The pulpal nerve fibers, A-delta (which respond to cold and the EPT) and C-fibers (which respond to heat and elicit the nerve response when a patient reports spontaneous tooth pain), are nociceptors. Nociceptors are sensory receptors that respond to stimuli by sending nerve signals to the brain. This stimulus can cause the perception of pain in an individual.9 By objectively testing the pulpal nerve fibers, a dentist can best determine pulpal status. Below are the current pulpal diagnosis terminologies.10
Normal pulp tests within normal limits to cold. Clinically, a patient will respond to a cold stimulus, and after the stimulus is removed, the cold sensation will dissipate immediately. The length of time it takes for a patient to respond to cold has no correlation to the diagnosis and therefore does not need to be recorded.
Reversible pulpitis is pain from an inflamed pulp that can be treated without the removal of the pulp tissue. It is not a disease, but a symptom. Classic clinical symptoms are sharp, quick pain that subsides as soon as the stimulus is removed. Physiologically, it is the A-delta fibers that are firing, not the C-fibers of the pulp.11 A-delta fibers are the myelinated, low-threshold, sharp/pricking pain nerve fibers that reside principally in the pulp-dentin junction. They can be stimulated by cold and the EPT and cannot survive in a hypoxic (low oxygen) environment. Reversible pulpitis also does not involve an unprovoked (spontaneous) response.
Symptomatic irreversible pulpitis is an inflamed pulp that cannot be treated except by the removal of the pulp tissue. Classic clinical symptoms are lingering of cold/hot stimulus greater than 5 seconds and/or patient reporting of spontaneous tooth pain. Physiologically, the A-delta fibers and/or the C-fibers can fire the neural impulses. C-fibers are the unmyelinated, high-threshold, aching-pain nerve fibers. They are distributed throughout the pulp. They are stimulated by heat and can survive in a hypoxic environment.
Asymptomatic irreversible pulpitis is a vital pulp that is incapable of healing, and endodontic treatment is consequently indicated. Although asymptomatic irreversible pulpitis is actually a histologic diagnosis to determine the inflammatory extent of the pulp, clinical examples of this diagnosis include a pulp polyp and internal resorption (Figure 4).
Pulpal necrosis can result from an untreated irreversible pulpitis or immediately after a traumatic injury that disrupts the vascular system of the pulp. A necrotic pulp does not respond to cold tests, EPT, or heat tests.
Previously treated: A tooth that has already been endodontically treated.
Previously initiated therapy: Endodontic treatment was started on a tooth but not completed with obturation.
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