Sealing Ability of White and Gray Mineral Trioxide Aggregate Mixed with Distilled Water and 0.12% Chlorhexidine Gluconate When Used as Root-end Filling Materials

Sealing Ability of White and Gray Mineral Trioxide Aggregate Mixed with Distilled Water and 0.12% Chlorhexidine Gluconate When Used as Root-end Filling Materials

Basic Research—Technology Sealing Ability of White and Gray Mineral Trioxide Aggregate Mixed with Distilled Water and 0.12% Chlorhexidine Gluconate W...

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Basic Research—Technology

Sealing Ability of White and Gray Mineral Trioxide Aggregate Mixed with Distilled Water and 0.12% Chlorhexidine Gluconate When Used as Root-end Filling Materials Shahriar Shahi, DDS, MSc,* Saeed Rahimi, DDS, MSc,* Hamid Reza Yavari, DDS, MSc,* Sahar Shakouie, DDS, MSc,* Saeed Nezafati, DDS, MSc,† and Majid Abdolrahimi, DDS* Abstract This in vitro study used dye penetration to compare the sealing ability of white and gray mineral trioxide aggregate mixed with distilled water and 0.12% chlorhexidine gluconate when used as root-end filling materials. Ninety-six single-rooted human teeth were cleaned, shaped, and obturated with gutta-percha and AH26 root canal 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 20 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 decoronation of the teeth and application of nail polish, the teeth were exposed to India ink for 72 hours and longitudinally sectioned, and the extent of dye penetration was measured with a stereomicroscope. Statistical analysis showed that there were no significant differences among the 4 experimental groups. (J Endod 2007;33:1429 –1432)

Key Words Chlorhexidine gluconate, microleakage, MTA, root-end filling material

From the *Endodontic Department and †Oral and Maxillofacial Surgery Department, Tabriz Dental School, Tabriz University of Medical Sciences, Tabriz, Iran. Address requests for reprints to Dr Shahriar Shahi, Endodontic Department, Tabriz Dental Faculty, Golgasht Street, 5166614713, Tabriz, Iran. E-mail address: [email protected] yahoo.com. 0099-2399/$0 - see front matter Copyright © 2007 by the American Association of Endodontists. doi:10.1016/j.joen.2007.08.008

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he goal of root canal treatment is the cleaning, shaping, and complete obturation of the root canal system, thus preventing the proliferation of microorganisms and their by-products. When failure occurs, retreatment by an orthograde approach is the treatment of choice. However, when a nonsurgical attempt proves unsuccessful or is contraindicated, surgical endodontic therapy is indicated to obtain an apical seal and save the tooth. Because most endodontic failures are due to inadequate cleaning and shaping and/or insufficient obturation (1), placement of root-end fillings in the roots of almost all the teeth that require root-end resection is needed (2). The aim of placing root-end filling material is to develop an apical seal. The ideal root-end filling material seals the contents of the root canal system within the canal, preventing egress of any bacteria, bacterial by-products, or toxic material into the surrounding periradicular tissues. The material should be nonresorbable, biocompatible, and dimensionally stable over time (3). Numerous materials have been used as root-end fillings, such as zinc oxide– eugenol cements (IRM and Super-EBA), glass ionomer cement, Diaket, composite resins, resin-glass ionomer hybrids, and mineral trioxide aggregate (MTA) (3). A gray MTA was developed at Loma Linda University in 1993 as a root-end filling material and for the repair of lateral and furcal perforations (4, 5). 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 (5–9). When various in vitro leakage models were used, MTA prevented leakage as well as composite resin and glass ionomer cement (10 –12). 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 (13–15). Shahi et al (16) 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 gluconate (CHX) for sterile water in ProRoot MTA (17). Yan et al (18) suggested that 2% CHX has no adverse effect on MTA-dentin bond strength. This could be a potential improvement to the overall therapeutic effect of MTA in endodontics. However, further studies on the physical properties, sealing ability, and biocompatibility of MTA mixed with 0.12% CHX would be needed before advocating its clinical use. Therefore, the purpose of this study was 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 Methods Ninety-six human single-rooted teeth were used in this study. Preoperative radiographs showed absence of multiple canals, calcification, or severe apical curvatures. 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 file (K-file; Maillefer, Ballaigues, Switzerland) into the canals. When the tip of the file was visible at the apex, 0.5 mm short of the file penetration length was

