[The hydrodynamic behavior of dentinal tubule fluid under occlusal loading]

In an in-vitro study, the fluid movements were quantitatively recorded in natural teeth incorporated rigidly in a closed measuring system and exposed to an occlusal load of 122.6 N. Fluid movements under load are the result of elastic deformations of the tooth. Occlusal loads which were repeated within a short period of time caused a reversible plastic deformation. In comparison to the unfilled tooth the placement of an MOD restoration combined with a glass ionomer cement base caused the following alterations in fluid movements: composite inlay -24.7%, ceramic inlay +34.7%, MOD amalgam -3.1%; the placement of the base per se induced a reduction of -12.7%. In this in-vitro study, the physical properties of the restorative materials governed the magnitude of the fluid movements under load. The results are in contradiction to clinical findings and favor the pulpitis-related genesis of postoperative sensitivity. The intratubular and intrapulpal fluid movements under occlusal load simply seem to trigger the pain sensation.