| Abstract|| |
Aim: The aim of this study was to evaluate the sealing ability of white and gray mineral trioxide aggregate (MTA) mixed with distilled water and 0.12% chlorhexidine (CHX) gluconate when used as a root-end filling material using the dye-penetration technique.
Materials and Methods: A total of 48 single-rooted human teeth were cleaned, shaped, and obturated with gutta-percha and AH Plus sealer. The apical 3 mm of each root was resected, and 3-mm deep root-end cavity preparations were made. The teeth were randomly divided into 4 experimental groups, each containing 8 teeth, and 2 negative and positive control groups, each containing 8 teeth. Root-end cavities in the experimental groups were filled with the experimental materials. After application of nail polish, the teeth were exposed to India ink for 72 h and longitudinally sectioned, and the extent of dye penetration was measured with a stereomicroscope.
Results : No statistically significant differences were observed in the sealing ability of gray and white MTA mixed with distilled water and 0.12% CHX.
Conclusion : CHX appears to be a good alternative to replace distilled water, as a solution to be mixed with MTA.
Keywords: Chlorhexidine gluconate, microleakage, mineral trioxide aggregate, root-end filling material
|How to cite this article:|
Sreegowri, Shetty K H, Prathap M S, Prithviraj K J. Sealing ability of white and gray mineral trioxide aggregate mixed with distilled water and 0.12% chlorhexidine gluconate as a root end filling material: An ex vivo evaluation. Indian J Dent Res 2013;24:395
When endodontic failure occurs, non-surgical retreatment is the treatment of choice. In certain clinical situations where the root canal space cannot be adequately sealed with non-surgical endodontic therapy; or are contraindicated, surgical endodontic therapy is indicated to obtain an apical seal and save the tooth. This procedure routinely consists of root-end exposure of the involved apex, resection of its apical end, a retro-filling preparation, and the placement of a root-end filling material to seal the root canal system. The main objective of a root-end filling material is to provide an adequate apical seal, by sealing the contents of the root canal system within the canal. This prevents the ingress of any bacteria, bacterial by-products or toxic material into the surrounding periradicular tissues.
|How to cite this URL:|
Sreegowri, Shetty K H, Prathap M S, Prithviraj K J. Sealing ability of white and gray mineral trioxide aggregate mixed with distilled water and 0.12% chlorhexidine gluconate as a root end filling material: An ex vivo evaluation. Indian J Dent Res [serial online] 2013 [cited 2020 Sep 23];24:395. Available from: http://www.ijdr.in/text.asp?2013/24/3/395/118007
Gartner and Dorn  proposed that an ideal root-end filling material should be easy to manipulate, be radiopaque, biocompatible, dimensionally stable, non-absorbable, insoluble in tissue fluids, unsusceptible to the presence of moisture, non-toxic, and should be well-tolerated by the periradicular tissues and promote healing. In addition, it should not corrode, be electrochemically active, and not stain the periradicular tissues.
A number of materials have been used as root-end fillings such as silver amalgam, zinc oxide eugenol cements (IRM and super EBA), glass ionomer cement, Diaket, composite resins, and resin-glass ionomer hybrids. However, to date, no material has been found to satisfy all the requirements of an ideal root-end filling material. 
Mineral trioxide aggregate (MTA) was developed at Loma Linda University in 1993 as a root-end filling material. It was formulated as gray MTA. Since its introduction as a root-end filling material, the use of MTA has expanded to many applications of root repair and bone healing. These applications include direct pulp-capping, repair of perforations, apexification, and, lately, in re-vascularization procedures as well. It is reported to seal off all the pathways of communication between the root canal system and the external surface of the tooth. 
Numerous in vitro and in vivo investigations have compared MTA's various properties with those of super-EBA, IRM, and amalgam. In vitro sealing ability and biocompatibility studies comparing root-end filling materials have shown MTA to be superior to other commonly used materials. ,
White MTA, a new type of MTA, has recently been introduced to the profession, and, as a consequence, only limited research has been carried out on the properties of this new material.  Shahi et al.,  reported that white MTA was more biocompatible than gray MTA and amalgam after 3 days, and gray MTA was more biocompatible than white MTA and amalgam after 7 days. However, there were no significant differences between white and gray MTA and amalgam after 21 days.
A recent study reported an enhanced antimicrobial activity by the substitution of 0.12% chlorhexidine (CHX) gluconate for sterile water in MTA.  Therefore, this study was done to compare the sealing ability of white and gray MTA mixed with distilled water and 0.12% CHX by using dye-penetration technique.
| Materials and Method|| |
The materials and methods used for this study are described under the following subheadings.
Selection of specimens
Non-carious, non-fractured, non-restored single rooted teeth were selected for the study. Carious, fractured, restored, and multi-rooted teeth were excluded. All 48 teeth were thoroughly cleaned to remove all calculus and stains. The teeth were then immersed in 5-% sodium hypochlorite for 15 min to remove the tissue tags. Any remaining tissue was mechanically removed using a curette, taking care not to damage the root surface. All teeth were then stored in normal saline until further use.
