2021, Number 4
Apical filtration in vitro after the use of three obturation techniques. A preliminary study
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ABSTRACT
The objective of this in vitro study was to determine the degree of apical microfiltration using the methods of the lateral obturation, the vertical condensation technique and the Obtura II obturation system through linear measurement and cement-dentinary transparency. A total of 38 fresh human uniradicular teeth were used, the roots were intact (without fractures) with a curvature below 20 degrees. Three groups were formed, each with 10 teeth and used four teeth as positive controls and another four teeth as negative controls. The teeth were diafanized, submitted to the apical filtration test by liquid diffusion of Chinese ink and finally their cuts were observed with a Vasconcellos microscope. The information acquired was subject to a descriptive statistical analysis. In the present study it was possible to evidence that none of the obturation systems used an ideal apical seal, however, the use of the obturation with the Obtura II obturation technique showed the least amount of apical microfiltration. Further studies are required under the same methodology that confirms the findings found in the present study.INTRODUCTION
Successful root canal treatment is based on obtaining a good hermetic seal, instrumentation, cleaning, and shaping of the root canals. However, the desired objective is to obtain a tight seal in endodontic obturation.1,2
When discussing the obturation techniques available, each has its relative position in historical development about filling techniques. Over the years, different difficulties have arisen with these techniques, which has led to the development of new obturation methods, along with the recognition that no one method can satisfy all clinical cases.3
It is well known that the root anatomy of the tooth is varied and complex, so there has always been a constant search for multiple sealing techniques to achieve the tightest possible canal filling. Since its inception, gutta-percha has been used more frequently, and this is because it has several properties that make it an ideal material for this purpose, such as its inert nature and that it has the particularity of adapting to different thermal changes, likewise, it can adapt to the canal walls since when heated it has the property of flowing and presents low irritation to the tissues.3,4
Multiple techniques have been recommended to achieve a perfect seal, and many of these have been evaluated through in vitro studies to determine the degree of microleakage at the apical level that they may have, however, when purchasing the results obtained from the different obturation techniques they are usually counterproductive or not significant1-3,5,6 so it is still suggested to continue with this type of studies to determine which technique presents less leakage at the apical level. For this reason, the main objective of this research is to determine the degree of apical microleakage using lateral obturation, the vertical condensation technique, and the Obtura II system using linear measurement and cement-dentin transparency.
MATERIAL AND METHODS
A total of 38 fresh human uniradicular teeth were used, whose roots were without fractures and with a curvature of fewer than 20 degrees. The teeth were washed in abundant water and immersed in 5.25% sodium hypochlorite for two days with 100% humidity at 37 oC temperature, then kept in distilled water until instrumentation.
Tooth preparation. Each tooth had the coronal portion removed with a DIATECH diamond disc (Coltene), with a low-speed handpiece, leaving a length of 19 mm. The opening was performed with a small head KaVo turbine and a medium carbide bur, and for the preparation of the canals, the corono-apical instrumentation technique was applied with Profile files with the Dentsply® Technika motor, using a rotation of 250 rpm with a speed reducer of 16:1. To patent the canals of the measurement obtained, a K-File no. 10 file was used and when visualizing the tip of the file at the canal-dentin-cement junction (CDC), 1 mm was subtracted and thus working to a length of 18 mm.
Preparation of the canal. For the cleaning and shaping of the canals, the Orifice Shapper file was used which opened and shaped the canal, indicating on the Technika F2 at 350 degrees and was placed at 15 mm (a measure that was only used with this drill); then proceeded to the use of the lilac Profile file (no. 10) and white (no. 15) of the first group, the process was started indicating on the Technika F1 at 350 degrees of torque. We proceeded to use the files of the 2nd group, which corresponds to the yellow file (no. 20), so it was placed in the Technika F2 and continued with the same torque, then the files of the 3rd group were used, red (no. 25) and blue (no. 30) successively, being these the last ones, F3 was placed in the Technika using the same torque and always reaching the measure. Glyde was used with each file. It should be noted that after each instrumentation with the different files, the canal was irrigated with 5% sodium hypochlorite. At the end of the preparation of the canals, they were dried with 70% alcohol.
Study groups. Once the canals were prepared the teeth were divided and distributed as follows:
Group 1: 10 teeth obturated with the lateral obturation technique.
Group 2: 10 teeth obturated with the vertical condensation technique.
Group 3: 10 teeth filled with the Obtura II system.
Group 4: four positive control teeth.
Group 5: four negative control teeth.
Lateral obturation technique (group 1): for this group, one M-F gutta-percha was used as the main cone and two F-F as accessories, for sealing, Top Seal/Maillefer was prepared in a 1:1 ratio and the consistency was "wire", using the necessary amount that covered approximately 1.5 mm of the tip of the gutta-percha cone to then be placed in the apical third, in the same way, it was done with the accessory cones and they were laterally condensed until no more cones could be introduced.
