A cavity, also known as dental caries, is essentially a hole that forms in a tooth as a result of decay. This process begins when bacteria in the mouth convert sugars and starches from food into acids, which then erode the tooth’s hard outer layer, the enamel. The sensation experienced depends entirely on how far this decay has progressed through the layers of the tooth.
The feelings can range from a complete lack of sensation in the earliest stages to a sharp, sudden jolt of pain, and finally, to a deep, persistent ache. Understanding these distinct phases of discomfort is the first step in knowing when to seek professional help.
Subtle Signs of Early Decay
In the initial stage, when decay is only affecting the enamel, a person will often feel nothing at all, which is why regular dental check-ups are so important. The decay begins as a demineralization process, sometimes appearing as a white or chalky spot on the tooth surface. This early phase, sometimes called a “white spot lesion,” may still be reversible with fluoride treatments.
As the acid erosion continues, a person might notice a very minor change in the tooth’s texture. You may feel a slight roughness or a small catch in the tooth surface when running your tongue over it. Any sensitivity at this point is usually extremely fleeting, lasting less than a second, and is easily dismissed or ignored.
When the decay just penetrates through the enamel and barely enters the underlying dentin, the first true signs of sensitivity may occur. This mild discomfort is momentary and non-reactive, meaning it does not linger after the stimulus is gone.
Sharp Pain Triggered by Stimuli
Once the cavity breaches the enamel and exposes the dentin layer, the experience shifts dramatically from subtle awareness to sharp, reactive pain. Dentin is a porous layer filled with millions of microscopic tubes called dentinal tubules, which contain fluid and lead directly to the tooth’s pulp where the nerves reside. When the protective enamel is lost, these fluid-filled tubules are exposed to the oral environment.
Specific external stimuli cause the fluid within these tubules to move rapidly. Extreme cold from ice cream or cold air causes the fluid to shrink and pull away, while sugary foods create an osmotic effect, both leading to fluid movement. This fluid shift stimulates mechanoreceptors on the nerve endings near the pulp, resulting in a sudden, intense jolt of pain.
The defining characteristic of this stage is that the pain is sharp but transient. The discomfort immediately stops once the stimulus is removed, such as when you finish a cold drink. Sensitivity to heat, cold, or sweetness that lasts only a few seconds is a classic sign that decay has reached the dentin.
Constant Pain and Severe Discomfort
A throbbing, persistent ache indicates the decay has progressed significantly deeper, reaching the pulp chamber, the soft tissue core of the tooth containing blood vessels and nerves. Bacteria and their toxins now cause inflammation in this confined space, a condition called pulpitis. Since the pulp is encased in hard dentin, there is no room for the inflamed tissue to swell, which puts immense pressure on the nerves and causes severe discomfort.
The pain at this stage is often described as deep, aching, and throbbing, and it may radiate into the jaw, ear, or temple. A clear sign of irreversible damage is spontaneous pain that starts without any apparent trigger, sometimes waking you up in the middle of the night. Another red flag is pain that lingers for several minutes or even hours after a hot or cold stimulus has been removed, signaling that the inflammation is significant.
Pressure sensitivity also becomes noticeable, with sharp pain occurring when you bite down or chew food. If the infection exits the tooth root and causes a pocket of pus to form in the surrounding bone, an abscess develops. This advanced stage can cause visible swelling in the gum tissue near the tooth or even in the jaw and face, accompanied by a foul taste in the mouth.
When to See a Dentist
Any pain, sensitivity, or change in a tooth’s feeling is an indication that professional attention is necessary. If you experience lingering pain that persists for more than a few seconds after a trigger is gone, or if you have any spontaneous, throbbing pain, you should schedule an appointment immediately. These symptoms suggest the pulp is inflamed or infected, requiring prompt intervention to prevent tooth loss.
Visible signs like a dark spot, a noticeable hole, or swelling of the gums around a tooth also warrant an urgent visit. The dentist will perform a visual examination and typically take dental X-rays to determine the depth of the decay. This allows the dentist to confirm if the decay is minor and confined to the enamel or if it has reached the sensitive inner layers.