|DENTAL SCIENCE - ORIGINAL ARTICLE
|Year : 2015 | Volume
| Issue : 6 | Page : 607-611
An assessment of coronal leakage of permanent filling materials in endodontically treated teeth: An in vitro study
Kishore Shetty1, V Ashiq Habib1, S Vidhyadhara Shetty1, Jaishri N Khed1, Vishnudas Dinesh Prabhu2
1 Department of Conservative and Endodontics, Yenepoya Dental College, Mangalore, Karnataka, India
2 Department of Oral Pathology, Yenepoya Dental College, Mangalore, Karnataka, India
|Date of Submission||28-Apr-2015|
|Date of Decision||28-Apr-2015|
|Date of Acceptance||22-May-2015|
|Date of Web Publication||1-Sep-2015|
Dr. Kishore Shetty
Department of Conservative and Endodontics, Yenepoya Dental College, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: The present in vitro study was undertaken to evaluate and compare the sealing ability of hybrid composite, glass ionomer cement type II, silver amalgam and Ketac molar as permanent filling material in root canal treated teeth. Methodology: Hundred maxillary central incisors were selected for the study. After cleaning all the teeth, root canal treatment was carried out on all of them. The crown portion was cut-off at the cervical level. Three millimeter of coronal Gutta-percha was replaced by four different restorative materials. Then after thermocycling, samples were immersed in dye for 2 weeks. The amount of dye penetration was measured using stereomicroscope. Data were collected and analyzed statistically with ANOVA test and Student-Newman-Keuls test. Results: Coronal leakage was seen in all groups. Composite hybrid showed least amount of microleakage as compared to the other three experimental groups, and Ketac molar showed more leakage compared to other experimental groups. Conclusion: This study showed that hybrid composites offer better sealing ability compared to other materials tested in this study.
Keywords: Coronal seal, glass ionomer, hybrid composite, Ketac molar, silver amalgam
|How to cite this article:|
Shetty K, Habib V A, Shetty S V, Khed JN, Prabhu VD. An assessment of coronal leakage of permanent filling materials in endodontically treated teeth: An in vitro study. J Pharm Bioall Sci 2015;7, Suppl S2:607-11
|How to cite this URL:|
Shetty K, Habib V A, Shetty S V, Khed JN, Prabhu VD. An assessment of coronal leakage of permanent filling materials in endodontically treated teeth: An in vitro study. J Pharm Bioall Sci [serial online] 2015 [cited 2019 Dec 9];7, Suppl S2:607-11. Available from: http://www.jpbsonline.org/text.asp?2015/7/6/607/163566
The failure or success of endodontic treatment depends on the ability to completely remove the bacterial load.  Numerous studies have suggested that unprotected tooth and root canal structures are vulnerable to reinfection. ,,,,,
In addition to a good apical seal, an intact coronal seal is important for successful endodontic therapy. Coronal microleakage must be considered a potential etiological factor for failure of root canal treatment. The importance of the coronal seal should be emphasized between appointments as well as after obturation. Coronal leakage studies generally demonstrated extensive leakage in experimental models in vitro and in vivo.  Coronal leakage provides a viable source of microorganisms and nutrient that initiate and maintain periradicular inflammation and may well be the largest cause of failure in endodontic therapy. 
Many investigators have compared materials and techniques in an attempt to identify a means of attaining a fluid impermeable seal at the root canal terminus. This desired result has yet to be achieved. The question then arises that if apical microleakage is a cause of endodontic failure, what role might coronal microleakage plays in the prognosis of root canal treatment. The effect of various restorative procedures subsequent to endodontic therapy is often missing from most prognosis studies. Several recent studies have addressed the issue of the effect of restoration on the endodontic treatment outcome. ,,,, The results of these recent studies indicate that the coronal seal is of critical importance for a successful treatment, and the obturated root canal is not an adequate barrier to leakage. Hence, there is a need to conduct a study to assess the coronal microleakage with different permanent restorative materials. Glass ionomer cement (GIC), composite and silver amalgam have not been compared to each other for there sealing ability as coronal seal.
| Methodology|| |
A total of 100 matured extracted human intact maxillary incisors with fully formed apices and free of root caries, resorption or fracture were selected for the study. The teeth were cleaned of the biological debris and were stored on normal saline until use.
The crowns were removed at the cementoenamel junction with a tapered fissured carbide bur in a high-speed handpiece under the water spray. The canals of the remaining roots were instrumented to a size of 40 K files using 2.5% sodium hypochlorite as the irrigant. Working lengths were designated as 1 mm short of the point at which a number 15 file exited the apical foramen. Coronal flaring was accomplished by a step-back technique and the gates Glidden burs, sizes 2 and 3. Throughout the cleaning and shaping procedures, apical patency was maintained by recapitulation with a number 15 file. All teeth were instrumented in the same manner. The canals were then dried by paper points and obturated. Then laterally condensed with Gutta-percha and zinc oxide-eugenol sealer. Gutta-percha was cut with a heated instrument and vertically condensed right at the orifice opening of the canals. The teeth were divided into five groups. Each group consisting of 20 teeth. First four were experimental groups and the fifth group was a control group. The control group consisted of 10 positive and 10 negative controls. Three mm of the Gutta-percha was removed from the coronal part of the experimental teeth by using a marked heated plugger to prepare a clean 3 mm deep cavity. Gutta-percha was kept intact at the canals orifice of specimens in group 5, which consisted of 10 positive and 10 negative controls.
