|Year : 2015 | Volume
| Issue : 1 | Page : 33-38
A comparative evaluation of sealability of three different obturation techniques using rotary instrumentation for canal preparation
Kitty Sidhu1, BK Raghavendera Rao2, Soheyl Sheikh3, Neha Bansal4, Ritika Bahuguna3
1 Department of Conservative Dentistry, Dr. H. S. Judge Institute of Dental Sciences, Chandigarh, India
2 Department of Conservative Dentistry, M R Ambedkar Dental College and Hospital, Bengaluru, Karnataka, India
3 Department of Oral Medicine and Radiology, Mullana, Ambala, Haryana, India
4 Department of Oral Medicine and Radiology, Dr. H. S. Judge Institute of Dental Sciences, Chandigarh, India
|Date of Web Publication||30-Jul-2015|
Dr. Kitty Sidhu
Punjab University, Sec 25, Chandigarh
Source of Support: None, Conflict of Interest: None
Introduction: A well-fitted root canal filling prevents percolation and microleakage of periapical exudate into the root canal space, prevents reinfection and creates a favorable biological environment for healing to take place. Several techniques using gutta-percha have been used in an attempt to achieve a void-free, homogeneous filling.
Aim: Three different obturation techniques that are Thermafil obturation, cold lateral condensation and warm vertical condensation using rotary canal technique were compared.
Materials and Methods: This study was in vitro study. Forty-five extracted permanent human premolars with single canal, and fully developed apices were selected for the study.
Statistical Analysis: This was done with the help of analysis of variance.
Results: There was leakage measuring 0.5-3.5 mm in 73.3% of roots in group I, 80% in group II and 40% in group III. Similarly, the leakage was 3.51-6.5 mm in 20% of the roots in group I, 13.3% in group II and group III. The leakage was found to be more than 6.5 mm in 6.7% of the roots in group I and II and 46.7% in group III. There was sealer extrusion in two teeth in group I and II and in four teeth in group III.
Conclusions: It was observed that the warm vertical condensation and lateral condensation techniques were more effective in restricting apical dye penetration. However, the results of this in vitro study need to be confirmed by further in vivo research.
Keywords: Leakage, obturation, rotary
|How to cite this article:|
Sidhu K, Raghavendera Rao B K, Sheikh S, Bansal N, Bahuguna R. A comparative evaluation of sealability of three different obturation techniques using rotary instrumentation for canal preparation. Saint Int Dent J 2015;1:33-8
|How to cite this URL:|
Sidhu K, Raghavendera Rao B K, Sheikh S, Bansal N, Bahuguna R. A comparative evaluation of sealability of three different obturation techniques using rotary instrumentation for canal preparation. Saint Int Dent J [serial online] 2015 [cited 2019 Nov 18];1:33-8. Available from: http://www.sidj.org/text.asp?2015/1/1/33/161799
Evolution of concepts and techniques over the years has perfected the endodontic success rate to around 95%. The success achieved with any obturation technique depends highly on canal cleaning and in particular canal shaping. Shaping of root canals is necessary to facilitate obturation. Schilder stated:- "The objective of root canal filling procedures should be the total three dimensional filling of the root canal and all accessory canals." A well-fitted root canal filling prevents percolation and microleakage of periapical exudate into the root canal space, prevents reinfection and creates a favorable biological environment for healing to take place. Several techniques using gutta-percha have been used in an attempt to achieve a void-free, homogeneous filling, which are namely, single cone technique, cold lateral condensation, warm vertical condensation, warm lateral condensation, thermoplasticized gutta-percha techniques, core carrier technique (Thermafil), injectable gutta-percha technique.
