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Alginate - Composition and Properties

Last updated September 8, 2025

Objectives

By the end of these revision notes, you should be able to:

What is alginate?

Alginate is an irreversible hydrocolloid impression material that is routinely used in dentistry. Common uses include primary impressions and impressions for study models.

Composition

Dental alginate is a powder that is mixed with water. The components are:

Ingredient	Function
Sodium alginate	Base material that reacts to form a gel
Calcium sulphate dihydrate	Reactor - provides calcium ions for cross-linking
Sodium phosphate	Slows down the reaction to allow for working time
Diatomaceous earth (fillers)	Adds strength and consistency
Potassium sulphate	Helps setting of model
Sodium silicofluoride	Controls pH

Setting Reaction

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Alginate – Composition & Properties