Evaluation and comparison of sealing ability of three different obturation techniques - Lateral condensation, Obtura II, and GuttaFlow: An in vitro study.

AIM: To evaluate and compare the sealing ability between the conventional cold lateral condensation technique and two different obturating techniques - Obtura II and GuttaFlow under a stereomicroscope at 40× magnification.
MATERIALS AND METHODS: Sixty single-rooted teeth were selected and the canals were shaped with ProTaper rotary files. Irrigation was performed with 5% sodium hypochlorite and 17% EDTA. The teeth were then separated into three groups depending on the type of obturation technique. Group A (n = 20) - obturated using the Lateral condensation technique and AHplus sealer, Group B (n = 20) - obturated with Obtura II injection-molded thermoplasticized technique and AHplus sealer, and Group C (n = 20) obturated using GuttaFlow. After storing the teeth in 100% humidity for seven days at 37°C, the roots of the teeth were sectioned at five levels. The sections were then observed under a stereomicroscope at 40 × magnification and the images were analyzed for area of voids (AV) and frequency of voids. STATISTICAL ANALYSIS USED: The data was statistically analyzed using the SPSS version 17 software. The 95% confidence intervals (CI) were calculated. One-way analysis of variance with post-hoc test and non-parametric Mann-Whitney U test was carried out, to compare the means.
RESULTS: The lowest mean of AV was recorded in the Obtura II group, 1.0% (95% CI = 0.5 - 1.5). This was statistically and significantly different from the GuttaFlow group, 3.0% (95% CI = 2.1 - 3.9). There was no significant difference between the Obtura II group and the lateral condensation group, 1.6% (95% CI= 1.0 - 2.2) with regard to the area of voids, but there was a statistically significant difference between the Lateral condensation and GuttaFlow groups. The GuttaFlow group showed the maximum number of voids, 56% (95% CI = 48 - 64), which was significantly higher than those in the lateral condensation, 26% (95% CI= 19 - 34), and Obtura II, 15% (95% CI= 10 - 21) groups.
CONCLUSION: The Obtura II technique utilizing the injection-molded thermoplasticized gutta-percha had better adaptability to the canal walls when compared to the GuttaFlow obturation and lateral condensation techniques.

INTRODUCTION

A key to successful endodontics and a major goal of contemporary nonsurgical root canal treatment is to seal completely, both the apical and coronal avenues of potential leakage and maintain the disinfected status reached by the chemical and / or mechanical cleaning, to prevent reinfection and percolation of bacterial substrates , allowing the periodontium to maintain its integrity and to achieve healing.[1-4] Ingle found that nearly 60% of endodontic failures were due to the incomplete obturation of the root canal system.[5]

Cold lateral condensation, after being successfully tested and used, has set the golden standard in endodontics. However, it has been found that cold gutta-percha techniques rely heavily on a root canal sealer to address the problem of the accessory anatomy, as the core filling material will not move out of the main canal. Voids, spreader tracts, incomplete fusion of the gutta-percha cones, and lack of surface adaptation have been reported.[6]

One of the newer techniques utilizing thermoplasticized gutta-percha is Obtura II. It is an injectable, heated gutta-percha technique and has been found to be significantly superior to lateral condensation and has a better adaptation to the three-dimensional root canal system.[7]

A silicon-based sealer, RoekoSeal Automix (Roeko Dental Products, Langenau, Germany) has been shown to provide a consistent seal over a period of 18 months.[8] The new root canal filling paste GuttaFlow (Coltene / Whaledent, Raiffeinsenstra, Germany) is a modification of this sealer. It contains gutta-percha particles as a filler. The manufacturer claims a better seal and good adaptability because of the increased flowability and the fact that this material expands slightly on setting.

The present study was undertaken to compare the adaptability of the gutta-percha-based endodontic filling materials to the root canal walls, using three different obturating techniques — Lateral condensation, Obtura II, and GuttaFlow.

MATERIALS AND METHODS

Sixty extracted human mandibular single-rooted premolar teeth, with intact crowns, were collected for the study from the Department of Oral and Maxillofacial Surgery, Kamineni Institute of Dental Sciences, after visual and radiographic examination. No data regarding age, sex or reason for extraction was available. Teeth were stored, disinfected, and handled as per the recommendations and guidelines laid down by Occupational Safety and Health Administration (OSHA) and Centers for Disease Control and Prevention (CDC). Teeth that were excluded from the study included those showing incompletely formed apex, evident root fracture, extreme calcifications, and extreme canal curvatures.

The teeth were divided into three groups of 20 teeth each, using stratified randomization. The teeth were stored in distilled water during the entire study.

Canal preparation

Conventional access cavities to the pulp chamber were prepared. Gates Glidden drills (#2 – 4) (Mani, Prime dental, Mumbai) were used to flare the coronal third of each canal. The working length was defined to be 1 mm short of the apical foramen, determined by inserting a size #15 K-file (Mani, Prime dental, Mumbai) into the canal until the tip of the file was just visible at the apical foramen. Patency of the canal was maintained throughout the procedure by passing a #10 K-file approximately 0.5 mm through the apex.