The aim of this study was to evaluate and compare the apical leakage based on linear measurement of dye penetration in root canals obturated with Thermafil obturation technique, with the cold lateral condensation and warm vertical condensation. ProFile rotary technique was used for canal instrumentation in conjunction with the removal of smear layer.
| Materials and Methods|| |
A total of 45 extracted human premolars with intact crowns, single root with fully developed apices were selected for the study. These teeth were stored in 5% NaOCl to remove adhering tissue on the root surface. The teeth where rinsed in tap water and stored in normal saline till use.
| Methods|| |
The access to the root canal was made in the usual manner. The estimated working length was established by deducting 1 mm from the actual canal length, which had been determined by inserting a size 10 file into the canal until the tip of the file was just visible at the apical foramen. The patency of each canal was confirmed by inserting a size 15 file through the apical foramen before and after completion of the root canal preparation. The rotary instruments used in this study were ProFile 0.04, 0.06 taper files with international International Organization for Standardization-size tips used in a crown-down manner. For coronal shaping serial use of orifice shaper #3, #2, ProFile 0.06/25, ProFile 0.06/20 to one-half of the root and 0.04/25, 0.04/20-2/3 of the canal were performed in a crown-down manner. For apical shaping, ProFile 0.04/20, 0.06/20, 0.04/25, 0.06/25, 0.04/30 were sequentially used to the working length in an "in and out" pecking motion according to the manufacturer's instruction. The operational sequence with profile 0.04 and 0.06 rotary instruments are crown down, determination of exact working length, apical preparation, and final shaping. Canals were irrigated between each file with 2 mL 2.5% solution of NaOCl using a syringe and needle. Finally, each canal was flushed with 10 mL of 17% ethylenediaminetetraacetic acid (EDTA) followed by 10 mL of 5% NaOCl to remove the smear layer. The canals were dried with paper points. The teeth were randomly divided into three experimental groups of 15 teeth each and three positive and three negative controls.
The canals in group I were obturated with cold lateral condensation technique with #30 master gutta-percha cones, which gave "tugback" at the working length for each root canal. After drying the canal lateral condensation was carried out using accessory gutta-percha cones and spreaders until the spreader could not be introduced more than 3-4 mm into the canal beyond the orifice. Vertical condensation of the coronal part of the canal was accomplished with finger pluggers.
The canals in group II were obturated with warm vertical condensation technique. A standard size (#30) master cone was fitted with tug back to the working length. A small amount of root canal sealer was placed into the root canal, and the primary cone was inserted into the prepared root canal. After placing the master cone in the canal, the gutta-percha was condensed in an apical direction with pluggers. In between the additions of the gutta-percha and heat transfer, cold pre fitted pluggers were used for condensation of the gutta-percha to a homogeneous mass. This was continued until the entire root canal was packed.
The canals of the teeth in group III were obturated with Thermafil as specified by the manufacturer. We selected a Thermafil obturator the same size as the size of verifier that fit passively at working length. The obturator was heated in the Thermaprep Oven (Dentsply, Maillefer) automatically regulated. The shaft level with the orifice was severed using a tungesten carbide inverted cone bur in a high-speed handpiece while the carrier was stabilized with the index finger.
After obturation of all specimens access preparation was sealed with Kalzinol (Dentsply) and the teeth were then stored in 100% humidity for 1-week to ensure the setting of the sealer. Radiographs were taken from the buccal aspect of each root to visually evaluate the obturation. The extrusion of sealer and/or gutta-percha through the apical foramen was recorded using a yes/no scheme.
The obturated teeth were then dried and coated on their external surfaces with nail polish except for the apical 2 mm so that the dye could only penetrate the canal via the apical region. A second layer of nail varnish was applied only after the first layer had dried.
Two other groups of six instrumented unobturated teeth each was included as positive and negative controls. After the microleakage measurement, the entire surface of the teeth of the three negative control specimens were coated with nail varnish including the apex. After the polish dried the specimens, including controls, were suspended vertically with their apical 3-4 mm immersed in a 1% methylene blue solution for 2 weeks with 100% humidity. The teeth were then removed from the dye, washed, air-dried, and nail polish was removed. Each tooth was grooved longitudinally on buccal and lingual surface before being split into two halves with a diamond disc. Linear apical dye penetration was measured for each specimen using a stereo zoom microscope at × 5 and an endodontic ruler as a reference scale.
