One of the main objectives of endodontic treatment is to achieve full three-dimensional filling or obturation of the root canals, in order to prevent the microleakage of bacteria and their waste products (1, 2). To achieve this effect, guttapercha is used as filler material, whether in semisolid or plastic state (3). On the other hand, since guttapercha does not effectively seal the canal when used alone, we must use a sealing cement in an attempt to adhere the material to the dentin, and for filling the irregularities and small discrepancies between the guttapercha and the canal walls (4). Sealing cement plays a very important role, since its dissolution increases microfiltration, and can therefore lead to endodontic treatment failure (5).
The lateral condensation method has been used for decades by most dentists and specialists, and it is the technique taught in most dental schools (6, 7). New materials and techniques have been introduced in an attempt to improve apical sealing. In this context, Obtura II® (Obtura Spartan, Fenton, MO, USA) is a thermoplastic guttapercha product that is injected into the canal and is combined with a sealing cement capable of resisting high temperatures. The Soft-Core® technique (Soft-Core® System, Copenhagen, Denmark) in turn consists of a biocompatible plastic stem enveloped by phase α thermoplastic guttapercha that is heated in an oven. It is also used with common sealing cement. The Guttaflow® system (Roeko, Coltene / Whaledent, Germany) is a cold fluid technique combining the sealing agent and guttapercha in the same product. Heat is not required for softening the guttapercha and chemical condensation. No conventional sealing cement is therefore needed. Lastly, Resilon® (Pentron Technologies, Wallingford, CT, USA) is a new root filling material composed of polycaprolactam polymers that are able to bind to dentin adhesives and resins in a methacrylate base. As sealing cement, use is made of a primer that conditions the dentin and of a dentin adhesive that binds the Resilon® tips to the walls of the canal, forming a single three-dimensional sealing block.
The present study compares the apical sealing capacity of five root canal obturation techniques: lateral condensation, Obtura II®, Soft-Core®, Guttaflow® and Resilon®.
Materials and methods
A total of 212 single-root teeth removed for orthodontic or periodontal reasons were used. Calculus and adhered periradicular tissues were mechanically removed with a universal curette, and the teeth were stored in saline solution until instrumentation.
The first opening was made with a round drill, followed by the use of an Endo-Z bur once the pulp chamber was reached. Access to the root canal was confirmed by inserting a size 20 K-file (Maillefer, Ballaigues, Switzerland). The working length was then established by displacing the file through the apical foramen, withdrawing it to within 0.5 mm of the latter, and registering the resulting length. For cleaning and conformation of the canals, Hero 642 continuous rotary endodontic system (Micromega, Besançon, France) was used. The procedure was started using the number 20 file with a conicity of 6% at 4 mm from the working length, to widen the coronal third. In the case of very wide canals we used files of numbers 25 and 30, with a conicity of 6%. In elliptic canals, such as those of the lower incisors and canines, number 3 Gates-Glidden burs were employed for cleaning the coronal third, followed by the use of files of numbers 20, 25 and finally 30 with a conicity of 4% directly at the working length. Larger files (sizes 35, 40 and 45) were used in the case of very wide canals. Between each file size the canal was abundantly irrigated with 0.2% chlorhexidine digluconate. Once instrumented, the canals were dried with paper tips, and the apexes were again surpassed to confirm their permeability. Six teeth were used as positive controls, and another 6 teeth as negative controls. The rest of the samples were randomized to 5 groups as follows:
Group 1: 40 teeth obturated with the lateral condensation technique
Group 2: 40 teeth obturated with Soft-Core®
Group 3: 40 teeth obturated with Obtura II®
Group 4: 40 teeth obturated with Guttaflow®
Group 5: 40 teeth obturated with Resilon®
The positive controls were instrumented but not obturated, and were used to confirm the validity of the experimental filtration model used in the study, since it allows penetration of the ink into the root canal in the absence of filler material. In contrast, the negative controls were instrumented, obturated and entirely coated with nail varnish. Those teeth were used to confirm that when ink is found within the canal it is because it has penetrated through the non-varnished apical foramen, not through any other route or access.
