Evaluation of the Correlation between Bacterial Leakage and the Quality of the Filling in Root Canals Obturated by using different Sealer-core Material Combinations

Research Article

J Dent App. 2014;1(5): 81-87.

Evaluation of the Correlation between Bacterial Leakage and the Quality of the Filling in Root Canals Obturated by using different Sealer-core Material Combinations

Akman M1*, Eldeniz AU2 and Belli S2

1Department of Endodontics, Necmettin Erbakan University, Konya, Turkey

2Department of Endodontics, Selcuk University, Konya, Turkey

*Corresponding author: Melek Akman, Department of Endodontics, Necmettin Erbakan University, Faculty of Dentistry, Konya, Turkey

Received: August 11, 2014; Accepted: September 20, 2014; Published: September 22, 2014


Objective: To evaluate the obturation quality of roots filled with different resin based sealer-core material combinations and to investigate the correlation between quality of the filling and bacterial leakage.

Materials and Methods: Single-rooted human teeth were divided into seven test (n=15) and two control groups (n=12) as follows: HybridRootSEAL/ K3 gutta-percha, HybridRootSEAL/Resilon, RealSeal/Resilon, RealSeal/K3 gutta-percha, AH Plus Jet/K3 gutta-percha, Acroseal/K3 gutta-percha and Diaket/K3 gutta-percha. Leakage was assessed for turbidity of the broth in the lower chamber every day during the test-period of 60 days. Survival analysis was performed (Kaplan-Meier Test). Six roots were then randomly selected from each group and were serially sectioned to obtain fifteen sections from each. Digital images were taken under microscope (50X; LeicaMZ16A) using IC3D camera (Leica). The mean area of the gaps/voids between the sealer-root dentin, sealer-core materials and inside the sealer mass was measured and recorded as μm2. The data was statistically analyzed.

Results: No significant difference was found among the test groups according to their resistance to bacterial leakage (p=0.76). The percentage of non-leaked specimens was highest for the RealSeal/Resilon group (%40). Groups, sections and locations have an effect on the quantity of the gaps/voids (p<0.001). Hybrid Root SEAL/Resilon group showed more gaps/voids when compared with the other groups (p<0.05). The gaps/voids occurred mostly between the core material and sealer (p<0.05).

Conclusions: No correlation was found between the quality of the root filling and bacterial leakage values. Adhesion between the core materials and resin-based root canal sealers still needs to be improved.

Keywords: Bacterial leakage; Gap; Resin based sealer; Single cone technique; Root filling quality


One of the requirements for a successful root canal filling is the achievement and maintenance of a tight seal [1] that entombs the remaining microorganism or prevents the ingress of new bacteria and their by-products to the periradicular tissues [2]. Therefore, complete obturation of the pulp space with a core material, which usually is gutta-percha in combination with a root canal sealer, is a standard method of care [3]. In 2003, Resilon (Pentron Clinical Technologies, Wallingford, CT), a thermoplastic filled polymer, has been introduced to the dental market as an alternative to gutta-percha. Resilon contains methacryloxy groups and thus can be used in conjunction with all multi-methacrylate based sealers such as; Epiphany (Pentron Clinical Technologies, Wallingford, CT), RealSeal and RealSeal SE (Sybron Endo, Orange, CA).

A self-adhesive, methacrylate resin-based sealer (Hybrid Root SEAL; Parkell Inc, Farmington, NY) has been introduced commercially [4]. The sealer is self-etching and hydrophilic due to the inclusion of an acidic resin monomer 4-methacryloyloxyethyl trimellitate anhydride and is recommended for use exclusively with either cold-compaction or single-cone techniques [5].

The quality of a root canal filling is highly dependent upon the distribution of the sealer and its adherence to the dentinal walls and gutta-percha [6]. Endodontic sealers are capable of filling imperfections and increasing the adaptation of gutta-percha [7]. On the other hand, root canal sealers are not dimensionally stable and may dissolve partially over time [8,9]. Therefore, to achieve optimal results, it is important to maximize the amount of solid core material and minimize the amount of sealer [10]. Non compaction, the single-cone filling of root canals, has been reviewed [11,12] with the introduction of greater taper master cones that closely match the geometry of nickel-titanium instrumentation systems [13]. Manufacturers claim that the matched taper points can effectively fill tapered canals because they correspond to canal shapes created by similarly tapered instruments [13].

Many studies have been performed to evaluate coronal leakage with various methods until now; dyes, radioisotopes, fluid filtration, electrochemical circuits, endotoxin or bacteria [14]. Using bacteria as a leakage tracer is believed to provide more biologically significant and clinically relevant information [15]. Enteroccocci, especially Enterococcus strains are frequently found in filled root canal systems [16]. The relatively low isolation rate of Enterecocci in primary root canal infections [17] proves that they might colonize the root canal system through coronal leakage after the root filling.

In recent years, the quality of filling techniques and related areas in the gutta-percha region has received increasing attention in studies. This approach was first described by Eguchi et al. [18]. Gaps in gutta-percha sealer-filled areas were measured at the horizontal sections in other similar studies, and the percentages of the filled areas were calculated [10,19]. Previous studies in this field were limited because they only measured and calculated the percentages of the surface area of filling materials and voids by analyzing the sectioned roots and using digital imaging software [11,20,21]. Three-dimensional (3-D) measurements can give more information about the dimensions and the locations of the gaps or voids.

