|Year : 2016 | Volume
| Issue : 4 | Page : 165-170
Sealing ability and obturation quality of root canals filled with gutta-percha and two different sealers
Rabab A Gad1, Ali M Farag2, Hatem A El-Hediny2, Abeer M Darrag2
1 Ministry of Health, Elbatanon Hospital, Alexandria, Egypt
2 Endodontics Department, Faculty of Dentistry, Tanta University, Tanta, Egypt
|Date of Submission||28-Mar-2016|
|Date of Acceptance||24-Aug-2016|
|Date of Web Publication||14-Dec-2016|
Rabab A Gad
Ministry of Health, Elbatanon Hospital, Alexandria 31111
Source of Support: None, Conflict of Interest: None
To evaluate sealing ability and quality of obturation when canal filled with gutta-percha and either mineral trioxide aggregate (MTA), or AH Plus sealer with detection of any possible correlation between microleakage and voids.
Materials and methods
Human freshly extracted 30 maxillary one-rooted teeth were prepared and assigned to experimental groups (n = 10), designated as group I: gutta-percha/AH Plus, group II: gutta-percha/MTA sealer, group III positive control group (n = 5) teeth unobturated, group IV: negative control group (n = 5) teeth obturated with gutta-percha, AH Plus sealer. After obturation, each tooth was prepared for fluid filtration assessment. Voids detection was performed through cross-sectional analysis at three root levels. Data were analyzed using one-way analysis of variance at a level of confidence of 95%.
None of the tested obturation systems was able to provide leak proof filling. The sealing ability of MTA FillApex sealer showed higher parameters than AH Plus sealer even if it was not significant. The lowest percent of voids was recorded at the apical third for both tested sealers. The correlation between leakage and voids percentage was nonsignificant.
Calcium silicate root canal sealer (MTA FillApex) and AH Plus sealer can provide adequate seal with low voids percent. None of the root canal filled teeth were gap-free. Voids percentage cannot be used as an indicator for sealing ability.
Keywords: AH Plus, leakage, MTA FillApex, sealing ability, obturation quality
|How to cite this article:|
Gad RA, Farag AM, El-Hediny HA, Darrag AM. Sealing ability and obturation quality of root canals filled with gutta-percha and two different sealers. Tanta Dent J 2016;13:165-70
|How to cite this URL:|
Gad RA, Farag AM, El-Hediny HA, Darrag AM. Sealing ability and obturation quality of root canals filled with gutta-percha and two different sealers. Tanta Dent J [serial online] 2016 [cited 2017 Dec 16];13:165-70. Available from: http://www.tmj.eg.net/text.asp?2016/13/4/165/195703
| Introduction|| |
The ultimate goal of a root canal treatment is to clean and fill the root canal in all dimensions to create a fluid-tight seal, which is essential to optimize the outcome of endodontic treatment and prevent reinfection . The long-term success of endodontic therapy is directly depends on the effectiveness of the apical seal . Conventional root fillings consist of a core material and sealers. Suitable physical properties of gutta-percha (GP) as the most common root canal obturation material allow it to be applied in several obturation techniques. GP should be closely adapted to the canal wall and sealer that seals the interface between the core and dentin .
Several types of endodontic sealers are commercially available, which may be broadly classified into zinc oxide eugenol based sealers, calcium hydroxide based sealers, glass-ionomer sealers, resin-based sealers, silicon based sealers, bioceramic based sealers and calcium silicate based sealers .
With the aim of improving the marginal sealing properties, new sealers have been developed. AH Plus is a hydrophobic epoxy-resin sealer that most commonly used in root canal obturation because of its good physical and chemical properties with good sealing ability. It is considered as a gold standard against which all new sealers can be compared . AH Plus has advantages of AH26 but without releasing formaldehyde with shorter setting time. Moreover, it appears to be more radiopaque and has less microleakage compared to AH26 .
Mineral trioxide aggregate (MTA) cements are hydrophilic hydraulic calcium silicate materials used in endodontic for a number of clinical applications and able to form a biomimetic apatite layer on their surface in the presence of phosphate-containing simulated body solutions . Sealers based on MTA have been reported to be biocompatible, stimulate mineralization and encourage apatite-like crystalline deposits along the apical and middle thirds of canal walls .
Formation of voids may be happen within root canal obturation due to spaces between individual GP cones and the root canal walls when the cones of GP filling material are not firmly condensed. It can be seen with poor root canal preparation, curved canals, and inadequate lateral pressure during condensation, or mismatches between GP cones and root canal . The resulting filling in such cases would lack homogeneity and have to rely on sealer to fill the voids, and thus would have a poor prognosis because areas filled by sealer are more vulnerable as a sealer may dissolve over time and leakage may occur .
