When a back tooth—a molar or premolar—produces sharp pain specifically when pressure is applied, it signifies a mechanical or inflammatory issue requiring immediate attention. This pain upon biting or chewing is a specific indicator of internal compromise within the tooth or its supporting structures. The discomfort may range from a fleeting sting when you release your bite to a throbbing ache that makes chewing impossible. Since the posterior teeth bear the brunt of occlusal force, this symptom signals that the tooth’s ability to withstand that pressure has been damaged. The underlying source of this pain can stem from structural failure, internal biological damage, or problems external to the tooth itself.
Structural Damage Under Pressure
One of the most common causes of this precise pain pattern is a subtle fracture known as Cracked Tooth Syndrome (CTS). This condition occurs when a crack extends from the chewing surface vertically into the tooth structure, often invisible on standard X-rays. When pressure is applied, the two fractured segments flex apart slightly. This momentary separation causes rapid fluid movement within the dentinal tubules, stimulating the nerve endings inside the tooth’s pulp and resulting in sudden, sharp pain.
The pain is frequently described as a sharp, brief jolt, sometimes more intense upon the release of biting pressure as the fractured pieces snap back together. Teeth with large, old fillings or those subjected to significant force are most vulnerable to developing these cracks. Another structural cause involves a dental restoration, such as a filling or crown, that is failing or “high” in the bite. If a restoration is too high, it absorbs excessive force, overloading the tooth and causing pain in the periodontal ligament.
Inflammation and Infection Within the Tooth
Pain on biting points to problems within the dental pulp, the innermost layer of the tooth containing the nerves and blood vessels. Deep decay or trauma allows bacteria to penetrate the dentin and cause inflammation of the pulp, a condition called pulpitis. Because the pulp is encased in rigid dentin walls, swelling creates internal pressure that irritates the nerve endings. Biting down further pushes pressure onto this sensitized tissue, intensifying the pain.
If the bacterial infection progresses, it can result in a periapical abscess, a pocket of pus that forms at the root tip. This infection causes inflammation and swelling in the surrounding bone. The pressure from the abscess can elevate the tooth slightly within its socket. When pressure is applied, this elevated tooth contacts the opposing tooth prematurely, compressing the inflamed tissue and bone, which causes throbbing pain.
Supporting Structure and Referred Pain
Pain from chewing is not always caused by the tooth itself, but by the surrounding supportive tissues. Chronic clenching or grinding (bruxism) can strain the periodontal ligament (PDL), the soft tissue fibers that anchor the tooth to the jawbone. This strain leads to inflammation called periodontal ligamentitis, making the tooth feel tender or bruised when chewing.
In cases of advanced periodontal disease, the bone supporting the tooth can be compromised, leading to increased tooth mobility. When biting force is applied, the loose tooth shifts, irritating the weakened supporting structures and resulting in pain.
Maxillary Sinusitis
Maxillary sinusitis can cause pain that mimics a toothache in the upper back teeth. The roots of the upper molars and premolars lie close to the floor of the maxillary sinuses. When the sinus lining becomes inflamed or congested, the resulting pressure pushes downward on the sensitive nerve endings near these roots. This is referred pain, where the issue is in the sinus cavity, but the brain interprets the sensation as originating from the tooth. This pain often affects multiple upper teeth at once and may worsen when bending over or lying down.
Why Self-Diagnosis is Impossible
The various causes of biting pain—from a microscopic crack to a muscle strain or a sinus infection—require completely different treatment approaches. Attempting to manage the pain without a professional diagnosis can lead to the worsening of serious underlying conditions, such as an abscess or an expanding tooth fracture. A visual examination alone cannot differentiate between these diverse etiologies.
A dentist must employ diagnostic tools like targeted X-rays, specialized lights to reveal subtle cracks, and specific biting pressure tests to isolate the exact source of the discomfort. Since issues like an abscess or a propagating crack can lead to rapid tooth loss if left untreated, professional evaluation is necessary to formulate an effective treatment plan. While waiting for an appointment, switching to a soft diet and using over-the-counter anti-inflammatory medication can help manage immediate discomfort.