Darkening in the middle of two incisors may be pigmentation, tartar buildup, or there may be adjacent caries, which need to be examined in the hospital. 1. Pigment, tartar buildup. Normal incisors if the gap is too large, if the cleaning is not in place, the gap area may appear pigmentation, tartar buildup, resulting in black teeth. 2. Caries on neighboring surfaces. Teeth cleaning is not in place, teeth are prone to caries, dental tissue can have different degrees of defects, the initial black neighboring parts of small, but to the later black area becomes larger, can cause food impaction, pulpitis tooth pain. Two incisors in the middle of the black specific recommendations to the hospital examination, tartar, pigmentation of the feasible periodontal treatment, caries need to remove the decay after resin filling.