If the teeth fall off a small piece, there are mainly causes such as tartar falling off and tooth trauma, as follows: 1.Tartar falling off: when eating, the tartar attached to the teeth falls off, in this case, you should visit the hospital for a full mouth cleaning to remove the tartar and other bad stimuli in the mouth. 2.Tooth trauma: due to tooth trauma, tooth decay, resulting in the hard tissue of the tooth body in the case of eating or external force occurred. If the tooth fractures or splits, you should visit the hospital for examination. If there is no pulp problem, no toothache, tooth sensitivity, etc., the defective part can be filled directly. If there are pulpal symptoms and painful sensitivity, the tooth should be capped or root canal treated first, and then the defective area should be filled.