Clinical applications of mineral trioxide aggregate

Clinical applications of mineral trioxide aggregate

JOURNALOF ENDODONTICS Copyright © 1999 by The American Association of Endodontists Printed in U.S.A. VOL. 25, No. 3, MARCH 1999 Clinical Application...

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JOURNALOF ENDODONTICS Copyright © 1999 by The American Association of Endodontists

Printed in U.S.A. VOL. 25, No. 3, MARCH 1999

Clinical Applications of Mineral Trioxide Aggregate Mahmoud Torabinejad, DMD, MSD, PhD, and Noah Chivian, DDS, FICD, FAC

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.

include microleakage, varying degrees of toxicity, and sensitivity to the presence of moisture (3). Recently, a material called mineral trioxide aggregate (MTA) has been investigated as a potential compound to seal off the pathways of communication between the root canal system and the external surface of the tooth. MTA is a powder that consists of fine hydrophilic particles that sets in the presence of moisture (4). Hydration of the powder results in a colloidal gel with a pH of 12.5 that solidifies to a hard structure. The setting time for the cement is --4 h. The compressive strength of MTA at 21 days is - 7 0 MPa, which is comparable with that of IRM and Super-EBA, but significantly less than amalgam (311 MPa). In vitro and in vivo experiments have compared the sealing ability and biocompatibility of MTA with those of amalgam, Super-EBA, and IRM. The sealing ability of MTA has been shown in dye and bacterial leakage studies to be superior to that of amalgam and to be equal or better than Super-EBA (3, 5-8). The cytotoxicity of MTA was investigated, using the agar overlay and radio chromium release methods (9) and was found to be less than that of IRM or Super-EBA. With implantation of MTA in the tibias and mandibles of guinea pigs, the tissue reaction to MTA implantation was the most favorable observed at both sites. As in every specimen, it was free of inflammation. In the tibia, MTA was the material most often observed with direct bone apposition (10).

The dental pulp communicates with the periodontium through the apical foramen and via lateral canal(s). The periodontium consists of cementum, the periodontal ligament, and the alveolar bone. The pulp and the periodontium are physically separated from the oral flora by enamel, dentin, and gingival attachment. Exposure of the dental pulp and periradicular tissues to microorganisms results in the development of pulpal and periradicular pathosis. Investigators using experimental animals have shown the absence of pulpal and periradicular pathosis in germ-free conditions and development of lesions when these tissues were exposed to bacteria (1, 2). Microorganisms are the main irritants of the dental pulp and the periodontium. To preserve vitality of pulp tissue and prevent pathological changes in the periradicular tissues, mechanical pulp exposures and carious pulp exposures in teeth with immature apexes without signs of irreversible pulpitis must be sealed. In addition, pathways of communication between the root canal system and the periodontium, such as iatrogenic perforations, must also be sealed with restorative materials that prevent bacterial leakage. Because these materials come in contact with vital tissues they must also be biocompatible and should favor regeneration of the involved tissues to their prediseased status. Many materials have been used to seal the pathways of communication between the root canal system and the oral cavity, as well as the periradicular tissues. These include amalgam, zinc oxide-eugenol-based cements such as Super-EBA (Harry J. Bosworth Co., Skokie, IL) and IRM (L. D. Caulk Co., Milford, DE), Cavit (ESPE America, Norristown, PA), composite resins, and glass ionomer cements. The main disadvantages of these materials

FIG 1. Histological section of a mandibular incisor of a monkey demonstrating a complete dentin bridge (DB) formation and lack of inflammation in the pulp tissue after application of MTA as a pulpcapping material after mechanical exposure (hematoxylin and eosin stain; original magnification ×50). Permission from ADA Publishing Company, Inc. 197

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FIG 2. (A) A preoperative radiograph of the first mandibular right molar with decay, open apexes, and no symptoms of irreversible pulpitis. (B) Removal of decay, pulp capping with MTA, and placement of amalgam as the final restoration. (C) A 3-y postoperative radiograph showing closure of the apexes and lack of periradicular pathosis.

