized technique showed predominant voids between the cone in the coronal and middle thirds, whereas in the apical portion, voids were seen between the sealer and the wall [Table 1].{Table 1}

 Discussion



The presence of the surface irregularities, fins, accessory canals, lateral canals, and isthmuses along with the inability of gutta-percha to adhere to the root canal walls as well as to the sealers poses a great challenge in achieving a good seal during root canal obturation.[13],[14] Lack of the impervious seal of the root canal system will eventually lead to endodontic treatment failure.[13] Root canal obturation has been evaluated following obturation with gutta-percha and different sealers, however, with inconsistent results.[6],[15],[16],[17],[18]

With the growing popularity of rotary endodontics and availability of matched gutta-percha cones, the usage of single-cone obturation technique is highly increasing. This technique is preferred as it is simple, saves time, and causes less stress for the patient as well as to the clinician.[19],[20] However, there exists a mismatch in the shape of the master cone and the anatomy of the root canal. Thus, achieving the fluid-tight seal in this technique is dependent on the usage of a sufficient amount of sealant. Poor adaptation of the single cone at the middle and coronal thirds of the root canal is another disadvantage due to the shape mismatch.[21]

This was reflected in the findings of the present study, where single-cone technique showed predominant voids at the coronal and middle portions. On the other hand, the thermoplasticized technique showed predominant voids at the middle and the apical levels within the gutta-percha, which could be due to the poor condensation at these difficult-to-reach areas. However, on comparing both techniques as a whole, single cone showed lesser voids which can be justified based on the hypothesis that single-cone technique shows greater homogeneity as compared to other techniques of obturation.[22] This is further supported by the microscopic finding on an analysis of the location of the voids. The single-cone technique totally eliminated the problem of having voids between the cone, while the thermoplasticized technique showed voids at all the locations, namely between cone, cone–root canal wall interface, between sealer, sealer–cone interface, and sealer–root canal wall interface.

For estimation of the quality of root canal filling, previously published studies have used either microscopic method[23],[24] or radiographic technique.[22],[25] In the present study, we used CBCT for evaluation of the void volume as it helps in analyzing the porosity distribution 3D. We also made the use of microscopic analysis to locate the voids in relation to both the techniques at coronal, middle, and apical levels. This is because CBCT cannot differentiate between the sealer and the gutta-percha, thereby failing to identify the voids between the same.[26]

The results of the present study are supported by the findings of Moinzadeh et al.[10] who also showed significantly less porosity in root canals filled with the single-cone technique. However, the latter was in comparison to that of lateral condensation technique. Kierklo et al.[27] observed a greater percentage of voids in the cold lateral condensation group than the thermoplasticized group. There are no studies till date in literature comparing the porosity distribution between single-cone technique and thermoplasticized technique. Thus, future studies are recommended under simulated oral conditions to add further evidence to the obtained findings.

 Conclusion



Within the limitations of the present study, the following conclusions may be drawn:

The single-cone technique showed a comparable seal with the thermoplasticized techniqueVoids were predominantly seen at the sealer–cone interface and sealer–root canal wall interface in single-cone technique and in between the condensed gutta-percha in thermoplasticized technique.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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