It is not normal to have cracks in your teeth when you shine a flashlight on them. Teeth with cracks belong to the hidden cracks, caused by the hidden cracks of more reasons, such as enamel hypoplasia, bite force is too large, trauma caused by the fracture of the tooth. 1. Fracture caused by trauma: cracks on the teeth may be the cause, when the teeth suffer from external impact or collision, it may lead to cracks on the teeth, and there will be a toothache when eating hot and cold stimulating food. 2. Excessive biting force: If you have bitten harder items with your teeth, such as nuts and bones, or if the teeth are subjected to greater horizontal pressure due to the greater beveling of the tooth’s own cusp, it may cause cracks in the teeth. 3. Enamel hypoplasia: Cracked teeth can be caused by poor development of the tooth itself, or by loss of enamel due to a lack of calcium or trace elements in the body. When the teeth have cracks, it is recommended to consult a doctor as soon as possible to determine the cause of the problem and to carry out professional treatment under the guidance of the doctor.