The teeth in group 1 were obturated using the lateral condensation technique. After drying the canal, we selected the master apical guttapercha. Sealing cement (AH Plus, Dentsply / Maillefer, Ballaigues, Switzerland) was prepared and inserted into the canal with a lentulo. We then also impregnated the master cone, positioning it to the working length, and applying small oscillating movements to facilitate penetration of the cement. Number 30 or 25 digital spreaders were used for compacting to one millimeter short of the working length. In the space left by the condenser we then inserted an accessory number 20 guttapercha points and continued successively until complete obturation of the canal. Coronal gutta-percha was removed with a hot instrument and later to make vertical condensation with Machtou-Plugger 1-2 (VDW, München, Germany). The access cavity was filled with provisional obturating cement (Cavit®, 3M Espe, Germany).
The teeth in group 2 were obturated with thermoplastic guttapercha containing a plastic stem (Soft-Core®, Dental Production Aps., Copenhagen, Denmark). The size of the obturator to be used was checked with the verifiers. After drying of the canal, AH Plus Cavit® sealing cement was inserted and the obturator was placed in the oven (Soft-Core® Oven). Once the guttapercha was heated to the required temperature, the obturator was removed from the oven, and the tip was impregnated with sealing cement and inserted into the canal to the working length. After a few seconds, the surplus stem was cut with a round drill, and the access cavity was filled with Cavit®.
The third group of 40 teeth was obturated using the Obtura II® technique (Obtura S.A., Fenton, MO, USA). Cement (AH Plus, Dentsply / Maillefer, Ballaigues, Switzerland) was inserted into the canal with the help of a lentulo. Once the pistol display indicated that 200ºC had been reached, we injected guttapercha positioning the cannula at the junction between the apical third and the middle third, approximately 5 mm from the apex. After filling, the tip was removed and a B 60 vertical condenser (Maillefer, Ballaigues, Switzerland) was used for vertical compaction of the guttapercha. The cannula was then again inserted to fill the rest of the canal, gently withdrawing it as the canal was gradually filled. Following this operation, the excess material was removed with a hot instrument, followed by sealing of the access cavity with Cavit®.
The teeth in group 4 were obturated with Guttaflow® (Roeko, Coltène / Whaledent). After drying of the canal, we inserted the master cone and confirmed that it was adequate. The capsule was then activated by pressing both ends inwards. The white hood was removed from the capsule and placed in an amalgam vibrator (Ventura Mix) for 30 seconds at standard vibration frequency. After completing the cycle, the capsule was extracted, the green stem at one end was removed, and we fitted the application tip. The capsule was mounted in the pistol supplied with the kit, and the trigger was pulled until the material started to flow. We then inserted a small portion into the canal. The master apical cone was impregnated with guttapercha and inserted to the working length. The rest of the canal was filled with the fluid material, and the excess was removed with a hot instrument, followed by sealing of the access cavity with Cavit®.
Lastly, the teeth in group 5 were obturated with Resilon®. The self-etching primer (Epiphany primer, Pentron Clinical Technologies, Wallingford, CT, USA) was placed in a well for direct application within the root canal using a microbrush for 30 seconds. The sealing cement was inserted in the canal with the master cone well impregnated, and impulsion-traction movements were applied. We then inserted the Resilon® master cone to the previously determined working length, and performed the lateral condensation technique. After completing obturation, each canal was photopolymerized for 40 seconds to achieve immediate initial coronal sealing at the entrance, followed by total polymerization of the rest of the cement over the next 25 minutes.
Once all the groups of teeth were obturated, we painted the entire root surface with two layers of nail varnish, except for the three most apical millimeters. Each sample was then placed in an empty guttapercha or paper tips tube containing black ink. After 72 hours of exposure to the ink, the samples were rinsed with abundant water and the nail varnish was removed with a sharp spatula.
Transparentization of the teeth was then carried out in order to evaluate filtration, based on the technique described by Robertson (8).
Following this process, the teeth were examined with the stereoscopic microscope (Nikon SMZ 2T) under x100 magnification. The precision grid of the eyepiece was used to measure any ink filtration into the canal. The samples were photographed with a NIKON D90 camera fitted to the microscope. The filtration results of each sample (expressed in mm) were recorded using a Microsoft Excel spreadsheet.
The statistical analysis of the results (ANOVA and Post-hoc tests) was carried out using the SPSS version 12.0 statistical package (SPSS Inc., Chicago, IL, USA).