The mean leakage was recorded for each group together with standard deviation. Statistical analysis was carried out using Windows Excel (Software). To compare the means of two groups, student's t-test was used with appropriate degrees of freedom and level of significance. To compare the means of all the three groups, analysis of variance (ANOVA) was used.
| Results|| |
Dye leakage values in millimeters for groups I, II and III were measured [Table 1].
Then overall comparison of mean between three groups showed that the highest value for group III was (5.73 ± 4.6) followed by group I (2.9 ± 2.8) and group II (2.47 ± 1.8)[Table 2].
|Table 2: Overall comparison between three groups mean leakage and standard deviation |
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Test for equality of means between groups was analyzed using student's t-test [Table 3].
|Table 3: Test for equality of means between groups using students t-test |
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For group I and II, P = 0.31 (not significant), for group II and III P < 0.01 (significant) and for group I and III P < 0.05 (significant).
Test for equality of means for group I, II and III was analyzed using ANOVA. The P < 0.05. There was leakage measuring 0.5-3.5 mm in 73.3% of roots in group I, 80% in group II and 40% in group III. Similarly, the leakage was 3.51-6.5 mm in 20% of the roots in group I, 13.3% in group II and group III. The leakage was found to be more than 6.5 mm in 6.7% of the roots in group I and II and 46.7% in group III [Table 4] and [Table 5].
|Table 4: Test for equality of means for Group I, II and III using analysis of varience (ANOVA) |
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There was sealer extrusion in two teeth in group I and II and in 4 teeth in group III. There was no sealer extrusion in 13 teeth in group I and II and in 11 teeth in group III with P = 0.54. There was no gutta-percha extrusion in group I, whereas it was seen in two teeth in group II and in eight teeth in group III with P < 0.001 [Table 6].
|Table 6: Sealer/gutta-percha extrusion in specimens application of pearson's χ2 test |
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| Discussion|| |
The majority of nonsurgical endodontic procedures have been reported to have failed because of inadequate apical seal. The inadequate seal would allow percolation of water soluble proteins, enzymes and salts from the blood into apical foramen where stagnation would occur. These materials would seep back into periapical tissues and further act to stimulate inflammation.  It follows then that effective endodontic obturation must provide a dimensionally stable hermetic seal that will prevent the transmission or communication of fluids through the apical foramen into the surrounding periapical tissues. Thus, the root canal system should be completely obliterated while maintaining accurate apical control of filling materials.  Due to stability and success rate, combined with ease and accuracy of placement, semi-solid and solid endodontic obturants used with sealers have come to enjoy the greatest use in endodontics today.
In this study, passive dye penetration of 1% methylene, blue dye was evaluated using stereomicroscope. Methylene blue dye has been shown to penetrate further into the canal than any of the radioisotope tracers. Ahlberg et al.  in their study concluded that methylene blue penetrated more deeply along the root canal fillings than India ink. Wu and Wesselink  did pattern studies from 1980 to 1990 with similar results. This dye is visible under direct light, penetrates dental structures well and does not react with tissues thus allowing the measurement with a millimeter ruler directly on the teeth.  Longitudinal splitting of roots and linear measurement of the dye penetration were used in this study to measure apical leakage. Circumferential study of the root canal walls was used to obtain optimal measurements. Alternative methods are vertical sectioning or clearing of the roots. Vertical sectioning is more destructive than longitudinal splitting which allows for a better evaluation of the entire root surface and the leakage pattern. 
One of the major problems with studies of apical microleakage is the lack of standardization. In this study, all canals were prepared to the same size and a single operator conducted the preparation and obturation to try to overcome variations. However, natural anatomical variations among the teeth was still a factor but it was hoped that randomly assigning the teeth to experimental groups and examining each group as a whole rather than looking at individual teeth would give a fair comparison between the groups. 
Whole extracted human premolars with intact crowns were used in this study. This was done to improve the reliability of the investigations by simulating the clinical situation by including the effect of pulpal access since less apical microleakage might result because of easier preparation and obturation in shorter canals. The major disadvantages in using these instruments are that canal preparation can be time-consuming and tedious. In an attempt to reduce time, to simplify canal preparation and to reduce operator fatigue, automated devices have been developed.
