Question

4. Give the comparisons of Plaster of Paris bandage versus the Synthetic casting tape for casts and splints.

5. Give indications of various types of circular casts and splints you know for both the upper extremities and lower extremities.

6. Discuss in details the chemistry of Plaster of Paris.

Answer 1

A cast is used to immobilize the fractured or injured area which will keep a fractured bone or joint from moving to aid healing. There are two types of casts.

1. Plaster of Paris (POP) casts: It is made up of POP, a heavy white powder, when mixed with water, forms a thick paste that hardens quickly. They are heavy and may dissolve in water.

2. Synthetic (fibreglass) casts: is made out of fibreglass, which comes in different colours and are lighter than POP. The fibreglass covering is water-resistant.

Both s types are applied to injured or affected limbs to immobilize them and allow the bones, ligaments, tendons or muscles regain its anatomy and physiology after the fracture or injury. They can be utilized after surgical procedures after correction of congenital limb deformities.

4. Give the comparisons of Plaster of Paris bandage versus the Synthetic casting tape for casts and splints.

Characters	Plaster of Paris	Synthetic
A composition	made from a type of naturally occurring gypsum	made from woven fibreglass that is coated with polyurethane resin.
Appearance	White colour	Different colours are available
Weight	Heavy	lighter and stronger than plaster casts
Durability	Less durable (Easily reacts with water)	More durable (More water resistant)
Porosity	Less porous	More porous
Drying Time	48 hours	30 minutes
Flexibility	Easy to mould	Difficult to mould than POP
Cost	Cheap	Costly

5. Give indications of various types of circular casts and splints you know for both the upper extremities and lower extremities.

Immobilization of an acute fracture or soft tissue injury of an upper extremity.

Short arm casts (extending from distal palmar creases to proximal forearm: Fracture of metacarpals, stable wrist

Long arm casts ex: tending from distal palmar creases to proximal humorous.

Restricting movement of wrist and elbow.

Lower extremity casts:

Short leg casts: for stable ankle and foot injuries

Long leg casts: unstable ankle, fractured tibia, knee or soft tissue injuries

Cylinder cast: extends from groin to malleoli of the ankle. Used in case of knee injuries or fractures

6. Discuss in details the chemistry of Plaster of Paris.

  Chemical name: calcium sulphate hemihydrate

Chemical formula:CaSO4.1/2H2O

       Plaster of Paris is prepared by heating gypsum (CaSO₄.2H₂O) to a temperature of 373 K in a kiln. Heating of gypsum causes lose of one and a half molecules of water of crystallization, and half-molecule of water of crystallization remains attached with calcium sulphate. If gypsum is heated above the temperature of 373 K then all the water of crystallization is removed and results in anhydrous calcium sulphate or dead burnt plaster.

Properties:

Colour: white powder

Sets into the hard mass within half an hour of adding water due to hydration of t0 form crystals of gypsum.

Should be used in moist proof containers to prevent hardening