Mahmoud Torabinejad

Physical and chemical properties of a new root-end filling material.

This study determined the chemical composition, pH, and radiopacity of mineral trioxide aggregate (MTA), and also compared the setting time, compressive strength, and solubility of this material with those of amalgam, Super-EBA, and Intermediate Restorative Material (IRM). X-ray energy dispersive spectrometer in conjunction with the scanning electron microscope were used to determine the composition of MTA, and the pH value of MTA was assessed with a pH meter using a temperature-compensated electrode. The radiopacity of MTA was determined according to the method described by the International Organization for Standardization. The setting time and compressive strength of these materials were determined according to methods recommended by the British Standards Institution. The degree of solubility of the materials was assessed according to modified American Dental Association specifications. The results showed that the main molecules present in MTA are calcium and phosphorous ions. In addition, MTA has a pH of 10.2 initially, which rises to 12.5 three hours after mixing. MTA is more radiopaque than Super-EBA and IRM. Amalgam had the shortest setting time (4 min) and MTA the longest (2 h 45 min). At 24 h MTA had the lowest compressive strength (40 MPa) among the materials, but it increased after 21 days to 67 MPa. Finally, except for IRM, none of the materials tested showed any solubility under the conditions of this study.

Clinical applications of mineral trioxide aggregate

An experimental material, mineral trioxide aggregate (MTA), has recently been investigated as a potential alternative restorative material to the presently used materials in endodontics. Several in vitro and in vivo studies have shown that MTA prevents microleakage, is biocompatible, and promotes regeneration of the original tissues when it is placed in contact with the dental pulp or periradicular tissues. This article describes the clinical procedures for application of MTA in capping of pulps with reversible pulpitis, apexification, repair of root perforations nonsurgically and surgically, as well as its use as a root-end filling material.

Sealing ability of a mineral trioxide aggregate when used as a root end filling material.

This in vitro study used rhodamine B fluorescent dye and a confocal microscope to evaluate the sealing ability of amalgam, super EBA, and a mineral trioxide aggregate when used as root end filling materials. Thirty single-canal teeth were cleaned, shaped, and obturated with gutta-percha and root canal sealer. After application of nail polish to the external surface, the apical 3 mm of each root was resected and 3-mm deep root end preparations were made. The roots were randomly divided into three groups and the root end preparations filled with the experimental materials. All roots were then exposed to an aqueous solution of rhodamine B fluorescent dye for 24 h, longitudinally sectioned, and the extent of dye penetration measured using a confocal microscope. Statistical analysis showed that the mineral trioxide aggregate leaked significantly less than amalgam and super EBA.

Mineral Trioxide Aggregate: A Comprehensive Literature Review—Part III: Clinical Applications, Drawbacks, and Mechanism of Action

INTRODUCTION Mineral trioxide aggregate (MTA) has been recommended for various uses in endodontics. Two previous publications provided a comprehensive list of articles from November 1993-September 2009 regarding the chemical and physical properties, sealing ability, antibacterial activity, leakage, and biocompatibility of MTA. The purpose of Part III of this literature review is to present a comprehensive list of articles regarding animal studies, clinical applications, drawbacks, and mechanism of action of MTA. METHODS A review of the literature was performed by using electronic and hand-searching methods for the clinical applications of MTA in experimental animals and humans as well as its drawbacks and mechanism of action from November 1993-September 2009. RESULTS MTA is a promising material for root-end filling, perforation repair, vital pulp therapy, and apical barrier formation for teeth with necrotic pulps and open apexes. Despite the presence of numerous case reports and case series regarding these applications, there are few designed research studies regarding clinical applications of this material. MTA has some known drawbacks such as a long setting time, high cost, and potential of discoloration. Hydroxyapatite crystals form over MTA when it comes in contact with tissue synthetic fluid. This can act as a nidus for the formation of calcified structures after the use of this material in endodontic treatments. CONCLUSIONS On the basis of available information, it appears that MTA is the material of choice for some clinical applications. More clinical studies are needed to confirm its efficacy compared with other materials.

In Vitro Bacterial Penetration of Coronally Unsealed Endodontically Treated Teeth

Forty-five root canals were cleaned, shaped, and then obturated with gutta-percha and root canal sealer, using a lateral condensation technique. The coronal portions of the root filling materials were placed in contact with Staphylococcus epidermidis and Proteus vulgaris. The number of days required for these bacteria to penetrate the entire root canals was determined. Over 50% of the root canals were completely contaminated after 19-day exposure to S. epidermidis. Fifty percent of the root canals were also totally contaminated when the coronal surfaces of their fillings were exposed to P. vulgaris for 42 days.