In this study ProFile rotary 0.04 and 0.06 rotary instruments were used for canal preparation. The debris was extruded not apically but coronally which would seem to be a particularly favorable feature. This has also been shown in previous studies by Gulabivala et al. The smear layer was removed using 17% EDTA.
It has been proposed that the smear layer that is present following canal cleaning and shaping prevents the penetration and adaptation of the softened canal filling material into the dentinal tubules. By removing this layer surface contact between the canal wall and filling material can be increased and thus apical seal may be improved thereby decreasing the occurrence of microleakage. , Lateral condensation of gutta-percha has remained the most widely used method. Advantages to this technique include its predictability, relative ease of use and controlled placement of materials with good length control. Disadvantages include a lack of homogeneity of the gutta-percha mass and increased number of voids and sealer pools and less adaptation to canal walls and irregularities.  To overcome these disadvantages, vertical condensation of warm gutta-percha was introduced.
It is believed that a more homogeneous mass of gutta-percha is produced by heated instruments and that the softened gutta-percha adapts more intimately to canal walls and irregularities.  The introduction of the innovative Thermafil endodontic obturators was aimed at an extremely simple method of canal obturation using thermoplasticized gutta-percha.  It could be argued that since lateral condensation is a well tried and tested technique in wide clinical use, any other obturation technique which can match it in in vitro leakage studies may provide similar success assuming that the root canal has been rendered suitable bacteria and toxin free. In this study, apical seal of Thermafil obturators was compared to lateral condensation and warm vertical condensation technique as manifested by the degree of microleakage using dye leakage.
According to the results of dye leakage in this study, statistically significant differences in apical leakage were observed between lateral condensation and Thermafil (P < 0.01) and the warm vertical condensation and Thermafil (P < 0.05). There was no significant difference in apical leakage between lateral condensation and warm vertical condensation (P = 0.31).The negative controls showed no dye penetration and positive controls showed complete dye penetration.
The warm vertical condensation technique group showed the least leakage of methylene blue dye (2.47 mm mean). This result supports the statement made by the author of the technique, Schilder in 1976. There were uniformity and lack of voids in the apical section due to condensation of a single cone at apical level. Gutta-percha had a homogeneous appearance. The Thermafil group showed the maximum dye leakage (5.73 mm mean) whereas lateral condensation showed 2.9 mm mean dye leakage. These results are in agreement with Lares and elDeeb,  Hata et al.,  Haddix et al.,  Chohayeb  and Barkins and Montgomery. 
Another observation made in this study was the stripping of gutta-percha from the carrier near the apex. This is consistent with a study by Juhlin et al.,  Weller et al.,  Clark and ElDeeb,  and Kytridou et al.  Stripping may be due to characteristics of the alpha-phase gutta-percha. Also, canal length has been shown to be affecting obturation with Thermafil obturators in straight canals. The longer the canal, the more likely the fill was of poorer quality. Presumably gutta-percha was tending to be wiped off the shaft, became too solid or was of inadequate bulk for effective obturation to occur. This has also been shown by Dummer et al.  However no correlation could be made between this finding and canal leakage in previous studies (Gutmann et al.,  Kytridou et al.  A possible explanation for stripping could be the influence of canal curvature on the movement of alpha-phase gutta-percha during placement along with the force of placement. Another important consideration is, ironically, related to the excellent flow characteristics of the alpha-phase Thermafil gutta-percha. Based on the clinical guidelines for a successful obturation of the root canal system by American Association of Endodontists (1994), radiographically there should be a dense three-dimensional filling which extends as close as possible to the cemento-dentinal junction without gross overextension of the filling material into the periradicular tissues.  In this respect, the Thermafil obturation technique showed a predisposition for material extrusion beyond the apical foramen in 80% of the specimens. This finding is in agreement with almost all studies on Thermafil. ,,,
In contrast, only 26% specimens obturated with warm vertical condensation and 13% specimens of cold lateral condensation technique showed material extrusion. In lateral condensation, only sealer extrusion was seen. Lateral condensation provided the best length control. All cases of extrusion were accompanied by extrusion of sealer. There are several possible reasons for this observation. First, thermoplaticized techniques have been shown to improve flow properties of the gutta-percha which results in an increased incidence of extrusion. Second, the lack of resistance form of an in vitro environment results in linear, rod or cone shaped over extensions. The over extensions in in vivo setting are not as great in volume and tend to be in a shape of puffs, mushrooms, or fine strings extending into periapical tissues or following the periodontal ligament. 
