Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 6  |  Issue : 2  |  Page : 82-87

Comparative evaluation of sealing ability of mineral tri-oxide aggregate with intact, removed and modified smear layer: An in vitro study


1 Department of Conservative Dentistry and Endodontics, HS Judge Institute of Dental Sciences, Punjab University, Chandigarh, India
2 Department of Conservative Dentistry and Endodontics, DAV Dental College and Hospital, Yamuna Nagar, Haryana, India
3 Department of Oral Medicine and Radiology, HS Judge Institute of Dental Sciences, Punjab University, Chandigarh, India
4 Department of Public Health Dentistry, Gian Sagar Dental College and Hospital, Rajpura, Punjab, India

Date of Web Publication16-Oct-2014

Correspondence Address:
Ramandeep Singh Gambhir
Department of Public Health Dentistry, Gian Sagar Dental College and Hospital, Rajpura - 140 601, Punjab
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0975-8844.143045

Rights and Permissions
  Abstract 

Objective: The aim was to evaluate the sealing ability of mineral tri-oxide aggregate (MTA) with intact, removed, and modified smear layer. 5.2% sodium hypochlorite was used for irrigation to keep smear layer intact, 17% ethylenediamine tetraacetic acid (EDTA) followed by 5.2% sodium hypochlorite was used to remove the smear layer and 30% potassium oxalate was used for its modification. Materials and Methods: A total of 112 intact single canaled mandibular premolar teeth were selected for the study. Roots were separated from the crown portion. All 112 roots were then randomly placed into one of five groups: Three experimental groups of 28 roots each, one group of 14 roots (negative control), and one group of 14 roots (positive control). All specimens were immersed in 1% methylene blue dye for 72 h and viewed microscopically. The results obtained were subjected to statistical analysis using one-way ANOVA test and unpaired Student's t-test. Results: When group 1a was compared with 2a and 3a, there was a statistically significant difference (P < 0.05) between 1a and 2a and the difference was statistically insignificant (P > 0.05) when 1a and 3a were compared. When groups 1, 2, 3, 4 and 5 were compared irrespective of the subgroups, the results were statistically significant (P < 0.05) between 1 and 2, 1 and 4, 1 and 5, 2 and 3, 2 and 4, 2 and 5, 3 and 4, 3 and 5, and 4 and 5. Conclusion: About 5.2% sodium hypochlorite and MTA produced less leakage than 17% EDTA, followed by 5.2% sodium hypochlorite but more than 30% potassium oxalate.

Keywords: Modified smear layer, mineral tri-oxide aggregate, potassium oxalate, sodium hypochlorite


How to cite this article:
Brar P, Bogra P, Nikhil V, Singh SV, Brar R, Gambhir RS. Comparative evaluation of sealing ability of mineral tri-oxide aggregate with intact, removed and modified smear layer: An in vitro study . J Orofac Sci 2014;6:82-7

How to cite this URL:
Brar P, Bogra P, Nikhil V, Singh SV, Brar R, Gambhir RS. Comparative evaluation of sealing ability of mineral tri-oxide aggregate with intact, removed and modified smear layer: An in vitro study . J Orofac Sci [serial online] 2014 [cited 2021 Aug 5];6:82-7. Available from: https://www.jofs.in/text.asp?2014/6/2/82/143045


  Introduction Top


Predictable successful endodontic therapy involves a series of procedures that begin with the adequate knowledge of the biology of the pulp and periapical tissues and end with the subsequent evaluation of treatment carried out. It is observed that cleaning and shaping of root canal always produces a smear layer, which contains both organic and inorganic materials from the pulp and prepared dentin, and also the microorganisms. [1] The microorganisms in this smear layer remain inaccessible to the action of irrigating agents and intracanal medicaments. Smear layer is also postulated to interfere with the adhesion of sealers into the dentinal tubules causing significant microleakage and may ultimately cause failure of treatment. [1]

At present, sodium hypochlorite at a concentration of 2.5-5.25%, delivered with both a syringe and a needle or with the help of an ultrasonic unit, is universally accepted as the irrigant of choice for endodontic treatment, but is ineffective in removing the smear layer. [2] ethylenediamine tetraacetic acid (EDTA), 10% citric acid, EDTA-T, ethylene glycol-bis- (β-amino-ethyl ether) N, N, N', N'-tetra acetic acid and mixture of a tetracycline isomer, a detergent and an acid have been used for endodontic treatment to remove smear layer. [1],[2],[3] But complete removal of the smear layer is not possible due to the complexities of the root canal system.

