Establishing a diagnosis involves examination, review of medical and dental history, clinical data analysis, and tests that are specific to your condition. Only a dentist can evaluate your signs and symptoms to establish a diagnosis.
A tooth has four possible pulp diagnoses: Normal, reversible pulpitis, irreversible pulpitis, or necrotic (dead). Differentiating between reversible and irreversible pulpitis, and necrotic tooth usually involves the application of hot, cold and mild electrical stimuli. This is done to assess how the nerves inside the tooth respond, or if they respond at all.
Prolonged painful response to stimuli supports a diagnosis of irreversible pulpitis. No response to hot, cold or mild electrical stimuli supports a diagnosis of necrotic tooth (i.e. the tissues inside it are no longer living). Sharp response to stimuli that quickly diminishes upon removal of the stimuli supports a diagnosis of reversible pulpitis. Often a tooth with reversible pulpitis won't be as sensitive to heat. A tooth may have a diagnosis of reversible pulpitis one day, and then take a turn for the worse. Steps can be taken to help prevent that, but they are not always successful.