In order to explain the way pain is transmitted to dentin many scientists proposed many theories of pain transmission through dentin to the pulp where the nerves are largely crowded. Pain in general is defined by International Association for the study of Pain (IASP) as – “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
Pain is defined by Monheim as – “an unpleasant emotional experience usually stimulated by a noxious stimulus and transmitted over a specialized neural network to the CNS where it is interpreted as such.”
The pain or the stinging sensation seen on the teeth is due to the dentin which makes up the bulk of the tooth, and is a living tissue, it contains Odontoblastic processes which arise from the Pulp and are considered to be the main transporter of pain.
Some of the most accepted theories of Pain are:
1) Direct Neural stimulation theory
2) Transduction theory
3) Hydrodynamic theory
Now let us get to know about each of these theories briefly.
1) Direct neural stimulation theory: According to this theory the pain stimuli reaches the nerve endings in the inner dentin. But how it reaches the nerve endings could not be explained. Due to little scientific proof it is not accepted now.
2) Transduction theory: According to this theory, the Odontoblastic processes are excited by the stimulus and transmit the impulses to the nerve endings. This theory is also of little importance as it has been noticed that there are no neurotransmitters in the dentin.
3) Hydrodynamic theory: This theory is also known as ‘Fluid theory’, According to this theory the harmful stimuli such as heat, cold, air blast, mechanical pressure. . etc cause some changes in the fluid movement in the dentinal tubules either inwards or outwards which causes some mechanical disturbances due to mechanoreceptors present at the nerve endings, which stimulates the pain mechanism.
The various types of pain are – Vague pain, Burning pain, Throbbing pain, Stabbing pain, Shooting pain (Trigeminal neuralgia).