The wisdom tooth, or third molar, is the last tooth to emerge, typically between the ages of 17 and 25. Because the modern human jaw often lacks sufficient space, these teeth frequently become “impacted,” meaning they are partially or completely trapped beneath the gum line or bone. This impaction causes the wisdom tooth to push against the adjacent second molar, raising concerns about potential damage. The main question is whether the pressure from this crowding can cause the second molar to structurally fail.
Mechanical Stress and Potential for Cracking
The physical force exerted by an impacted wisdom tooth is known as mesial pressure, directed toward the front of the mouth. This constant, low-level pressure can cause the second molar to shift slightly, contributing to mild dental crowding. While the force is sufficient to cause movement, it is generally insufficient to cause a true crack or fracture in the crown or root of the second molar, as tooth structure is designed to withstand high chewing forces.
However, chronic pressure can cause micro-trauma within the supporting structures. The body responds to sustained pressure through bone remodeling, a slow biological process that facilitates tooth movement. Severe pressure, especially from a horizontally impacted wisdom tooth, can create a wedge effect leading to structural micro-damage.
The More Common Risk: Decay and Root Resorption
While true cracking is rare, the relationship between the two molars creates a more prevalent danger: a biological hazard zone. An impacted wisdom tooth angled toward the second molar forms a tight, inaccessible pocket beneath the gum line. This space is nearly impossible to clean, becoming a sanctuary for bacteria and food debris. This bacterial accumulation leads to two distinct forms of damage to the adjacent second molar.
Decay (Caries)
The first is decay, or caries, which forms on the distal (back) surface of the second molar. This decay is often deep and undetected because it is hidden by the wisdom tooth and gum tissue. If the decay penetrates the enamel and dentin, it can quickly reach the tooth’s pulp, requiring extensive treatment to save the tooth.
External Root Resorption
The second common issue is external root resorption, the body’s reaction to chronic pressure and inflammation. When a wisdom tooth pushes directly against the root of the second molar, the immune system can treat the root surface as foreign material. This process slowly dissolves the tooth root structure of the second molar. Extensive resorption can severely compromise the stability of the second molar, potentially leading to the loss of both teeth.
How Dentists Confirm Damage
Diagnosing damage caused by a problematic wisdom tooth requires clinical assessment and advanced imaging. During examination, the dentist uses a periodontal probe to measure the depth of the gum pocket between the two molars. A deep pocket, often greater than five millimeters, suggests a high risk for bacterial accumulation and periodontal disease.
The most definitive diagnostic tool is radiographic confirmation, typically a panoramic X-ray, which provides a comprehensive view of the entire jaw. This image allows the dentist to visualize the exact angle of the wisdom tooth and its proximity to the second molar’s root. For advanced or complex damage, a three-dimensional Cone-Beam Computed Tomography (CBCT) scan may be necessary.
These images identify pathological patterns, such as the “scooped out” appearance on the distal root of the second molar indicating resorption. They also reveal the presence and depth of decay hidden on the second molar’s back surface. X-rays and scans are also used to assess bone loss surrounding the second molar, which indicates chronic inflammation.
Options for Treatment and Resolution
Once an impacted wisdom tooth is confirmed to be causing damage or posing a high risk, the primary resolution is surgical extraction of the problematic third molar. Removing the source of pressure and the bacterial trap eliminates the threat to the adjacent tooth. This procedure is often performed by an oral surgeon, with complexity depending on the tooth’s position.
Treatment for the second molar depends on the extent of the damage incurred. If decay is minor and isolated to the outer surface, a simple restorative filling can be placed. When decay is deep and has reached the pulp chamber, a root canal procedure and subsequent crown may be required to save the tooth.
If external root resorption is found, the second molar is monitored closely after the wisdom tooth is removed. Minor resorption may not require further intervention, but severe compromise to the root structure diminishes the long-term prognosis. In the most severe cases, where the second molar is unrestorable due to extensive decay or root damage, its extraction may also be necessary.