Teeth are very important to the organism and can have an impact on diet as well as internal organ functions. When brushing teeth and eating, teeth tend to be sour and soft, usually caused by tooth decay, tooth malocclusion, periodontitis, gum recession, etc. 1.Dental caries: If you do not brush your teeth on time in your daily diet, food accumulated in your teeth for a long time will easily cause dental caries, and dental caries is one of the common causes of sour and soft teeth. It is mainly because the nerve of dental pulp is exposed and easily stimulated by the outside world, causing tooth acidity and discomfort. 2.Incorrect teeth: In the process of organism development, the teeth may appear incorrectly, and the incorrect teeth will have certain influence on the gums of the surrounding teeth, so the teeth will also appear sour and soft. 3, periodontitis: usually patients with periodontitis will have bleeding in the morning when brushing their teeth, and at the same time will have soreness when chewing something, and also have red and swollen gums. 4, gum atrophy: physiological atrophy and pathological atrophy phenomenon will lead to sour and soft teeth symptoms. This is mainly due to the periodontal nerve endings are very vulnerable to cold, heat and other adverse physical factors stimulation caused. Sour and soft teeth are usually due to the above mentioned causes. It may also be due to the long-term consumption of more acidic foods, and the teeth may also become sour and soft, and it is recommended to take appropriate treatment according to the severity of the condition.