In teeth that have undergone root canal treatment, the first examination that should be performed in cases of recurring infections in advanced stages is radiological. If the canal treatment is found to be insufficient based on the findings obtained, a procedure called retreatment, which involves repeating the canal treatment, can be performed.

Although generally successful results are obtained after a good retreatment, the desired result may not be achieved due to anatomical or iatrogenic factors in the root of the tooth. In such cases, the first surgical method to be applied to keep the tooth in the mouth is apical resection. This procedure involves removing a certain portion of the root tip of the tooth through a surgical intervention, and filling the canal after clearing it of bacteria.

In teeth with multiple roots, if the condition of the roots other than the infected one is found to be sufficiently healthy, restoration can be performed on the remaining roots after the problematic root is removed with a hemisection procedure.

It should be known that although these procedures are successful to some extent, they are the last resort treatment methods to be applied before extraction of the teeth. In case of any failure, the teeth will need to be extracted.