Furthermore, the use of MTA as a root-end filling material in dogs and monkeys provided superior results, compared with amalgam, and it had an inductive effect on cementoblasts (11, 12). In addition, MTA has been used as a capping material in mechanically exposed pulps (13), for root-end induction (14, 15), repair of root perforation (16, 17), and as a ban'ier during internal bleaching of endodontically treated teeth (18). Based on these experiments, it

seems that MTA has several potential clinical applications. The purpose of this article is to describe the indications and procedures tot various clinical applications of MTA.

MIXING MTA MTA should be prepared immediately before its use. MTA powder must be kept in containers with tight lids and away from

FIG 3. Cementum (C) formation after obturation of a cleaned and shaped canal of a mandibular premolar of a dog with MTA (Masson trichrome stain; original magnification ×50). Courtesy of Dr, Shahrokh Shabahang.

F~G4. (A) A preoperative radiograph of a maxillary left central incisor with an open apex. (B) Placement of 3 to 4 mm of an MTA plug after complete instrumentation. (C) Obturation of the rest of the canal and the access cavity preparation with a composite-bonded resin. (D) A 6-month postoperative radiograph immediately after extraction of the impacted cuspid. Courtesy of Dr. Marshall Gomes.

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moisture. The powder should be mixed with sterile water at a ratio of 3:1 on a glass or paper slab with the aid of plastic or metal spatulas. The mixture can be carried in a plastic or metal carrier to its intended site of the operation. If the area of application is very wet, the extra moisture can be removed with a dry piece of gauze or foam. In cases where the mixture is very dry, more water can be added to the dry mix. Because M T A requires the moisture to set, leaving the mixture on a glass or paper slab will result in dehydration of the material and a dry sandy mixture. After its use, the mixture can be washed off the slab with running water.

Vital Pulp Therapy FIG 5. Furcation perforation of a mandibular premolar of a dog that was repaired with MTA. Note the formation of cementum and lack of inflammation in the periodontal ligament even after extrusion of MTA into the furcation (hematoxylin and eosin stain; original magnifica-

Cox and associates (19) investigated the biocompatibility of silicate cement, zinc phosphate cement, amalgam, and composites on pulps of monkeys with and without surface seal with zinc

FIG 6. (A) A preoperative photograph showing growth of granulation tissue into the pulp chamber of a mandibular right first molar after a long-standing furcation perforation. (B) A postoperative radiograph of the tooth after removal of the granulation tissue, repair of the perforation with MTA, and placement of IRM as a temporary filling material. (C) A postoperative radiograph showing retreatment of previous root canal treatment and improvement of furcation lesion after 3 months. (D) Postoperative radiograph demonstrating complete resolution of the furcation lesion after 9 months. Courtesy of Dr. Randall Garland.

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FIG 7. (,4) A preoperative radiograph of a mandibular right first molar with a large midroot post perforation, (B) A clinical photograph showing the presence of pus at the perforation site and the extent of it after removal of the post (arrows). (C) A postoperative radiograph showing retreatment of the previous root canal therapy and repair of the perforation with MTA. (D) A postoperative radiograph showing complete repair of the perforation site 31/2yr later. Courtesy of Dr. Douglas McKendry.

oxide-eugenol cement. Their results indicate that the healing of dental pulp exposures is not dependent on the pulp-capping material, but is related to the capacity of these materials to prevent bacterial leakage. Because MTA has been shown to prevent dye and bacterial leakage (3, 5-8) and has a high level of biocompatibility (9), it was used as a pulp-capping material in mechanically exposed pulps of monkeys (13). The results of this study showed that MTA stimulates dentin bridge formation adjacent to the dental pulp (Fig. I). Dentinogenesis of MTA can be due to its sealing ability, biocompatibility, alkalinity, or possibly other properties associated with this material (13).

INDICATIONS Pulp capping and pulpotomies are indicated only in teeth with immature apexes when the dental pulps are exposed, and pulp vitality should be maintained. These procedures are contraindicated in teeth with signs and symptoms of irreversible pulpitis.

