Why do people change their teeth?

I remember when I was 6 years old, my mother used to make me cheese. Eating and eating, I feel that one tooth is loose. Another tooth fell into my job. Then I remembered my grandfather, who lost his tooth and never grew back. I am worried that I will become toothless. I thought to myself, I am so young that if I become toothless, the whole class will laugh at me. So I asked my mother, "Mom, if I lose a tooth, will it become missing?" Mother replied, "No, there are two sets of teeth in life, one is deciduous teeth and the other is permanent teeth." . Generally, 6-year-old deciduous teeth will fall off one by one. Until 12 years old, all primary teeth were replaced by permanent teeth. From then on, permanent teeth are the world in the mouth. However, after the permanent teeth are lost, they can no longer grow. "Ha ha! I don't have to worry about losing my teeth, so I showed my mother my loose tooth and heard her say, "You can pull this tooth out." Hearing this, he quickly said, "no, no, I don't want to pull it out." "However, how can children persuade adults! After pulling out my teeth, my curiosity came again. " Mom, why do people change their teeth? "I stared at my mother curiously." I don't know. "Therefore, this question will always be hidden in my heart. A few years later, my mother gave me 100 thousand why. As soon as I received this gift, I hurried to find the question that my mother couldn't answer a few years ago: Why do people change their teeth? I didn't know until I read it. At the age of six, deciduous teeth began to fall off gradually. The first molar comes out first, most of the permanent teeth come out at the age of 14, and the third molar comes out at the latest, delaying the emergence of teeth and wisdom teeth. About 30% of teeth never erupt. After reading it, I realized that changing teeth is very important for every child. Be sure to protect your teeth, brush your teeth in the morning and evening, and rinse your mouth after meals. Li Xinhao, a teacher in Class Two, Grade Three, Olin Primary School, jinniu district, Chengdu, Zhang Li.