Recently efforts have been made to modify the smear layer with the help of 30% potassium oxalate and 4% titanium tetrafluoride. [4],[5] Titanium is a polyvalent metal and has remarkable binding capacity to organic material of the dentin forming a tenacious coating of titanium dioxide, which is resistant to dissolution by potassium dio-oxide washing or hydrochloride treatment. [6] Pashley et al. have shown that oxalate treatment removes the smear layer and replaces it with a layer of crystalline precipitates that occlude dentin and are acid resistant. [5] The large crystals that form following application of 30% neutral potassium oxalate are likely to be calcium oxalate dihydrate. The source of the calcium may be ions in the fluids within the smear layer.

Mineral tri-oxide aggregate (MTA) is a mixture of three powder ingredients: Portland cement, bismuth oxide and gypsum. The major constituents of Portland cement are dicalcium silicate, tricalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. [7] The powder consists of fine particles that are hydrophilic and set in the presence of water. Hydration of powder results in a colloidal gel that solidifies to a hard structure. [8] MTA is a biocompatible material and has been used for pulp capping, repair of root perforations, root end fillings and apexification, etc. [8] The material holds promise because of its sealing capabilities [9],[10],[11] and ability to set in the presence of blood and biocompatibility. [12],[13],[14] In addition, the material has demonstrated long term success when used as a perforation repair material, which may be a result of its capabilities to induce hard tissue formation. [15],[16] However, its potential as an obturating material has not been explored.

Various studies have been conducted to compare the adaptation of gutta-percha and cement sealer to the dentinal walls of prepared root canals in the presence and absence of smear layer. But, it is not known whether the smear layer influences the sealing ability of MTA. The purpose of the present study was to evaluate the sealing ability of MTA with intact, removed and modified smear layer.


  Materials and methods Top


Selection of teeth for the study

Ethical clearance was obtained from the Institutional Ethics Committee of DAV Dental College, Yamunanagar prior to the start of the study. 112 intact single canaled mandibular premolar teeth were taken from Department of Oral and Maxillofacial Surgery. All the teeth were then sectioned at the cement-enamel junction using a diamond disc and water spray to separate the crown portion from the root. The working length for each root was established and evaluation was done using a radiograph. Five groups were constituted. All 112 roots were then randomly placed into one of five groups: Three experimental groups of 28 roots each, one group of 14 roots (negative control), and one group of 14 roots (positive control). The biomechanical preparation was done in the four groups using the standardized step back technique. [17] The canals were prepared upto number 55 k-file and step back preparation was done till number 80 k-file. Different irrigants were used in all the groups. The MTA was carried to the canal and condensed with the help of pluggers and the plug was verified radiographically. A moist cotton pellet was packed in the canal for 24 h. The remaining part of the roots was obturated after 24 h with the master cone gutta-percha and MTA.

Various groups

  • Group 1: 28 roots were taken, and the irrigation was done using 15 ml of 5.2% sodium hypochlorite solution. They were further subdivided into 2 subgroups of 14 teeth each.
    • Group 1a: A 2 mm apical plug of MTA was formed.
    • Group 1b: A 5 mm apical plug of MTA was formed.
  • Group 2: 14 roots were taken and irrigation was done using 5 ml of 17% EDTA solution, followed by a final rinse with 10 ml of 5.2% sodium hypochlorite. They were further subdivided into 2 subgroups of 14 teeth each.
    • Group 2a: A 2 mm apical plug of MTA was formed.
    • Group 2b: A 5 mm apical plug of MTA was formed.
  • Group 3: 28 roots were taken, and irrigation was done with 30% potassium oxalate. They were further subdivided into 2 subgroups of 14 teeth each.
    • Group 3a: A 2 mm apical plug of MTA was formed.
    • Group 3b: A 5 mm apical plug of MTA was formed.
  • Group 4 (positive control): 14 roots were taken and instrumented using a standardized technique, but not obturated.
  • Group 5 (negative control): 14 roots were taken and were neither instrumented nor obturated.