A data dispersion chart was plotted to gain an overview of the behavior of the samples (Figure 1). The vertical axis shows the microleakage (in mm), while the horizontal axis indicates the obturation techniques used. The groups were seen to behave differently, with important dispersion that proved greatest in the Soft-Core® group and smallest in the Obtura II® group. The Soft-Core® technique yielded a mean filtration of 1.16 mm, while lesser values were recorded for the rest of the techniques: Guttaflow® (0.49 mm), lateral condensation (0.33 mm), Obtura II® (0.21 mm) and Resilon® (0.15 mm). Analysis of variance (ANOVA) revealed significant differences between the means corresponding to the different groups. Post-hoc testing showed the Soft-Core® technique to exhibit significant differences versus the other groups, with no differences among the rest of the groups (Table 1).
Figure 2 shows a sample obturated with the Soft-Core® technique. The ink was seen to have penetrated between the wall of the root canal and the filler material. The non-obturated lateral canals likewise showed ink filtration (Figure 3). This sample corresponded to the lateral condensation group.
Different methods have been developed for evaluating apical microleakage associated with the different root canal obturation systems. We chose tooth transparentization because it is a simple and fully standardized technique; the materials required are easily found and are inexpensive; no complex machinery is needed; and there is no sample degradation resulting from longitudinal or cross-sectioning of the teeth.
De Moor et al. (9) compared three obturation techniques: lateral condensation, vertical condensation and Soft-Core®. They used ink and transparentization of the samples as in our study, and concluded that Soft-Core® showed greater apical filtration than the other two techniques, which in turn presented no statistically significant differences. In a later study, De Moor et al. (10) compared one same sealing cement (AH 26) in application to 5 different obturation techniques: lateral condensation, vertical condensation, hybrid guttapercha condensation, Thermafil® and Soft-Core®. The results showed Thermafil® and Soft-Core® to produce greater coronal filtration than the other techniques, with no differences between them. Apical filtration was greatest in the Soft-Core® group. For this study, the authors immersed the samples in ink and then sectioned them longitudinally, with observation of filtration under the stereoscopic microscope. In a more recent publication, De Moor et al. (11) compared the sealing capacity of two cements (AH 26 and AH Plus) in relation to three different techniques: lateral condensation, hybrid condensation and Thermafil®. As before, the samples were immersed in ink and then sectioned longitudinally. There were no differences in apical filtration among the three groups. However, Thermafil® showed greater coronal filtration than the other two techniques. Our results are largely consistent with these findings in that the greatest apical and coronal filtration values corresponded to thermoplastic guttapercha with the internal stem (Soft-Core®).
Lares et al. (12) also compared the Thermafil® technique with lateral condensation and used the technique developed by Robertson for observation of the samples. Their results were similar to our own, with significantly greater ink filtration values when using the Thermafil® technique (p=0.02).
On the other hand, Haikel et al. (13) studied apical microfiltration using lysozyme labeled with radioactive iodine, comparing lateral condensation, Thermafil® and the McSpadden technique. They recorded differences between lateral condensation and Thermafil®, while the McSpadden technique showed significantly greater values than the other two techniques.
Pommel and Camps (14) conducted a comparative study of apical filtration with System B® versus four other techniques: single cone, lateral condensation, vertical condensation and Thermafil®, employing saline solution as filtration marker, with measurement using an infrared device. The results showed the plastic guttapercha techniques to generate less filtration than the other two procedures – maximum microfiltration corresponding to the single cone technique.
Abarca et al. (15) compared lateral condensation with the Thermafil® technique using the same methodology as in our own study. They recorded no statistically significant differences between the two groups, though the greatest microleakage values corresponded to the Thermafil® group. Although there were no significant differences, the latter technique tended to produce comparatively greater filtration, in accordance with our own findings.
Gençoglu et al. (16) compared lateral condensation, Thermafil®, Quick-fill® and System B®. They also used ink to assess filtration, sectioning the samples horizontally at 1, 2, 3 and 4 mm from the apex. The authors found both Thermafil® and Quick-fill® to produce less filtration than System B® or lateral condensation. Boussetta et al. (17) in turn compared apical filtration with Soft-Core® versus the lateral condensation technique, using methylene blue as filtration agent and performing cross-sections at 500, 1000 and 1500 μm. The results showed Soft-Core® to produce significantly less filtration than the lateral condensation technique. The findings of the above two studies differ from our own, though it must be stressed that they involve a different methodological approach, with sectioning of the samples instead of transparentization.