Preparation of experimental groups
- Group I: After the root canal treatment, this group teeth were restored with 3 mm thick GIC type II (GC Fuji II)
- Group II: After the root canal treatment, this group teeth were restored with 3 mm thick Ketac molar (3 M ESPE)
- Group III: After root canal treatment this group teeth were restored with composite (composite hybrid; 3 M). The cavity was etched with phosphoric acid, dried and applied with 2 coats of bonding agent. Subsequently, the bonding agent was light-cured for 20 s then cavity was filled with composite. It was then smoothened with a plastic instrument and cured with a light cure for 20 s
- Group IV: After root canal treatment this group teeth were restored with silver amalgam. Two coats of cavity varnish (Copalite; Colley and Colley Ltd., Houston, TX) were applied on the cavity walls at 1-min intervals. Amalgam was mixed according to the manufacturers instructions. Then, it was carried and condensed to the dry, isolated cavity with a small condenser until the cavity was overfilled. It was then burnished and carved toward the cavity walls until it was all set, and the excess of amalgam was removed.
Preparation of specimens for control groups
Group IV: Gutta-percha was kept intact at the canal orifice of specimens which consisted of 10 positive and 10 negative controls.
Preparation of specimens for dye leakage test
After the root canal treatment and the restoration, all the teeth were stored in 100% humidity for 48hrs to allow for the root canal sealer to set. Subsequently, they were coated with three layer of nail polish excluding the area of canal orifice. The negative control group, on the other hand, were given three coats of nail polish including the orifices.
Thermocycling of the different groups was carried at 70°C and 550°C for 100 cycles. A complete cycle lasted 2 min and consisted of 30 s at each bath. After thermocycling, the teeth were recoated with sticky wax, leaving the canal orifices uncovered except for the negative controls in which the whole tooth was covered. The teeth were then immersed in 2% methylene blue dye for 2 weeks. After 2 weeks the roots were rinsed in tap water and dried. Nail polish and sticky wax were completely removed with a scalpel.
All teeth were then grooved on the mesial and distal surfaces with the use of a tapered fissure carbide bur in a high speed hand piece to nearly the depth of the canal. Using pliers, all samples were split through their longitudinal axis. The tooth sealing material interface was examined under a stereomicroscope at 10° power for evidence of dye penetration of the material and along the canal wall [Figure 1]. All sealing materials and Gutta-percha were then gently removed from all walls of the canal, and the entire circumference was re-examined for evidence of dye penetration.
Dye leakage was graded in two categories: (i) No leakage - if leakage was <3 mm and the dye never penetrated into the Gutta-percha; and (ii) total leakage - if leakage was >3 mm and the dye penetrated the entire thickness of sealing material into the Gutta-percha. The recorded results of dye penetration were subjected to statistical analysis. Results were treated as contingency tables of independent samples, and the generalized Fisher's exact test was applied for statistical significance. Statistical analysis was used to determine the presence of leakage between various groups using one-way ANOVA test.
| Results|| |
The test materials compared statistically by using ANOVA test and Student-Newman-Keuls test for the analysis [Table 1].
The difference observed is highly significant. This signifies at least one of the groups differs from the others. One-way ANOVA test was done to compare among the group tested. The test showed a highly significant difference among the groups (P = 0.001).
Composite hybrid showed least amount of microleakage as compared to the other three experimental groups [Figure 2].
|Figure 2: Bar graph shows comparison of mean apical leakage of four groups by ANOVA test|
Click here to view
Silver amalgam showed more microleakage when compared to composite, but less than other two (GIC and Ketac molar).
Glass ionomer cement showed more microleakage than the composite and silver amalgam, but much less than Ketac molar.
Ketac molar showed more leakage compared to other three experimental group.
| Discussion|| |
The success of endodontic therapy depends on a thorough cleaning and shaping for the removal of necrotic debris and bacteria from the root canal, followed by sealing the root canal to prevent ingress of bacteria and tissue fluids. Dow and Ingle observed that failure in root canal treatment most commonly occurs due to inadequate apical seal. Studies have shown that a good coronal seal is equally important. Balto et al(2002)  found that the failure rate was twice as high in cases without an adequate coronal restoration compared to cases, which were adequately restored. 
From previous clinical studies, a number of conclusions concerning the importance of a coronal seal relative to prognosis have been drawn. Ray and Trope stated that the technical quality of the coronal restoration might be significantly more important than the technical quality of the endodontic treatment for apical periodontal health.  Rapp et al. evaluated various factors related to surgically treated endodontic cases. He found significantly better healing with teeth that were permanently restored after surgery.  Fortunately, research has shown that a second barrier can slow or prevent coronal leakage. Carman and Wallace restored the root canals and pulp chambers with various materials and said that a coronal barrier of Gutta-percha and sealer showed significantly more leakage than teeth restored with amalgam, composite resin, GIC or intermediate restorative material.  Despite research supporting the effectiveness of coronal sealing, a universally accepted protocol that states a coronal barrier as a must after root canal therapy is nonexistent.
