Objective To investigate the effects of overdose fluoride, boron and two factors on the expression of enamelin in rat incisor. Methods 32 Wistar rats were randomly divided into 4 groups. GroupⅠ：The distilled water was given. Group Ⅱ：220 mg/L NaF were given. GroupⅢ：382 mg/L Na2B4O2·10H2O were given. Group Ⅳ：220 mg/L NaF and 382 mg/L Na2B4O2·10H2O were given. The rats were sacrificed in the eighth week. HE staining was used to observe the morphology of ameloblasts. Immunohistochemical staining was used for study the expression of enamelin in rat incisors. Results The results showed that the expression of enamelin was reduced in the group Ⅱ（P
