Denis Katić (1), Sonja Pezelj-Ribarić (2), Ivana Miletić Karlović (3), Ivica Anić (3)

1 - Health Centre Sinj, Dental Office Dicmo, Dicmo, Croatia

2 - University of Rijeka, School of Medicine,  Department of Oral Pathology, Rijeka, Croatia

3 - University of Zagreb, School of Dental medicine, Department of Endodontics and Restorative Dentistry, Zagreb, Croatia 

Address for correspondence:

Ivana Miletić Karlović

University of Zagreb

School of Dental Medicine

Department of Endodontics and Restorative Dentistry

Gundulićeva 5, HR-10 000 Zagreb, Croatia

miletic@sfzg.hr

Received: February 9, 2007

Accepted: May 10, 2007

Available online: June 1, 2007

Acta Stomatol Croat. 2007;41(2):115-21.

Original scientific article

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Objective of work: To asses the leakage of three different root canal filling techniques: cold lateral condensation, Touch’n Heat and Thermafil technique by fluid transport model. The root canals of 70 single rooted teeth were prepared using step-back technique and obturated with tested techniques and Diaket sealer. The leakage was measured by the movement of an air bubble in a capillary glass tube connected to the experimental root. Thermafil technique showed statistically significantly less leakage (0,46 µL ±0,13) than Touch’n Heat (0,77 µL ±0,50) and cold lateral condensation technique (0,71 µL ±0,19).

Under the conditions of this study, specimens obturated with Thermafil techniques showed the least leakage.

Key Words: Dental Leakage; Dental Pulp Diseases; Root Canal Filling Materials

• Introduction
• Materials and methods
• Results
• Discussion
• Conclusions
• Acknowledgements
• References

One of the goals of  the root canal treatment is well-compacted and tightly adapted root filling. Cold lateral condensation technique is the most commonly used root canal filling technique (1,2,3) and is regarded as the benchmark against which others must be evaluated. A key limitation of cold lateral condensation technique is when the root canal system has an abrupt change of diameter, as seen in internal resorption. Adaptation may be equally limited in ribbon-shaped canals (4). In such cases the application of thermoplastic technique is required. Various root canal filling techniques based on heated or preheated gutta-percha have been introduced in order to enhance complete filling of the root canal (5). During warm vertical compaction of gutta-percha, heat can be applied using heated instrument such as Touch’n Heat (Analytic Technology, Redmond, WA, USA).  The temperature of the heat carrier of that device may exceed 250°C (6). Thermafil system (Dentsply Tulsa Dental, Tulsa, Oklahoma, USA) represents another way of delivering thermally softened gutta-percha into the endodontic space which involves the obturation of the root canal with heated -phase gutta-percha on a plastic carrier. This is a low temperature technique with little risk of overheating tissues (7).

Dye leakage, fluid transport and bacterial penetration are currently the methods which are used most often (8). Dye penetration has been frequently measured in order to compare the sealing ability of root-filling materials and techniques (9). However, it has been suggested that the fluid transport model is more sensitive than dye penetration for the detection of full-length voids along root canal, and at the same time it is highly reproducible (9).

The objective of this study was to evaluate the sealing ability of three different filling techniques: cold lateral condensation technique, Touch’n Heat and Thermafil using fluid transport model.

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Seventy single-rooted permanent teeth (middle incisives of upper jaw and canines from both jaws) were used for this study. The teeth were obtained from Department of Oral Surgery, School of  Dental Medicine, University of Zagreb and from Health Centre Sinj. After mechanical cleaning and sterilization the crowns were removed on the cemento-enamel junction, using fissure diamond drill with permanent water-cooling, leaving the roots 11 mm in length. Apical part of all samples was prepared to Kerr file (Maillefer, Ballaigues, Switzerland) #40 (ISO #40), and step-back technique was prepared to Kerr #80 (Maillefer). For irrigation, after the use of each file, 5 mL of a freshly prepared solution of 2.5% NaOCL was used. After instrumentation, the smear layer was removed with 17% EDTA for 2 min. Final irrigation of all samples was carried out with 3 mL 2.5% NaOCl and the canals were dried with sterile paper points (Johnson & Johnson, Slough, UK).  After the instrumentation the teeth were divided in three experimental groups, each consisting of 20 specimens, and two control groups consisted of five specimens.

Group A was obturated using cold lateral condensation technique with gutta-percha points (Kerr, Romulus, MI, USA) and Diaket sealer (ESPE, Seefeld, Germany). A standardized gutta-percha cone #40 was placed into each root canal to working length with tugback. The master cone was coated with the sealer and seated in root canal. Spreader #25 (Anataeos, Munich, Germany) and standardized gutta-percha points #25 were used for lateral condensation. Cones were added until the spreader would penetrate beyond the coronal third of the canal.

