Chewing gum regularly can increase saliva secretion, thus better cleaning the mouth and teeth and reducing the formation of bacterial spots. In addition, the mandible, masseter muscles and teeth can be fully exercised during repeated occlusal movements, which is very beneficial to periodontal health. On the other hand, Fox, director of the Los Angeles Neurology Medical Center, also found that if you chew gum for about 15 minutes every day, it will have a cosmetic effect. First of all, most chewing gums use sucrose as a sweetener, and sugar will stay in the mouth for a long time. Cariogenic bacteria in the mouth will use sucrose to produce acidic substances, which will corrode teeth and cause decalcification of teeth, thus inducing dental caries. The Journal of American Dental Association suggests that people choose a new chewing gum with xylitol instead of sucrose, because xylitol and sucrose have the same taste and nutritional value, but it will not ferment to produce acid and will not damage teeth. At the same time, chewing can increase saliva secretion and reduce saliva acidity, so it also helps to prevent dental caries. Secondly, people who fill their teeth with mercury-containing materials had better not chew gum. A study by Swiss scientists found that chewing gum often destroys the substances used to fill teeth in the mouth and releases amalgam, resulting in excessive mercury content in blood and urine, which is harmful to the brain, central nervous system and kidneys. In addition, chewing gum is not good for children, because children have poor self-control ability. If they chew gum in their mouth all day, they may swallow it or enter the trachea by mistake, which is life-threatening. In addition, chewing gum for a long time, the masticatory muscles are always in a state of tension, which may develop the habit of grinding teeth during sleep, thus affecting the quality of children's sleep. Someone once joked that Americans' habit of grinding their teeth while sleeping is "all because of chewing gum". Doctors suggest that chewing gum should not exceed 15 minutes, and people with stomach problems should not chew gum too much, because chewing gum for a long time will reflexively secrete a lot of stomach acid. Especially on an empty stomach, not only nausea, loss of appetite, acid reflux and other symptoms will appear. But in the long run, it may also lead to diseases such as gastric ulcer and gastritis. Chewing gum for a long time, the masticatory muscles are always in a state of tension, and it is possible to develop the habit of grinding teeth at night. In addition, if teenagers chew gum during their physical development, it may cause excessive movement of masseter muscles, stimulate the muscle and bone development of mandibular angle, and finally present a "square Chinese face" in appearance, which will affect women's face shape.