Endodontic preparation of the teeth
Straight line access cavities were obtained, and the working lengths were established within 0.5 mm of the apical foramina. The lengths of the canals were measured by inserting a #10 K file into the canals. When the tip of the file was visible at the apex, 0.5-mm short of the file penetration length was considered to be the working length. The canals were cleaned and shaped by using the step-back method, and #30K file was chosen as the master apical file. The canals were then flared to #40 K file.
For irrigation, 5.25% NaOCl was used, followed by saline as the final irrigant. The instrumented canals were dried with paper points and obturated with laterally condensed gutta-percha and AH Plus sealer. After removal of the coronal 2-mm of the filling material, the access cavities were closed with Cavit. The roots were stored at 37°C for 1 week. Apical root resections were then performed by removing 3 mm of the apex at a 90° angle to the long axis of the root; with a carborundum disc. Apical cavity preparations of 3-mm depth were made in each root with a straight fissure bur. Then, the teeth were randomly divided into 4 experimental groups, each containing 8 teeth and 2 positive and negative control groups, each containing 8 teeth.
In the groups,
Group A: The preparations were filled with gray MTA mixed with distilled water.
Group B: The preparations were filled with gray MTA mixed with 0.12% CHX.
Group C: The preparations were filled with white MTA mixed with distilled water.
Group D: The preparations were filled with white MTA mixed with 0.12% CHX.
Two coats of nail polish were applied to the external surface of each root except for the resected apical root-end.
Group E: Eight teeth with root-end preparations, but without root-end fillings, were used as positive controls
Group F: In another set of 8 teeth, apical root preparations were filled with tested materials (2 teeth for each material), and their entire external root surfaces were covered with 2 coats of nail polish and sticky wax to be used as negative controls.
Roots were then totally immersed in India ink for 72 h. The teeth were then rinsed in water. Vertical grooves were cut and the teeth were separated longitudinally. Gutta-percha was removed, to assess microleakage. The degree of microleakage was determined by the linear measurement of dye penetration with a stereomicroscope at 0.1-mm accuracy.
Data was analyzed using one way analysis of variance (ANOVA) and Tukey multiple comparison test by statistical software SPSS Ver 17 and MS- Excel. P < 0.05 was considered statistically significant.
| Results|| |
Representative stereomicroscopic pictures illustrate the amount of microleakage in respective groups. The depth of dye penetration was measured for each specimen. [Table 1] demonstrates the mean dye leakage values of each of the groups. [Table 2] demonstrates the comparison among the groups.
|Table 1: Demonstrates the mean dye leakage values of each group: Groups A, B, C, D, E and F|
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An objective description of all observations was recorded and statistically analyzed.
Group A: The mean dye leakage value-was 0.963-[Figure 1].
Group B: The mean dye leakage value-was 0.938-[Figure 2].
Group C: The mean dye leakage value was 1.0-[Figure 3].
Group D: The mean dye leakage value was 0.875-[Figure 4].
Group E: The mean dye leakage value was 3.95-[Figure 5].
Group F: The mean dye leakage value was 0.0-[Figure 6].
|Figure 1: Group A, where the preparations were filled with gray MTA mixed with distilled water, and stereomicroscopy showing the dye penetration|
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|Figure 2: Group B, where the preparations were filled with gray MTA mixed with 0.12% CHX, and stereomicroscopy showing the dye penetration|
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|Figure 3: Group C, where the preparations were filled with white MTA mixed with distilled water, and stereomicroscopy showing the dye penetration|
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|Figure 4: Group D, where the preparations were filled with white MTA mixed with 0.12% CHX, and stereomicroscopy showing the dye penetration|
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|Figure 5: Group E, where teeth had root‑end preparations, but without root‑end fillings, were used as positive controls, and stereomicroscopy showing dye penetration|
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|Figure 6: Group F, where apical root preparations were filled with tested materials (2 teeth for each material)‑.used as negative controls, and stereomicroscopy showing dye penetration|
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[Figure 7] demonstrates the mean extents of dye penetration in the study groups and the 2 positive and negative control groups. The findings of this study showed that there was complete dye penetration into the prepared root-end cavities in the positive control samples. No dye penetration was observed in the negative control samples.
|Figure 7: Demonstrates the mean extents of dye penetration in the study groups and the 2 positive and negative control groups|
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| Discussion|| |
The apical seal is the single most important factor in achieving success in surgical endodontics. The quality of root-end filling is an important determinant of healing after periapical surgery. Therefore, complete obturation of the root canal system and the development of a fluid tight seal are critically important elements of successful endodontic therapy. Since root-end filling has become the accepted method of sealing the root canals, a wide variety of materials have been advocated for use as root-end filling materials.
Total 48 human, single-rooted teeth were used. Canals were prepared using the step-back technique. All teeth were obturated with GP and AH Plus sealer, a resin-based sealer, using the lateral condensation method. Review of the literature over the last decade supports the following common indications for resection of the apical portion of the root during periradicular surgery, i.e., removal of pathological processes, removal of anatomic variations, removal of operator errors in non-surgical treatment, enhanced removal of the soft tissue lesion, access to the canal system, evaluation as well as creation of an apical seal, reduction of fenestrated root apices, and evaluation for aberrant canals and root fractures.