Group B was obturated using Touch’n Heat device, model 5004 (Kerr, Analytic Technology) with standardized gutta-percha points and Diaket sealer. Canals were coated with Diaket sealer using a #40 reamer (Maillefer). Gutta-percha cone #40 was positioned 1 mm short of the canal length with few additional gutta-percha points which were heated by Touch’n Heat device (Kerr). The procedure was repeated until the coronal third of the root canal was filled.

In group C, Thermafil obturators with Diaket sealer were used and they were chosen by the verifier. A #40 Thermafil verifier was used to check the size of the canal. Before obturation, the walls of the canal were coated with a small amount of sealer using file. Thermafil obturator was placed in special heater (Dentsply Tulsa Dental) and 10 seconds afterwards the obturator was inserted to working length. The excess was removed with hot plugger.

The teeth of all the groups were coated with nail polish, leaving 2 mm at the end of the apex. After 24h each sample was mounted in fluid transport model.

Five roots were obturated with gutta-percha without sealer and were used as the positive control. Five root canals, obturated with cold lateral condensation technique using gutta-percha cones and Diaket sealer, were completely coated with two layers of nail varnish and served as the negative controls.

The sealing ability was measured by the movement of an air bubble in capillary tube for five min. intervals under the pressure of 120 kPa (1.2 atm), using the fluid transport model described by Wu et al. (9) (Figure 1). Each specimen was tested four times and the mean value was calculated. The results were expressed in L.

Results were statistically analyzed using one-way analysis of variance with post hoc LSD tests. Samples with high deviation from expected values haven’t been considered in the statistical evaluation.

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Figure 1 Fluid transport model

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Table 1 shows the results of leakage measurement by fluid transport model. Leakage in all samples range between 0.46 um to 0.77 um. In the negative controls, no fluid transport was recorded, whereas in positive controls the air bubble moved too fast to be measured.

In Figure 2 it could be noted that the results were grouped between 0.6 um and 0.9 um(higher values) with the cold lateral condesation technique. For Thermafil techniques the results were grouped between 0.3 im and 0.6 um (around the middle of distribution) while in the Touch’n Heat technique the significant grouping of the results was not recorded.

The one-way ANOVA showed that differences between leakage in groups filled using different techniques were statistically significant (p=0.016). Post hoc test showed that specimens obturated with Thermafil had significantly less leakage than either specimens obturated by Touch’n Heat or lateral condensation technique (p=0.02 and p=0.007, respectively). No significant differences were found between Touch’n Heat and cold lateral condensation technique (p>0.05).

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Figure 2 Leakage distribution: number of specimens in each group

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The results of this study showed that root canals obturated with lateral condensation and Touch'n Heat leaked more than those obturated with Thermafil. Karagenc et al. (10) found, by using fluid filtration test, that lateral condensation showed statistically less leakage than Thermafil technique which is not in accordance with our results. However, in the bacterial leakage test, they found that Thermafil showed less leakage than lateral condensation (10). This confirms that the method of testing the sealing ability has major influence on the results. Also, in our previous study (11) it was found by dye penetration method, that samples obturated with Touch'n Heat provide less leakage than samples obturated with lateral condensation technique, while in this study there was no statistical difference between those two techniques.

The sealer has major influence for the leakage. Without sealer, root fillings leak (12). The results for samples obturated with Touch’n Heat could be explained by the fact that the gutta-percha was heated for 4 s using Touch'n Heat at a power setting of 8. Under these conditions, the setting of Diaket was a concern. During the heating procedure, not only the gutta-percha in the canal is heated but also the sealer. Himel & Cain (13) found that the use of heat increases the viscosity of some sealers. Due to that, the original properties of sealer could be changed at high temperature, and this could negatively influence the sealing ability of root fillings.

In this study Thermafil technique showed the least leakage. The Thermafil system used gutta-percha in the heated alpha-phase during obturation. This type of gutta-percha has specific characteristic: high radiopacity, excellent viscosity and fluidity, and enhanced adherence. The results of De Deus et al. (14) showed that coated carrier gutta-percha system Thermafil produced significantly higher percentage of gutta-percha filled area than lateral condensation and System B techniques which indicated that the Thermafil system can reduce the sealer component. This could be the reason for the superior results of Thermafil technique in this study because the leakage may occur within the sealer or by its dissolution, either in the interface between sealer and dentin, or between sealer and the gutta-percha (15).  Also, the areas filled by sealer are more vulnerable because gutta-percha is dimensionally stable whilst the sealer can dissolve over time (16).

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In this study none of the obturation techniques combined with Diaket sealer prevented leakage. However, Thermafil technique showed the least leakage.

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This study was performed and financed within the research projects „Experimental and Clinical Endodontology“ No. 065-0650444-0418 and “Biological effect of dental materials” No. 062-0650444-0442 approved by the Ministry of Science, Education and Sports of the Republic of Croatia.

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