Plaster of Paris is the most commonly used material for immobilization of fractures. Chemically the plaster o… - AIIMS CRE SNO - 2023

AIIMS CRE SNO - 2023

Biochemistry and Nutrition

Easy

Appeared in: AIIMS CRE SNO - 2023

Explanation

Plaster of Paris is chemically known as calcium sulphate hemihydrate (CaSO₄·½H₂O).
It is produced by heating gypsum (calcium sulphate dihydrate), a naturally occurring mineral.
When mixed with water, it undergoes an exothermic (heat-releasing) reaction as it rehydrates and hardens into a rigid gypsum cast, which is ideal for immobilizing fractures.

Option A: Calcium phosphate, primarily as hydroxyapatite, is the main mineral component of human bones and teeth. It provides structural integrity to the skeleton but is not the material used to make orthopedic casts.
Option B: Calcium hydroxide, also known as slaked lime, is an alkaline compound used in various industrial applications and in dentistry as a component of cements and root canal fillers due to its antibacterial properties. It is not used for making casts.
Option C: Calcium carbonate is commonly found in rocks like chalk and limestone. Medically, it is widely used as an oral calcium supplement and as an antacid to neutralize stomach acid. It does not have the chemical properties to set and harden like Plaster of Paris.

Visual 1: Diagram: Illustrates the chemical process: Gypsum (CaSO₄·2H₂O) is heated to become Plaster of Paris (CaSO₄·½H₂O). When water is added, it reverts to Gypsum, forming a hard cast.
Visual 2: Infographic: Compares the four calcium compounds from the options, showing their chemical formulas and primary medical or biological uses.

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 (POP) used for fracture immobilization as background academic context rather than a clinical decision trigger.
Nurses must educate patients about the normal exothermic reaction (sensation of warmth) as a plaster cast sets to prevent anxiety.
A critical nursing skill is to handle a wet plaster cast only with the palms of the hands. Using fingertips can create indentations that may lead to pressure ulcers under the cast.
What if? If a patient complains of a persistent burning sensation or a 'hot spot' under a dry cast, it is not the normal setting reaction. The nurse must immediately assess for potential pressure necrosis or infection and report it to the provider.

How to Approach the Question

This is a factual recall question testing knowledge of common medical materials.
First, identify the key term in the question: 'Plaster of Paris'.
Recall its primary use in healthcare, which is immobilizing fractures.
Access your knowledge of basic chemistry related to medical supplies. The name 'Plaster of Paris' is historically linked to the large gypsum deposits found in Paris.
Evaluate the options, which are all different calcium compounds. Differentiate their common uses (e.g., calcium carbonate is an antacid, calcium phosphate is in bones).
Select the compound that correctly matches the chemical identity of Plaster of Paris.

Concept Tested & Keywords

Concept Tested: Chemical composition of Plaster of Paris (POP) used for fracture immobilization.
Stem keywords: Plaster of Paris, immobilization, fractures, chemically
Lead-in keywords: is
Negative lead-in flag: false

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