CLINICAL PROCEDURES After obtaining anesthesia and application of a rubber dam, rinse the exposed pulp with diluted NaOCl. In pulpotomy cases, the coronal pulp should be removed with a large diamond bur in a high-speed handpiece and constant water spray. Rinse the cavity and exposure site(s) with diluted NaOC1. Heavy bleeding from the exposure site(s) can be controlled with a cotton pellet moistened with NaOCI. Mix MTA powder with sterile water and place the mixture in the access cavity with a large plastic amalgam carrier. Pad the mixture against the exposures site(s) with a moist cotton pellet. Place a moist cotton pellet on the MTA and fill the rest of the cavity with a temporary filling material. In compliant patients, fill the entire cavity with MTA, place a wet piece of gauze between the treated tooth and the opposing teeth, and ask the patient not to use that side for 3 to 4 h. Because MTA has low compressive strength (4) and cannot be used as a permanent filling material, remove the coronal 3 to 4 mm of MTA 1 wk later and place the final restoration over set MTA. Assess the vitality and status of the

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FIG 8. (,4) A preoperative radiograph of a maxillary right central incisor with an extensive internal resorption perforating to the external surface of the tooth after entering into the root canal. (B) A postoperative radiograph after cleaning and shaping the root canal, obturation of the apical portion of the root canal with gutta-percha and sealer apical to the defect, as well as filling the resorptive defect with MTA and closing the access cavity with a composite resin. (C) A postoperative radiograph showing the absence of periradicular pathosis 18 months later. Courtesy of Dr. John Stropko.

pulp clinically and radiographically every 3 to 6 months as needed (Fig. 2). Root canal therapy can be performed if needed after vital pulp treatments.

Apical MTA Plug Several materials have been used as intracanal medications to create a hard tissue formation or as an apical plug to prevent extrusion of filling materials during obturation of the teeth with open apexes (14). Recently, in two separate investigations, MTA was used as an apical plug in immature premolars of dogs that had been purposely infected and then disinfected with calcium hydroxide (14, 15). The results of these investigations showed that MTA induced apical hard tissue formation more often, and its use was associated with less inflammation than the other test materials (Fig. 3). Based on these results, it seems that MTA can be used as an apical barrier in teeth with immature apexes.

INDICATIONS Apical plug is indicated in teeth with necrotic pulps and open apexes.

CLINICAL PROCEDURES After obtaining anesthesia, application of a rubber dam, and preparing an adequate access preparation, the root canal system should be cleaned using intracanal instruments and NaOCI irrigation. To disinfect the root canal, a calcium hydroxide paste should be placed in the root canal for 1 wk. After rinsing calcium hydroxide from the root canal with NaOCI and drying it with paper points, mix the MTA powder with sterile water and carry the mixture with a large amalgam carrier to the canal. Condense the MTA mix to the apical end of the root with pluggers or paper

points. Create a 3 to 4 mm apical plug of MTA and check its extension radiographically. If creation of an ideal plug fails in the first attempt, rinse out the MTA with sterile water and repeat the procedure. Place a moist cotton pellet in the canal and close the access cavity preparation with a temporary restoration material for at least 3 to 4 h. Obturate the rest of the canal with gutta-percha or a composite-bonded resin in teeth with thin walls as indicated and seal the access cavity with a final restoration (Fig. 4). Assess periradicular healing clinically and radiographically as indicated.