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Basic Research—Technology considered to be the working length. The canals were cleaned and shaped by using the step-back method, and #35 file (K-flexofile; Maillefer) was chosen as the master apical file. The canals were then flared to #60 file (K-flexofile; Maillefer). For the irrigant, 5.25% NaOCl was used. The instrumented canals were dried with paper points (Ariadent, Tehran, Iran) and obturated with laterally condensed gutta-percha (Ariadent) and AH26 sealer (Dentsply, Konstanz, Germany). After removal of the coronal 2 mm of the filling material, the access cavities were closed with Cavit. The roots were wrapped in moist gauze and stored at 37°C and 100% humidity for 1 week. Apical root resections were then performed by removing 3 mm of the apex at a 90-degree angle to the long axis of the root, with a fissure bur (Dentsply, Milford, DE) in a high-speed handpiece with water coolant. Apical cavity preparations 3 mm in depth were made in each root with an ultrasonic device (Spartan Corp, Fenton, MO) with Kis 2-dimensional head (Spartan Corp). Then the teeth were randomly divided into 4 experimental groups, each containing 20 teeth, and 2 positive and negative control groups, each containing 8 teeth. In group A, the apical preparations were filled with gray ProRoot MTA (Dentsply, Tulsa Dental, Tulsa, OK) mixed with distilled water according to the manufacturer’s instructions. In group B, the preparations were filled with gray ProRoot MTA mixed with 0.12% CHX to a putty consistency by using a powder-to-liquid ratio of 3:1. In group C, the preparations were filled with white Pro-Root MTA (Dentsply) mixed with distilled water. In group D, the preparations were filled with White Pro-Root 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. Eight teeth with root-end preparations, but without root-end fillings, were used as positive controls (group E). 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 (group F). Roots were then totally immersed in India ink for 72 hours. The teeth were then rinsed in tap water. Vertical grooves were cut on the buccal and palatal aspects of all the specimens, and the teeth were separated longitudinally. Gutta-percha was removed, and a stereomicroscope was used to assess microleakage. The degree of microleakage was determined by the linear measurement of dye penetration with a stereomicroscope (Zeiss, Munich, Germany) at ⫻16 magnification and 0.1-mm accuracy. The extent of dye penetration into the specimens was measured separately by 2 individuals at 2 different times, and the mean value of the recorded measurements was chosen as the extent of dye penetration into each specimen. The examiners were blinded to which groups they were examining. Statistical analysis was performed with Kruskal-Wallis test and one-way analysis of variance (ANOVA) followed by a post hoc Tukey test. Statistical significance was defined as P ⬍ .05.

Results Complete dye penetration into the prepared root-end cavities was noted in the positive control samples (Figs. 1 and 2). No dye penetration was observed in the negative control samples (Fig. 2). The results of statistical analyses carried out with nonparametric Kruskal-Wallis and one-way ANOVA tests revealed no statistically significant differences between the 4 experimental groups (P ⫽ .684). Post hoc Tukey test, which was used for two-by-two comparison of the groups, demonstrated no statistically significant differences between any 2 groups with respect to microleakage (P ⬎ .05).

Figure 1. Photographs of the experimental and control groups. (A) Gray MTA (GMTA)/W. (B) GMTA/CHX, remained MTA into the root-end cavity (arrow). (C) White MTA (WMTA)/W. (D) WMTA/CHX. (E) Positive control; dye penetration was seen in the entire root-end cavity (arrow). (F) Negative control; no dye penetration was seen.

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Figure 2. Mean of microleakage in the experimental and control groups.

Fig. 2 demonstrates the mean extents of dye penetration in the study groups and the 2 positive and negative control groups.

