Patterns of vertical root fracture: factors affecting stress distribution in the root canal

By Lertchirakarn V1, Palamara JE, Messer HH

Date: 01/2003
Journal: JOE


To use finite elements analysis to examine stress distribution patterns in simulated root sections


N=6 tooth root models and 2 vertical root fractured tooth roots

simulated root sections were varied systematically with respect to canal shape and size, external root morphology, and dentin thickness to determine relative contributions to vertical root fracture

6 models:

I: round root and canal

II: oval root, round canal

III: round root, oval canal

IV, V, VI: oval root and canal with varying degrees of dentin thickness

similar models were constructed based on cross sections of human roots that had been fractured clinically or experimentally

applied various face loads to models in the finite elements program and observed stress patterns


  • models showed that canal curvature seems more important than external root morphology (in terms of stress concentration)
  • also, decreased dentin thickness increases the magnitude but not direction of maximum tensile stress
  • models based on actual root fracture showed strong similarity between tensile-stress distribution and fracture patterns

Clinical Significance:

Vertical root fracture generally follow a B-L fracture pattern.