The term “posterior teeth” refers to the teeth located toward the back of the mouth, primarily designed for grinding and crushing food. These teeth include the premolars and the molars, which form the bulk of the chewing surface. The absolute farthest teeth in the dental arch are the third molars, commonly known as the wisdom teeth.
Identifying the Most Posterior Teeth
The permanent human dentition includes twelve molars, three in each quadrant of the mouth. The first molars are the largest and erupt earliest, typically appearing around six or seven years of age. The second molars follow, usually emerging between the ages of 12 and 13 years. The third molars are the last in the sequence and are the most posterior teeth in the mouth.
The third molars are known as “wisdom teeth” because they appear much later in life than the other permanent teeth. Eruption typically occurs between 17 and 21 years of age, a time associated with reaching adulthood. Since the dental arch is largely established by this time, the third molars must emerge behind the fully erupted second molars.
Their position at the end of the dental arch means they are positioned against the ascending part of the jawbone. If the jaw is not long enough to accommodate these teeth, complications with eruption can occur. The presence of these four teeth marks the completion of the permanent adult dentition, totaling 32 teeth in a complete set.
The Primary Function of Molars
Molars are designed to withstand the forces generated during mastication, or chewing. They possess the broadest crowns of all the teeth, featuring a complex surface of elevated areas called cusps and valleys. This morphology provides a high surface area for catching and grinding food material.
The position of the molars close to the primary muscles of mastication, such as the masseter and temporalis, allows them to generate significant bite force. These teeth can withstand forces up to 200 pounds per square inch, necessary to break down tough food into a manageable bolus for swallowing. The grinding action of the cusps pulverizes the food, preparing it for digestion.
Common Issues Associated with Third Molars
Because third molars are the most posterior teeth, they frequently encounter developmental problems related to limited available space in the jaws. The most common issue is impaction, which occurs when the tooth is unable to fully erupt due to obstruction by the jawbone, gum tissue, or the adjacent second molar. Impaction can be complete (remaining entirely beneath the gumline) or partial (where a portion of the crown breaks through).
A partially erupted wisdom tooth often creates a flap of gum tissue, called an operculum, over the chewing surface. This flap easily traps food particles and bacteria, making the area difficult to clean with normal brushing and flossing. The accumulation of bacteria beneath this flap commonly leads to a localized infection and inflammation known as pericoronitis.
Symptoms of pericoronitis include localized pain, swelling of the gum tissue, an unpleasant taste, or difficulty opening the mouth. If left untreated, this infection can spread to surrounding tissues. The difficult-to-clean position of impacted third molars increases the risk of tooth decay and gum disease for both the wisdom tooth and the adjacent second molar. Dentists often recommend the surgical removal, or extraction, of third molars to prevent these recurring problems and protect the health of the adjacent teeth.