Grading and quantification of dental fluorosis in zebrafish larva

Objective The prevalence and severity of dental fluorosis in primary teeth are different from permanent teeth. Previous animal models of dental fluorosis mainly focus on juvenile rats, mice and zebrafish. Our experiment aims to set a dental fluorosis model using zebrafish larva and explore the characteristics of the first generation teeth by fluoride treatment. Materials and methods After the zebrafish eggs were laid, they were exposed to excess fluoride (19 ppm, 38 ppm and 76 ppm) for five days. The morphological characteristics of first generation teeth were examined by H&E staining, whole-mount alizarin red and alcian blue staining, and scanning electron microscope (SEM) technique. Results With whole-mount alizarin red and alcian blue staining, the tooth cusps presented red in normal control. 19 ppm and 38ppmm fluoride resulted in extensive red staining from tooth cusps to the lower 1/3 of teeth. 76 ppm fluoride caused malformed teeth with uneven red staining. H&E staining showed that excess fluoride caused cystic-like changes in 38 ppm and 76 ppm groups. SEM revealed the dose dependent pathological changes in zebrafish enameloid with fluoride treatment. Based on SEM findings, we set 0–4 dental fluorosis index (DFI) score to label the severity of dental fluorosis. Conclusions Excess fluoride presented a dose dependent fluorosis changes in the teeth of zebrafish larva. The DFI scores in our experiment reflect dose dependent fluorosis changes in a good way and will benefit the future research of dental fluorosis.