Introduction

 One of the objectives of endodontic treatment is to totally fill the root canal system after it has been prepared.

 The most commonly used core filling material is gutta-percha, but this material does not seal the canal when used alone because it adapts but does not adhere to the dentine walls. The sealer fills the irregularities and minor discrepancies between the core filling material and the canal walls thereby providing a seal.

 The sealer has flow and may fill any patent lateral accessory canals.

 Many sealers have been developed for use in the root canal and can be classified according to the chemical composition ( zinc oxide, calcium hydroxide or resin).

 Clinically the quality of a root canal filling can only be determined by radiographic examination. However, there are various methods for assessing apical leakage of root canal fillings in vitro.

 Ingle (1985) wrote that the most common cause of endodontic failure is incomplete obturation of the root canal and he reported that 59% of these failures were due to leakage in the canal seal.

 Many different obturation techniques have been introduced specifically to increase the quality of the apical seal.

 Lateral condensation of gutta-percha has been proven to be a very common and clinically effective filling technique in many countries.

 McSppaden techniques have been utilised in the modern day situation, which involves the use of ultrasonic energy to thermoplasticise the gutta-percha points used in the root canal filling.

 Branstetter and Von Fraunhofer (1982) found that no currently available sealer meets each of the ideal criteria for a root canal sealer.
Laboratory evaluation of the sealing ability of new endodontic products is necessary prior to clinical use. Although in-vitro leakage studies provide a relative comparison of sealers, they have minimal value in terms of clinical extrapolation. Magura and Kafraway (1991) discussed that earlier philosophies placed great importance on the prevention of apical microleakage; current thinking suggests that prevention of lateral and coronal microleakage are also important. Nonetheless the in vitro apical microleakage studies does provide a basis for the comparison of sealers.

 Hata et al (1992) tested the sealing ability of Thermafil with sealer, without sealer and laterally condensed gutta-percha using India Ink and a profile projector. Two different instrumentation techniques were used, conventional step-back preparation and traditional instrumentation, but the authors didn’t find significant differences between them. However, there were significant differences for the obturation techniques: The mean linear dye penetration for the Thermafill technique was greater than that for lateral condensation.

 Limkangwalmongkol et al (1992) studied the apical dye penetration with four root canal sealers and gutta-percha using longitudinal sectioning and found that the AH-26 sealer had significantly less dye penetration than the other three sealers, followed by Apexit, Sealapex and Tubli-Seal. These last 2 sealers had no significant difference between them.

Purpose of the Study

 The purpose of this in vitro study is to compare the level of apical dye penetration when four different sealers (AH-Plus, Roth Type 511, Sealer 26 and Tubliseal ) are used with lateral condensation of gutta-percha.

Materials & Method

 The sealants used in this research are listed in Table 1 and shown in Figure 1.

Table 1. Sealants used.
 

Figure 1. The root canal sealers used in the research.

  Fourty four extracted mandibular human canines with intact crowns, extracted for various reasons were used, and kept in a 1.0% thymol solution and 9ºC prior to utilisation.

 They were divided into four groups of ten teeth, two were used as the negative control and two as the positive control, the teeth were rinsed in tap water for four hours to remove all traces of the thymol solution.

 Access was gained to the pulp chamber using high speed, diamond stone and water spray, after this a steel bur was used at low speed to grant free access to the root canal.

 Instrumentation of the root canals was completed by the use of a modification of the crown down technique, by begining instrumentation in the coronal portion of the root canal with file size 140. The files used were K type (Maillefer).

 The instrumentation was advanced to 1mm short of the apex and the final file used was size 55. During the instrumentation 15ml of sodium hypochlorite solution 1.0% was used to irrigate the canal (This solution was prepared and evaluated by The Endodontics Research Laboratory and the amount of chlorite was determined by iodine titration).

 Once instrumentation was complete the teeth were dried with paper points (Dentsply-Brazil). Following this a gutta-percha point was selected that fitted the canal at 1mm short of the apex. The sealers were mixed according to the manufacturers instructions and introduced into the root canal by the use of a size 30 K-file, then the master point was coated in the sealer and fitted into the root canal.

 Lateral condensation was then completed with the use of a finger spreader and accessory points (Dentsply-Brasil).

 A red-hot instrument was used to remove the gutta-percha points to the cervical region, then the coronal pulp chamber was cleaned and sealed with the tempoary filling material CaviTEC (DentalTEC Ltd., Brazil).

