Sealing ability of lateral condensation, thermoplasticized gutta-percha and flowable gutta-percha obturation techniques: A comparative in vitro study.

AIM: To evaluate and compare the sealing ability between the clod lateral condensation, thermoplasticized gutta-percha, and flowable gutta-percha obturation technique, under a stereomicroscope at ×40 magnification.
MATERIALS AND METHODS: Sixty single rooted teeth were selected and canals were shaped with K3 NiTi files. Irrigation was performed with 5.25% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA). The teeth were then separated into three groups depending on the type of obturation technique: Group A, obturated using the lateral condensation technique and AH Plus sealer; Group B, obturated with thermoplasticized gutta-percha tech (Obtura III Max) and AH Plus sealer; and Group C, obturated using flowable gutta-percha technique (GuttaFlow). After storing the teeth in 100% humidity for 7 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. The data were 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 were carried out to compare the means.
RESULTS: The lowest mean of AV was recorded in the thermoplasticized gutta-percha (Obtura III Max) group [1.0% (95% CI=0.5-1.5)]. This was statistically and significantly different from flowable gutta-percha (GuttaFlow) group [3.0% (95% CI=2.1-3.9)]. There was no significant difference between the thermoplasticized gutta-percha group and lateral condensation group [1.6% (95% CI=1.0-2.2)] with regard to the AV, but there was a statistically significant difference between the lateral condensation and flowable gutta-percha groups. The flowable gutta-percha 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 thermoplasticized gutta-percha [15% (95% CI=10-21)] groups.
CONCLUSION: The thermoplasticized gutta-percha technique (Obtura III Max) had better adaptability to the canal walls when compared to the flowable gutta-percha (GuttaFlow) obturation and lateral condensation techniques.

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 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 (GP) techniques rely heavily on a root canal sealer to address the problem of the accessory anatomy, as the core filling material does not move out of the main canal. Only voids and spreader tracts are reported.[6]

One of the newer techniques utilizing thermoplasticized GP is Obtura III Max. It is an injectable, heated GP 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, Langenau, Germany) is a modification of this sealer. It contains GP particles as 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 GP based endodontic filling materials to the root canal walls, using three different obturating techniques: Lateral condensation, thermoplasticized GP (Obtura III Max), and flowable GP (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, JKK Natarajah Dental College and Hospitals, after visual and radiographic examination. No data regarding age, sex, or reason 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 (No. 1–4) (Mani, Tochigi, Japan) 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 No. 15 K-file (MANI, Japan) into the canal until the tip of the instrument was just visible at the apical foramen. Patency of the canal was maintained throughout the procedure by passing a No. 10 K-file approximately 0.5 mm through the apex.

Instrumentation of the canal was carried out with the help of K3 NiTi files (SybronEndo, West Collins, USA). During preparation and between each file, 2 ml of 5.25% sodium hypochlorite (DENTPRO, Mohali, India) was used as an irrigant. All the canals were prepared to 6% No. 30 size K3 NITI file. The smear layer removal was done using 10 ml of 17% ethylenediaminetetraacetic acid (EDTA) (Dent Wash, Prime Dental, Mumbai, India) 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, Switzer).

Obturation Protocol for the Study Groups

The three study groups of obturation were as follows:

Group A: Lateral condensation group

A standardized GP master point (Dentsply Maillefer, 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 counterclockwise 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, Japan) and colored GP point sizes of # 15, #20, #25, and # 30.

Group B: Thermoplasticized GP (Obtura III Max) group

The Obtura III Max system (Obtura Spartan, Fenton, MO, USA) was prepared according to the manufacturer's instructions (Obtura III Max 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 in a counterclockwise rotation.[9] At the time of obturation, the injection of the thermoplasticized GP was performed twice separately. First, the needle was inserted in the apical direction until it was bound to the canal wall, and the thermoplasticized GP, heated to 185°C in the delivery system, was injected. The needle was removed after injecting a few millimeters of GP near the tip of the preparation. The softened GP in the apical portion was then vertically condensed to the apex with a hand plugger (Dentsply Maillefer, Switzerland) dipped in alcohol to avoid adherence to the GP. The remaining root canal was then back filled in increments until the GP was observed in the cervical aspect of the root.

Group C: Flowable GP (GuttaFlow) group

A standardized GP 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, 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 7 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 the 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 AV 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 (Cl) 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 thermoplasticized GP group [1.096 (95% CI=0.5–1.5)]. This was statistically and significantly different from the flowable GP group [3.096 (95% CI=2.1–3.9)]. There was no significant difference between the thermoplasticized GP group and the lateral condensation group [1.6% (95% CI=1.0–2.2)] with regard to the AV, but there was a statistically significant difference between the lateral condensation and flowable GP groups [Tables 1 and 2].

Table 1

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

Table 2

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

The flowable GP 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 thermoplasticized GP groups [15% (95% CI=10–21)].

In all the three groups, at Level 1, there was good adaptation of the GP 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 flowable GP group showed the minimum number of voids at the periphery and the maximum number 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 5.25% 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 III Max is an injectable, thermoplasticized GP technique and it has been found to be significantly superior to lateral condensation and has a better adaptation to the three-dimensional root canal systems.[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 the 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 may be easier to perform in the short root canals rather than in the 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 AV 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 thermoplasticized GP group showed the lowest percentage of AV (1.0%). However, most of the time, the voids were surrounded by the GP. 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 flowable GP 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 flowable GP 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=17,545.6 μm for lateral condensation, and mean=1824.4 μm for the Obtura III Max 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 highly 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 III Max 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 thermoplasticized 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:

Thermoplasticized GP (Obtura III Max) 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 thermoplasticized GP (Obtura III Max) and most of the voids were seen at the periphery.

Although the flowable GP (GuttaFlow) group 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 thermoplasticized GP (Obtura III Max) group exhibited a homogenous obturation, followed by lateral condensation and flowable GP (GuttaFlow).

Thermoplasticized GP group exhibited good adaptation, followed by flowable GP (GuttaFlow) and lateral condensation.

One particular method does not exhibit significant superior qualities over the other two methods in all aspects.

Each method exhibited its own unique qualities that are better than the other two.

It is imperative to identify which of these qualities have more influence on a positive treatment outcome in real-life situation.