Because the body has a self-cleaning mechanism for teeth. Some people achieve this by having their teeth aligned properly. Look at these people, they eat apples by biting them. And their diet is generally not carbohydrate-heavy. They consume plenty of water. The general health of the individual is very effective here. In addition, the body's teeth defense mechanism is also important in smoking, alcohol and cola consumption. This mechanism was working well in these people. Their eating habits are also very, very important.