Instrumentation of the canal was carried out with the help of ProTaper files (Dentsply Maillefer, Ballaigues, Switzerland). During preparation and between each file 2 ml of 5% sodium hypochlorite (Vishal Dentocare Pvt. Ltd., Ahmedabad, Gujarat) was used as an irrigant. All canals were prepared to F3 ProTaper file. The smear layer removal was done using 10 ml of 17% EDTA (Dent Wash, Prime Dental, Mumbai) followed by 10 ml of 5% sodium hypochlorite. The final rinse was done with saline. The canals were then dried with paper points (Dentsply Maillefer, Ballaigues, Switzerland).

Obturation protocol for the study groups

The three study groups of obturation were as follows:

Group A: Lateral condensation group

A standardized gutta-percha master point (Dentsply Maillefer, Ballaigues, Switzerland) was selected and introduced into the root canal to full working length and was checked for tugback criteria. AH plus sealer (Dentsply De Trey GmbH, Konstanz, Germany), was mixed according to the manufacturer's directions and applied to the canal wall using file size #20, in a counter clockwise rotation.[9] The master point was then coated with a sealer and introduced slowly into the root canal until the working length was reached. Lateral condensation was performed using standardized finger spreaders (Mani, Prime dental, Mumbai) and colored gutta-percha point sizes of # 15, # 20, #25, and # 30.

Group B: Obtura II group

The Obtura II system (Obtura Spartan, Fenton, Missouri, USA) was prepared according to the manufacturer's instructions (Obtura II Operator's manual). Silver injection needles of 23 gauges were used for all obturations and a silicone stop was placed 2 – 5 mm from the working length. The AH-Plus sealer was placed into the canal using a file size #20 using counter clock wise rotation.[9] At the time of obturation, the injection of the thermoplasticized gutta-percha was performed twice, separately. First, the needle was inserted in the apical direction until it bound to the canal wall, and the thermoplasticized gutta-percha, heated to 185°C in the delivery system, was injected. The needle was removed after injecting a few millimetres of gutta-percha near the tip of the preparation. The softened gutta-percha in the apical portion was then vertically condensed to the apex with a hand plugger (Dentsply Maillefer, Ballaigues, Switzerland) dipped in alcohol, to avoid adherence to the gutta-percha. The remaining root canal was then back-filled in increments until the gutta-percha was observed in the cervical aspect of the root.

Group C: GuttaFlow group

A standardized gutta-percha master point was selected and introduced into the root canal to full working length and was checked for tugback criteria. The GuttaFlow capsule (Coltene Whaledent, Raiffeinsenstra, Langenau / Germany) was pressed to break the barrier between the powder and liquid and it was placed in a triturator (Ultramat 2, SDI Ltd, Victoria, Australia) and allowed to vibrate for 30 seconds. The capsule plug was then removed and the disposable cannula attached to the capsule tip. The material color was checked to match with the one in the manufacturer's manual. GuttaFlow was then introduced into the canal, 3 mm short of the working length. The tip of the master point was coated with GuttaFlow paste and introduced into the root canal and was taken to the working length, slowly and gently back and forth, twice, to ensure complete wetting of the point and the canal wall. Then the master point was permanently placed in the canal.

Access cavities in all the three groups after obturation were sealed with Cavit G (3M ESPE, Seefeld, Germany).

Storage

These specimens after obturation were stored at 37°C and 100% humidity for seven days to allow adequate time for the obturated materials to set.

Each root was sectioned at five levels. Level 1 was at the apical end of the working length and other four levels were determined according to the individual root length. In general the thickness of the section was 1 – 2.5 mm.

Sectioning was done with double-ended diamond disks at low speed, with water cooling. A total of 600 surfaces were obtained (60 root canals ×5 sections ×2 surfaces per section). The coronal surfaces of the sections were labeled, digitally photographed, and measured at ×40 magnification, using a Stereomicroscope (Magnus).

The following parameters were recorded.

Area of voids (AV)

Number of sections with voids

Location of the voids (either in the filling core or along the root canal wall)

The area of voids was calculated as a percentage of the canal area in the sections

The frequency of sections with voids was calculated as a percentage of the total number of sections

Statistical analysis

For all the parameters, the 95% confidence intervals (CI) were calculated. One-way analysis of variance with a post-hoc test and non-parametric Mann-Whitney U test were carried out, to compare the means, by using the SPSS Version 17 software.

RESULTS

The lowest mean of AV was recorded in the Obtura II group 1.0% (95% CI = 0.5 – 1.5). This was statistically and significantly different from the GuttaFlow group 3.0% (95% CI = 2.1 – 3.9). There was no significant difference between the Obtura II group and the lateral condensation group 1.6% (95% CI= 1.0 – 2.2) with regard to the area of voids, but there was a statistically significant difference between the lateral condensation and GuttaFlow groups [Table 1 and 2].

