Pain in the back teeth experienced specifically while eating signals an underlying problem within the tooth structure, its surrounding support, or the jaw mechanism. Molars and premolars bear the highest forces during chewing, so any compromise in their integrity manifests as discomfort when pressure is applied. Understanding the potential origins of this pain, from structural defects to deep infections, is the first step toward effective treatment.
Structural Damage and Decay
Physical defects in the hard tissues of the tooth frequently cause pain when biting down, as chewing pressure exacerbates these weaknesses. Dental caries, or cavities, weaken the enamel and dentin layers, creating a hollowed area that flexes under force. When decay progresses close to the internal pulp, the pressure of food against the compromised structure translates into a sharp, localized sensation. This stress is particularly noticeable in weakened tooth walls, such as those with decay hidden beneath old fillings or located between teeth.
Cracked Tooth Syndrome, involving a fracture line extending into the dentin, is a common source of biting pain. When pressure is applied, the tooth segments move independently, briefly irritating the internal pulp tissue. The pain is often sharp and fleeting, manifesting most acutely when the pressure is released and the segments snap back together. Fractures are frequently caused by chronic teeth grinding or biting hard objects like ice or kernels.
Existing dental restorations can cause chewing discomfort if they are worn or failing. Over time, the bond between an old filling or crown and the natural tooth can break down, creating microscopic gaps. These breaches allow bacteria and food particles to seep inside, leading to new decay and inflammation. Additionally, a worn filling may cause an uneven distribution of occlusal forces, placing excessive strain on the remaining tooth structure during meals.
Inflammation and Deep Infection
Pain originating from within the tooth often signals irritation or infection of the dental pulp, the soft tissue containing nerves and blood vessels. This condition, known as pulpitis, is classified by the severity of inflammation and the pulp’s potential to recover. In a reversible state, the pain is a sharp, non-lingering response to a stimulus like cold or pressure. This indicates the pulp is inflamed but can still heal if the underlying cause, such as a shallow cavity, is removed.
Irreversible pulpitis is a more concerning development where the pulp tissue cannot recover due to severe inflammation. The pain is usually intense, can be spontaneous, and often lingers after the stimulus is removed, sometimes presenting as a throbbing sensation. Since this inflammation is confined within the rigid tooth walls, it creates pressure on the nerve. The added force of chewing dramatically increases this internal stress. If untreated, the pulp tissue dies, and the infection can spread beyond the root tip.
If the infection spreads, it results in a periapical dental abscess—a collection of pus and inflammatory tissue within the jawbone near the root apex. The immune response creates swelling trapped within the bone. When chewing pressure is applied, the tooth is pushed into this swollen area, resulting in severe pain. Separately, dentin hypersensitivity (root sensitivity) causes sharp discomfort when chewing, especially with cold foods. This occurs because gum recession or enamel wear exposes the dentin, allowing fluid movement in the tubules leading to the nerve.
Jaw, Gum, and Alignment Issues
Pain during chewing does not always stem from the tooth itself, but can originate from supporting structures or the jaw mechanism. The periodontal ligament (PDL) anchors the tooth root to the jawbone and acts as a shock absorber. When the PDL is inflamed or damaged, such as from advanced periodontal disease or trauma, its compression during chewing becomes painful. The sensation is often described as the tooth feeling “bruised” or slightly elevated in the socket.
Advanced gum disease (periodontitis) destroys the bone supporting the teeth, leading to increased tooth mobility. As bone recedes, the periodontal ligament becomes less stable. Normal chewing forces can cause the tooth to shift excessively, irritating the remaining ligament fibers and causing discomfort. This instability is a direct mechanical cause of biting pain, separate from decay or infection within the tooth crown.
Temporomandibular Joint Disorder (TMD) is a non-dental cause of referred pain, affecting the jaw joint and the muscles controlling movement. Dysfunction in the masticatory muscles, often exacerbated by clenching or grinding, can radiate pain to the back teeth, mimicking a toothache. This referred pain is typically a dull, broader ache affecting multiple teeth on one side and intensifies when the jaw muscles are engaged during chewing.
Occlusal interference, or a high spot, commonly causes pain, particularly following a new filling or crown placement. If the restorative material is slightly taller than surrounding teeth, it takes the brunt of the biting force, creating localized trauma. This constant, uneven pressure strains the tooth and the periodontal ligament, leading to pain when chewing. A simple adjustment to shave down the high spot resolves this issue.
Seeking Relief and Diagnosis
Immediate steps for temporary relief focus on minimizing force and inflammation until professional help is available. Switching to a soft diet and avoiding chewing on the painful side prevents further trauma to a potentially cracked tooth or inflamed ligament. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, help manage pain by reducing inflammation in the dental tissues. Rinsing the mouth with warm salt water several times a day can also provide relief by reducing inflammation and cleansing the area.
Certain symptoms indicate a need for immediate dental attention, suggesting a rapidly worsening infection. These signs include:
- Severe, throbbing pain that does not respond to pain relievers.
- Swelling of the face or gums.
- A fever.
- Pain that prevents sleep.
Such symptoms point to an abscess or acute infection requiring prompt intervention to prevent the spread of bacteria. Delaying treatment significantly raises the possibility of complications, including tooth loss.
A dentist uses specialized methods to pinpoint the exact cause of the pain, which can be difficult to locate. Diagnostic tools include dental X-rays to visualize decay, bone loss, and abscesses, though they are often insufficient for detecting fine cracks. A common technique uses a specialized biting instrument, like a plastic stick, allowing the patient to apply pressure to individual cusps to isolate a fracture or inflamed ligament. Transillumination, shining a bright fiber-optic light through the tooth, can make a crack line visible.
Treatment is determined directly by the diagnosis, addressing the root cause of the discomfort. Pain from a high spot is resolved with an occlusal adjustment, and a new cavity requires a simple filling. If a small crack or reversible pulpitis is diagnosed, the tooth may be protected with a full-coverage crown to prevent further flexing and allow the pulp to heal. If irreversible pulpitis or an abscess is present, root canal therapy is necessary to remove the infected pulp tissue and save the tooth.