Alginate
Pronunciation: AL-jih-nayt
An irreversible hydrocolloid impression material derived from alginic acid salts, widely used in dentistry to record dental arch form for study casts, orthodontic models, and provisional appliance fabrication.
Full Definition
Alginate is an irreversible hydrocolloid impression material composed of potassium or sodium alginate, calcium sulphate (reactor), sodium phosphate (retarder), fillers, and colouring agents. It sets by an irreversible chemical reaction and cannot be returned to its original sol state. While alginate provides adequate detail for study models, orthodontic working casts, and fabrication of temporary appliances, it is dimensionally unstable over time and must be poured in dental stone immediately or stored under humid conditions for no more than one hour. Editors should note that alginate is not suitable for crown and bridge impressions, where dimensionally stable materials such as polyvinylsiloxane or polyether are required. The term is sometimes misspelled 'algenate'.
Usage
Usage note: Always specify immediate pour or storage instructions when alginate impressions are referenced in laboratory prescriptions, due to dimensional instability.
In Context
- "Alginate impressions of both arches were taken at the start of orthodontic treatment to produce study models." — Orthodontic patient records
- "The nurse mixed the alginate to a smooth, lump-free consistency before loading the impression tray." — Dental nursing training manual