Discussion 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 (19). Each of these methods has advantages and disadvantages. The dye penetration technique is the easiest and the most frequently used method. Therefore, we used dye penetration for assessing microleakage in the current study. Several studies have reported that India ink is a more reliable and suitable tracer in dye leakage studies when compared with methylene blue (20, 21). 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 (22). Therefore, all the specimens were immersed in India ink for 72 hours. 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 (3–5). 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 (23). In addition, some studies have demonstrated antibacterial properties for MTA (19). Stowe et al (17) have demonstrated in a recent study that MTA has better antibacterial properties when mixed with 0.12% chlorhexidine instead of water. Chlorhexidine is a disinfecting agent that is effective against a wide range of microorganisms including Enterococcus faecalis, Staphylococcus aureus, and Streptococcus salvarius (24). Chlorhexidine can be suitably mixed with MTA instead of water when MTA is used as a retrofilling material, provided its sealing ability and biocompatibility are confirmed. The present study was carried out to evaluate the sealing ability of MTA mixed with CHX. To this end, white and gray MTA were mixed with water and 0.12% CHX. The results demonstrated no statistically significant difference between the sealing abilities of white and gray MTA mixed with water and 0.12% CHX. This finding does not coincide with the results of a study carried out by Matt et al (25). In that study, white and gray MTA were used to form an apical seal in teeth with open apices in an intracanal method, and it was shown that white MTA had a greater microleakage compared with gray MTA. However, the present study did not demonstrate any difference between white and gray MTA with respect to microleakage.

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The different results of the 2 studies might be attributed to differences in the methods used in the studies; in the study carried out by Matt et al, MTA was placed in the root canal as a barrier in an orthograde procedure, but in the present study MTA was placed in a retrograde procedure in the cavities prepared at root end. The difference in results might be attributed to the difference in the methods in which MTA was placed in the root canals and improper packing of the material in the orthograde method. 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-to-solution ratio of 3:1 to achieve a putty consistency (5). 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 (26) 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 hours 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 (27) used implants of MTA mixed with CHX in rat connective tissue and concluded that this mixture is biocompatible. However, further studies are recommended to evaluate the chemical and physical properties of this mixture before it can be safely recommended for clinical use.

Conclusion In the conditions observed in the present study, no statistically significant differences were observed in the sealing ability of gray and white MTA mixed with distilled water and 0.12% CHX, and chlorhexidine appears to be a good alternative to replace water as a solution to be mixed with MTA. However, further studies are recommended before this mixture can safely be used in clinical situations.

Acknowledgments The authors would like to extend their appreciation to the Office of Vice Chancellor for Research, Tabriz University of Medical Science for supporting this research.

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18. Yang P, Peng B, Fan B, Fan M, Bian Z. The effects of sodium hypochlorite (5.25%), chlorhexidine (2%), and Glyde File Prep on the bond strength of MTA-dentin. J Endod 2006;32:58 – 60. 19. Taylor MJ, Lynch E. Microleakage. J Dentist 1992;20:3–10. 20. Oztan MD, Ozgey E, Zaimoglu L, Erk N. Effect of particle sizes in India ink on its use in evaluation of apical seal. J Oral Sci 2001;43:245– 8. 21. Yashikawa M, Nogochi K, Toda T. Effect of particle sizes in India ink on its use in evaluation of apical seal. J Osaka Dent Univ 1997;31:67–70. 22. Higa RK, Torabinejad M, McKendry DJ, McMillan PJ. The effect of storage time on the degree of dye leakage of root-end filling materials. Int Endod J 1994;27:252– 6. 23. 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. 24. Estrela C, Bammann LL, Estrela CR, Silva RS, Recora JD. Antimicrobial and chemical study of MTA, Portland cement, calcium hydroxide paste, Sealapex and Dycal. Braz Dent J 2000;11:3–9. 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. 26. Kogan P, He J, Glickman GN, Watanabe I. The effects of various additives on setting properties of MTA. J Endod 2006;32:569 –72. 27. Sumer M, Muglali M, Bodrumlu E, Guvenc T. Reactions of connective tissue to amalgam, intermediate restorative material, mineral trioxide aggregate and mineral trioxide aggregate mixed with chlorhexidine. J Endod 2006;32:1094 – 6.

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