Resection-of-the-roots were carried out as close to 90 0 to the long axis of the tooth as possible with a carborundum disc. This reduces the number of exposed-dentinal tubules,  and 3-mm of root end was removed to eliminate natural or iatrogenic anomalies in the root canal system.
In this study, the root-end preparation was done using a straight fissure bur. Root-end preparation is also best carried out with an ultrasonically,- or sonically,- powered tip. , The ultrasonic tips-allow good access to the root end and provides a better shape to the root-end preparation. These should be used at low power and with a light touch to reduce the risk of root cracking. Two coats of nail polish was applied to the external surface of the roots, except the resected apical root end, in order to prevent any microleakage through the lateral canals.
Several in vitro methods have been used to assess the sealing ability of root-end filling materials such as dye penetration, radioisotopes, bacterial leakage studies, electrochemical techniques, scanning electron microscopy, and fluid filtration methods.  Each of these methods has advantages and disadvantages. The most popular method is dye-penetration test. The dye-penetration technique is easiest and most frequently used because it is convenient and does not require sophisticated materials. Therefore, dye penetration was used for assessing microleakage in this study.
Microleakage as related to endodontics refers to the movement of fluid and microorganisms along the interface of the dentinal walls and the root-canal-filling material or through the voids within the root-filling materials. Studies have indicated that microleakage, whether from an apical or coronal direction, adversely affects the success of root-canal therapy. 
Several studies have reported that India ink is a more reliable and suitable tracer in dye leakage studies than methylene blue.  Wu et al.,  reported that 1% methylene blue dye solution may be discolored in contact with alkaline substances such as MTA, which may result in unreliable results, affecting the leakage depth measurements. Thus, India ink was used in the present study. On the other hand, it has been shown that storage time has no significant influence on the amount of dye leakage.  Therefore, all specimens were immersed in India ink for 72 h.
Since the introduction of MTA in 1993 by Torabinejad,  this material has been used for different purposes including repairing perforations, filling root-end, and capping the pulp. The use of MTA in endodontic surgeries has led to cementum formation on MTA and the regeneration of periradicular tissues with the least inflammation induction.  In addition, some studies have demonstrated antibacterial properties for MTA.
Stowe et al.,  have demonstrated in a recent study that MTA has better antibacterial properties when mixed with 0.12% chlorhexidine instead of water. CHX gluconate is widely used in disinfection because of its excellent antimicrobial activity. It has gained increased popularity as an irrigating solution as well as an intracanal medicament. It is available in both solution as well as gel form.  It is a cationic bis biguanide with optimal antimicrobial action over the pH range of 5.5-7. CHX acts by absorbing into the cell wall of microbes and causing leakage of intra cellular components. Antimicrobial effect of CHX is related to cationic molecule binding to negatively charged bacterial cell walls that alters bacterial osmotic equilibrium.
CHX is effective against a wide range of microorganisms including Enterococcus faecalis, Staphylococcus aureus, and Streptococcus salivarius.  CHX can be suitably mixed with MTA instead of water when MTA is used as a retro-filling material, provided its sealing ability and biocompatibility are confirmed.
This study was done to evaluate the sealing ability of MTA mixed with CHX. To this end, white and gray MTA were mixed with distilled water and 0.12% CHX. The results demonstrated no statistically significant difference between the sealing abilities of white and gray MTA mixed with distilled water and 0.12% CHX. This finding is compatible with the results reported by Arruda et al.,  who did not observe differences in the sealing ability of gray and white MTA mixed with distilled water or 0.12% CHX.
In the present study, to preserve the optimum properties of the material, MTA was mixed with 0.12% CHX and distilled water according to the manufacturer's instructions and with a powder liquid ratio of 3:1 to achieve a putty consistency.
There were no differences in the sealing abilities of gray and white MTA mixed with water and 0.12% CHX. It appears that mixing MTA with CHX does not compromise the sealing ability of the material.
Kogan et al.,  recently evaluated the effects of various additives on setting properties of gray MTA and found a discrepancy in setting time for the MTA-CHX gel mixtures between the setting time experiment, that showed-a set time to be 4 h and the compressive strength experiment in which the mixture did not set even after 7 days. They suggested that the difference in the size of the specimens used in that study and the sensitivity of the different testing apparatus might have contributed to that discrepancy. Furthermore, the gel form of CHX might influence the setting properties of MTA. Moreover, Sumer et al.,  used implants of MTA mixed with CHX in rat connective tissue and concluded that this mixture is biocompatible.
| Conclusion|| |
To conclude that
- There is no statistically significant differences were observed in the sealing ability of gray and white MTA mixed with distilled water and 0.12% CHX.
- CHX appears to be a good alternative to replace distilled water, as a solution to be mixed with MTA.
- However, further studies are recommended before this mixture can safely be used in clinical situations.
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Department of Conservative Dentistry and Endodontics, Yenepoya Dental College, Deralakatte, Mangalore
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]