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The Hydrodynamic or Fluid Movement theory is one of three main theories in dentistry developed to explain dentine hypersensitivity, which is a sharp, transient pain arising from stimuli exposure. It states that different types of stimuli act on exposed dentine, causing increased fluid flow through the dentinal tubules. In response to this movement, mechanoreceptors on the pulp nerves trigger the acute, temporary pain of dentine hypersensitivity.
The fluid flow mechanism behind hydrodynamic theory was first introduced by Alfred Gysi in 1900, and subsequently developed by Martin Brännström in the 1960s through a series of experimental studies. Further supporting evidence has since been collected from epidemiological surveys and experimental data comparing dentinal tubule numbers in hypersensitive and non-hypersensitive teeth.
Alternate theories include the “dentine innervation” and “odontoblast transduction” theories, both of which lack substantial supporting evidence. The hydrodynamic theory is currently the accepted explanation for dentine hypersensitivity, upon which several treatment and diagnostic strategies have been built by dental practitioners.