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6 Dental Tribune Middle East & Africa Edition | January - February 2014mcme media Mineral trioxide aggregate revisited: a cement for all seasons ByGaryGlassman,DDS,FRCD P ulpal and periradicu- lar pathology develop when the dental pulp and periradicular tis- sues become exposed to mi- croorganisms. In experimen- tal, germ-free conditions, pulpal and periradicular tis- sues fail to show the develop- ment of pathosis and associ- ated lesions when exposed to bacteria.1,2 The conclusion: Microorganisms are the main irritants of the dental pulp and periodontium, and sealing the pathways of communication between the root canal system and the periradicular tissues is imperative if bacterial leak- age is to be prevented. An ideal orthograde or ret- rograde filling material that seals the pathways of com- munication between the root canal system and its sur- rounding tissues should be non-toxic, non-carcinogenic, biocompatible, insoluble in tissue fluids and dimension- ally stable.3,4 Furthermore, the presence of moisture should not affect its sealing ability; it should be easy to use and be radiopaque for recognition on radiographs.4 Because existing restorative materials used in endodontics did not possess these “ideal” characteristics, 4 mineral tri- oxide aggregate (MTA) was developed and recommended initially as a root-end filling material and subsequently has been used for pulp cap- ping, pulpotomy, apexogen- esis, apical barrier formation in teeth with open apices, re- pair of root perforations and, most recently, in revasculari- zation cases. MTA has been recognized as a bioactive ma- terial.5,6 MTA has been shown to seal off the pathways of commu- nication between the root ca- nal system and surrounding tissues, significantly reduc- ing bacterial migration.7 It is made up of fine hydrophilic particles that set in the pres- ence of water, and it is com- posed of tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium alu- minoferrite, calcium sulfate dihydrate (gypsum) and bis- muth oxide, which provides it with radiopacity.8 Portland cement is the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco and most nonspecialty grout. It usually originates from lime- stone. MTA is available as gray MTA and white MTA. The crystal- line structure and chemical composition of gray and white MTA are similar, except for the presence of iron in gray MTA. Both contain bismuth oxide and calcium silicate oxide. Portland cement is composed mainly of calcium silicate ox- ide and does not contain bis- muth oxide but does contain potassium. Calcium oxide is added in both Angelus white and gray MTA (Angelus, Lond- rina, Brazil) to reduce the set- ting time, which is too long in MTA cements of other brands (Fig. 1). MTA has a similar mechanism of action to calcium hydrox- ide9 in that the main compo- nent of the material, calcium oxide, when in contact with a humid environment, is con- verted into calcium hydrox- ide.10 This results in a high pH of 12.5, making its surround- ings inhospitable for bacte- rial growth and producing an antibacterial effect for a long period of time. But unlike calcium hydroxide products, such as Dycal® (DENTSPLY, York, Pa.) and MTA Angelus (Angelus, Londrina, Brazil), it has very low solubility, so it maintains a hard, excellent marginal seal. Finally, unlike most dental materials, MTA actually needs moisture to set, so it thrives in a moist environment. Of the commercially available MTA products, MTA Angelus is well suited for most of the indi- cated endodontic procedures due to its setting time of 10 minutes, compared with the four-hour setting time of the other commercially available MTA. It is also packaged in air-tight bottles, allowing the practitioner to use only what is exactly needed, without introducing undue moisture into the remainder and with- out waste.11 Endodontic revasculariza- tion Treatment of the immature, non-vital tooth with apical pathology presents several challenges. The mechanical cleaning and shaping of such a tooth with a blunderbuss canal is difficult, if not impos- sible, to achieve predictably. The thin, fragile lateral den- tinal walls can fracture dur- ing mechanical filing, and the large volume of necrotic de- bris contained in a wide root canal is difficult to completely disinfect.12 A new technique is presented to revascularize immature permanent teeth with apical periodontitis. The canal is disinfected with copious irri- gation and a combination of three antibiotics. After the dis- infection protocol is complete, the apex is mechanically irri- tated to initiate bleeding into the canal to produce a blood clot to the level of the cemen- toenamel junction. A double seal of the coronal access is then made, first with MTA over the blood clot and then a bonded composite. The combination of a disinfected canal, a matrix into which new tissue could grow, and an effective coronal seal appears to have the ability to produce an environment necessary for successful revasculariza- tion.13 The development of normal, sterile granulation tissue within the root canal is thought to aid in revascu- larization and stimulation of cementoblasts or the undiffer- entiated mesenchymal cells at the periapex, leading to the deposition of a calcific mate- rial at the apex as well as on the lateral dentinal walls.12 A case of mistaken identity A 15-year-old girl of Asian de- scent was referred to the au- thor’s private endodontic clin- ic for evaluation on the lower left second premolar. The healthy young patient with an unremarkable medical his- tory presented with a history of buccal swelling of the left mandibular area and discom- fort to direct pressure on the tooth. On clinical examina- tion, the patient was asympto- matic, and the tooth appeared intact, without caries. The presence of an enamel pearl on tooth #45 suggested that one may have been present on this tooth, which was frac- tured during function, result- ing in a microexposure and necrosis of the pulp. The tooth had an open apex associated with a large radio- lucency (Fig. 2). Periodontal probings were within normal limits for all teeth in the lower left region. Diagnostic testing was nega- tive to cold and electric pulp testing, with mild sensitivity on percussion and palpation. Because of the presence of a wider than 4 mm open apex and thin dentinal walls prone to possible future fracture,14 it was felt that an attempt to achieve regeneration of the pulp should be made by a technique similar to that de- scribed by Rule and Winter15 and Iwaya et al.16 An access cavity was made, purulent hemorrhagic drain- age obtained, and the necrotic nature of the pulp confirmed. The root canal was slowly flushed with 20 ml of 5.25 per- cent NaOCl for 15 minutes. It was delivered with the mas- ter delivery tip and the macro canulae of the EndoVac api- cal negative pressure deliv- ery system (Axis/SybronEndo, Coppel, Texas) (Fig. 3). The canal was dried with pa- per points, and a mixture of ciprofloxacin, metronidazole and minocycline paste as de- scribed by Hoshino et al.17 was prepared into a creamy Fig. 2 Radiograph of a necrotic lower left second premolar with large periradicular radiolucency with an incompletely formed root, both longitudinally and laterally. Fig. 3 EndoVac apical negative pressure delivery system (Axis/ SybronEndo, Coppel, Texas) mCME articles in Dental Tribune have been approved by HAAD as having educational content for CME credit hours. This article has been approved for 2 CME credit hours. Centre for Advanced Professional Practices (CAPP) is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. CAPP designates this activity for 2 CE credits. Fig. 1 MTA Angelus (Angelus, Londrina, Brazil) available in resealable vials. (Photos/Provided by Gary Glassman, DDS, FRCD(C))