|Year : 2017 | Volume
| Issue : 1 | Page : 20-25
A comparison of apical seal and tubular penetration of mineral trioxide aggregate, zinc oxide eugenol, and AH26 as root canal sealers in laterally condensed gutta-percha obturation: An in vitro study
KM Attur1, S Kamat2, KA Shylaja3, V Tegginmani4, D Patil4, RP Choudary5
1 Department of Conservative Dentistry and Endodontics, Narsinhbhai Patel Dental College and Hospital, Visnagar, Gujarat, India
2 Department of Conservative and Endodontics, Bharati Vidyapeeth Dental College and Hospital, Sangli, Maharashtra, India
3 Department of Oral Pathology and Microbiology, Narsinhbhai Patel Dental College and Hospital, Visnagar, Gujarat, India
4 Department of Conservative and Endodontics, AME Dental College, Raichur, India
5 Department of Conservative and Endodontics, HKES Society's S. Nijalingappa Institute of Dental Science and Research, Gulbarga, Karnataka, India
|Date of Web Publication||25-May-2017|
K M Attur
Department of Conservative Dentistry and Endodontics, Narsinhbhai Patel Dental College and Hospital, Visnagar - 384 315, Gujarat
Source of Support: None, Conflict of Interest: None
Aims and Objectives: To study the possible correlation of dentinal tubule penetration and microleakage by three root canal sealers: AH26, zinc oxide eugenol (ZOE), and mineral trioxide aggregate (MTA) using a dye leakage and scanning electron microscopy (SEM) methods.
Materials and Methods: Fifty-one maxillary anterior teeth with completely formed apex divided into three groups. Root canals were enlarged till No. 60 K-file using step-back technique. Alternate 5.25% and 17% ethylenediaminetetraacetic acid irrigants were used and obturated with gutta-percha and one of the three sealers: MTA, AH26, and ZOE. The extent of leakage was determined under stereomicroscope after immersion in methylene blue and also observed the tubular penetration of sealer under SEM.
Results: AH26 had lower microleakage scores than the other sealers, and MTA demonstrated the least penetration (P < 0.05).
Conclusion: There was an inverse relationship between microleakage and tubular penetration of root canal sealers. Deeper the penetration, lesser is the leakage.
Keywords: AH26; microleakage; mineral trioxide aggregate; scanning electron microscopy; tubular penetration; zinc oxide eugenol.
|How to cite this article:|
Attur K M, Kamat S, Shylaja K A, Tegginmani V, Patil D, Choudary R P. A comparison of apical seal and tubular penetration of mineral trioxide aggregate, zinc oxide eugenol, and AH26 as root canal sealers in laterally condensed gutta-percha obturation: An in vitro study. Endodontology 2017;29:20-5
|How to cite this URL:|
Attur K M, Kamat S, Shylaja K A, Tegginmani V, Patil D, Choudary R P. A comparison of apical seal and tubular penetration of mineral trioxide aggregate, zinc oxide eugenol, and AH26 as root canal sealers in laterally condensed gutta-percha obturation: An in vitro study. Endodontology [serial online] 2017 [cited 2017 Dec 15];29:20-5. Available from: http://www.endodontologyonweb.org/text.asp?2017/29/1/20/206996
| Introduction|| |
In endodontic practice, the success of root canal therapy depends on the root canal filling which seals the canal walls, apically and laterally. This in turn prevents the ingress of microorganisms and tissue fluids into the canal space. Many filling materials are used in root canal therapy to achieve a compact fluid tight seal at the apical region of the root canal prevent the ingress and accumulation of irritants which cause biological breakdown of attachment apparatus and eventually lead to failure of root canal therapy. Root canal sealers with solid core material play an important role to achieve the fluid tight seal.
According to Ingle and Beveridge, the majority of endodontic failures are caused mainly by incomplete sealing of the root canal. To combat this, it becomes necessary to use materials that will create fluid tight seal between the root canal system and the periapical tissues.
Gutta-percha (GP) is usually used with a sealer for root canal obturation. Ideal root canal sealer should have low viscosity and good wetting properties to fill the space between the GP cones and root canal walls. None of the sealers has the ability to bind chemically to canal walls, except for glass ionomer cement-based sealers that bond chemically to root canal walls.
