For example, while some of the front teeth may have already erupted into the mouth, some of the back teeth will have chewing surfaces just beginning to calcify within the jawbones.
The primary teeth begin to calcify before birth when the fetus is about three months old. The chewing parts of all the baby teeth are completed about one year after birth.When babies are about three months old the first of the 32 adult teeth begin their calcification within the jawbones. The last of the adult teeth complete their root formation some 16 to 20 years later.
We develop two sets of teeth in our lifetime. The first set of baby or primary teeth is made up of incisors, canines and molars to give a total of 20 teeth in all. The second set (permanent teeth) which replace the baby teeth consist of incisors, canines, premolars and molars. In all there are 32 permanent teeth. With both primary and permanent teeth, half the teeth are in the upper jaw and half in the lower jaw.
The incisors at the front of the mouth have sharp biting edges to cut food. The canines at the sides of the incisor teeth have pointed crowns which originally were meant for tearing foods such as meat. The teeth are very prominent in many animals such as the dog – hence the name ‘canine’. The premolars and molars at the back of the mouth have broad flatter surfaces designed for the grinding of food.