Introduction It was introduced by Mahmoud Torabinejad and colleagues at Lomalinda University in 1993. Has been used on experimental basis by endodontists for several years with anecdotally reported successes, some of it quite impressive. It was approved for the human usage by the FDA in 1998. The material appears to be an improvement over other materials for some endodontic procedures that involve root repair and bone healing.
MTA may be ideal material for use against bone, because it’s the only material that consistently allows for the overgrowth of cementum and formation of bone and may facilitate the regeneration of periodontal ligament
MTA should be prepared immediately before its use. MTA powder should be kept in container with tight lids and away from 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 a metal or plastic spatula, the mixture can be carried in a metal or plastic carrier to its intended site of the operation.
After complete filling of the root end cavity, the surface of the resected root and MTA mixture is cleaned with a wet piece of gauze or telfa.
Because MTA sets in the presence of moisture some hemorrhage is created from the periodontal ligament and bone and blood is brought over the resected root end and MTA. The field of operation is not rinsed. Soft tissue flap is sutured and the healing is assessed periodically.
Koh et al in 1997 used set MTA in their study of biological response of human osteoblasts to the material. They found that MTA caused an increase in the production of interlukin (IL)-1 , IL -1 , IL-6 and osteocalcin.
IL-1 and IL -1 interact with receptors on osteoblasts, which in turn activate osteclasts. Second only to collagen, osteocalcin is an abundant protein, which is present in bone and may be an indicator of bone matrix production
Super EBA was very popular in the 1990’s and was slowly replacing amalgam as “the” material in the endodontic practice. MTA is relatively a new material that became available in the late 1990’s.This material appears to be the most promising to date, as it comes closest to being the ideal material for retrofilling and the results of reported are indeed impressive.
Because of these disadvantages, Zinc oxide eugenol based such as Super EBA and IRM have been advocated as root end filling materials. The potential disadvantages however, of Zinc oxide eugenol based cements include:
Irritation of vital tissue.
Difficulty in clinical handling of material.
Inability to promote regeneration of the periradicular tissues to their prediseased state and normalcy.
In two separate investigations, Torabinejad etal; compared the efficacy of MTA with amalgam as a root end filling material in dogs and monkeys. The results of these investigations showed significant differences between the two materials.
The use of MTA as root end material was associated with significantly less inflammation, cementum formation over MTA, and regeneration of the periradicular tissues to almost normal pre experimental status.
Keiser et al used the human periodontal ligament fibroblasts to evaluate the cytotoxicity of MTA and compared with amalgam and SuperEBA and found that in both freshly mixed as well as set state, the MTA was less toxic.
The process of placing MTA in an orthograde manner and then resecting the set material with a high-speed handpiece apparently does not significantly disturb the apical seal of MTA and has no significant bearing on the subsequent apical tissue regeneration.
The ultimate success of the surgery depends on the regeneration of a functional periodontal attachment apparatus, including cementum overlying the resected root end surface, periodontal attachment and alveolar bone
Caries Resorptive processes Iatrogenically induced like misdirected bur during access preparation and during preparation of post space. Excessive flaring of cervical portion of curved roots in molars can cause lateral root perforations Strip perforations during preparation of curved canals
Historically, materials used to repair root perforations have been associated with the formation of a fibrous connective tissue capsule a contact with the adjacent bone at best.
In fact, formation of a periodontal defect has been a more common finding adjacent to the majority of previously used materials.
A characteristic that differentiates MTA from other materials is its ability to promote regeneration of cementum, despite its extrusion in to the periradicular tissues, thus facilitating regeneration of periodontal apparatus.
For successful treatment of such defect, the root surface should be reconstructed in order to allow reattachment of periodontal ligament. Success of such treatment obviously depends on elimination of bacteria from the root canal system and the perforation site.
. Lemon et al (1992) introduced the “internal matrix concept” for treatment of root perforations. He recommended the use of amalgam for sealing the perforation, which would be condensed against an external matrix of hydroxyapatite, carefully pushed through the perforation thus serving as an external barrier of matrix.
It is described by C.Bargholz for perforation repair with MTA in an article published in 2005.
For application of MTA, no such pressure resistant support is necessary. Freshly mixed MTA has a soft consistency and may be applied without pressure. Small pieces of Collagen (Kollagen-Resorb; Resorba, Nuremberg, Germany.) are used to push the granulation tissue out of the perforation and keep it in place outside the root.
MTA may be layered against the collagen until the perforation is repaired. For this process no pressure is required at any time due to the consistency of the material.
Direct observation of the material site through the operating microscope is very helpful to avoid inadvertent blockage of the still empty root canal space with MTA to confirm correct placement of the repair material.
Following application of the collagen the sealed perforation and the newly accomplished reconstruction of the root surface are monitored radiographically.
Different leakage models have been used in the past to assess the ability of materials to seal furcation perforations. These include the fluid filtration model, dye leakage model and bacterial leakage model.
A search of the literature revealed two short term studies that evaluated the clinical efficacy of MTA as a perforation repair material.
Arens and Torabinejad (1996) reported on two cases in which MTA had been used to repair furcal perforations. The first case showed bone regeneration after 3 months. Continued healing was observed radiographically at 6 and 12 months. The second case had similar findings, with radiographic evidence of resolution of a lesion in the furcation region at 9 and 12 months. In a similar case report using MTA to repair perforations,
Schwartz et al 2 (1999) found radiographic evidence resolution of a furcal perforation lesion and absence of any clinical symptoms 6 months after the repair procedure.
