It is worthwhile to know that root canal retreatment is less successful than the original root canal treatment attempt because of structural factors (lack of tooth structure due to aggressive root canal preparation or crown preparation) or microbial factors (presence of resistant microbes that have survived the disinfection process of the initial root canal treatment). Both these factors may lead to failure of the retreatment.
Here are some factors that determine whether a tooth will survive repeating root canal treatment:
Tooth structure remaining
This will only be known after all existing filling material and crown material is removed.
Presence of cracks
Cracks may be present in the coronal part (these can be visualized under a microscope during re-entry for root canal retreatment) or the root.
Root fractures are not visible unless the tooth is extracted or a gum flap is opened to check.
Presence of gum disease
If a tooth is currently affected by severe bone loss caused by gum disease, redoing the root canal treatment will not solve this and the tooth may still be lost later on.
Patient preference
Some patients do not want to deal with the uncertainty that accompanies root canal retreatment, so an extraction may be more suitable.
Some patients cannot have extractions for medical reasons or prefer to delay implant placement for as long as possible, so root canal retreatment is appropriate.
