Apexification is a procedure used to stimulate root development or closing of the root end ("open apex"). Endodontists are specially trained to treat these difficult situations through apexification. The goal of this treatment is to form a hard tissue barrier at the end of a root with an open apex. This allows the root canal to be sealed in a traditional manner.
If, during a comprehensive exam, your dentist finds an open apex in teeth that are not fully developed or whose roots have been eroded away, apexification will likely be recommended. When there's an open apex in teeth that aren't fully developed or a tooth's roots have been eroded, this complicates root canal therapy by making it difficult to seal the root canals with routine methods.