Root canal treated teeth are highly susceptible to fracture due to both the reduced water content within them and the significant tissue loss caused by decay. If more than half of the tooth’s remaining crown is missing, a support post is placed inside the root canal to hold the filling; this is called a “fiber post.” According to mechanical principles, the length of the fiber post to be placed inside the root canal should be at least equal to the remaining crown portion, and at least 4-5 mm of gutta-percha filling should be left apically to maintain the seal of the root canal filling at the root tip. Because the elasticity modulus of fiber posts is very close to that of the tooth’s own dentin tissue, they do not concentrate the fracture energy at the root tip like traditional metal posts, but distribute the load homogeneously throughout the root, minimizing the risk of vertical root fracture.
