Root strains associated with different obturation techniques.

The influence of different obturation techniques (lateral condensation, Obtura, and Thermafil) on root strains was assessed in 27 upper central incisors using strain gauges mounted on the coronal and apical one-thirds of the root surface. The vertical load applied with each obturation technique was also measured. Comparison of the strains was conducted with two-way analysis of covariance (with condensation load as covariate). The technique of obturation significantly influenced the root strains, with the Obtura generating the highest strains. The Thermafil group showed significantly less strain than the Obtura or lateral condensation groups. Thermal expansion of dentin was an unexpected finding. A large proportion of strain in the Obtura and Thermafil groups was found to be thermal strain. The mean load required to cause vertical root fracture was five to six times higher than the load used in obturation.