Jong lee S, Monsef M and Torabinejad M (1993) tested the sealing ability of amalgam, IRM and MTA for repair of experimentally created root perforations. They found that MTA had significantly less leakage than IRM or amalgam.
The MTA also showed the least overfilling tendency while IRM showed least underfilling tendency.
Ferris D M and Baumgartner (2004) evaluated the two types of MTA to seal furcal perforations in extracted human molars using an anaerobic bacterial leakage model and found no significant difference between the two types of MTA in preventing leakage of Fusobacterium nucleatum past furcal perforation repairs.
In teeth with incomplete root end and necrotic pulps, the root canals must be completely debrided. Because of a lack of apical seal and the presence of thin and fragile walls in these teeth, it is imperative to perform apexification to obtain an adequate apical seal.
Schwartz R S et al (1999) used MTA for apexification of right maxillary central incisor with two step apical barrier technique.
In the first visit MTA was placed in the canal and condensed to a minimal thickness of 2mm. Rest of the canal space was filled with Ca(OH)2 paste and the tooth was temporized to allow the MTA to set overnight.
The next day the MTA was found to be hard and the root canal space was obturated with ZOE sealer and vertical condensation of injectable gutta-percha.
At nine and twenty month recall visits the tooth was asymptomatic and normal periapical bony architecture was present.
Matt G D et al (2004) investigated the use of MTA as an apical barrier by comparing the sealing ability of white and gray MTA.
Apical barriers of white and gray MTA were placed to a thickness of 2mm or 5 mm. The samples were obturated immediately (one step) or after the MTA set for 24 hrs (two steps). After placement in methylene blue dye for 48 hrs the samples were sectioned for leakage analysis and microhardness testing of the barrier.
Gray MTA demonstrated significantly less leakage than white MTA and the two step technique showed significantly less leakage than one step. The 5 mm thick barrier was significantly harder than 2 mm barrier, regardless of the MTA types or no. of steps.
Leimburg M L et al (2004) used polymerase chain reaction (PCR) followed by reverse dot blot to detect Enterococcus faecalis leakage through MTA apical obturation of pulpless teeth with open apices and reported MTA provides adequate seal even in cases of orthograde apical obturation.
Al Kahatani et al (2005) evaluated the seal created by varying depths of MTA plugs placed in an orthograde fashion in five groups and results showed a statistically significant difference in only 5mm apical plug which completely prevented bacterial leakage.
Al Hezaimi et al (2005) assessed in-vitro leakage of orthograde placed grey MTA white MTA and vertically condensed gutta-percha with sealer and found both MTA preparations were more resistant to human saliva leakage than vertically condensed gutta percha.
A major difficulty in obtaining successful results with pulp therapy is the prevention of recontamination by bacteria after treatment has been completed. . The inability of the Ca(OH)2 to provide a permanent seal and the porous nature of bridge allows the ingress of bacteria and inflammatory byproducts. These irritants can compromise pulpal vitality, often leading to dystrophic calcification, root canal therapy or potential extraction.
Once MTA has been placed, no further irrigation can be accomplished, since the unset MTA can be easily washed off.
1-1.5 mm thick layer of freshly mixed MTA is placed over the exposed pulp; a wet thinned, flattened cotton pellet is placed over it. The cotton pellet provides the moisture for a proper set. Due to its hygroscopic nature, Cavit absorbs water and can be inflammatory to the vital pulp and therefore should not be used as a temporary filling material in vital teeth. Light cured photocore, IRM, or other suitable material is used for temporization.
With relation to the studies that have evaluated the pulpal response to the MTA, Pittford etal, capped the teeth of monkeys and verified the formation of a mineralized tissue bridge in all specimens; in only one case pulp inflammation was reported.
Junn etal has demonstrated that pulps capped with MTA exhibited less inflammation and higher dentin bridge formation than in the group of teeth treated with Ca(OH)2.
Holland etal compared the dogs pulp responses on capping with either MTA or Ca(OH)2 In teeth treated with MTA, all bridges were tubular morphologically. In the superficial portion of these bridges, the presence of a slight layer of necrotic pulp tissue was observed suggesting that material, similar to Ca(OH)2, initially causes necrosis by coagulation in contact with pulp connective tissue. This reaction may occur because of the product’s high alkalinity, whose pH is 10.2 during manipulation and 12.5 after 3 hours. The results were similar to the findings of Pittford etal.
According to Seax etal those calcite crystals attract fibronectin, which is responsible for cellular adhesion and differentiation. Therefore it is believed that MTA mechanism of action is similar to that of Ca(OH)2 .
Jafari SM indicated that tooth colored PROROOT MTA induced proliferation and not apoptosis of pulpal cells in vitro and these findings suggests a potential mechanism to explain the regenerative effect observed in the dentin pulp complex when MTA was used for direct pulp capping.
Hollan G etal assessed the effect of MTA as pulp dressing material following pulpotomy in primary molars with carious pulp exposure and compared them to those of Formocresol and obtained a success rate of 97% for MTA and 83% for Formocresol.
Aeinehchi compared the MTA with Ca(OH)2 as pulp capping agent and on histological evaluation there was less inflammation,hyperaemia and necrosis plus thicker dentinal bridge formation and more frequent odontoblastic layer formation with MTA than Ca(OH)2.