Repair of Root Perforations Root perforations can occur during root canal therapy or post space preparation and also as a result of the extension of an internal resorption into the periradicular tissues. PerfOration repair after an accidental procedure or as a consequence of an internal resorption can be achieved intracoronally and/or by an external surgical approach. Materials such as Cavit, zinc oxide-eugenol, calcium hydroxide, amalgam, gutta-percha, tricalcium phosphate, and hydroxyapatite have been used to repair root perforations (16). In an in vitro study, Lee and associates (161 compared the sealing ability of MTA with that of amalgam o1 IRM for repair of experimentally induced root perforations in extracted teeth. The results showed that MTA had significantly less leakage than IRM or amalgam, and it showed the least overfilling tendency whereas IRM had the least underfilling tendency. In a recent study, Nakata and associates (8) compared the effectiveness of MTA and amalgam in repairing furcal perforations using a dual-chambered, anaerobic bacterial leakage model and reported that MTA was superior to amalgam in preventing leakage of Fusobacterimn nucleatum past furcal perforation repairs. Pitt Ford and co-workers (17) examined the histological response of intentional perforations in the furcations of mandibular premolars of dogs repaired with MTA or amalgam. In the immediately repaired group, all the amalgam specimens were associated with inflammation, whereas only I of 6 samples with

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FIG 9. (A) A preoperative radiograph of a maxillary left central incisor with a sectional silver point and a distolingual post perforation. (B) A clinical photograph of the tooth after its rotation with a forceps and determining the extent of the perforation (arrows). (C) A postoperative radiograph after repair of the perforation with MTA. (D) A postoperative radiograph showing resolution of the lateral lesion 5 yr later.

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Boca Raton, FL) or a small amalgam carrier and packed with small pluggers or paper points. A 3 to 5 mm apical plug is needed to prevent coronal leakage and extrusion of obturation material into the periapical tissues. After inducing an apical plug, place a wet cotton pellet against it and close the access cavity with a temporary filling material. Remove the cotton pellet at least 3 to 4 h later and obturate the rest of the canal with gutta-percha and root canal sealer. In cases with a large apical perforation, and ample moisture, placement of the apical plug and obturation of the root canal system can be accomplished in one visit.

Repair of Perforations as a Consequence of an Internal Resorption-After obtaining anesthesia and preparing the access cavity,

FIG 10. A histological section of a maxillary central incisor of a monkey after periapical surgery and use of MTA as root-end filling material showing formation of cementum (C) over resected root-end surfaces and MTA. Note the presence of normal periodontal ligament and bone adjacent to the newly formed cementum (hematoxylin and eosin stain; original magnification x50).

MTA was inflamed. Furthermore, the five noninflamed MTA specimens had some cementum over the repair material (Fig. 5). In the delayed group, all the amalgam samples were associated with inflammation; in contrast only 4 of 7 filled with MTA were inflamed. Based on the results of these studies (16, 17), it seems that MTA is a suitable material for perforation repair.

INDICATIONS Repair of roots is indicated after perforation during root canal therapy, post space preparation, or as a consequence of internal resorption. This can be achieved through the access cavity (intracanal repair) or by surgical intervention (extracoronal repair).

CLINICAL PROCEDURES

lntracanal Repair of Accidental Perforations--After obtaining anesthesia, application of rubber dam and locating the perforation site, the area should be rinsed thoroughly with diluted NaOC1. In cases of long-standing perforations or in the presence of contamination, NaOC1 should be left in the root canal system for a few minutes to disinfect the site of the perforation. After complete instrumentation and obturation of the canals with gutta-percha and root canal sealer apical to perforation sites (furcation and stripping), mix MTA with sterile water and place it at the perforation site with an amalgam carrier and pack it against the site with a plugger or a cotton pellet. After repairing the perforation area with MTA, place a wet cotton pellet over MTA and seal the access cavity with a temporary filling material. Remove the temporary and the wet cotton pellet at least 3 to 4 h, later and place a permanent filling material in the root and/or in the access cavity preparation. When MTA is placed in perforations with a high degree of inflammation, the material remains soft when checked at the second appointment. This is due to the presence of low pH, which prevents proper setting of MTA. In these cases, rinse out the MTA and repeat the procedure. Assess the healing in 3 to 6 months as indicated (Figs. 6 and 7). For apical perforations, mixed MTA should be placed into the apical portion of the canal with a messing gun (R. Chige, Inc.,