The smear layer formed on the root canal walls after endodontic instrumentation acts as a barrier for the adaptation and penetration of root canal sealers into dentinal tubules.
Removal of smear layer will increase the interface between the sealer and root canal dentin. This will result in increased penetration of sealers into dentinal tubules which in turn reduces the microleakage.
The sealers play a role of binding agents to adapt GP to canal walls and fill the voids, accessory canals, and irregularities in the canal. Several types of root canal sealers are available with each having their own merits and demerits. Mineral trioxide aggregate (MTA) was introduced by Lee et al. at Loma Linda University in 1993. It has been used on experimental basis by endodontists with substantial success. Experimental studies have suggested that MTA appears to be an improvement over other materials for some endodontic procedures as it helps in root repair and bone healing. It was approved for human usage by the Food and Drug Administration in 1998.
Reports have suggested that MTA may be an ideal material for use against bone, as it is the only material that allows for the overgrowth of cementum, induce osteogenesis, and may facilitate the regeneration of periodontal ligament. It is also useful for the repair of troublesome problems of strip perforations and perforating resorptive defects. MTA and its modifications have been studied by numerous authors against microleakage. The tubular penetration of sealers has not been studied much, and paucity of studies on MTA and their modifications for tubular penetration have been noted. Attempt has been made to study its tubular penetration and to correlate with commonly used materials such as AH26 and zinc oxide eugenol (ZOE).
Hence, we study to evaluate and correlate the microleakage and tubular penetration of MTA, ZOE, and AH26 as a root canal sealer used in conjunction with laterally condensed GP.
| Materials and Methods|| |
Fifty-one freshly extracted human single-rooted anterior teeth with completely formed apex and free of apical root resorption, caries, enamel, and dentin defects were collected and stored in normal saline. The crowns of the teeth were sectioned at the cementoenamel junction, and gross pulp tissue was removed with coarse barbed broaches. A No. 15-file was then inserted into the root canal of each specimen until it was seen just exiting at the apical foramen. The working length was determined by deducting 1.0 mm from this length.
Root canal preparation was done using hand instruments (K-files, 15–60) by step-back technique. A volume of 3 ml of 5.25% NaOCl and 3 ml of 17% ethylenediaminetetraacetic acid (EDTA) were alternatively used as irrigants, to remove the smear layer for each specimen.
The canals were dried with paper points, and patency of the apical foramen was confirmed by passing a No. 15 K-file 1.0 mm through it before obturation was carried. No. 60 master GP cone was placed in the canal, and its fit and length was confirmed. The canal walls were coated with sealer using engine-driven lentulo spiral unit. The tip of the master cone was coated with sealer and seated. Obturation was completed using a standard lateral condensation technique. Excess GP was removed from the coronal portion of the root canal with a warm instrument, and the material was vertically compacted. The access was then sealed with intermediate restorative material (IRM Dentsply, Tulsa, OK, USA).
Teeth were randomly divided into three groups:
- Group 1: 13 teeth obturated with ZOE as sealer
- Group 2: 13 teeth obturated with AH26 as sealer
- Group 3: 13 teeth obturated with MTA as sealer (Dentsply, Tulsa, OK).
Positive control: 3 teeth (obturated with no sealer).
Negative control: 3 teeth (left empty and sealed with IRM).
All specimens were then covered with two-layer fingernail varnish so that only 1 mm of the apical foramen remained exposed. The negative controls were completely covered with fingernail varnish including the apical foramen. All specimens were immersed in 1% methylene blue dye for 72 h. After removal from the dye, the roots were rinsed in tap water, and the fingernail varnish was completely removed by scraping with a Bard–Parker number 11 blades.
The roots were grooved longitudinally on the buccal and lingual surface using cylindrical diamond point in a high-speed handpiece under constant air–water spray and then they were split into two halves with chisel and mallet. Out of two halves, one half was used for leakage evaluation, and the other was evaluated for tubular penetration.
The amount of microleakage on the fractured side of the spilt root was scored from apex to the maximum extent of dye penetration in coronal direction. Scoring was done by viewing the greatest extent of the dye with a stereo-microscope at ×15 magnification on an arbitrary scale.
