Objective This study aimed to determine the minimum toenail mass needed for reliable fluoride analysis, and to compare fluoride extraction efficiency (%FE) using two protocols. Methods Toenail samples (n = 98 from 11 participants) were grouped into masses ranging from 1.0 to 5.0 mg (± 0.5 mg). Fluoride content was analyzed using a hexamethyldisiloxane(HMDS)-facilitated diffusion method and a fluoride-ion selective electrode. P...