The roots were coronally sealed with a temporary restorative material. All groups were stored for 7 days in 100% humidity at room temperature. The roots were then covered with two layers of nail polish so that only the apical foramen remained exposed. The negative controls were completely covered with two layers of nail polish, 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 were then longitudinally sectioned with a chisel and mallet after placing two grooves, one bucally and one lingually. Each section was then viewed under a stereomicroscope. Linear apical leakage was measured from the apex to the most coronal extent of dye penetration.

Statistical analysis

The recorded data was transferred to an excel sheet, and statistical analysis was carried out using Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, version 13.0 for Windows). The results obtained were subjected to statistical analysis using one-way ANOVA test and unpaired Student's t-test. Statistical significance was set to P < 0.05.


  Results Top


[Figure 1] depicts the mean microleakage values in various groups and the control group. The mean microleakage values of group 1a was 2.19 mm, group 1b was 3.26 mm, group 2a was 4.77 mm, group 2b was 5.39 mm, group 3a was 1.78 mm, group 3b was 1.74 mm, positive control were 8.89 mm and negative control were 0.12 mm. The mean microleakage irrespective of the subgroups in group 1 was 2.73 mm, group 2 was 5.08 mm and group 3 was 1.76 mm.

When group 1a was compared with 2a and 3a, there was a statistically significant difference (P < 0.05) between 1a and 2a (0.016) and the difference was statistically insignificant (P > 0.05) when 1a and 3a were compared (0.29). There was a statistically significant difference between 2a and 3a (0.005) [Table 1]. When group 1b was compared with 2b and 3b, there was a statistically significant difference (P < 0.05) between the groups 1b and 2b (0.011), and 1b and 3b (0.03). There was also statistically significant difference between 2b and 3b (0.0).
Table 1: Statistical evaluation of various groups using Student's t-test

Click here to view
Figure 1: Bar graph depicting mean micro-leakage in experimental groups and control groups

Click here to view


When groups 1, 2, 3, 4 and 5 were compared irrespective of the subgroups, the results were statistically significant (P < 0.05) between 1 and 2 (0.0), 1 and 4 (0.0), 1 and 5 (0.0), 2 and 3 (0.0), 2 and 4 (0.0), 2 and 5 (0.0), 3 and 4 (0.0), 3 and 5 (0.0), and 4 and 5 (0.0). However, when groups 1 and 3 were compared the results were found to be statistically insignificant (P > 0.05) [Table 2].
Table 2: Statistical evaluation of various groups irrespective of the subgroups using Student's t-test

Click here to view


When group 4 was compared with other groups, there was a statistically significant difference (P < 0.05) between group 1a and 4 (0.0), group 2a and 4 (0.001), group 3a and 4 (0.0), group 1b and 4 (0.0), group 2b and 4(0.0) and group 3b and 4 (0.0) [Table 3]. When group 5 was compared with other groups, there was a statistically significant difference (P < 0.05) between group 1a and 5 (0.0), group 2a and 5 (0.0), group 3a and 5 (0.0), group 1b and 5 (0.0), group 2b and 5 (0.0) and group 3b and 5 (0.0) [Table 4].
Table 3: Statistical evaluation of various groups with group 4 (positive control)

Click here to view
Table 4: Statistical evaluation of various groups with group 5 (negative control)

Click here to view


When group 4 was compared with group 5, there was a statistically significant difference (P < 0.05) between them (0.0).


