All content published in the Journal of Dental School, Shahid Beheshti University of Medical Sciences, is open access and licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/). This license permits personal, non-commercial use and sharing of the materials as long as proper attribution is given, and the content is not altered. Authors retain the copyright of their work.