Results of several studies were shown at the First World conference of Dental and Pulpal Pain.
Conclusions were formulated based on various in-vitro/in-vivo capillary flow tests which supported the hydrodynamic theory of dentinal sensitivity. Rapid fluid movement in dentinal tubules sensitizes Odontoblasts, triggering sensations of pain.
1)Effect of removing fluid from dentin and activation of capillary forces:
a)Per histology, Odontoblast nuclei outwardly displaced in dentinal tubules.
b)Comparable results when air blast/heat applied. Evaporation of fluid caused outward nuclei movement.
c)Confirmed with desiccating dentin 1 min, absence of sensitivity on stimulus. Once moistened, sensitivity returned and SEM confirmed nuclei moved into tubules.
2)Effect of mechanical stimulation of dentin:
- a) Pressure application resulted in fluid being displaced.
3)Effect of temperature variation and pressure:
- a) Cold produced outward and heat produced inward flow of dentinal fluid. Cold pain was sharp (A-d
fibers) and heat pain was dull (c fibers).
4) Theory for sensations associated with cavity preparations, caries, and Dental Crack Syndrome:
- a) Pain on cavity preparation due to orientation and density of tubules.
- b) Irregular dentin can block tubules, preventing sensitivity.
- c) Cold resulted in heightened fluid movement in cracked teeth.
The Hydrodynamic Theory of Dentinal Sensitivity has been supported by additional evidence.