Teeth serve as the first mechanical step in digestion. While front teeth, such as incisors and canines, are designed for biting and tearing, the teeth at the back of the mouth, known as molars, are highly specialized. These large, broad teeth are positioned at the rear of the jaws. Their unique design and powerful location make them the primary workhorses for processing food into a manageable state before swallowing.
Molar Purpose and Structure
The function of molars is to crush and grind food into small, easily digestible particles. This mechanical breakdown is achieved through distinct anatomical features adapted for managing heavy chewing forces. The most noticeable feature is the large, relatively flat top surface, known as the occlusal surface, which provides a wide area for grinding action.
The occlusal surface features a series of raised points called cusps, typically numbering four or five on a single molar. These cusps interlock with the opposing molar in the opposite jaw, acting like millstones to pulverize tough foods. The sturdy structure is anchored firmly in the jawbone by multiple roots, ensuring stability under the pressure generated during chewing. Lower molars often have two roots, while upper molars commonly have three roots, maximizing resistance to strong vertical and sideways forces.
The Two Sets of Molars
Humans develop two sets of molars: the primary (baby) molars and the permanent (adult) molars. The primary dentition includes eight molars, two in each quadrant of the mouth. The primary first molars typically appear between 13 and 19 months of age, and the second molars erupt between 25 and 33 months, completing the first set of chewing teeth.
These eight primary molars are later replaced by premolars, not by adult molars. Permanent molars emerge behind the primary teeth and do not replace any predecessors. The first set of permanent molars, often called the “six-year molars,” erupt around age six and are functionally important as they help establish the adult bite.
The second set of permanent molars typically appears between the ages of 11 and 13. In a fully developed adult mouth, there are generally twelve permanent molars, including the four third molars, which are positioned furthest back in the jaw. This sequence of eruption and replacement ensures a continuous set of working teeth throughout childhood and into adulthood.
Understanding Wisdom Teeth
The third molars are commonly known as wisdom teeth because they are the last teeth to emerge, typically between the ages of 17 and 25. While they function like other molars, their late development often presents challenges. Modern human jaws are frequently too small to accommodate these final four teeth, which can lead to a condition called impaction.
Impaction occurs when the wisdom tooth is blocked by the second molar or grows at an incorrect angle, preventing full eruption through the gum line. This inability to emerge properly can cause pain, swelling, and lead to oral health problems, including infection, decay, and damage to neighboring teeth. When an impacted wisdom tooth causes symptoms or is likely to cause future dental issues, surgical removal is often recommended as a preventative measure.
The procedure to remove an impacted wisdom tooth usually involves a local anesthetic and sometimes sedation, with the surgeon cutting the gum and sometimes removing bone to extract the tooth. Although it is a common procedure, potential complications like dry socket or nerve damage are possible, though rare. Many people have their wisdom teeth removed, resulting in an adult mouth with 28 teeth instead of the full 32.