  Discussion Top


Whenever the tooth structure is cut, the mineralized matrix shatters. Considerable quantities of cutting debris are scattered over the enamel and dentin surfaces to form what is called the smear layer. [18] The advantages and disadvantages of smear layer and whether it should be removed or not from the instrumented root canals is still controversial. If it is retained, it acts as a physical barrier to bacteria and bacterial byproducts. The dentinal plugs stop bacterial invasion into dentinal tubules. [19],[20] The smear layer has been shown to reduce the permeability of radicular dentin by 25-49%. [21]

The complete removal of the smear layer may not be possible due to the complexities of the root canal system. Several methods have been tried to remove the smear layer. Cross-linking the smear layer to improve its bonding to underlying dentin has been tried. [21] Some researchers have tried removing the smear layer and replacing it with an uncontaminated chemical sealing layer to reduce the permeability. [22] The present study involved the in vitro comparison of microleakage of endodontically treated teeth filled with an apical plug of MTA when 5.2% sodium hypochlorite; 17% EDTA and 5.2% sodium hypochlorite; and 30% potassium oxalate were used as irrigants. MTA is a material developed at the Loma Linda University to seal communications between the tooth and the external surface. [14]

When group 1a was compared with group 2a, the mean microleakage score of group 1a (2.19 mms) was less than 2a (3.26 mms) and the results were statistically significant (P < 0.05). The possible reason for this result could have been that 5.2% sodium hypochlorite did not remove the smear layer. It only flushed out the organic debris, whereas 17% EDTA and 5.2% sodium hypochlorite have the capability to remove the smear layer, cause enlargement of the dentinal tubules and denaturation of collagen fibrils. The smear layer in group 1a could have prevented the dye leakage since MTA has putty like consistency and does not penetrate the dentinal tubules and so the removal of smear layer could have paved way for dye leakage. A study done by some other authors suggests that the combination of 17% EDTA followed by 5.2% hypochlorite is effective in removing the smear layer. [23]

When group 1a was compared with group 3a, the mean microleakage score of group 1a (2.19 mms) was more than 3a (1.78 mms), but the results were statistically insignificant (P > 0.05). The possible reason for this could be that smear layer is present in both cases. Potassium oxalate could have reacted with smear layer, reducing its permeability. [5],[21]

When group 2a was compared with group 3a, the mean microleakage score of group 2a (4.77 mms) was more than 3a (1.78 mms) and the results were statistically significant (P < 0.05). AA possible reason for this could be that EDTA and hypochlorite combination in group 2a must have removed the smear layer creating gap for dye penetration. Whereas potassium oxalate in group 3a could have modified the smear layer. When group 1b was compared with group 2b, the mean microleakage score of group 1b (3.26 mms) was less than 2b (5.39 mms) and the results were statistically significant (P < 0.05). The same reasoning can be applied here as for groups 1a and 2a.

When group 1b was compared with group 3b, the mean microleakage score of group 1b (3.26 mm) was more than 3b (1.74 mm) and the results were statistically significant (P < 0.05). The same reasoning can be applied here as for groups 1a and 3a. But as the length of the plug increased, the results have changed from statistically insignificant (in 2 mm group) to significant (5 mm group).

When group 4 (positive control) was compared with various groups, group 1a, 1b, 2a, 2b, 3a and 3b, the mean microleakage value of group 4 (8.89 mm) were higher as compared to group 1a, 2a, 2b, 3a and 3b and the results were statistically significant (P < 0.05). The reason could be that there was no obturating material present to seal the instrumented canals. This allowed dye penetration. Similarly, when group 5 (negative control) was compared with various groups, group 1a, 1b, 2a, 2b, 3a and 3b, the mean microleakage value of groups 1a, 1b, 2a, 2b, 3a and 3b were higher than group 5 and the results were statistically significant (P < 0.05). The reason could be that the teeth that were neither instrumented nor obturated retained a good amount of healthy tooth structure and hence the leakage was negligible.

