Pain originating from a third molar—commonly known as a wisdom tooth—can manifest as a unilateral headache. These teeth are the last molars to emerge, typically between the ages of 17 and 25. They often lack the necessary space to grow properly within the jawbone. When this occurs, the resulting irritation in the back of the mouth can trigger pain signals that the brain misinterprets as coming from the temple, jaw, or head region.
Understanding Referred Pain and Unilateral Headaches
The mechanism behind a one-sided headache stemming from a dental problem is known as referred pain. This occurs because the sensory nerves supplying the teeth, jaw, face, and head all share a common pathway to the brain. The major neural structure responsible for sensation in these areas is the trigeminal nerve (Cranial Nerve V).
The trigeminal nerve has three primary branches, including the mandibular and maxillary branches that cover the teeth, jaw, temples, and forehead. When an impacted wisdom tooth irritates nerve endings in the jaw, the pain signal travels along this pathway. The brain receives the signal from the shared nerve trunk and mistakenly localizes the pain to another area, such as the temple or ear on the same side.
Since a person has wisdom teeth on both sides of the jaw, any problem is localized to the side where the affected tooth is located. For example, an impacted tooth on the left side irritates the left mandibular nerve branch. Consequently, the referred headache pain is felt predominantly on the left side of the head, creating the distinct unilateral symptom.
Primary Causes of Wisdom Tooth Discomfort
Impaction Pressure
Impaction pressure is one of the most common causes, occurring when the third molar is unable to fully erupt and grows in at an angle. This impaction causes the tooth to exert physical pressure on the adjacent second molar or directly against the jawbone. The resulting force triggers nerve irritation and muscle tension that radiates upward into the face and head.
Pericoronitis
Pericoronitis is the inflammation and infection of the gum tissue surrounding a partially erupted wisdom tooth. When the tooth breaks through the gum only halfway, a flap of tissue (called an operculum) is created where food debris and bacteria can easily become trapped. This localized infection leads to swelling, throbbing pain, and inflammation. This inflammation can extend to the neck and cause a severe headache.
Temporomandibular Joint (TMJ) Strain
The third source of discomfort is strain on the temporomandibular joint (TMJ), which connects the jaw to the skull. An erupting or misaligned wisdom tooth can disrupt the natural alignment of the bite. This forces the jaw muscles to work harder to compensate. This muscular overcompensation and strain on the joint can lead to a unilateral tension headache resulting from the dental imbalance.
When to Consult a Dentist
Recognizing when a headache warrants a dental visit requires focusing on accompanying symptoms that suggest localized infection or severe impaction.
A dentist should be consulted if the unilateral headache is accompanied by any of the following signs:
- Pain or tenderness at the very back of the jaw.
- Visible swelling of the gums or cheek on the affected side.
- A persistent bad taste in the mouth, indicating an ongoing infection.
- Fever.
- Difficulty swallowing.
- Trismus (limited ability to open the mouth).
These more serious symptoms suggest the infection may be spreading beyond the immediate area of the tooth. Only a professional examination, typically involving a panoramic X-ray, can confirm if the wisdom tooth is the true source of the chronic head pain.