Pulpal pain

A great majority of teeth with irreversible pulpitis are symptom-free which makes the diagnosis of pulpitis difficult. On the other hand, the presence of pain is not necessarily an indication of irreversible reactions in the pulp. Ninety per cent of the sensory nerve endings in the pulp are found in the coronal pulp and only 10% in the canal(s). There are two types of sensory nerves in the pulp: myelinated A-delta fibers of the pulp have a relatively low threshold and react to stimuli with sharp pain that ceases rapidly when the irritation is removed. Unmyelinated C-fibers have a higher threshold and mediate more severe, long lasting pain stimulated by a severe pulpal inflammation. Dentinal pain in hypersensitive dentine or triggered by other irritation of dentine (bur, heat, e.g.) is typically mediated by A-fibers and is often related to weak or absent inflammatory reaction in the pulp. Finally, in severe pulpal pain both A-fibers and C-fibers may be involved.