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Dentin Sensitivity Theories
Exposed dentin is very sensitive. Three main theories have been proposed to explain dentin sensitivity.
- Direct neural stimulation theory
- Fluid or hydrodynamic theory
- Transduction theory
Direct Neural Stimulation
This theory states that the nerve endings inside the dentinal tubules are directly stimulated and cause sensitivity/pain.
The arguments against this theory are as follows:
- Even though nerve endings are seen inside the dentinal tubule, they are confined to the inner dentin and are absent in the outer dentin.
- Topical application of the local anaesthetic to the surface of dentin does not eliminate dentin sensitivity.
Fluid Or Hydrodynamic Theory
- This theory states that dentin sensitivity is due to the movement of fluid inside the dentinal tubules.
- Various stimuli such as heat, osmotic pressure and drying can cause outward movement of fluid, whereas cold stimulus causes inward movement of fluid.
- Movement in either direction causes mechanical disturbance of the nerve endings which are present in the inner dentin and are close to the odontoblasts and their process.
- The free nerve endings in the plexus of Raschkow sense these disturbances, resulting in sensitivity/pain.
- This widely accepted theory proposes that nerve endings act as mechanoreceptors.
Transduction Theory
This theory states that various stimuli stimulate the odontoblastic process which conducts the impulses to the nerve endings located in the inner dentin.
The arguments against this theory are as follows:
- Neurotransmitter vesicles are absent in the odontoblastic process.
- There is no synaptic relationship between the odontoblastic process and the nerve endings