Mineral Trioxide Aggregate: A Comprehensive Literature Review—Part II: Leakage and Biocompatibility Investigations

INTRODUCTION Mineral trioxide aggregate (MTA) was developed because existing materials did not have the ideal characteristics for orthograde or retrograde root-end fillings. MTA has been recommended primarily as a root-end filling material, but it has also been used in pulp capping, pulpotomy, apical barrier formation in teeth with open apexes, repair of root perforations, and root canal filling. Part I of this literature review presented a comprehensive list of articles regarding the chemical and physical properties as well as the antibacterial activity of MTA. The purpose of part II of this review is to present a comprehensive list of articles regarding the sealing ability and biocompatibility of this material. METHODS A review of the literature was performed by using electronic and hand-searching methods for the sealing ability and biocompatibility of MTA from November 1993-September 2009. RESULTS Numerous studies have investigated the sealing ability and biocompatibility of MTA. CONCLUSIONS On the basis of available evidence it appears that MTA seals well and is a biocompatible material.

Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys

Mineral Trioxide Aggregate (MTA) has been shown in a number of experiments to be a potential root-end filling material. The purpose of this study was to examine the periradicular tissue response of monkeys to MTA and amalgam as root-end fillings. The pulps were removed from all the maxillary incisors of three monkeys. The root canals were prepared and filled with laterally condensed guttapercha and sealer, and the access cavities were restored with amalgam. Buccal mucoperiosteal flaps were raised, and root-end resections were performed before root-end cavity preparation with burs. The root-end cavities in half of the teeth were filled with MTA, while amalgam was placed in the other cavities. After 5 months the periradicular tissue response was evaluated histologically. The results showed no periradicular inflammation adjacent to five of six root ends filled with MTA; also five of six root ends filled with MTA had a complete layer of cementum over the filling. In contrast, all root ends filled with amalgam showed periradicular inflammation, and cementum had not formed over the root-end filling material, although it was present over the cut root end. Based on these results and previous investigations, MTA is recommended as a root-end filling material in man.

Investigation of mineral trioxide aggregate for root-end filling in dogs

Numerous compounds have been used as root-end filling materials. Based on the results of in vitro and intraosseous implantation tests, mineral trioxide aggregate (MTA) seems to have potential as a root-end filling material. The purpose of this study was to examine the periradicular tissue response of dogs to MTA and amalgam. Lesions were developed in periradicular tissues of 46 roots in six beagle dogs. The canals on half of the roots were instrumented and obturated with gutta-percha and sealer, and their access cavities were sealed with MTA. The remaining root canals were instrumented and obturated with gutta-percha and sealer, and their access cavities were sealed with MTA. The remaining root canals were instrumented and obturated with gutta-percha without root canal sealer. The access cavities of the teeth in this group were left open to the oral cavity. After surgical resection of roots, half of the root-end cavities were filled with amalgam and the rest with MTA. The periradicular tissue response of the dogs was evaluated histologically 2 to 5 and 10 to 18 wk following periradicular surgery. Statistical analysis of the results showed less periradicular inflammation and more fibrous capsules adjacent to MTA, compared with amalgam. In addition, the presence of cementum on the surface of MTA was a frequent finding. The results show that MTA can be used as a root-end filling material.

Dye leakage of four root end filling materials: Effects of blood contamination

The purpose of this study was to compare the amount of dye leakage (in the presence versus absence of blood) in root end cavities filled with amalgam, Super EBA, IRM, and a mineral trioxide aggregate. After removing the anatomical crowns of 90 extracted human teeth, their roots were instrumented and obturated. Except for their apical 2 mm, the root surfaces were sealed with nail polish. After removal of the apical 2 to 3 mm of each root, a standardized root end cavity was prepared. Five root ends were filled with gutta-percha and no sealer, and another five root ends were filled with sticky wax. These served as positive and negative controls, respectively. The remaining 80 roots were divided into four equal groups and filled with the test materials. For each material, half of the root end cavities were dried prior to placing the filling material. The remaining half were filled after they were contaminated with blood. All 90 roots were then immediately placed in 1% methylene blue dye for 72 h. Finally, the roots were split and linear dye penetration was measured and statistically analyzed (analysis of variance). Presence or absence of blood had no significant effect on the amount of dye leakage. However, the results showed that there was a significant leakage difference between the root end filling materials (p < 0.0001). Mineral trioxide aggregate leaked significantly less than other materials tested with or without blood contamination of the root end cavities.

A New Solution for the Removal of the Smear Layer

Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) as a final rinse on the surface of instrumented root canals. Forty-eight extracted maxillary and mandibular single-rooted human teeth were prepared by using a combination of passive step-back and rotary 0.04 taper nickel-titanium files. Sterile distilled water or 5.25% sodium hypochlorite was used as intracanal irrigant. The canals were then treated with 5 ml of one of the following solutions as a final rinse: sterile distilled water, 5.25% sodium hypochlorite, 17% EDTA, or a new solution, MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that MTAD is an effective solution for the removal of the smear layer and does not significantly change the structure of the dentinal tubules when canals are irrigated with sodium hypochlorite and followed with a final rinse of MTAD.