Rheological material characterisation in dentistry

 RHEOLOGY

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:

  1. Newtonian
  2. Pseudoplastic
  3. Dilatant
  4. plastic
1) Newtonin :
  • 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.
2) Pseudoplastic:
  • Pseudoplastic fluid is a shear thinning fluid
  • Viscosity decreases ,shear rate increases until it reaches constant value.
  • For example: polycarboxylate cement ,elastomeric impression material.


3)
Dilatant:
  • 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.


Factors affecting:

1) TEMPERATURE:
When temperature  increases , velocity decreases 
for example: ghee
2)Pressure

FLOW:

Term used in dentistry to describe rheology of atmospheric material such as wax.


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