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# Gypsum, waxes and dental alloys

- Dental material

Models are poured in gypsum, restorations are shaped in wax, and many crowns and denture frameworks are cast in metal alloys.

Updated Nov 12, 2026

## Key points

- Plaster, stone and die stone: more strength and accuracy in that order.
- Cobalt–chromium for partial denture frameworks; titanium for implants.
- Ask about nickel allergy.

## What it is

Gypsum products turn an impression into a model: plaster for study models, dental stone for working models and high-strength die stone for crowns, where accuracy and hardness matter most. Waxes are used to shape restorations and dentures before they are cast or processed. Dental alloys are grouped by how much gold, platinum and palladium they contain, from high noble to base metal.

## Composition and properties

- More water in the gypsum mix gives a weaker, more porous model.
- High noble (gold) alloys resist corrosion and are kind to opposing teeth but are expensive.
- Base metal alloys: cobalt–chromium (strong, light, used for partial denture frameworks) and nickel–chromium (nickel can cause allergy).
- Titanium is the standard metal for implants because bone grows onto its oxide surface.
- Metal–ceramic crowns hold their porcelain through an oxide layer that forms on the alloy when it is fired.

## Uses, limits and safety

- Nickel allergy is common, especially in women: nickel-containing alloys are avoided in people with a known allergy.
- Two different metals in the mouth can produce small galvanic currents, felt as a metallic taste or a brief shock.
- Metal frameworks show grey at the gum line when it recedes.

## Next step / Initial management

- Ask about metal allergy before metal restorations; refer to dermatology for patch testing if the history is unclear.
- Metallic taste or sharp brief pain when two restorations touch: refer to the dentist.
- Record the alloy used in each indirect restoration in the clinical record.

## Test yourself

Think of the answer, then tap the question to see it.

## Which gypsum product is used for crown dies?

High-strength die stone.

## Which alloy is typical for removable partial denture frameworks?

Cobalt–chromium.

## Why is titanium used for implants?

Its stable oxide surface is biocompatible and lets bone grow directly onto it (osseointegration).

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## Connections

## Related 3

- [Impression materials: alginate, silicones and polyether](https://durgical.com/en/dentistry/impression-materials-alginate-silicones-and-polyether/)
- [Dental ceramics and zirconia](https://durgical.com/en/dentistry/dental-ceramics-and-zirconia/)
- [Biocompatibility and allergy to dental materials](https://durgical.com/en/dentistry/biocompatibility-and-allergy-to-dental-materials/)

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Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.

Sources: [Cobalt-chromium alloys in fixed prosthodontics in Sweden](https://pmc.ncbi.nlm.nih.gov/articles/PMC5724798/) (Acta Biomaterialia Odontologica Scandinavica (PMC open access), 2017); [Titanium and titanium alloys in dentistry: current trends, recent developments, and future prospects](https://pmc.ncbi.nlm.nih.gov/articles/PMC9640965/) (Heliyon (PMC open access), 2022); [Dental Impression Materials](https://www.ncbi.nlm.nih.gov/books/NBK574496/) (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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