Abigail Spinoglio, of Green Island School, asks :-

Why and how do your teeth fall out?

Tom Kardos, of the National School of Dentistry at the University of Otago, responded.

Humans have two sets of teeth, the first 20 deciduous or “milk” teeth, appear between six months and two years of age. These are replaced by the permanent set of 32 teeth, most of which appear in the mouth between 6 and 14 years of age.

There are two important reasons why the deciduous teeth are replaced. Firstly they wear rapidly and secondly from the time of birth we increase in size with dramatic changes occurring during puberty. However, teeth do not increase in size so we need a new set of teeth to fit the adult mouth.

All teeth have a crown, the part that you see in the mouth, and a root that is within the jawbone. As the crowns appear in the mouth their roots and supporting bone are formed. The roots are separated from the bone by a thin layer of soft tissue that allows small movements of the tooth within the jaw. Permanent teeth develop in bone beneath the deciduous teeth and once their crowns have been formed these teeth start their journey into the mouth. Special cells remove the bone covering the crown, and at the same time they also remove the roots of the deciduous teeth. Loss of their roots results in the deciduous teeth falling out. Adult teeth may also fall out. This is commonly due to loss of the supporting soft tissue and bone caused by dental disease or a lack of essential nutrients.

Occasionally teeth can be accidentally knocked out following an impact force that disrupts the soft tissue between the root and the bone. A dentist can put the tooth back, but it is important not to handle the root and to keep it moist. Advice for such an emergency can be obtained from your dentist or local hospital.