In a previous study, De Deus et al. [22] have evaluated the correlation between canal filled area and bacterial leakage in oval shaped canals and as a result they have found no correlation between the apical seal and the quality of root filling.

The aim of this study was to evaluate the correlation between the bacterial leakage and the quality of the root fillings using a 3-D Topographical Measurement System. Thus the hypothesis tested was that a correlation exists among the bacterial leakage values and the quality of the root fillings.

Materials and Methods

One hundred twenty nine teeth extracted for orthodontic reasons or periodontal problems with similar size and single canals were used after obtaining IRB approval. The crowns were sectioned at the cemento-enamel junction with diamond disc under water cooling. The calculus and soft tissues on the root surfaces were removed with scalpel blades. Working length (WL) was determined by subtracting 1-mm from #10 K-file that was visible at the foramen. All roots were adjusted to 15 ± 0.5-mm in length. The apical part of the root canals was prepared with K3 Ni-Ti rotary instruments (SybronEndo, Orange, CA) to a size of .06/#45. The prepared root samples were randomly divided into 7 experimental groups (15 roots each) and another 2 groups as the positive and negative controls (12 roots each).

The smear layer were removed in an ultrasonic bath (Bandelin Sonorex, Berlin, Germany) using 5.25% NaOCl followed by 17% EDTA and the specimens were rinsed with distilled water for 3 min to remove remnants of these solutions and autoclaved in vials containing distilled water for 20 min at 121°C. Canals dried with sterile paper points (Dentsply-Maillefer, Ballaigues, Switzerland), and filled with five different sealers to create seven test-groups and two control-groups as follows:

Group 1: Hybrid Root SEAL/K3 gutta-percha,

Group 2: Hybrid Root SEAL/Resilon,

Group 3: RealSeal/K3 gutta-percha,

Group 4: RealSeal/Resilon,

Group 5: AH Plus Jet/K3 gutta-percha,

Group 6: Acroseal/K3 gutta-percha,

Group 7: Diaket/K3 gutta-percha.

The sealers were mixed according to the manufacturer's instructions, and applied to the canals with a lentulo spiral (Dentsply, Maileffer, Ballaigues, Switzerland). The root canals were filled with either .06/#45 gutta-percha (K3, SybronEndo, CA, USA) or Resilon (Resilon Research LLC, Madison, CT) cones under aseptic conditions. In RealSeal/Resilon and RealSeal/K3 gutta-percha groups, self-etching primer of the RealSeal system (RealSeal; SybronEndo, Glendora, CA, USA) was applied to the root canal walls with a micro-brush and excess primer was blotted dry with paper points. The teeth in the positive control group were filled with gutta-percha but without sealer. The teeth in the negative control group were also filled with gutta-percha without sealer and completely covered with sticky wax. All experimental, negative and positive control groups were stored under same conditions for 14 days at 37°C and 100% relative humidity to allow enough time to the sealers for complete setting before the evaluation.

Bacterial leakage test

Bacterial leakage was tested using the same model and materials explained by Eldeniz and Ørstavik [23] with using streptomycin resistant Enterococcus faecalis. The mounts were kept at 37°C throughout the experiment for 60 days. The bacteria in the upper chamber were replaced with fresh broth every second day. Bacterial penetration along the root fillings was detected by turbidity observed in the lower chamber. The Kaplan-Meier method was used to construct survival curves for each group and alpha type error set at 0.05. Specimens showing no leakage over the 60 day observation were computed with an event time of 60 days as censored variables.

Scanning electron microscope (SEM) preparation

One specimen with microbial leakage was randomly selected from each group after the completion of the leakage test. The specimen was sectioned horizontally to see dentin-sealer-core interfaces. After fixation with 3% glutaraldehyde (Sigma-Aldrich, St. Louis, MO), they were mounted onto a SEM specimen stub, gold-sputtered (Polaron Sc7620, VG Microtech Inc., Japan) and SEM photomicrographs (Leo 440, Electron Microscopy Ltd.Cambridge, UK) were taken at x500 to x5000 original magnification.

Measurement of the root filling quality

Six roots were randomly selected from each group. Fifteen 0.3 ± 0.02 mm thick sections were obtained under water cooling using Isomet Saw (Isomet, Buehler, Ltd., Lake Bluff, IL, USA) from each root beginning from 1 ± 0.3 mm apically. Stereo digital images were taken from the sections at 50X magnification under a microscope (Leica MZ16A) (Figure 1). A 3-D Topographical Measurement System was used for the quantitative measurement of the voids or gaps in the root fillings. This system consisted of an integrated stereo camera, software and a display system. In order to digitally capture, display, and measure a 3-D object in the accurate fashion, a pair of photos, each with a slightly different perspective of the specimen, needed to be attained. The Leica IC 3D is a digital camera with two independent RGB sensors and captures pairs of stereo images (stereo-pairs) for 3-D analysis. The 3-D reconstruction was based on two images of the specimen taken from slightly different angles. Leica Stereo Explorer software automatically determined which pixels in the two images of the stereo-pair belong together and calculated the topography of the specimen (taking into consideration the parameters of angle and magnification) as a Digital Surface Model (DSM) (Figure 2). This complete 3D data record served as the basis for a variety of different surface analyses.