When group 1 was compared with group 3 (teeth irrigated with 30% potassium oxalate), the mean microleakage of group 1 (2.73 mm) was more than group 3 (1.76 mm) and the results were statistically insignificant (P > 0.05). When group 2 was compared with group 3 the mean microleakage of group 2 (5.08 mm) was more than group 3 (1.76 mm) and the results were statistically significant (P < 0.05). Therefore, it is evident from this study that 30% potassium oxalate has the least microleakage followed by 5.2% sodium hypochlorite and 17% EDTA, and 5.2% sodium hypochlorite have produced the maximum leakage.

When subgroups a (2 mm MTA plug) and b (5 mm MTA plug) were compared, there was a statistically insignificant (P > 0.05) between them in all the groups, although the 2 mm group produced less leakage than the 5 mm group. Similar findings were reported by some authors who showed that MTA is usually not used in bulk; therefore, it is possible that some of the midroot material deep to the apical ends of the canal remained unset due to lack of exposure to water for the setting reaction affecting the seal. [24] Some other study conducted elsewhere also showed that there was no significant difference in the dye leakage between the 2 mm and 5 mm plugs. [25]

Mineral tri-oxide aggregate is rich in CaO, which is converted to calcium hydroxide on contact with tissue fluid. The calcium hydroxide separates into calcium and hydroxide ions, resulting in increased pH and Ca ion release. Ca ions may cross the cell membrane by depolarization or activation of membrane-bound channels. Therefore, it is likely that this ion would play a greater role in the reparative process than would the hydroxyl ion. It must be stressed, however that the correlation of this study in vitro with the one done under clinical conditions is yet to be investigated.


  Conclusion Top


Irrespective of the size of the MTA plug formed, 30% potassium oxalate and MTA produced the best results. 5.2% sodium hypochlorite and MTA produced less leakage than 17% EDTA, followed by 5.2% sodium hypochlorite but more than 30% potassium oxalate.17% EDTA, followed by 5.2% sodium hypochlorite, and MTA produced the maximum amount of leakage. When the 2 mm and 5 mm apical MTA plugs were compared, 2 mm apical MTA plug leaked less than the 5 mm plug.

 
  References Top

1.
Garberoglio R, Becce C. Smear layer removal by root canal irrigants. A comparative scanning electron microscopic study. Oral Surg Oral Med Oral Pathol 1994;78:359-67.  Back to cited text no. 1
    
2.
Torabinejad M, Handysides R, Khademi AA, Bakland LK. Clinical implications of the smear layer in endodontics: A review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:658-66.  Back to cited text no. 2
    
3.
Scelza MF, Pierro V, Scelza P, Pereira M. Effect of three different time periods of irrigation with EDTA-T, EDTA, and citric acid on smear layer removal. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;98:499-503.  Back to cited text no. 3
    
4.
Pashley DH, Michelich V, Kehl T. Dentin permeability: Effects of smear layer removal. J Prosthet Dent 1981;46:531-7.  Back to cited text no. 4
    
5.
Pashley DH, Galloway SE. The effects of oxalate treatment on the smear layer of ground surfaces of human dentine. Arch Oral Biol 1985;30:731-7.  Back to cited text no. 5
    
6.
Timpawat S, Vongsavan N, Messer HH. Effect of removal of the smear layer on apical microleakage. J Endod 2001;27:351-3.  Back to cited text no. 6
    
7.
Sarkar NK, Caicedo R, Ritwik P, Moiseyeva R, Kawashima I. Physicochemical basis of the biologic properties of mineral trioxide aggregate. J Endod 2005;31:97-100.  Back to cited text no. 7
    
8.
Parirokh M, Torabinejad M. Mineral trioxide aggregate: A comprehensive literature review - Part III: Clinical applications, drawbacks, and mechanism of action. J Endod 2010;36:400-13.  Back to cited text no. 8
    
9.
Tselnik M, Baumgartner JC, Marshall JG. Bacterial leakage with mineral trioxide aggregate or a resin-modified glass ionomer used as a coronal barrier. J Endod 2004;30:782-4.  Back to cited text no. 9
    
