Objective To evaluate the effects of root canal size on the distribution of the stress located on the root. Methods A three-dimensional finite element model of maxillary second premolar（single tube） was created, by varying the root canal size to analyze the distribution of the stress located on different root models. Results The root canal size slightly affected the stress level. The stress variety located on the coronal 1/3 of the root. Conclusion The results suggest that clinical root canal treatment should be just removing the infected tissue and avoiding over-cutting of dentin, root canal preparation no more than 1/3 of the original root canal is secure.