Microleakage in root canal obturation is a complex phenomenon that can be defined as the passage of bacteria, fluids and chemical substances between root filling material, and canal wall . Although a variety of laboratory-based experimental models are used to detect and measure leakage along root fillings, fluid transport (FT) was the most frequently used method as lack of standardization and consequent noncomparability of leakage studies led to the use of a fluid filtration system to enhance reliability .
Software image analysis is used to evaluate the quality of root canal obturation using root cross-sections that are digitally photographed and transferred to the computer. A software program is then used to calculate the cross-section area of the root canal obturation and areas of voids and the percentage of voids in relation to the cross-sectional area was calculated .
Correlation between microleakage values and voids of root canal fillings remains to be under research, additionally there were little reports available on void percentage within MTA FillApex sealer. So, this study was performed to evaluate the apical seal of MTA FillApex sealer and compare it with a widely used root canal sealer (AH Plus sealer) using fluid filtration method and obturation quality via voids detection through cross-sectional analysis at three section level.
| Materials and methods|| |
Freshly extracted maxillary single-rooted teeth were collected from age group of 35-45 years, patients that were extracted for periodontal reasons. The patients were informed and written consent forms were signed from them for using their extracted teeth in this research according to the ethical committee of Faculty of Dentistry, Tanta University. All teeth were cleaned from soft tissues and calculus using hand scalers, washed with tap water and radiographed to evaluate the patency of the root canals. Thirty teeth were selected with mature fully developed roots. Teeth with root fractures, cracks, resorption, or canal calcifications were excluded. The selected teeth were stored in sterile saline solution at room temperature that is changed daily until use .
All crowns were removed using low speed diamond disk (Dica, Dendia, USA) under copious amount of water leaving roots of nearly 16 ± 1 mm to standardize the length of the root canals. The working length of each root canal was established using K-file (NIC; Shenzhen Superline Technology Co. Ltd, Shanghai, China) size 10 with its tip just visible through the apical foramen, the length was recorded as working length after subtraction of 1 mm. Roots in which initial apical stainless steel K-file #35 was fitted snugly at working length was selected to standardized canal dimension.
Thirty root canals were prepared using hand stainless steel K-files with step-back technique up to master apical file #50.The stepping-back was continued for at least three successive size larger than the master apical size as, #55, #60, #70, where each file was1mm shorter than the previous one. Coronal 2/3 of the canal was then prepared by stainless steel K-hand file larger than the last file used in step-back up to #80 which was used for coronal flaring of the canal in circumferential filing motion.
All canals were irrigated with 5 ml of 2.5% sodium hypochlorite (Clorox Co., 10 th of Ramadan, Egypt) solution with a 27 G needle after every instrument during all steps of preparation. Canals were then rinsed with 1 ml of 17% EDTA (Pulpdent Corporation, Watertown, Massachusetts, USA) that was remained in the canals for 1 min to remove the smear layer . Finally each canal was flushed with 3 ml of distilled water after completion of preparation and dried with sterile paper points (Diadent Group International, Burnaby, British Columbia, Canada).
After canal preparation, 20 roots were randomly assigned into equal two experimental groups (I and II) of 10 roots for each group according to the type of sealer used in the root canal obturation. Group I: 10 teeth were obturated by GP and AH Plus sealer using cold lateral compaction technique according to manufacturer's instructions. Group II: 10 teeth were obturated by GP, MTA FillApex. Mixing of two pastes of MTA was performed with the self-mixing tip attached to the syringe. The cement was used immediately after mixing and dispensing with the syringe and the remaining self-mixing was discarded after each use according to manufacturer's instructions. On the other hand, group III is used as a positive control group where five unobturated roots were used to demonstrate the sensitivity of the system whenever the canal was not filled. Although group IV is used as a negative control group where five roots were obturated by GP and AH Plus sealer and the entire root was painted with nail varnish to seal the root surface and apex then dipped into molten sticky wax, to demonstrate that the model system prevented movement of fluid. [Table 1] summaries the obturation materials used in this study.
