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PERFORATION REPAIR WITH MTA

The prognosis for a perforation has improved with the use of the operating microscope14 and with the availability of MTA to seal the defects.15 MTA was developed by Torabinejad and colleagues.16 It is an endodontic cement that is extremely biocompatible, hydrophilic, and capable of stimulating the healing processes and osteogenesis.17,18 MTA is a powder that consists of fine trioxides and other hydrophilic particles that set in the presence of moisture. Hydration of the powder results in a colloidal gel that solidifies to a hard structure in about 4 hours. This cement is different from all other materials used because of its biocompatibility, its antibacterial activity, its marginal adaptation and sealing properties, and of primary importance because it is hydrophilic and therefore resistant to moisture.
Concerning biocompatibility,19,20 Koh, et al21,22 and Pitt Ford, et al23 demonstrated that MTA was not cytotoxic for fibroblasts or osteoblasts, and promoted the formation of dentin bridges when used in direct pulp capping.24 Other studies25,26-29 demonstrated the formation of cementum, periodontal ligament, and bone adjacent to MTA when used to seal perforations and as a retrofilling material in surgical endodontic procedures.30
Concerning antibacterial activity,31,32 Torabinejad, et al33 have demonstrated that MTA is superior to amalgam, zinc-oxide eugenol cement, and SuperEBA. Nonetheless, its spectrum of activity is limited, and if a bacterial contamination is suspected, it is advisable to use calcium hydroxide before MTA.33 Marginal adaptation and sealing properties of MTA are far superior to those of amalgam, IRM (DENTSPLY Caulk), and SuperEBA.27,10,34-39
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Figure 1. Stripping of the mesial root of the mandibular left first molar, caused by the introduction of a screw post into the mesiobuccal canal. Preoperative radiograph.

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Figure 2 The recall radiograph after 5 years demonstrates complete healing.
As noted, the characteristic that distinguishes MTA from all the other materials used to repair iatrogenic perforations is that it is hydrophilic. Materials used to repair perforations, seal the retro-preparation in surgical endodontics, close open apices, or protect the pulp in direct pulp cappings are inevitably in contact with blood and other tissue fluids. MTA is the only material that is not affected by moisture or blood contamination.28 On the other hand, MTA sets only in contact with moisture. Due to the above-mentioned characteristics and primarily because it is hydrophilic, MTA can be considered the ideal material to seal perforations40,41-57 (Figures 1 and 2).
The following is the operative sequence to treat a perforation of the root or of the floor of the pulp chamber:
At the patient’s first visit, (1) isolate the operative field with rubber dam, (2) clean the perforation site; in case of bacterial contamination, medicate with calcium hydroxide for one week, (3) apply a 2-to-3mm thick layer of MTA; radiograph to verify the correct positioning of the material, (4) apply a small wet cotton pellet in contact with MTA, and (5) place temporary cement.
At the second visit (after 24 hours), remove the temporary cement to check if the MTA has set and then complete therapy.
As far as the operative sequence is concerned, it is important to differentiate between a perforation that has the configuration of a cavity with 4 walls having no association with the root canal space (eg, the perforation of the pulp chamber floor in a molar), and one that is a strip perforation inside the canal space. If the perforation is in the floor of the pulp chamber and therefore is a cavity completely independent of the canal orifices, the situation is different from a perforation that is in the middle third of a root and is caused by stripping due to excessive enlargement of the root canal. In the latter case, the perforation is not independent from the root canal but is inside the root canal (in a root canal wall). It is not a cavity with 4 walls, but is rather a thinning of the root.
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Figure 3. Perforation of the mesial aspect of the distal root of a mandibular right first molar caused by preparation for an amalgam pin. Preoperative radiograph.

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Figure 4. Clinical aspect of the perforation adjacent to the old amalgam.

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Figure 5. The amalgam has been removed, and the perforation has been repaired with MTA. At the following visit the MTA is set.

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Figure 6. The radiograph shows the MTA in place.

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Figure 7. Postoperative radiograph.

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Figure 8. A 3-year postoperative radiograph.

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Figure 9. In the attempt to find the mesiobuccal canal, a perforation was made in the floor of the pulp chamber. Preoperative radiograph.

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Figure 10. Clinical aspect of the access cavity. The red tissue on the left is the pulp tissue in the lingual canal. On the mesial aspect of the perforation the orifice of the buccal canal is visible.

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Figure 11. A No. 10 K-File negotiating the mesiobuccal canal.

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Figure 12. Working length of the mesiobuccal canal.

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Figure 13. After cleaning and shaping, the perforation is seen as the small opening about 7 mm below the canal orifice.

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Figure 14. Fitting the gutta-percha cones.

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Figure 15. The gutta-percha cone of the mesiobuccal canal has been partially pre-sectioned apical to the perforation, and is bent and coated with sealer before being introduced in the canal.

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Figure 16. Because of the partial cut, the gutta-percha point is separated in 2 fragments: one apical, which remains in the canal apically to the perforation, and one coronally, which is removed. The canal has been obturated with the Schilder technique only apical to the perforation.

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Figure 17. Positioning the MTA with a Dovgan carrier.

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Figure 18. The canal has been filled with MTA to the orifice.

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Figure 19. Postoperative radiograph.

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Figure 20. A 2-year postoperative radiograph.

In the first instance, it is advisable to seal the perforation before obturating the root canals (Figures 3 to 8). This approach is easier and saves time. Since one consideration for prognosis is the time interval between perforation and treatment, the longer treatment is delayed, the more likely the perforation site will be contaminated, with resultant periodontal involvement. After positioning small amounts of gutta-percha at the orifices of the canals using the Obtura III (Obtura Spartan), or in a retreatment case before removing the previous obturating material to prevent blockage of the canals with MTA, MTA is used to completely fill the perforation. Once the complete set of the material is verified at the second visit, the cleaning, shaping, and obturation of the root canal system is completed in the standard fashion.
In the case of a strip perforation due to a thinning of the root dentinal wall, it is extremely difficult to repair the perforation site with MTA before obturating the root canal without blocking the canal itself with MTA. Therefore, it is advisable to obturate the canal space apical to the perforation first, and then to repair the perforation using MTA to seal the perforation site and fill the entire coronal portion of the root canal, to the orifice (Figures 9 to 20). In order to do this, it is necessary to measure the level of the perforation using the operating microscope and then to partially cut or score the prefitted gutta-percha cone just apical to that level. Once it is introduced into the root canal, the gutta-percha cone is digitally rotated, separating it into 2 pieces: the coronal fragment pulls away, leaving the apical fragment in the canal, which is just apical to the perforation. After compaction of the apical gutta-percha cone, the canal is filled with MTA to the orifice, sealing the perforation site.
When questioned, the patient revealed that she had been taking alendronate for the previous 5 years (but had not informed the office as part of the medical history/ medication periodic updates). Previous dental surgical experience included ex-tractions of teeth No. 30 in 1998 and No. 4 in 1999 with subsequent implant placement, and endodontic treatment of tooth No. 3 in March 2004. On August 17, 2005, the patient was instructed to rinse with a phosphate buffer-stabilized 0.1% chlorine dioxide-containing mouthwash (CloSYS II [Rowpar Pharmaceuticals]) for 30 seconds 3 to 4 times a day until further notice. On June 30, 2006, the patient reported, A piece of bone fell off of the roof of my mouth, which was likely exfoliation of a sequestrum. A clinical examination on August 17, 2006, revealed that the area was, and remains as of this writing, completely healed (Figure 4).
This patient and all subsequently described patients have been instructed to continue using this mouthwash indefinitely.