When a molar hurts during chewing, it signals that the tooth’s structural integrity or inner health is compromised. This pain, triggered by direct mechanical pressure, is distinct from generalized sensitivity and requires professional diagnosis. Ignoring this symptom can allow a minor issue to progress into a serious infection or permanent damage. Understanding the root cause of this pressure-induced discomfort is the first step toward preserving the molar.
Decay and Failed Dental Work
Chewing pain may result from a deep cavity exposing the sensitive inner layers of the tooth. Dental decay progresses through the enamel into the dentin, which contains tubules leading directly to the nerve-filled pulp. When chewing forces material into these exposed tubules, the fluid movement irritates the nerve tissue, causing sharp, immediate pain.
Existing dental restorations, such as fillings or crowns, can also fail and cause pressure-related pain. A fractured or loose filling allows bacteria and food debris to seep underneath its edges. Chewing pressure forces this material into the micro-gap, irritating the underlying tooth structure or causing secondary decay that progresses toward the nerve.
A new or existing restoration placed too high can also create an issue when biting down. The molar hits it prematurely, causing excessive force on that single tooth. This uneven pressure irritates the periodontal ligament surrounding the tooth root, leading to soreness and pain when the jaw closes. Adjusting the bite to redistribute the forces evenly often resolves this issue quickly.
The Hidden Danger: Cracked Tooth Syndrome
Cracked Tooth Syndrome (CTS) involves a fracture often too fine to be seen on a standard X-ray. This syndrome is characterized by a crack, typically running vertically, extending from the chewing surface into the dentin or pulp. The pain from a cracked tooth is often intermittent, erratic, and difficult to pinpoint.
The pain mechanism occurs when the tooth flexes under biting pressure. As the jaw releases pressure, the cracked segments snap back together, causing a sharp “rebound pain” that stimulates the nerve. This flexing action irritates the pulp tissue inside the tooth, which is sensitive to movement and pressure changes.
Common triggers include biting on hard objects, like ice, or chronic grinding (bruxism). Teeth with large restorations are vulnerable to cracking because their original structure has been weakened. If left untreated, the crack can propagate further, leading to irreversible damage to the pulp or a complete split of the tooth.
Infection of the Tooth’s Inner Core
Chewing pain may signal a problem involving the dental pulp, which houses the nerves and blood vessels. When deep decay or trauma causes irreversible pulpitis, the inflamed pulp tissue swells within the rigid tooth walls. Chewing exacerbates this trapped inflammation, leading to intense, lingering pain that persists long after the biting stimulus is removed.
If the pulpal infection progresses, bacteria can spread beyond the root tip into the jawbone, forming a periapical abscess. This abscess creates a painful pocket of pressure at the end of the root. Chewing force is transmitted through the tooth onto this inflamed area, resulting in severe, throbbing pain.
An abscessed molar is tender to the touch and can cause symptoms like fever or swelling in the face or neck. The pain is constant and throbbing, intensifying when pressure is applied during chewing. Prompt intervention, such as a root canal procedure to remove the infected tissue, is necessary to prevent the infection from spreading.
Pain from Surrounding Tissues and Structures
Not all chewing pain originates from the molar itself; surrounding tissues can be the source of discomfort. Advanced periodontal disease destroys the supporting bone and ligaments around the tooth root. Biting down on a tooth with compromised support irritates the inflamed periodontal ligament, causing pain.
Inflammation in the maxillary sinuses, located above the roots of the upper molars, can mimic dental pain. When a sinus infection or allergy causes fluid to accumulate, the pressure pushes down on the molar roots. This leads to referred pain that feels like a toothache, often affecting several upper molars and worsening when bending over.
Chronic habits like teeth clenching or grinding (bruxism) cause generalized soreness in the molars and jaw muscles. The excessive force exerted on the teeth and supporting structures leads to muscle fatigue and tenderness. This soreness is then aggravated by the normal forces of chewing, resulting in a dull ache felt across multiple teeth.