After complete obturation, all root samples were kept moist by keeping them in gauze moistened with sterile saline for 1 week at 37°C in an incubator to ensure complete setting of the sealer. The experimental 20 root specimens were painted with two layer of nail varnish except coronal 1 mm and apical 2 mm. Each sample was embedded in an acrylic resin cylinder. The coronal 1 mm and apical 2 mm of the root were left exposed and not included in the resin cylinder. The margins adjoining the acrylic resin and root were sealed with cyanoacrylate. Each root was mounted in a FT device [Figure 1] as previously described by Wu et al. . The resin cylinder of the specimen (A) was fitted into a plastic tube (B) of the FT model, the smooth surface of the resin cylinder ensured a good fit with the plastic tube. The plastic tube was filled with water and connected to the inlet end of the resin cylinder, that is, the coronal end of the root fragment, whereas the other end of the plastic tube was connected to a headspace pressure (C) of 60 kPa (0.6 atm). A standard glass capillary (micropipette) (D) in which an air bubble was introduced with a microsyringe, was connected to the outlet end of the resin cylinder (the apical end of the root fragment). All of the connections were tightly sealed by twisting pieces of stainless steel wire around the plastic tubes while they were immersed in a water bath. The pressure should be constant during all steps of the experiments.
Forcing water through any voids along the root canal filling results in movement of the water which was recorded by linear displacement of the air bubble in the capillary tube per minute (unit of time). Linear displacement of this air bubble was converted to volume of fluid displacement and was recorded as the fluid flow rates (i.e. leakage) with a specific quotient. The values were expressed as µl/min as shown in the following formula: V=πPrt /8Lή. Where P (Pa) is the pressure at the ends (the pressure used was 0.6 atm (0.6 × 10 5 Pa); r (mm) is the radius of the micropipette; t is fluid passing time; L (mm) is air bubble movement; ή (Pa × s) is the viscosity of water (10−3 Pa × s) . The mean values of leakage for each group were calculated and recorded.
Each control root was embedded in an acrylic resin cylinder as for the experimental roots. Fluid movements along both negative and positive controls were recorded first before the two experimental groups. After assessment of leakage, the specimens of each experimental group were detached from the measuring apparatus and stored in 100% humidity by wrapping them in saline soaked gauze until they were ready for cross-section analysis.
Each root was sectioned horizontally using a circular diamond disk at low speed with constant fresh cooling water. Three sections were obtained in the apical, middle and coronal third. The apical sections were at 3 mm from the apex, middle sections were at 7 mm from the apex. The coronal sections were at 11 mm from the apex and the coronal surface of each section was coded . A total of 60 sections were obtained, the coronal surface of each section was digitally photographed by digital microscope (Olympus DP11 and SZ, Tokyo, Japan) at a fixed distance for all samples and transferred to an IBM compatible personal computer system. The micrographs were then analyzed using AutoCAD 2009 software program (Autodesk Inc., San Rafael, California, USA) to measure the cross-sectional area of the root canal and the surface area that was devoid of obturating material (voids) . The percentage of voids was calculated according to the following formula :
The data were collected and tabulated for statistical analysis using SPSS Package, v. 17.00 (SPSS Inc., Chicago, Illinois, USA) The mean and SD of the volume of fluid filtration were calculated. Significances were analyzed using t-test with a level of confidence at 95%. The data of variations in the voids percentage value of the obturation filling material for each section level were collected. Statistical comparison between root sections was performed using one-way analysis of variance and Tukey's test at a level of confidence at 95%. A statistical correlation between percentage of voids and leakage results was performed using Pearson's correlation analysis.
| Results|| |
Fluid filtration test in positive controls was 100% leakage. For negative controls the leakage was zero. The mean leakage value for each group is presented in [Table 2]. No significant difference between the two groups was recorded (P = 0.462).
The mean values of voids percentages were compared between two tested obturation materials in each root canal section. No significant difference between the two groups at any sectional level was obtained (P > 0.05) as shown in [Table 3]. While comparing between the tested root canal sections for each group using one-way analysis of variance recorded a statistical significant difference was recorded at each group (P = 0.013 and 0.026 for groups I and II, respectively). So pair-wise comparison between each group was performed using Tukey's test. For both tested groups, statistical significance differences were recorded between coronal versus apical levels and coronal versus middle sections (P ≤ 0.05). However there was no significance difference between middle and apical levels (P > 0.05).
When correlating the fluid filtration volume and voids percentage [Table 4] at all tested root canal levels, positive no significant correlations were recorded.
|Table 4 Pearson's correlation between fluid filtration and voids percentage |
Click here to view
| Discussion|| |
Attempts have been made to ensure standardization of the experimental groups in this study. Maxillary one-rooted teeth were selected in this study, and root length was standardized (16 ± 1 mm) in all samples to obtain standardization for leakage measurements. Root canal preparations were performed using step-back technique up to size #50 to obtain similar apical preparation diameter and standardize the amount of dentin removed in the apical portion (apical 3 mm) for all samples as advised by Wu and Wesselink .
Many attempts have been developed to resolve sealing problems through variations in sealer types. Two types of sealer were chosen in this study. One epoxy-resin-based sealer (AH Plus sealer) which is famous for their adhesive ability, good sealing ability, short setting time, without release of formaldehyde.