The apex of teeth is this study was kept patent resulting in less than ideal resistance form. In the presence of a patent apical foramen, there is a predisposition for extrusion of filling material beyond the apex with the Thermafil technique. , The same has been observed in this study. In short terms such extruded material is likely to cause irritation of the perapical tissue. It is possible that in clinical conditions apical blockage with a dentin plug may reduce the frequency of overfilling (Hata et al.  Scott and Vire. 
The overextended gutta-percha/sealer was removed to a level flush with external surface of the apical foramen. It is not known whether the removal of the overextended gutta-percha could have had a detrimental, beneficial or no effect on the linear extent of apical dye penetration.  The lateral condensation and warm vertical condensation and Thermafil appeared to completely fill the primary root canal spaces. However, only Thermafil obturation technique group showed the filling of lateral/accessory canals. These results are in agreement with Clark and ElDeeb and Goldberg (2001).  A further problem with the Thermafil obturator was noted during carrier-handle removal with whipping during bur contact. This vibration may have affected the apical seal. This effect could be minimized using a notching/twisting off of the handle.  One of the most impressive differences between the techniques was the speed with which obturation could be achieved. Although not specifically measured, time of obturation was shortest with Thermafil obturators. The warm vertical condensation took the longest time. Although the speed of obturation taken in isolation is not the most important criterion by which a technique should be judged, it forms part of the overall assessment. The use of Thermafil obturators was the most expeditious technique.  The variation in standard deviations observed may be a good indicator of how consistent the technique will be in providing adequate clinical obturation.  In this study, Thermafil resulted in remarkably higher standard deviation compared with other techniques. This may indicate that this technique in a clinically more complex situation will result in less predictable results than other methods.
The fact that all specimens showed dye leakage suggests that the obturated roots most likely have a large number of microlumina. Even with most respected obturation methods and utilizing a sealer with excellent physical properties, traceable microlumina will nearly always occur. Thus by deductive reasoning it is obvious that the clinical success of endodontic treatment occurs regularly despite the presence of microlumina in the apical part of obturated roots.  Clinical assessment of root fillings is restricted to the use of radiographs usually in the buccolingual plane, in this study radiographs were exposed for all teeth in the buccolingual plane. The overall radiographic quality of obturation was similar in all three groups. In no case could a radiographically detectable void be found. The relationship between the radiographic quality and apical leakage has been studied previously with little if any correlation normally being found. The rather weak association between dye leakage and radiographic scores highlights the difficulty of assessing canal obturation. 
This points toward an issue in endodontic research more important than dye penetration studies. From previous studies, we know that the presence of radiographically detectable voids is associated with an increase in failure rate. It must be considered however that a void must be large before it is detectable on a radiograph, therefore a strict extrapolation of results from radiographs cannot be made to clinical importance of mircolumina found when explored by dye studies.  All scientific evidence point toward microorganisms as the dominating or sole cause of periapical disease of endodontic origin. Therefore, it is important to concentrate on better understanding the importance of quality and quantity of microorganisms and/or their metabolites in the pathogenesis of the periapical disease. This will lead us toward highly successful treatment modalities compatible with the obvious presence of apical microlumina. 
| Conclusions|| |
From the present study it can be concluded that linear dye penetration was observed in all groups irrespective of obturation techniques. Thermafil obturation technique though fastest had the most dye penetration. The warm vertical condensation and lateral condensation techniques were more effective than Thermafil in restricting apical dye penetration. Thermafil technique showed more material extrusion, that is, it is largely uncontrollable if the apex is maintained patent. The results of this in vitro study need to be confirmed by further in vivo research.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]