The number of teeth a human has changes dramatically over the course of a lifetime. Humans develop two distinct sets of teeth, and the total count present depends entirely on the person’s stage of development. While children have one count, the adult replacement set features a significantly higher total.
Teeth During Childhood
The first set of teeth, known as primary or deciduous teeth, is composed of 20 individual units. These teeth begin to erupt into the mouth during infancy, typically starting around six months of age. Most children achieve a full complement of 20 teeth by the time they reach three years old.
These teeth are evenly distributed, with ten in the upper jaw and ten in the lower jaw. Primary teeth maintain correct spacing within the jaw, acting as natural guides for the 32 permanent teeth developing beneath them.
The roots of the primary teeth are gradually reabsorbed by the body, allowing them to loosen and fall out, a process called exfoliation. This shedding typically begins around age six and continues until the early teenage years. Premature loss of a primary tooth can cause adjacent teeth to drift, potentially causing alignment problems for the permanent tooth.
Teeth During Adulthood
A full set of permanent teeth in an adult totals 32, based on 16 teeth in the upper jaw and 16 in the lower jaw. This set should be fully present by the early twenties. However, the exact number of teeth an adult retains often varies, making 28 a common count.
This variation is due entirely to the third molars, or wisdom teeth. There are four wisdom teeth in a full set, one in each corner of the mouth, and they are the last teeth to emerge, usually between the ages of 17 and 25. The human jaw has gradually become smaller, often leaving insufficient space for these late arrivals.
When there is not enough room, a wisdom tooth may become impacted, trapped beneath the gum line or growing at an angle, which can cause pain or infection. Because of these complications, many people have all four wisdom teeth surgically removed, reducing the adult count to 28.
Classifying Teeth by Type and Function
The 32 permanent teeth are composed of four distinct types, each with a unique shape and role in chewing and digestion. These types include incisors, canines, premolars, and molars.
Incisors
The eight incisors are the flat, chisel-shaped teeth positioned at the front of the mouth. Their thin, sharp edges are designed to bite into and cut food cleanly.
Canines
Flanking the incisors are the four canines, characterized by their pointed, conical shape. These teeth are responsible for gripping and tearing tougher foods, such as fibrous meats or vegetables.
Premolars
Moving further back in the jaw are the eight premolars, also known as bicuspids, located between the canines and the molars. Premolars have a broader surface than the canines and work to crush and grind food into smaller pieces. These permanent teeth replace the primary molars present in the childhood set.
Molars
The 12 molars, which include the four wisdom teeth, are the largest and strongest teeth in the mouth. Located at the back of the jaw, molars have a wide, flat surface covered with cusps and ridges. Their primary function is crushing and grinding food into a fine paste suitable for swallowing and digestion.