The emergence of wisdom teeth, known scientifically as third molars, often coincides with subtle shifts in bite or tooth alignment. This observation has led to a widely held belief that these late-erupting teeth physically push the jawbone outward, causing it to expand or noticeably increase in size. This article examines the biological timeline of skeletal development and the scientific reality behind this common concern.
The Timeline of Jaw Development
The development of the upper jaw (maxilla) and the lower jaw (mandible) follows a predictable schedule of growth starting early in life. Major growth of the facial skeleton, particularly the maxilla, is largely complete by early adolescence, around 12 to 16 years old.
The mandible continues to grow for a longer period, often showing significant development until the late teenage years. Most major skeletal growth of both jaws ceases between the ages of 16 and 18. This maturation process means the jawbones are largely rigid and structurally mature when third molars begin to emerge, usually between the ages of 17 and 25.
Do Wisdom Teeth Increase Jaw Size?
Scientific consensus and detailed anatomical studies confirm that wisdom teeth do not cause the jawbone itself to expand or get bigger. The jaw is a dense, mature skeletal structure by the time the third molars begin their eruption path. There is no known biological or mechanical mechanism by which the force of tooth eruption could stimulate the outward growth or enlargement of an already mature bone.
The size and shape of the jaw are primarily determined by genetics and the major growth phases that occur during childhood and adolescence. If the wisdom teeth do not have sufficient space to erupt, they become impacted or grow at an angle. Any pressure exerted by the emerging tooth is contained within the existing bone structure and does not lead to an increase in the jaw’s overall dimension.
Why Teeth Shift in Adulthood
The perception that the jaw is getting bigger often stems from the subtle but noticeable crowding of the front teeth that occurs in late adolescence and early adulthood. This shifting is not caused by third molars pushing the entire arch forward, but rather by more subtle, age-related factors.
Mandibular Growth and Mesial Drift
One contributing factor is minor, natural forward rotational growth of the mandible that can continue into the third decade of life. This late growth, though small, can contribute to crowding in the lower front teeth. Another element is the natural, lifelong tendency for all teeth to drift forward, known as mesial drift, which can cause teeth to crowd together over decades.
Soft Tissue Pressure
Pressure from the surrounding soft tissues also influences tooth position throughout life. The pressure from the lips and cheeks pushing inward is balanced by the tongue pushing outward. If this balance is disrupted, or as facial tissues change with age, teeth can shift, creating the appearance of crowding mistakenly attributed to the wisdom teeth.
Common Problems Caused by Third Molars
While third molars do not enlarge the jaw, they can cause problems when they become impacted, meaning they are partially or fully trapped beneath the gums or bone. The lack of space often causes the tooth to erupt at an angle, which can lead to damage to the adjacent second molar, sometimes causing root resorption or decay.
Impacted third molars are difficult to clean, making them susceptible to decay and gum disease. If a partially erupted tooth is covered by a flap of gum tissue, bacteria and debris can become trapped, leading to a localized infection called pericoronitis. In rare cases, the sac surrounding the crown of an unerupted tooth can develop into a fluid-filled cyst that can destroy the surrounding jawbone.