Teeth are important structures in the human body, playing an important role in digestion, speech, and facial aesthetics. The number and types of teeth change significantly from childhood into adulthood, reflecting developmental and dietary needs. Understanding these transitions and tooth roles offers insight into human dentition.
The Typical Number of Teeth
Humans develop two sets of teeth during their lifetime. The first set, primary or deciduous teeth, are commonly called baby teeth. Children typically have a full set of 20 primary teeth by the age of three. These teeth emerge around six months of age, with lower front incisors often appearing first.
As a child grows, primary teeth loosen and fall out, making way for the permanent teeth. This transition starts around age six, with the first permanent molars erupting behind the existing baby teeth. Shedding of baby teeth and emergence of permanent teeth continues until age 12 or 13. Most adults have 32 permanent teeth: eight incisors, four canines, eight premolars, and 12 molars (including wisdom teeth). This set typically forms by age 21.
Different Types of Teeth and Their Jobs
Adult permanent dentition consists of four distinct tooth types, each with specialized functions. Incisors are the eight teeth at the front of the mouth, four on top and four on the bottom. These flat, sharp teeth are used for biting and cutting food into smaller pieces.
Next to the incisors are the four canines, one on each side in both the upper and lower jaws. Resembling a dog’s fangs, these pointed teeth tear and rip food. Canines are the longest teeth in the mouth and are well-anchored by their roots, withstanding considerable pressure during chewing.
Behind the canines are the eight premolars, also known as bicuspids. There are two premolars on each side of both jaws. These teeth have a flatter surface with ridges, enabling them to crush and grind food, acting as a bridge between the tearing function of canines and the grinding function of molars. The molars are the largest and strongest teeth, located at the back of the mouth, with 12 in total. Their broad, flat surfaces and multiple cusps are optimized for grinding and chewing, breaking down food into a paste for easier swallowing.
When Tooth Counts Differ
While 32 is the standard number of permanent teeth, variations occur. A common reason for differing tooth counts involves wisdom teeth, also known as third molars. These are the last molars to erupt, between ages 17 and 21. Many individuals have wisdom teeth removed due to lack of space, impaction, or complications, which reduces the total tooth count to 28.
Other variations include hypodontia, where one or more teeth are congenitally missing. This affects 2% to 8% of the population, often involving upper lateral incisors or second premolars. Conversely, some individuals have supernumerary teeth, which are extra teeth beyond the typical number. These additional teeth can appear in almost any area of the mouth and may resemble normal teeth or be unusually shaped.