Plaster of Paris is the most commonly used material for immobilization of fractures. Chemically the plaster of Paris is?

Appeared in: UPRVUNL - 2021

Explanation

Plaster of Paris is the common name for calcium sulphate hemihydrate (CaSO₄·½H₂O).
It is created by heating gypsum (calcium sulphate dihydrate) to remove most of its water content.
When mixed with water, it rehydrates back into gypsum, releasing heat (an exothermic reaction) and hardening into a rigid cast.
Among the given options, Calcium sulphate is the correct chemical classification.

Option A: Calcium phosphate is the primary mineral that makes up human bones and teeth, giving them their strength and rigidity. It is not the chemical composition of Plaster of Paris.
Option B: Calcium hydroxide, also known as slaked lime, is an inorganic compound used in industrial settings, such as in cement and mortar, and has applications in dentistry as a pulp-capping agent. It is not Plaster of Paris.
Option C: Calcium carbonate is a common substance found in rocks (limestone, marble) and is the main component of pearls and the shells of marine organisms. It is also used medically as a calcium supplement or an antacid.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Chemical composition of Plaster of Paris as background academic context rather than a clinical decision trigger.
Understanding that the setting of a plaster cast is an exothermic reaction is crucial for patient education. The nurse must warn the patient about the sensation of warmth to prevent anxiety.
Proper handling of a wet plaster cast (using palms, not fingertips) is a key nursing skill to prevent the formation of pressure points that can lead to skin breakdown and pressure ulcers under the cast.
What if? If a patient needs a cast that is water-resistant and allows for showering, a synthetic fiberglass cast would be chosen over Plaster of Paris. The nursing care would then involve teaching the patient how to properly dry the waterproof lining to prevent skin maceration.

How to Approach the Question

This is a factual recall question that tests your knowledge of common medical materials.
First, identify the key term in the question: 'Plaster of Paris'.
Recall or deduce the chemical name associated with this material.
Evaluate the given options, which are all calcium compounds.
Eliminate the options that are known for other uses (e.g., Calcium phosphate in bones, Calcium carbonate as antacid).
Select the option that correctly identifies the chemical nature of Plaster of Paris, which is a form of Calcium Sulphate.

Concept Tested & Keywords

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E6 Nursing Brunner Adult Health 3SA Vol 1 Part 4 p. 116-118

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