Evaluation of dental shade guide variability using cross-polarized photography - Gurrea, Jon; Gurrea, Marta; Bruguera, August; Sampaio, Camila S.; Janal, Malvin; Bonfante, Estevam Augusto; Coelho, Paulo G.; Hirata, Ronaldo (The International Journal of Periodontics & Restorative Dentistry, 2016)