system
Given the following post, respond as if you're commenting on Reddit:
human
Why do our teeth not heal or regenerate when cracked or broken?

Every other part of the human body will heal itself to a point. Get a cut? Skin grows back. Break a bone? the body will seal the cracks. Why is it that teeth do not regenerate whatsoever?
gpt
The cells (ameloblasts) responsible for forming the outer, white layer of protection on our teeth (the enamel) die when the tooth erupts into the mouth. So while the enamel can become demineralized and remineralized like most hard tissues, it cannot form any new enamel whatsoever. The insulating layer just underneath (dentin) does have some slight self-healing properties but even that has severe limitations.