Vertical condensation technique (group 2): for the second group, a Fine-Medium (Hygenic) was used as the main cone, which was cut 2 mm from the tip and tested in the canal, the preparation of the sealer and gutta-percha was the same as the one used in the lateral obturation technique, with the difference that in this technique the master cone was cut in the apical third with the Touch 'n Heat (SybronEndo Touch 'n Heat Mod 5004). The master cone was condensed with the Hu-Friedy no. 9.5 obturator, the gutta-percha was heated in the apical third and condensed again, then the Obtura II was placed in two stages to finish obturation of the roots of this group.
Obtura II technique (group 3): for group three the technique Obtura II-Heated Gutta-Percha System mod. 823600 at 180 degrees was used for which 23 gauge needles were used for Obtura II system and gutta-percha to obturate the canals whose content was zinc oxide, gutta-percha, barium sulfate, and coloring agents, manufactured by Obtura Spartan. The cement used was Top Seal-Maillefer®, which was taken to the canal with the help of a standard gutta-percha no. 30, and then placed in the apical third. Once the gun had reached 180 oC, the gutta-percha was injected in two stages, the first from the apical third to half of the working length. After filling, the tip was removed, and a Hu-Friedy® no. 9.5 condenser was used for vertical compaction of the gutta-percha, and this process was repeated once more, from the middle of the middle third to the cervical third, condensing it with the Hu-Friedy® no. 10 obturator, leaving 2 mm in cervical for the placement of provisional cement (occlusal closure).
Control group (groups 4 and 5): each experimental group had its positive control (group 4) which were instrumented and obturated in the same way, however, they were not sealed, since this group was used to confirm the validity of the experimental filtration model used in the study, because it allows the penetration of the ink into the root canal. On the other hand, the negative controls (group 5) were instrumented, and red sticky wax was placed apically and occlusally and covered with two layers of nail varnish on the rest of the root surface. At 3 mm from the anatomical apex in the occlusal direction, a mark was placed and from that mark, towards occlusal at 3 mm another mark, between the first mark and the second mark the double layer of nail varnish was placed (Figure 1A). These teeth were used to confirm that when the dye is found in the canal it is because it has penetrated through the unvarnished apical foramen, and not through any other route or access.
Dye penetration (indirect dye seepage). Finally, all the roots were left wrapped with moistened gauze and placed in the humidifier at 37 degrees for five days for the sealer to effectively finish setting. After completing the obturation of the samples, 4 mm of gutta-percha was removed from the cervical-radicular third and filled with zinc oxide and eugenol (3 mm), and sticky wax (1 mm).
Once all root groups were obturated, the entire root surface was painted with two coats of nail varnish, except for the three most apical millimeters. The roots were placed on a horizontal platform with holes, where each root was held with yellow wax to keep the roots in a vertical position, and in this way, all the apices were exposed to the filtration with black Pelikan ink from the anatomical apex to cover only 3 mm (Figure 1B). After five days of exposure to the ink, the specimens were rinsed with plenty of water and the nail varnish and sticky wax were removed with a Hu-Friedy® no. 12 curette.
Diaphanization. It is important to point out that at the beginning of the study a standardization of the technique described by Tagger et al (1983) was carried out for this phase, finding better results in the group that used the following protocol (Figure 1C):
- 1. Decalcification: 5% nitric acid × 5 days.
- 2. Dehydration:
- a. Ethyl alcohol 80% × 1 day.
- b. Ethyl alcohol 90% × 1 day.
- c. Ethyl alcohol 100% × 1 day.
- 3. Transparency: methyl salicylate × 1 day.
Once the staining was finished, the teeth were clarified or decalcified (Tagger's modified method), using 5% nitric acid for five days, shaking three times a day (8 pm, 9 am, and 1 pm) and the acid was changed once a day. Finally, the nitric acid was discarded and the pieces were washed with abundant water for 4 hours to then begin dehydration with 80% ethyl alcohol for one day shaking three times a day (8 pm, 9 am and 1 pm) without changing the alcohol, then the alcohol was changed to 90% for 1 hour and then to 100% (98%) for 3 hours (shaking c/hour). Then we proceeded to perform the transparency with methyl salicylate for one day. Before and after making the measurements in the microscope the samples remained in the salicylate to avoid any change in the transparency.
Filtration evaluations were performed with a DF Vasconcellos MUM 119 microscope with magnifications of 16× and 25× and measurements were made with a flexible metal ruler marked every 5 mm and the filtration results for each sample (expressed in mm) were recorded using a Microsoft Excel spreadsheet. GraphPad Prism 8 statistical software was used for descriptive statistical analysis and graphs.
RESULTS
The present study was carried out to quantitatively determine in vitro the degree of apical microleakage using lateral (group 1), vertical (group 2), and Obtura II system (group 3) obturation techniques, for which the relative amount of ink penetration through the apex was measured.