the root canal should be completely cleaned and shaped. Because of the presence of granulation tissue and the presence of communication between the root canal and the periodontium, heavy hemorrhage is usually encountered during the instrumentation of these cases. Use of NaOC1 during cleaning and shaping and placement of calcium hydroxide paste between appointments reduce excessive bleeding. After rinsing calcium hydroxide from the canal with NaOC1 at the next appointment, obturate the apical portion of the canal with a sectional obturation technique with gutta-percha and root canal sealer. Place MTA mixture in the defect and condense it with the aid of pluggers and cotton pellets. Place a wet cotton pellet over MTA and close the access cavity with a temporary filling material. Remove the temporary and cotton pellet at least 3 to 4 h later and place a permanent filling in the access cavity. Assess the healing as indicated (Fig. 8). Surgical Repair of Perforations--When repair of perforations fails after an intracanal approach or if the perforations are inaccessible through the access cavity, surgical repair of these accidents is indicated.

CLINICAL PROCEDURES After raising a flap and locating the site of the perforation, the defect should be modified with a small bur if indicated. Because MTA does not set for 3 to 4 h, it is imperative to control the hemorrhage completely before making any attempt to repair the perforated site. Presence of excessive moisture in the field of operation causes the material to be very soft and unmanageable. After mixing MTA powder with sterile water, place the mixture in the prepared cavity and condense it well with a plugger. Remove the excess with a spoon excavator and/or with a piece of wet gauze or Telfa (Kendall Health Care Co., Mansfield, MA). Do not rinse the area after placing MTA in the perforation site. Suture the soft tissue flap in place and assess the healing as indicated (Fig. 9).

ROOT-END FILLING Numerous substances have been used as root-end filling materials (11, 12). The main disadvantage of these materials include their inability to prevent egress of irritants from infected root canals into the periradicular tissues, lack of complete biocompatibility with vital tissues, and their inability to promote regeneration of the periradicular tissues to their prediseased status and normalcy. In two separate investigations, the efficacy of MTA was compared with amalgam as a root-end filling material in dogs and monkeys (11, 12). The results of these investigations showed significant differences between the two materials. The use of MTA

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FIG 1 1. (A) A preoperative radiograph of a left central incisor with a large threaded post extending to the apical foramen and a periradicular lesion. (B) A postoperative radiograph after periapical surgery and use of MTA as root-end filling material. (C) A postoperative radiograph showing periradicular healing 15 months later.

as root-end filling material was associated with significantly tess inflammation, cementum formation over MTA, and regeneration of the periradicular tissues to almost normal pre-experimental status (Fig. 10).

Indications Placement of root-end filling materials is indicated to prevent penetration of irritants from the root canal system into the periradicular tissues.

Clinical Procedures After raising a soft tissue flap, ostectomy, root-end resection, and root-end preparation, periradicular hemorrhage should be controlled. A lack of moisture control and presence of excessive bleeding during placement of M T A in the root-end cavity makes M T A very soft and unmanageable. With the use of a small carrier (0.9 mm RR Carrier, Chige, Inc., Boca Raton, FL), place a mixture of M T A into the root-end cavity and condense it with a small plugger. After complete filling of the root-end cavity, remove and clean the surface of the resected root and MTA mixture with a wet piece of gauze or telfa. Because M T A sets in the presence of moisture, create some hemorrhage from the periradicular ligament and bone and bring the blood over the resected root end and MTA. Do not rinse the field of operation after placement of MTA in the root-end cavity preparation. Suture the soft tissue flap and assess the healing as indicated (Fig. 11).

