Teeth: Types, Dental Formula and Tooth Anatomy

Each tooth is embedded in a socket of jaw bone. Most of the animals including humans have two sets of teeth during their life. First set is of temporary milk or deciduous teeth, which is replaced by a set of permanent or adult teeth. Adult human has 32 permanent teeth which are of four different types viz. Incisors, Canines, Premolar and Molars.

Incisors are the eight front teeth (4 up, 4 down). Canines are another four teeth on either side of incisors in both sides (2 up, 2 down). Beyond canines are eight premolars (4 up, 4 down). These teeth have two pointed cusps on their biting surface and are sometimes referred to as bicuspids. Beyond Premolars are 12 molars (6 up and 6 down) thus making a set of 32 teeth in humans. The three pairs of molars in upper or lower jaw are denoted as first, second and third molars. Third molar is also known as wisdom teeth that come up in 30s.  The above system is arranged in the form of a dental formula, which is 2123/2123 in humans.

In children, there are only 20 deciduous teeth or milk teeth. They begin to develop before birth and begin to fall out when a child is around 6 years old. The dental formula for milk teeth is 2102. We note here that Children don’t have premolars. Their premolar is called by dentists as first molars rather. These baby molars are replaced by adult premolars.

Human teeth are made up of four different types of tissues viz. pulp, dentin, enamel, and cementum.

Pulp is the innermost portion of the tooth and consists of connective tissue, nerves, and blood vessels, which nourish the tooth. Pulp is surrounded by Dentin, a hard yellow substance that makes up most of the tooth and is as hard as bone. Enamel which covers the dentin is hardest tissue in the body and forms the outermost layer of the crown. A bony layer of cementum covers the outside of the root, under the gum line, and holds the tooth in place within the jawbone. Cementum is also as hard as bone.