Abstract: A dental hygienic device comprising an n-type semiconductor disposed on or in a main body consisting of an inserting portion and a handle. At least one portion of the semiconductor is exposed while at least the other portion being located at the inserting portion of said main body. The semiconductor, when irradiated with a natural and/or man-made light, is activated to produce therein a number of holes whereas teeth becomes reverse-phased due to an electron density higher than that in the semiconductor to thereby give rise to a reduction which decompose tartars and colored scales on the teeth.