Rheological material characterisation in dentistry
Rheology is the study of deformation and flow characteristic of matter.
Importance of Rheology in dentistry :
In dentistry we are subjected to manipulate material which flow or deform when subject to stress.
Classification of fluid based on rheology:
- Newtonian fluid have a constant viscosity they,have ideal fluid shear stress proportional to strain rate .
- For example- water and newly mixed zinc phosphate cement.
- Pseudoplastic fluid is a shear thinning fluid
- Viscosity decreases ,shear rate increases until it reaches constant value.
- For example: polycarboxylate cement ,elastomeric impression material.
- Dilatant fluid is a shear thickening fluid
- Viscosity increases ,shear rate increases
- For example:traditional resin composite
4) Plastic fluid:
- Plastic fluid until certain yield stress is applied ,attain constant viscosity.
- The application of yield stress to cause flow in material is known as bingham characteristic.
- Example ketchup bottle- ketchup is a thixotropic material ,when subjected to constant shear rate for a period of time the viscosity drops.
When temperature increases , velocity decreases
for example: ghee
Term used in dentistry to describe rheology of atmospheric material such as wax.