Table 1

Mean, standard deviation, and 95% CI of the area of voids in the three study groups

Table 2

Percentage frequency of voids in the three study groups and their 95% CI

The GuttaFlow group showed the maximum number of sections with voids 56% (95% CI= 48 – 64), which was significantly higher than that in the lateral condensation 26% (95% CI= 19 – 34) and Obtura II 15% (95% CI= 10 – 21) groups.

In all the three groups, at Level 1, there was good adaptation of the gutta-percha to the canal wall, with a minimum number of voids or no voids. Voids were present in the periphery and core in all the groups, but the GuttaFlow group showed the minimum number of voids at the periphery and the maximum in the core of the material.

DISCUSSION

In this study, 60 extracted single-rooted human teeth were used to enhance the reliability of the investigation by duplicating the clinical situation. Selection of the teeth and their assignment into different study groups was done using stratified randomization. This assured one of having comparable groups with respect to tooth type and form (long / short and straight / curved). Moreover, only teeth with intact or restored crowns were used. This was done to simulate the clinical conditions, because decoronation of teeth might ease the accessibility to root canals.[9] To reduce variability, all the canals were prepared by one operator using standard techniques.

The presence or absence of a smear layer plays an important role in the apical seal produced by various obturating techniques.[10] Studies have shown that the smear layer can serve as an avenue for leakage of microorganisms and as a source for the growth and activity of variable bacteria, which remain entrapped in dentinal tubules.[11] Hence, the root canals were irrigated with 5% sodium hypochlorite solution and 17% EDTA to remove the smear layer.

In the present study lateral condensation was used because it is the most commonly used and studied technique, and therefore, it served as a standard with which other techniques could be compared.[12-15]

Obtura II is an injectable, thermoplasticized, gutta-percha technique and it has been found to be significantly superior to lateral condensation and has a better adaptation to the three dimensional root canal system.[6716]

GuttaFlow, a new root canal obturation material, is said to have good flowable properties at room temperature, and provides better sealing, has good adaptability because of its increased flowability, and also this material expands on setting.[917-21]

Sectioning of teeth was not performed at predetermined distances from the apex, but rather according to individual root length. This was done to obtain comparable information at the specific root levels, for example, at mid root level. Sectioning at predetermined distances from the apex did not give information about the position of the sectioning levels, in relation to the coronal access cavity. In this way, filling a root canal at a level 5 mm short of the apex (for example) may be easier to perform in the short root canals rather than in long ones.[9]

Stereomicroscopic examination was chosen for this study as this provides a three-dimensional view of the surface to be examined, it requires no pretreatment of the specimen (as in the Scanning Electron Microscopic Examination) and is associated with an image analysis software, which aids in eliminating human errors, in the interpretation of the parameters.

The areas of voids were calculated in this study to quantify the adaptation of the filling. The influence of this parameter on the leakage of the filling depended on the type (through and through or dead end voids) and location of the voids (within the filling or at the canal wall).

Based on the results of this study, the Obtura II group showed the lowest percentage of area of void (1.0%). However the voids, most of the time, were surrounded by the gutta-percha. Thus the adaptation to the root canal wall was complete. This was in agreement with the results reported by Monticelli et al. and ElAyouti et al.[2223]

In the GuttaFlow group, remarkably, a maximum number of voids were enclosed within the core of the filling material, which was in accordance with other studies.[92324] Therefore, the adaptation to the root canal wall was almost complete.

The GuttaFlow group showed the highest number of sections with voids. This is explained by the small size of the individual void in the GuttaFlow (mean = 349.4 μm for guttaflow, mean = 17545.6 μm for lateral condensation, and mean = 1824.4 μm for the Obtura II group). The minute voids, within the core of the GuttaFlow, may be a result of the manufacturing process. The GuttaFlow coated nearly all root canal walls. This may be a result of the mode of application of the high viscous GuttaFlow paste, which provided an extended condensation and pressing of the filling material into the narrow parts of the root canal, throughout the working time of the material.

Based on these observations, Obtura II was found to be the best in adaptability, in comparison with the other obturating techniques used.

Despite the presence of small voids within the core of the material, GuttaFlow seems to be a promising filling material because of the good adaptability to root canal walls, the ease of handling, and application of the material. It has also been seen in a recent computed tomography study that it had the highest volume of obturation when compared to the vertical compaction thermoplastiscized technique.[25]

Although these are in vitro results, they are of significance because these factors cannot be easily and quantitatively determined in vivo. Nevertheless, further clinical studies are necessary to confirm these results and evaluate their relevance to the treatment outcome.

CONCLUSIONS

Within the limitations of this study, the following conclusions were drawn:

Obtura II exhibited the best adaptation with less number of voids, as compared to the other two groups

The lateral condensation group had more voids when compared with the Obtura II and most of the voids were seen at the periphery

The GuttaFlow group, although they showed more number of voids, these voids were remarkably enclosed within the material, and hence, they exhibited good adaptation to the dentinal walls

Overall, the Obtura II group exhibited a homogenous obturation followed by lateral condensation and GuttaFlow

Obtura II exhibited good adaptation followed by GuttaFlow and lateral condensation