Prevention of tooth decay in children should first encourage them to develop good tooth-brushing habits, reducing bacteria and plaque on the tooth surface, and include brushing in the morning and evening, as well as rinsing after meals. Enamel is the hardest substance in the human body but is susceptible to cracking. Acidic or sugary substances are harmful to teeth, so it's best to avoid sweets and acidic foods in the evening and to brush teeth before going to bed. Brushing teeth before sleeping is crucial and some anti-cavity treatments should be done, such as fluoride application or dental sealants. It's also important to develop a habit of regular dental check-ups to detect and treat cavities early.