The standard number of molars in a human adult is twelve, including the third molars, commonly called wisdom teeth. However, it is also very common for an adult to have only eight molars, particularly if the wisdom teeth have been removed or never developed. Understanding the function and arrangement of these teeth provides a clearer picture of the typical human dental structure.
Defining Molars and Their Role
Molars are a class of teeth located at the back of the mouth, positioned behind the premolars. They are the largest teeth and are distinguished by their broad, relatively flat chewing surface. This wide, multi-cusped shape allows them to withstand significant force during mastication.
The primary function of molars is to grind and crush food into smaller, easily digestible pieces before swallowing. While incisors cut food and canines tear it, molars perform the final mechanical breakdown. Molars are anchored to the jawbone with multiple roots, typically two to four, providing stability for their intense grinding action.
The Standard Adult Molar Count
A complete set of permanent adult teeth totals thirty-two and includes twelve molars. These molars are symmetrically distributed across the upper and lower jaws. This arrangement places three molars in each of the four quadrants of the mouth: upper right, upper left, lower right, and lower left.
The twelve permanent molars are categorized by their position and the approximate age they erupt. The first molars, often called the “six-year molars,” are the most forward-facing and generally appear around that age. The second molars, or “twelve-year molars,” erupt next, filling the space behind the first molars. Finally, the third molars, known as wisdom teeth, are the last to emerge, typically between the ages of seventeen and twenty-five.
Variations in Molar Count
Children have a primary set of teeth, or deciduous dentition, which includes a different number of molars than the permanent set. A child has a total of twenty primary teeth, including eight molars—two in each of the four quadrants. These primary molars hold space for the permanent premolars that will eventually replace them. The permanent molars erupt further back in the jaw and do not succeed the primary molars.
The most frequent reason for a deviation in the adult count is the status of the third molars. Many adults have only eight molars because their wisdom teeth were surgically removed or never developed. The congenital absence of one or more wisdom teeth is common, affecting approximately 20 to 30 percent of the population. When third molars are missing or removed, the final count is reduced to eight, including only the first and second molars in each quadrant.