The most common cause of pulpitis in clinical practice is caries. One can observe a change in the color of the tooth surface, starting with a chalky white appearance in the early stages, followed by the formation of a cavity. Eventually, the decay reaches the inner part of the tooth, leading to a loss of integrity as a portion of the tooth's surface becomes damaged and softened.

These cavities harbor a large number of microorganisms. If an individual is vigilant and seeks dental care early—before the pulp is affected—the dentist can remove the decayed tissue, clear the infection, and seal the damaged area with restorative materials. This procedure prevents bacteria from further affecting the pulp.

However, if a patient neglects their dental health, thinking that minor damage is inconsequential, the caries will continue to destroy the tooth structure. As the decay progresses and approaches the pulp, the patient may begin to experience discomfort, particularly when consuming cold, hot, sour, or sweet foods. Additionally, when chewing, if food enters the cavity, it may cause pain. At this stage, seeing a dentist promptly can help stop the progression of pulpitis and preserve the healthy pulp tissue.

If the disease continues to advance without treatment, oral bacteria from the cavity may eventually penetrate the pulp tissue, leading to pulp infection. This can result in inflammation, swelling, and necrosis of the pulp. Since the pulp is surrounded by hard tooth tissue, inflammation causes the internal tissue to swell, increasing pressure. At this point, the affected tooth may cause severe pain, sometimes radiating to the same side of the face or even to the ear. The saying, "toothache is not a disease, but when it hurts, it's unbearable," is particularly relevant to this stage of the condition.