@article{oliveira_paes leme_giannini_2005,  title={Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness},  volume={16},  ISSN={0103-6440},  url={https://doi.org/10.1590/S0103-64402005000200003},  DOI={10.1590/S0103-64402005000200003},  number={2},  journal={Brazilian Dental Journal},  publisher={Fundação Odontológica de Ribeirão Preto},  author={Oliveira, Rogério de and Paes Leme, Adriana Franco and Giannini, Marcelo},  year={2005},  month={May},  pages={103–106} }