obturation of the root canal system and before internal bleaching of discolored teeth (18). For these uses, place a 3 to 4 mm thickness of MTA mixture in the prepared cavity. Place a wet cotton pellet over the mixture and fill the rest of the cavity with a temporary filling material. Place a permanent filling material in the access cavity at least 3 to 4 h later as indicated. As a temporary filling material, after placing a wet cotton pellet in the pulp chamber, fill the rest of the access cavity with MTA mixture and place a wet piece of gauze between the occlusa] surface of the operated tooth and the opposing tooth (teeth). Ask the patient not to use that side for 3 to 4 h. Remove the set MTA with a round bur the next appointment. To repair a vertical fracture, remove the root canal filling material fiom the treated root(s) and bond the pieces internally with composite bonded resin. After raising a flap or extracting the tooth for an intentional replant, groove the entire vertical fracture to the composite with a small bur under constant water spray. Place MTA in the groove, cover it with a resorbable membrane, and suture the soft tissue flap. To improve the prognosis of these cases. the patients should be instructed to follow meticulous oral hygiene and the treated tooth should not be probed for at least 12 wk. Despite its success in some cases in the repair of vertical fractures (Fig. 12), the use of MTA in cases where MTA comes in direct contact with the oral cavity for an extended period of time is unpredictable. This is due to the fact that MTA dissolves in an acidic pH.

Note: Consent forms were signed by the patients or their guardians before MTA was used in the clinical cases.

OTHER USES Because MTA provides an effective seal against penetration of dyes and bacteria (3, 5 - 8 ) and their metabolites such as endotoxins (20), it can be used as a coronal (3 to 4 mm) plug alter complete

Dr. Torabineiad is professor of Endodontics and director of Graduate Endodontics, Loma Linda University School of Dentistry, Loma Lind& CA. Dr. Chivian is director of Dentistry, Newark Beth Israel Medical Center, Newark, NJ. Address requests for reprints to Dr. Mahmoud Torabinejad, Department of Endodontics, School of Dentistry, Loma Linda University, Loma Linda, CA 92350.

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FIG 12. (A) A preoperative radiograph of a mandibular left second molar with a previous root canal treatment, periradicular lesions, and a vertical fracture extending to the apex of the mesiobuccal root. (B) A clinical photograph showing MTA in the grooved vertical fracture (arrows) and in the root-end cavity preparation. (C) A postoperative radiograph after periradicular surgery, repair of the vertical fracture with MTA, and placement of a resorbable membrane. (D) A postoperative radiograph 9 months later showing complete resolution of the lesions. No probable periodontal pocket was present at the 3-month check-up appointment and thereafter. Courtesy of Dr. Luciana Camargo.

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tion of mineral trioxide aggregate for root end filling in dogs. J Endodon 1995;21:603- 8. 12. Torabinejad M, Pitt Ford TR, McKendry DJ, Abedi HR, Miller DA, Kariyawasen SP. Histologic assessment of MTA as root end filling in monkeys. J Endodon 1997;23:225-8. 13. Pitt Ford TR, Torabinejad M, Abedi HR, Bakland LK, Kariyawasam SP. Mineral trioxide aggregate as a pulp capping material. J Am Dent Assoc 1996;127:1491-4. 14. Torabinejad M, Shabahang S, Boyne PJ, Abedi HR, McMillan P. A comparative study of root-end induction using osteogenic protein-I, calcium hydroxide, and mineral trioxide aggregate in dogs. J Endodon (in press) 15. Tittle KW, Farley J, Linkhardt T, Torabinejad M. Apical closure induction using bone growth factors and mineral trioxide aggregate [Abstract #41]. J Endodon 1996;22:198. 16. Lee SJ, Monsef M, Torabinejad M. The sealing ability of a mineral trioxide aggregate for repair of lateral root perforations. J Endodon 19:54144, 1993. 17. Pitt Ford TR, Torabinejad M, Hong CU, Kariyawasam SP. Use of mineral trioxide aggregate for repair of furcal perforations. Oral Surg 1995; 79:756-63. 18. Cummings GR, Torabinejad M. Mineral trioxide aggregate (MTA) as an isolating barrier for internal bleaching [Abstract ~53]. J Endodon 1995;21:228. 19. Cox CF, Keall CL, Keal HJ, Ostro E, Bergenholtz G. Biocornpatibility of surface-sealed dental materials against exposed pulp. Prosthet Dent 1987; 57:1-8. 20. Tang HM, Torabinejad M. Endotoxin leakage of four root-end filling materials [Abstract #42]. J Endodon 1997;23:259.