 The teeth were then put in a container at 37ºC and 95% humidity, and left for 48 hours. After that, they were removed and dried with gauze, and the external of the teeth surface was completely covered with 2 layers of transparent nail polish, except 1mm adjacent to the apex.

 After drying, the teeth were immersed in India Ink and kept at 37ºC for 96 hours. The teeth were then washed in tap water and the nail polish was removed with a scalpel blade and acetone. Then they were put in a plastic recipient containing 5% hydrochloric acid and kept in constant movement by a magnetic agitator until it could be observed that a sufficient decalcification for continuing the dyaphanization process had occured. Figure 2 shows the recipient used in this process.
 

Figure 2. Decalcification recipient and magnetic agitator.
 

  After the decalcification, the teeth were washed in running water for 4 hours and dehydrated in successive solutions of alcohol (75, 85, 96 and 100 GL) for 4 hours in each solution. Figure 3 shows the alcohol containers.
 

Figure 3. Alcohol containers.
 

 The teeth were immersed in methyl salicylate after the dehydratation, and after the dyaphanization was completed, the infiltration of India Ink in the apex was measured with a mensuration microscope, which can be seen in Figure 4.
 

Figure 4. Mensuration microscope Nikon.
 

 The reading showed in millimetres the India Ink infiltration from the gutta-percha point, not considering the 1 mm apical region that is not sealed. Some teeth have this region decalcified.

Results
 

 The results obtained using the forementioned method are shown in Table 2. The mean of the results are shown in Figure 6.
 The photographs observing the microleakage are shown in figures 6, 7, 8, 9, 10, 11, 12, and 13. Figure 14 shows dyaphanization enabling visualisation of the root filling. Figure 15 shows the positive and negative controls.
 

Table 2. Microleakage (mm)

Figure 5. Graph showing the mean microleakage of the sealers.
Figure 6. The microleakage observed using Sealer 26.
Figure 7. The microleakage observed using Sealer 26. A) The least microleakage, B) The most microleakage and C) Magnification of B.
Figure 8. The microleakage observed using Tubliseal.
Figure 9. The microleakage observed using Tubliseal. A) The least microleakage, B) The most microleakage and C) Magnification of B.
Figure 10. The microleakage observed using AH Plus.
Figure 11. The microleakage observed using AH Plus. A) The least microleakage, B) The most microleakage and C) Magnification of B.
Figure 12. The microleakage observed using Roth 511.
Figure 13. The microleakage observed using Roth 511. A) The least microleakage, B) The most microleakage and C) Magnification of B.
Figure 14. Using the process of dyaphinization it is possible to observe the position of the accessory gutta-percha points.
Figure 15. A) Positive control, no obturation and no nail polish, showing the ability of India Ink to infiltrate the root canal. B) Negative control obturation and complete coating in nail polish showing no infiltration.

  The analysis of the sample parameters of Table 2 showed that it was not possible to apply parametric statistical tests, thus the Kruskal-Wallis was used (software GMC).

 The Kruskal-Wallis statistical analysis test determined whether there was a significant difference in microleakage between the different root canal sealers. The results of this test are shown in Table 3  Kruskal-Wallis test.

 The Kruskal-Wallis test showed there to be differences between the microleakage of sealers used in this experiment, we continued the test and compared the sealers two by two and this is shown in Table 4.
 

 The results suggest that there is a significant difference (a=0.05) between the materials AH Plus and Roth 511, Sealer 26 and Roth 511 and Tubliseal and Roth 511. The sealers AH Plus, Sealer 26 and Tubliseal show no significant difference (a=0.05).

Discussion

 Use of the clearing technique allowed three-dimensional visualisation of the gutta-percha filling within the tooth structures with the aid of stereomicroscopy, the extent and distribution of India ink could also be evaluated and measured.

 In this study, linear ink penetration was only measured from the most apical extent of gutta-percha coronally.

 Lateral condensation was used in the study because it remains the most widely used method of root canal filling and it has been used with a control for evaluating the sealing ability of many obturating techniques (Torabinejad et al, 1978; El Deeb, 1985; La Combe et al, 1988 and Olson et al, 1989). This technique has been used many times with excellent results.

 The dyaphanization method used in this study for observation of microleakage is simple, easy, economic and permits three dimensional view.

