@article{graziottin_costa_silveira_veeck_2002,  title={Measurement of the optical density of packable composites: comparison between direct and indirect digital systems},  volume={16},  ISSN={1517-7491},  url={https://doi.org/10.1590/S1517-74912002000400004},  DOI={10.1590/S1517-74912002000400004},  number={4},  journal={Pesquisa Odontológica Brasileira},  publisher={Sociedade Brasileira de Pesquisa Odontológica e Faculdade de Odontologia da Universidade de São Paulo},  author={Graziottin, Luiz Felipe Rodrigues and Costa, Nilza Pereira da and Silveira, Ivori Dutra da and Veeck, Elaine Bauer},  year={2002},  month={Dec},  pages={299–307} }