Scoring for dye penetration for microleakage in root canal wall
- Score 0: Dye not visible on the root canal walls
- Score 1: Dye visible on the root canal walls
- Score 2: Dye infiltrations up to half of the distance longitudinally
- Score 3: Dye infiltrations more than half of the root surface longitudinally.
For scanning electron microscopy (SEM) evaluation, dehydration was carried out in ascending grades of ethyl alcohol, and the specimens were vacuum-dried, sputter-coated with gold, and viewed under SEM. The penetration depth of sealer into dentinal tubules was examined at cervical, middle, and apical third of the root. The mean of 10 readings of maximum penetration was taken for each part of the canal and was assessed.
Scoring for penetration depth of sealer into dentinal tubules
- Score 0: No penetration
- Score 1: 1–20 μ
- Score 2: 21–40 μ
- Score 3: 41–60 μ
- Score 4: More than 60 μ.
| Results|| |
The positive control group demonstrated leakage of the dye into whole length of the root canal and the dentinal tubule; the negative control group showed no dye penetration. Dye penetration in the experimental groups occurred mainly at the interface of the sealer and the root canal wall in the majority of specimens [Figure 1]. Groups 1 and 3 showed leakage at the interface of the GP and the sealer and throughout the sealer. Group 2 showed sealer forming a uniform structure with GP.
|Figure 1: Microleakage in different sealer groups (a) AH26, (b) zinc oxide eugenol, and (c) mineral trioxide aggregate|
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Examination with SEM showed that the sealer into root canal and dentinal tubules had a few granular appearances except AH26, which appeared to be homogeneous in penetration into the dentinal tubules. While dense dentinal tubular penetration of ZOE and MTA was observed near the canal wall, only scattered particles of MTA were seen deep in the tubules, presumably indicating that the matrix of the sealer was decomposed or had not been formed [Figure 2].
|Figure 2: Tubular penetration in different groups (a) AH26, (b) zinc oxide eugenol, and (c) mineral trioxide aggregate|
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When the correlation analysis was done with microleakage and tubular penetration, it revealed that there was an inverse relationship in each group, but the correlation was not statistically significant (P > 0.05). However, AH26 showed deepest sealer penetration into the dentinal tubules on average and least dye leakage. MTA had the least penetration and the highest microleakage scores.
| Discussion|| |
The microorganisms and toxins in the root canal are prevented from crossing into periradicular tissues by the root canal filling materials. A large percentage of failures in endodontic therapy is attributed to the difficulty in obliterating accessory canals, fins, anastomoses, apical deltas, and irregularities of the root canal and failure to get and adequate apical seal.
Although GP is a gold standard root canal filling material, it fails to provide a three-dimensional seal. Hence, sealers are used with GP to seal the root canal system into the inaccessible areas.
MTA with its flexible applications has created an era in the field of endodontics and is considered by some endodontists as a universal remedy for taxing endodontic procedures. It is biocompatible and satisfies most of the requirements of a perfect root canal sealer and allows for the steady overgrowth of the cementum over it and formation of bone and may facilitate the regeneration of periodontal ligament.,, This nature could be taken advantage to seal off the communications between root canal and periapical tissues. The high alkaline pH obtained by MTA, which is comparable to Ca(OH)2 acts as a bactericidal material. Hence, MTA is experimentally considered to be used as a root canal sealer.
Studies indicate that MTA has clinical advantages over other sealers in handling strip perforation and perforating resorptive defects.,,,
The present study compared MTA with conventional sealers (AH26 and ZOE). The parameters chosen in this study were microleakage using dye penetration with the help of stereomicroscope and tubular penetration of sealer with the help of SEM.
White et al. studied the effects of various irrigants on smear layer removal and concluded that removal of smear layer requires both organic (NaOCl) and inorganic (EDTA) solvents. The result of which was in correlation with that of previous studies.
When the smear layer is removed, the obturating material closely adapts to the dentinal wall, and in addition, the opened dentinal tubules permit increased surface contact between the dentin and the cement, which also results in improving the impermeability of the obturation.
