Whether the teeth can be washed white needs to be determined according to the condition of the teeth, exogenous yellow and black teeth will become white after washing, but endogenous can not be washed white. 1. Exogenous teeth yellow and black: mostly due to smoking, drinking tea and drinking pigmented beverages caused by exogenous stains attached to the teeth, resulting in yellow or black teeth. In this case, through scaling to remove the pigment and calculus attached to the teeth, the teeth will restore the original color and look obviously whiter. 2. Endogenous teeth yellow and black: endogenous teeth yellow and black for a variety of reasons, such as tetracycline teeth, dental fluorosis, etc., which is produced from the internal color changes, no matter how to clean the teeth can not be whitened. Usually pay attention to dental care in order to effectively avoid yellowing of the teeth, if necessary, dental restorative treatment to achieve the effect of whitening.