In addition, MTA sealer (MTA FillApex) was chosen due to its several advantages such as high flow rate, low film thickness, not adversely affected by heat, has ideal working time, excellent antibacterial properties, solubility is extremely low, and tendency toward maintaining the calcium releasing relatively constant until 14 days . However only scant knowledge is available with regard to its sealing ability, therefore new material needs to more evaluation.
The smear layer may interfere with the penetration of root canal sealer into dentinal tubules, or even the adhesion of resin material to dentin, there for 17% EDTA was used as the final rinse to remove the smear layer and to minimize the residual effect of NaOCl on free radical polymerization of resin sealer that negatively affect the bond of resin-based sealer to the dentinal wall .
The fluid filtration method was used in this study because it is reliable technique to quantitate the measurement of microleakage of the filling material or apical seal, very small volume can be recorded and allowing repeated measurements without destruction of the samples and the model uses positive pressure to rule out problems caused by entrapped air or fluid which may skew outcomes as in dye penetration studies .
To further describe the root filling quality in the current study, cross-sectional analysis was used in which determination of the percentage of voids in the root filling in relation to the total cross-sectional area of the prepared canal is obtained from transverse sections of the filled roots at three levels where three sections were obtained in the apical, middle and coronal third to provide an illustrative overview of the distribution of voids throughout the canal .
The cross-sectional analysis presents several advantages over the traditional methods for evaluating the quality of root canal sealer, as it can give indirectly an idea about the sealing ability along the length of root canal filling at several levels (apical, middle, and coronal). No tracer is needed with the related problems of molecular size and affinity for dentin; also no interact materials are required as in bacterial penetration studies or radioactive tracer studies. There is no modification of seal in this technique because measurement is made directly after filling without dipping the roots in acids, alcohol, or methyl salicylate .
The result of the present study revealed that MTA FillApex sealer showed superior sealing ability compared to resin-based AH Plus sealer even it was not significant, and this result confirmed the finding of previous studies using the same methodology; fluid filtration method . This finding may be attributed to the presence of MTA component suggesting possibility of setting expansion, which might have favored the sealability. MTA setting result in hydration of anhydrous material oxide compound to produce calcium silicate hydrate and calcium hydroxide phases which produce expansion against its confining margins, enhancing the seal and minimizing leakage .
On the other hand, leakage associated with AH Plus sealer was due to its lack of bond to GP points. Some component of AH Plus sealer, such as silicon oils which can affect the sealing ability of this material because oil based materials could prevent complete wetting of the root canal wall and adhere poorly to humid dentin. This may result in poor adaptation of the material to the root canal wall . However; the results are in contrary with other study that demonstrates the higher microleakage to MTA FillApex sealer . This controversy may be due to those authors used different methodology in preparation of root canals, the roots were prepared with Mtwo Ni Ti rotary system, also the linear dye penetration methodology used in measuring apical microleakage.
The results of the present study confirmed the finding of previous authors who proved that the highest percentage of voids within the root canal filling materials were associated with coronal and middle levels compared to the apical level. From a technical point of view, it is possible to hypothesize that the greater pressure produced in the apical third during the filling procedure may reduce the number of voids and may result in improved adaptation . Moreover, this finding may be related to increase apical diameter of root canal preparation as the canals was instrumented until the diameter of 50 K-file .
In the present study there was nonsignificant correlation between apical microleakage and voids collectively regardless root section and at apical, middle, and coronal root sections. These results are in agreement with Machedo et al.  who used fluid filtration test for leakage rate study. There was nonsignificant correlation between obturation limits and apical leakage. The fluid filtration test shows leakage only when there is at least one void extending from the apical to the coronal thirds. On the other hand, very small 'through and through' type voids are invisible on radiographs but may be detected by the fluid filtration test as having considerable leakage rates .
However these results are in contrary with Souza et al  who compared the correspondence between voids formation and apical microleakage in root canals filled with epoxy-resin-based (AH Plus) combined or not with resinous primer or with a methacrylate-based root canal sealer (Epiphany). The voids at apical third were observed by scanning electron microscopy. Apical microleakage was detected in the specimens by scanning electron microscopy/energy dispersive spectroscopy. There was correspondence between the presence of voids and microleakage. The difference in result may be due to different methodology in detection of voids and leakage rate.
| Conclusion|| |
Calcium silicate root canal sealer (MTA FillApex) and AH Plus sealer can provide adequate seal with low voids percent. None of the root canal filled teeth were gap-free. Voids percentage cannot be used as an indicator for sealing ability.
| Recommendation|| |
It is very important to assess leakage not only immediately after sealing but long-term evaluation is recommended, because sealing needs to be long lasting to be clinically effective.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]