Once there is tooth decay, there will be cavity formation, and there will be food residue in the cavity, and it is not easy to bring out the food residue through general brushing, so the food residue will be easily fermented or rotten after staying in the cavity for a long time, which will cause bad breath. If the tooth decay is very serious and ignored, it will gradually destroy the root of the tooth, and once the root is damaged, the mouth will be eroded by other bacteria, which may cause periodontal infection inside the mouth, and then a series of oral problems will arise, and bad breath is also one of the most common phenomena, so in daily life, we should pay attention to oral hygiene, and try to reduce the formation of tooth decay.