When a tooth aches, the common assumption is that a cavity is responsible. While dental decay is the most frequent cause of tooth pain, the absence of a visible cavity can be confusing. Tooth pain is a symptom of irritation to the dental nerve, or pulp, which can originate from numerous sources other than bacterial decay. The cause may be hidden deep within the tooth structure, in the supporting tissues, or even referred from another part of the face.
Internal Trauma and Inflammation
A common source of intense, non-carious tooth pain is inflammation of the dental pulp, known as pulpitis. The pulp is delicate tissue encased within the tooth’s hard layers, containing the nerves and blood vessels. When the pulp becomes inflamed, the pressure has nowhere to expand, leading to significant pain.
Pulpitis is categorized based on its severity. Reversible pulpitis involves mild inflammation, often causing brief, sharp sensitivity to cold or sweets that disappears immediately after the stimulus is removed. This stage is frequently caused by minor trauma, a new filling placed close to the nerve, or a small, superficial defect.
If the irritation is more severe, the condition progresses to irreversible pulpitis. This is characterized by throbbing, spontaneous pain that lingers after exposure to temperature changes, especially heat. This persistent pain indicates that the pulp tissue is damaged beyond its ability to heal and will require endodontic treatment, such as a root canal, to remove the dying nerve. This damage often originates from a deep crack or a failing restoration.
Cracked tooth syndrome is another source of internal pain, occurring when a hairline fracture extends from the chewing surface into the dentin or pulp. These cracks are often too small to be seen or detected on a standard X-ray. The pain is typically a sharp, fleeting sensation that occurs when biting down, especially when releasing biting pressure. This is caused by the movement of the fractured segments briefly stimulating the nerve endings.
Existing dental restorations can also cause pain if they begin to fail, even without new decay. A filling or crown may develop microscopic gaps at the margins, creating a “leaking” restoration. These spaces allow fluids, bacteria, and irritating substances to seep in and reach the underlying dentin, causing pulp inflammation. The pain signals irritation to the nerve underneath, necessitating replacement to re-establish a tight seal.
External Stressors and Surface Erosion
Pain originating from the tooth’s exterior layers is often related to the wearing down of protective enamel. This loss leads to dentin hypersensitivity, characterized by a short, sharp pain triggered by thermal, tactile, or osmotic stimuli. Beneath the enamel, the dentin contains thousands of microscopic channels called dentinal tubules that extend directly to the pulp chamber.
The most widely accepted explanation for this pain is the hydrodynamic theory, which posits that external stimuli cause rapid fluid movement within these exposed tubules. This fluid shift briefly excites the sensory nerves in the pulp, resulting in the characteristic jolt of sensitivity. Dentin exposure occurs when gums recede due to aggressive brushing or periodontal disease, or when enamel is worn away by physical or chemical processes.
Chemical erosion is caused by the frequent consumption of acidic foods and beverages, such as carbonated drinks, citrus fruits, and wine. These acids dissolve the mineral content of the enamel, thinning the protective layer. Conditions like gastroesophageal reflux disease (GERD) or chronic vomiting also expose the teeth to stomach acids, leading to significant erosion on the lingual surfaces.
Chronic teeth grinding or clenching, termed bruxism, is a potent mechanical stressor that causes pain without decay. The excessive forces generated by bruxism wear down the enamel and dentin (attrition), exposing sensitive structures. This constant trauma also transmits pressure through the root to the periodontal ligament, causing generalized soreness or tenderness to chewing.
Pain from Surrounding Tissues
Inflammation in the tissues supporting the tooth can easily mimic a traditional toothache. Periodontal disease, including gingivitis and periodontitis, involves the infection and inflammation of the gums, ligaments, and bone. As the disease advances, gum tissue pulls away from the root, forming deep pockets that harbor bacteria.
Gum recession exposes the root surface, which is covered only by a thin layer of cementum and is highly sensitive. This exposure leads to pain triggered by cold, sweet, or tactile stimulation near the gumline. Chronic inflammation of the periodontal ligament can also cause the tooth to feel tender or painful when chewing.
Infections can localize in the supporting structures, leading to an abscess. A periapical abscess forms at the root tip, typically resulting from an untreated infection within the tooth’s pulp. A periodontal abscess, conversely, begins in the gum tissue, often developing within a deep gum pocket caused by advanced periodontal disease. Both types create pressure and result in constant, throbbing pain and swelling around the affected tooth.
Non-Dental Sources of Oral Pain
Sometimes, tooth pain does not originate from any dental structure at all, a phenomenon known as referred pain. The complex network of facial nerves, particularly the trigeminal nerve, can transmit pain signals from one area to another, confusing the brain about the actual source of the problem. This is common with the upper back teeth.
The roots of the upper molars are close to the maxillary sinuses. When a person develops a sinus infection (sinusitis), the resulting inflammation and pressure can press down on the tooth roots, causing a dull, generalized ache. The pain often worsens when bending over, which helps distinguish it from a dental issue.
Disorders of the temporomandibular joint (TMJ), which connects the jawbone to the skull, are another common source of referred pain. Issues with the joint or surrounding facial muscles can cause spasms that radiate pain into the teeth, often the back molars. This pain is usually accompanied by jaw tenderness, headaches, or a clicking sound when opening the mouth.
Accurately identifying the non-carious source of tooth pain requires professional evaluation. Dentists use a systematic approach, including digital X-rays to check for bone loss or infection at the root tip, and specialized vitality tests. The cold test assesses the health of the pulp by timing the nerve’s reaction to a cold stimulus. The percussion test, which involves lightly tapping the tooth, determines inflammation in the surrounding periodontal ligament.