THE SANDWICH TECHNIQUE: repairing perforations
The use of MTA in the repair of perforations is a well-known technique that has been successfully employed for a long time. To repair a perforation in the middle third of the root can be extremely difficult because the position of the perforation can hinder the achievement of an adequate space for the setting of the material, due to the reduced thickness of the walls.
This situation is frequent in molars, where the shape of the defect (caused by the iatrogenic damage) is irregular and the walls have been eroded by mechanical instruments employed for shaping the root canal system and/or by the post space preparation. The stripping of the root makes even worse the case, because it is harder to achieve a stable position of the MTA that, sometimes, can be dislocated with a subsequent loss of seal and failure of the therapy.
From here rises the idea of a different technique that allows us having a whole portion of the root canal available for placing a thick MTA layer, which will be stable over time.