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 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 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.