Fractured teeth and leaking or missing temporary restorations are encountered clinically, leaving the access to the canals open to the oral cavity. Thus, the potential exists for oral fluids and bacterial contamination of the root canal space due to the dissolution of the coronal seal. Marshall and Massler reported obvious microleakage when the coronal portion of the root canals were exposed to isotopes. It seems imperative then that, in addition to a good apical seal, a coronal seal is also mandatory. 
Placement of an additional restorative material into the canal orifices after removal of a portion of the Gutta-percha and sealer up to three mm has several advantages. The coronal 3 mm of the canal is an ideal small cavity that is surrounded by intact tooth structure and can be easily sealed. Moreover, there is no occlusal load on the orifice area. Another advantage is that there is no esthetic disadvantage in this method as the material is placed within the canal. The whole procedure does not require extra appointment time.
The results of the various studies checking the coronal microleakage may be different. This is due to the fact that laboratory experiments demonstrate a potential, but not a clinical reality. There are so many variable in these studies that are not accounted for. 
In the present study methylene blue dye was used as a tracer because it is a sensitive indication of leakage and also molecular size of the dye is smaller than the bacteria. 
Glass lonomer exhibited poor sealing ability when it is used as a barrier to prevent coronal microleakage. The presence of smear layer can affect the sealing ability of GIC. And also there is a possibility of shrinkage of GIC upon setting. 
Beckham et al. observed a gap between GIC and dentinal walls after placement of the material in access opening.  This was likely due to shrinkage of the material upon setting, resulting in a potential avenue for microleakage.  On evaluation of coronal microleakage in endodontically treated multirooted teeth with different materials such as silver amalgam, zinc oxide eugenol, and glass ionomer cement, latter one exhibited inferior sealing ability compared to others. 
The more microleakage depicted by teeth restored with GIC, could be attributed to inadequate condensation and entrapment of air bubbles and/or improper adaptation of cement within the cavity of root canal orifices. These material lacks positive pack condensability and requires bulk packing for its condensation.
In the present study, GIC and Ketac molar restorations exhibited more microleakage than composite and amalgam.
In the present study, Ketac molar was found to be the least effective among the material tested.
The disadvantages of GIC like shrinkage, gap formation, air entrapment, lack of positive pack condensability and requirement of bulk packing may also be present with Ketac molar as the physical properties of these materials are not significantly different.
In the present study, silver amalgam showed better sealability compared to GIC and Ketac molar. This better sealability of amalgam is in accordance with other studies and could be related to the ability of amalgam to be condensed in irregular areas and the proper adaptation with cavity walls. 
And also over a period seepage of corrosion products will improve the marginal seal of Amalgam, but considering the short period of present study this is not at all a contributing factor.
The composite material showed lesser leakage compared to amalgam. It is a well-known fact that most of the modern amalgam materials will undergo a net contraction after setting.
Composites generally are classified with respect to the components, amounts and properties of their filler or matrix phases. They are also classified based on their handling properties. But classification based on filler content (weight or volume percent), filler particle size and method of filler addition is the most common one.
The supreme test of a filling is its ability to maintain an unfailing margin. Composite resin restorations are the first in the class of tooth colored materials to maintain marginal integrity during a clinically acceptable period.
Acid-etching, the application of a low-viscosity bonding agent, and the use of the rubber dam to maintain dryness should be routine procedures for all composite resin restorations. 
The composite material used in the present study is Z100™ (3 M ESPE). The bonding agent used is Adper™ Scotchbond™ . This is a fifth generation bonding agent. The use of total each technique removes the smear layer, widens dentinal tubules and causes demineralization of intertubular dentin. The primer in the bonding agent wets the collagen network, resulting in the formation of the hybrid layer. Because of the increased filler content (66% by volume) hybrid material is less susceptible to polymerization shrinkage. All this factors may be contributing to the better performance of composites in the present study.
So based on this study hybrid composite is a better choice compared to GIC, amalgam and Ketac molar as an intracoronal restorative material.
There is a wide variation in the results of microleakage studies due to lack of standardized techniques. Also, the methylene blue dye has smaller particle size than bacteria. Hence, result of dye penetration studies should be cautiously attributed to clinical situation. Long term clinical trials are necessary to obtain conclusive results about the sealing ability of materials in an environment in which they are deemed to be used.
| Conclusion|| |
The present study was conducted to evaluate the coronal microleakage through permanent restorative materials. The following conclusion can be drawn from this in vitro study.
- Composite showed the best sealing ability against coronal microleakage followed by silver amalgam
- Silver amalgam showed more microleakage when compared to composite but less than GIC and Ketac molar
- GIC showed more microleakage than the composite and silver amalgam, but much less than Ketac molar.
Based on the above findings it can be concluded that the hybrid composite has got the best sealing ability as compared to the other restorative materials.
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[Figure 1], [Figure 2]