Schafer et al. (18) published a study in which Thermafil® and lateral condensation were compared with the use of three different cements. They also evaluated the possible influence of canal morphology (i.e., curved or straight canals) upon filtration. In the same way as in our study, the authors immersed the teeth in ink, followed by transparentization of the samples. They found the apical sealing capacity of both systems to be similar, independently of the cement used, and canal morphology proved irrelevant, since it did not influence sealing.
Pallares (19) and Vizgirda et al. (20) compared the lateral condensation technique with the Obtura II® system, using the same methodology as in our study. These investigators concluded that the apical sealing capacity of the Obtura II® system is similar to that of the lateral condensation technique. The results of both authors are consistent with our own findings.
Kqiku et al. (21) used methylene blue as filtrating agent, comparing lateral condensation with Guttaflow® and Resilon®. They found Resilon® to yield better results than the other two systems. Vasiliadis et al. (22) in turn conducted a long-term (one week and three months) filtration study using a fluid transport model, comparing lateral condensation with Guttaflow®. They found no significant differences between the two techniques after either one week or three months. Irala Almeida et al. (23), in a comparison of lateral condensation with the hybrid technique and Guttaflow®, observed no significant differences among the three groups, though the best performance was obtained with the hybrid technique, while the poorest results corresponded to Guttaflow®. These studies reported findings similar to our own. In another study, Elayouti et al. (24) observed a greater presence of spaces or gaps with the Guttaflow® material than with either lateral condensation or vertical condensation.
In relation to Resilon®, the literature offers discordant results. Tay et al. (25) carried out an ultrastructural study based on electron microscopy to compare the sealing capacity of guttapercha / AH Plus versus Resilon® / Epiphany. Neither system was seen to afford complete and tight apical sealing, and moreover both materials presented gaps or binding defects between them and the canal walls. The investigators therefore concluded that Resilon® is not superior to guttapercha in terms of apical sealing. In a study using a fluid filtration technique, Biggs et al. (26) likewise compared these two materials (guttapercha / AH Plus® and Resilon® / Epiphany), and concluded that there are no differences between them in terms of microfiltration.
In a study of apical sealing capacity, Onay et al. (27) compared two sealing agents (AH Plus® and Epiphany) versus two filler materials (guttapercha and Resilon®), with the definition of four groups: guttapercha / AH Plus®, guttapercha / Epiphany, Resilon® / AH Plus® and Resilon® / Epiphany. A fluid filtration technique was used to measure apical filtration. The authors found the lowest filtration values to correspond to the guttapercha / Epiphany group, followed by the guttapercha / AH Plus® group. Nevertheless, there were no significant differences between guttapercha / AH Plus® and Resilon® / Epiphany. The authors therefore concluded that both combinations (which are those commonly used) show similar behavior.
Williamson et al. (28) compared Resilon® / Epiphany with guttapercha / AH Plus® in assessing bacterial filtration using pathogen cultures and explored whether the plastic state of the two materials exerts an influence upon canal obturation. Specifically, these authors used the cold lateral condensation technique and the continuous wave technique developed by Buchanan. They concluded that there are no differences between the two materials or differences in performance attributed to the plastic conditions of guttapercha and Resilon®.
In another study, Karapinar-Kazandağ et al. (29) compared obturation systems based on the monoblock concept (single cone / cement seeking adhesion to the canal walls, forming an obturation block). These systems were Resilon® / Epiphany, EndoRez® and Activ GP®. The authors used a glucose filtration model and concluded that the monoblock materials are not superior to conventional guttapercha / sealing cement, since there were no statistically significant differences between them.
Melih et al. (30) compared Resilon® versus guttapercha / AH Plus® and guttapercha / Acroseal® (Septodont) to assess filtration, using methylene blue followed by longitudinal root sectioning for performing the measurements. They found guttapercha / Acroseal® to produce significantly greater filtration that the other two systems. In turn, there were no significant differences between Resilon® and guttapercha AH Plus® - both of which afforded the best apical sealing performance.
As we have seen, the results of these studies coincide with our own findings in that they observe no differences among these obturation systems. Nevertheless, we have also found studies in which the performance of guttapercha / cement was reportedly superior to that of Resilon® (31, 32).
Under the conditions of this study, it can be affirmed that although none of the systems produced perfect apical sealing, Soft-Core® system showed significantly worse filtration results than the rest of the groups. There were no significant differences between the other groups. Nevertheless, further studies are needed in order to confirm our findings.