Table 1 shows the dental pieces used for each technique, as well as the length of each root, for which we worked with a mean of 18.35 mm in group 1, 18.05 mm in group 2, and 18.20 mm in group 3; likewise, the amount of ink filtered through the apex in each dental piece can be observed.
About the controls, it was evident that in the negative control there was no dye penetration (0.00), while the positive controls showed ink with a maximum penetration of 3.00 mm (Figure 1D and E, Table 2).
Table 3 shows the mean and standard deviation of each technique, for which it was observed that the teeth obturated with the lateral technique (group 1) presented a mean filtration of 0.8525 ± 0.5362, the vertical obturation technique (group 2) of 0.6575 ± 0.2404 and in the case of the Obtura II system (group 3) showed a mean value of 0.2000 ± 0.3162. Similarly, the minimum and maximum amount of dye penetration of each group are observed, where the Obtura II system stands out because it was the only technique where there were teeth that did not present apical filtration of the dye (0.000).
On the other hand, a graph was made to obtain an overview of the behavior of the samples (Figure 2). The vertical axis shows the microleakage (in mm), while the horizontal axis indicates the obturation techniques used. It can be seen that the groups behaved differently, and it is evident that there was significant leakage in the group that was obturated with the lateral technique and minimal leakage in the Obtura II group.
DISCUSSION
Apical microleakage has been considered a determining factor in the failure of root canal treatment,7 where success lies in achieving a good apical seal through three-dimensional obturation of the canal system with the help of endodontic cement and gutta-percha, to achieve a good hermetic seal.8
Although indeed, the technique or obturation system to be used and its success in achieving an airtight seal will depend basically on the knowledge, skills, and resources available, it is important to take into account the anatomical characteristics of the root canals, which leads to obtaining the most three-dimensional obturation possible.4
In this sense, there have been many experimental studies that have tried to demonstrate which obturation technique presents less apical filtration, such is the case of the work carried out by Noblecilla7 where they compared the level of apical filtration using both lateral and vertical canal obturation techniques, However, they concluded that the instrumentation technique can directly influence the quality of the obturation, especially in the lateral condensation technique, where adequate penetration of a spacer is necessary. These findings differ from those reported by Castañeda et al.,9 where they did find statistically significant differences between the lateral and vertical techniques, obtaining better results in apical sealing with the vertical technique, which coincides with the results of the present study, where less apical leakage is evidenced with the vertical technique compared to the lateral technique, these results could be because this technique is based on obturation with hot gutta-percha and condensed vertically, trying to ensure that the exit routes of the canal are obturated with a greater amount of gutta-percha and less sealer.9
For their part, Monterde et al.5 made a comparison between the lateral root canal condensation technique and other condensation techniques in which physical (temperature: Soft-Core®, Obtura II®) or chemical (condensation: GuttaFlow®, Resilon®) changes can affect the dimensional stability of the obturation and thus favor apical microleakage, and their results show that the groups behaved differently, with a significant dispersion that was greater in the Soft-Core® group and smaller in the Resilon® group. On the other hand, when comparing the lateral condensation technique with the Obtura II®, no statistically significant differences were found, however, it was evident that the Obtura II presented less filtration than the group obturated with the lateral condensation technique, these findings are consistent with those found in the present study concerning these two techniques, where the Obtura II group presented less filtration in comparison to the other groups. Similar results were found in the study by Samson et al,3 where they evaluated in vitro spectrophotometric analysis to quantitatively analyze the relative amount of dye penetration in root canals using the lateral condensation filling (group 2), Obtura II (group 2) and Thermafil filling technique (group 3).
CONCLUSION
About the findings found in the present study, it can only be certified that none of the obturation systems used produced a perfect apical seal, however, better results were obtained when using the Obtura II technique where there was less leakage compared to the other techniques. It is suggested to continue with future studies under this same approach to confirm our findings.
REFERENCES
Reyes Obando A, Pinto Romero C, Banegas Pineda A, Villanueva DO, Hernández Vásquez J, Ferrera Dubón H et al. Estudio comparativo in-vitro del sellado apical de tres cementos endodónticos. Revista Científica de la Escuela Universitaria de las Ciencias de la Salud. 2017; 4 (1): 15-21. doi: 10.5377/rceucs.v4i1.7064.
AFFILIATIONS
1 Cirujano Dentista. Posgrado en Endodoncia, Candidata a Doctora en Ciencias Odontológicas, Docente Titular de la Cátedra de Endodoncia, Facultad de Odontología de la Universidad de Guayaquil. Ecuador.
CORRESPONDENCE
Mary Lou Endara Abbott. E-mail: endaramarylou1@gmail.comReceived: Diciembre 2019. Accepted: Junio 2020.