 Hovland & Dumsha (1985) who tested the sealing ability of lateral condensed gutta-percha with three sealers, found no significant difference in the leakage between the group placed in the dye after a delay of 1 day , 7 and 30 days.

 Hata et al (1992) studied the sealing ability of Thermafil with and without sealer. The lateral condensed technique was used as a control and showed the best seal at the apex. The Thermafil without sealer leaked more than the group with sealer.

 Küçükay et al (1993) observed no significant difference in leakage among the experimental group whether the teeth were immersed in the ink immediately after obturation as after setting of the filling materials for 72 h and whether or not the teeth were centrifuged in ink prior to immersion.

 Smith & Steiman (1994) related that the use of sealer in conjunction with lateral condensed gutta-percha significantly decreased apical leakage.

 The results show that the two resin based sealers (AH Plus and Sealer 26) and the Zinc oxide eugenol sealer Tubliseal showed no significant difference between them. The Zinc oxide eugenol sealer Roth 511 showed significant difference to all the other sealers.

Therefore, in the experiment AH Plus, Sealer 26 and Tubliseal displayed equal ablility to prevent microleakage, Roth 511 sealer allowed a comparitively large amount of microleakage.

 At this point it is necessary to emphisize that both AH Plus and Sealer 26 are sealers based on bisphenol A. Limkangwalmongkol studied AH 26 (Bisphenol A) and found that it showed less dye infiltration than Sealer 26.

 Fidel et al (1994) wrote that Sealer 26 presented greater adhesive properties than the sealers based on zinc oxide and calcium hydroxide (Sealapex and Apexit). It can be concluded that Sealer 26 is able to infiltrate the dentine tubules thus increasing the adhesive strength. Sealer 26 and AH Plus (Epoxy resin) were found to allow less infiltration.

 This research showed that Tubliseal allows the least apical infiltration and Roth 511 the most dye infiltration which could be attributed to the particle size of the components in the sealer. Roth 511 has in its composition anhydrous sodium borate.

 Savioli (1992) found that of the chemical components of sealers based on zinc oxide and eugenol, anhydrous sodium borate is amongst the most soluble.

 Fidel et al (1994) observed that Sealer 26 has low solubility and degradation rates. The present study opens the perspective for new studies with the objective to verify the adhesion, solubility and degradation of the tested sealers.

Conclusion
 

 With the method used and the results obtained, it is possible to conclude the following:

1. Sealer 26, AH Plus and Tubliseal have equal ablility to prevent microleakage in vitro and are all superior to Roth 511 sealer.

2. Roth 511 permitted a greater amount of microleakage than Sealer 26, AH Plus and Tubliseal.

3. The dyaphinization method used allowed simple, easy and inexpensive three dimensional visualisation of the dye penetration.
 

Summary

 The purpose of this study was to compare the apical dye infiltration of different root canal sealers when used with lateral condensation of gutta-percha.

 Dyaphinization was used to allow visualisation of the dye infiltration.

 The results showed that microleakage seen with AH Plus, Tubliseal and Sealer 26 had no statistical significant difference and that Roth 511 sealer showed a much greater ability for microleakage when compared to the other sealers.

 Resumo

 A proposta desse estudo foi comparar a infiltração de corante em diferentes marcas de cimentos obturadores de canais radiculares onde usou-se cones de guta-percha e técnica de condensação lateral.
 Os dentes foram diafanizados para permitir a vizualização da penetração do corante. Os resultados evidenciaram que a infiltração ocorrida nos cimentos Sealer 26, Tubliseal e AH Plus mostraram resultados estatisticamentes semelhantes com os menores resultados de infiltração apical. O cimento Roth 511 mostrou os maiores resultados de infiltração.

References

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Fidel RAS, Souza Neto MD, Spanó JCE, Barbin EL, Pécora JD. Adhesion of calcium hydroxide-containing root canal sealers. Braz Dent J 5 (1): 53-57, 1994

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Lmkangwalmongkol S, Abbott P, Santler A. Apical dye penetration with four roor canal sealers and gutta-percha using longitudinal sectioning. J Endodontic 8: 535-539, 1992

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Smith MA, Steiman HR An in vitro evaluation of microleakage of two new and two old root canal sealers. J of Endodontics 20:18-21, 1994

Torabinejad M, Skobe Z, Trombly PL, Krakow AA, Gron P, Marlin J Scanning electron microscopic study of root canal obturation using thermo-plastcized gutta-percha. J Endodont 4:245-50, 1978