10.
de Leimburg ML, Angeretti A, Ceruti P, Lendini M, Pasqualini D, Berutti E. MTA obturation of pulpless teeth with open apices: Bacterial leakage as detected by polymerase chain reaction assay. J Endod 2004;30:883-6.  Back to cited text no. 10
    
11.
Yoshida T, Shibata T, Shinohara T, Gomyo S, Sekine I. Clinical evaluation of the efficacy of EDTA solution as an endodontic irrigant. J Endod 1995;21:592-3.  Back to cited text no. 11
    
12.
Koh ET, McDonald F, Pitt Ford TR, Torabinejad M. Cellular response to mineral trioxide aggregate. J Endod 1998;24:543-7.  Back to cited text no. 12
    
13.
Torabinejad M, Pitt Ford TR, McKendry DJ, Abedi HR, Miller DA, Kariyawasam SP. Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys. J Endod 1997;23:225-8.  Back to cited text no. 13
    
14.
Holland R, de Souza V, Nery MJ, Otoboni Filho JA, Bernabé PF, Dezan Júnior E. Reaction of rat connective tissue to implanted dentin tubes filled with mineral trioxide aggregate or calcium hydroxide. J Endod 1999;25:161-6.  Back to cited text no. 14
    
15.
Holland R, Filho JA, de Souza V, Nery MJ, Bernabé PF, Junior ED. Mineral trioxide aggregate repair of lateral root perforations. J Endod 2001;27:281-4.  Back to cited text no. 15
    
16.
Felippe WT, Felippe MC, Rocha MJ. The effect of mineral trioxide aggregate on the apexification and periapical healing of teeth with incomplete root formation. Int Endod J 2006;39:2-9.  Back to cited text no. 16
    
17.
Tan BT, Messer HH. The quality of apical canal preparation using hand and rotary instruments with specific criteria for enlargement based on initial apical file size. J Endod 2002;28:658-64.  Back to cited text no. 17
    
18.
Pashley DH. Smear layer: Physiological considerations. Oper Dent Suppl 1984;3:13-29.  Back to cited text no. 18
[PUBMED]    
19.
Dua D, Dua A, Uppin VM. A Scanning electron microscopic evaluation of intracanal smear layer removal by two different final irrigation activation systems. Contemp Clin Dent 2014;5:37-41.  Back to cited text no. 19
[PUBMED]  Medknow Journal  
20.
Sen BH, Wesselink PR, Türkün M. The smear layer: A phenomenon in root canal therapy. Int Endod J 1995;28:141-8.  Back to cited text no. 20
    
21.
Fogel HM, Pashley DH. Dentin permeability: Effects of endodontic procedures on root slabs. J Endod 1990;16:442-5.  Back to cited text no. 21
    
22.
Arruda M, de Arruda MP, de Carvalho-Júnior JR, de Souza-Filho FJ, Sousa-Neto MD, de Freitas GC. Removal of the smear layer from flattened canals using different chemical substances. Gen Dent 2007;55:523-6.  Back to cited text no. 22
    
23.
Yamada RS, Armas A, Goldman M, Lin PS. A scanning electron microscopic comparison of a high volume final flush with several irrigating solutions: Part 3. J Endod 1983;9:137-42.  Back to cited text no. 23
[PUBMED]    
24.
Vizgirda PJ, Liewehr FR, Patton WR, McPherson JC, Buxton TB. A comparison of laterally condensed gutta-percha, thermoplasticized gutta-percha, and mineral trioxide aggregate as root canal filling materials. J Endod 2004;30:103-6.  Back to cited text no. 24
    
25.
Matt GD, Thorpe JR, Strother JM, McClanahan SB. Comparative study of white and gray mineral trioxide aggregate (MTA) simulating a one- or two-step apical barrier technique. J Endod 2004;30:876-9.  Back to cited text no. 25
    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Materials and me...
Results
Discussion
Conclusion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed2396    
    Printed75    
    Emailed0    
    PDF Downloaded267    
    Comments [Add]    

Recommend this journal