The results of the present study revealed that the successive application of EDTA and NaOCl removed the smear layer and allowed sealers to penetrate into the dentinal tubules to varying depths and these findings are in correlation with the results of previous studies.,,
Methylene blue used as the leakage marker is readily detectable under visible light, which allows for rapid, artifact-free direct measurements. The advantages included were its water solubility, diffusibility, and hard tissue nonreactivity. Matloff et al. found that aqueous methylene blue penetrated obturated root canal spaces to a greater depth than some radioisotopes.
Precautions considered in the present study to avoid anatomical variations and to obtain standardization for the leakage, the length of the specimens were kept the same, instrumentation was accomplished with hand instruments (files), and canals were enlarged to size 60 using step-back technique. The canals were obturated by laterally condensed GP technique, and access cavities were closed with IRM. A sectioning method was employed for the calculation of dye leakage, and penetration of sealers into the dentinal tubules.
The leakage pathway in the specimens in the present study occurred mainly at the interface of the sealer and the root canal wall. Kazemi et al. reported that physical and chemical properties such as dimensional changes, absorption, and dissolution may affect sealing ability of the sealers.
The result of the present shows that AH26 showed better sealing ability [Table 1]. AH26 and ZOE had lower microleakage [Table 2]. This was in accordance with various other studies. It is also noted that AH26 had the best working characteristics with improved sealing ability, superior flow, good radiopacity, limited solubility, good adhesion, and adequate biocompatibility.
|Table 2: Comparison of three groups (AH26, zinc oxide eugenol, and mineral trioxide aggregate) with respect to microleakage scores by Kruskal-Wallis ANOVA|
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A statistically significant difference was found (P < 0.05) when the apical seal produced by MTA was compared with AH26 [Table 3]. This result was not in correlation with the results of previous studies, which reported MTA as an effective root end filling material.,
|Table 3: Comparison of pairs of groups by Mann-Whitney U-test microleakage scores|
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In the present study, MTA was mixed according to the manufacturer's directions and allowed to set for 7 days. After this, the set of the material was confirmed by probing the MTA at the apical foramen with an endodontic explorer and was found to be brick hard. Since MTA is not used in bulk, the material in the middle part of root may remain unset due to lack of water for hydration reaction, which affects the seal.
The factors affecting the tubular penetration of the sealers may be the surface activity of the sealer, the contact angle formed between the sealer and the dentinal tubules, and the obturation technique employed. Oksan et al. studied sealer as sole obturating material and observed that the sealer penetrated to approximately 60 μm.
The present study showed that an inverse correlation existed between the microleakage and tubular penetration, which recommended that when the penetration of the dentinal tubules increases, microleakage reduces.
The present study showed a higher penetration of AH26 when compared with ZOE and MTA [Table 4] and [Table 5]. Intergroup comparison that AH26, which is a resin-based sealer, appeared to fill the dentinal tubules more evenly and deeply compared to MTA and ZOE [Table 6].
|Table 5: Comparison of three groups with respect to tubular penetration by Kruskal-Wallis ANOVA|
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|Table 6: Comparison of pairs of groups by Mann-Whitney U-test tubular penetration|
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The finding obtained from both microleakage and SEM observations suggests that the physical integrity of the sealer matrix may also be important in offering resistance to leakage.
Sönmez et al. from their study concluded that MTA had similar sealing ability with AH Plus. Soleymani et al. in their study compared the apical microleakage of MTA Fillapex and AH26 in the presence of blood and found that AH26 had better sealing properties but without a significant difference. They also found that dried canals had better sealing properties.
Although MTA has proven successful in numerous other clinical applications, further investigations should be conducted to determine whether MTA itself or the technique for its placement could be modified to increase its efficiency as a root canal sealer.
| Conclusion|| |
The results of the present study show that microleakage of AH26 was significantly less compared to MTA and ZOE. Dentinal tubular penetration was more in AH26 group than MTA and ZOE groups. There was an inverse relationship between microleakage and tubular penetration of root canal sealers, deeper the penetration, lesser the leakage. On an average, AH26 showed deep sealer penetration, hence less dye leakage. Further studies are required to evaluate the efficacy of MTA as root canal sealer.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]