The wisdom teeth, formally known as third molars, are the last set of teeth to emerge into the mouth, typically appearing between the ages of 17 and 25. These molars do not keep growing indefinitely once they have erupted. Like all other permanent teeth, wisdom teeth are formed through a finite developmental process. Once the tooth structure is complete, the growth stops when the root reaches its final length and the surrounding jawbone matures.
The Difference Between Growing and Erupting
The process of a tooth forming and its movement into the mouth are two distinct biological events. Tooth development, or odontogenesis, begins much earlier than the eruption, with the initial tooth bud forming deep within the jawbone around age seven. This development involves the creation of the hard tissues—enamel, dentin, and cementum—which establishes the tooth’s final size and shape.
The crown, the visible part of the tooth, forms first, followed by the roots, which grow longer in the jaw. Eruption is the separate, physical movement of the tooth upward from its crypt in the bone until it reaches its functional position in the oral cavity. This movement is not the same as growth, but rather a migration driven by forces like root elongation and bone remodeling.
Root development is the factor that signals the end of a tooth’s growth phase. For wisdom teeth, the root is typically fully formed between the late teens and early twenties. It can continue to lengthen for up to three years after the tooth has appeared in the mouth. Once the root apex closes, the tooth is considered biologically mature, and no further growth occurs. The eruption process requires the breakdown of bone ahead of the moving tooth by specialized cells called osteoclasts, and the simultaneous formation of new bone behind it.
Why Teeth Seem to Shift Over Time
The common confusion about wisdom teeth “growing” after eruption stems from the fact that teeth can and do move throughout a person’s life. This movement is a slow, continuous process, not a renewal of growth.
One primary mechanism is known as mesial drift, which is the natural tendency of all posterior teeth to shift slightly forward toward the midline of the jaw. Mesial drift occurs to help maintain tight contact between teeth, compensating for the small amounts of wear that happen on the sides of the teeth from daily chewing. This forward migration is facilitated by the continuous, gentle remodeling of the alveolar bone that surrounds the tooth roots.
Specialized cells constantly resorb bone on the forward side of the tooth and deposit new bone on the trailing side, allowing for movement. Pressure from the surrounding soft tissues also contributes to gradual shifting. The constant, subtle forces exerted by the tongue pushing outward and the cheeks and lips pressing inward create a delicate balance that positions the teeth. As this muscle balance changes with age, the teeth can subtly shift, leading to crowding or misalignment that is mistakenly attributed to the wisdom tooth getting larger.
When Eruption Causes Problems
Issues arise when the physical process of eruption is blocked, which happens frequently with third molars due to the relatively small size of the modern human jaw. When a wisdom tooth cannot fully emerge into the dental arch because it is obstructed by another tooth, bone, or gum tissue, it is classified as impacted. Impaction can be full, where the tooth remains completely beneath the gum line, or partial, where part of the tooth has broken through.
The inability to fully erupt leads to pathological conditions often mistaken for continued growth. A common issue is pericoronitis, which is an infection of the flap of gum tissue, or operculum, that partially covers an erupting tooth. This area easily traps food debris and bacteria, causing painful swelling and infection.
An impacted tooth may also damage the adjacent second molar by creating a site for decay or causing root resorption on the neighboring tooth due to sustained pressure. Less commonly, a fluid-filled sac called a dentigerous cyst can form around the crown of a fully impacted tooth within the jawbone. These cysts can expand over time, leading to the destruction of the surrounding bone structure, which is a serious complication requiring professional assessment and removal.