What condition is diagnosed when a tooth responds to cold stimulus within 3 seconds during pulp testing?

Reversible pulpitis is characterized by a tooth's response to thermal stimuli, such as cold, typically lasting no longer than a few seconds. When a tooth exhibits a response to cold within 3 seconds during pulp testing, it indicates that the pulp is still vital and capable of healing. In reversible pulpitis, the inflammatory process has begun, but it is not extensive enough to cause irreversible damage. The patient's discomfort usually subsides quickly after the cold stimulus is removed, reflecting the transient nature of the condition.

In contrast, irreversible pulpitis would elicit a prolonged response to cold, often continuing to ache or throb after the stimulus is removed, indicating that the pulp is compromised and not capable of recovery. A healthy tooth would respond similarly to cold but would not cause any discomfort, while a necrotic pulp would not respond at all to the stimulus, indicating death of the dental pulp. Therefore, the rapid response and transient discomfort align with the characteristics of reversible pulpitis.