Dental Plaster: A Guide to Dental Stone and Models

What is Dental Plaster?

Dental plaster is a white powder we mix with water. It gets hard and makes models of teeth. Dentists use it to make copies of your teeth.

Dental plaster is made from calcium sulfate hemihydrate. When you mix it with water, it gets warm and turns hard. This is called an exothermic reaction.

There are different types of dental plaster:

• Type II – Model plaster (not very strong)
• Type III – Dental stone (stronger)
• Type IV – Die stone (very strong)
• Type V – High expansion stone (for big projects)

Dentists use dental plaster to make:

• Study models of your teeth
• Orthodontic models for braces
• Bases for dental prosthetics
• Crown and bridge work

Types of Dental Plaster

Let’s look at each type:

Type II – Model Plaster

This is basic plaster. It is:

• Not very strong (12-15 MPa)
• Used for simple models
• Made with beta-hemihydrate
• White in color
• Good for study models

Type III – Dental Stone

This is stronger plaster. It is:

• Stronger than Type II
• Good for working models
• Better at showing details
• Used for orthodontic appliances
• Made with alpha-hemihydrate

Type IV – Die Stone

This is very strong plaster. It is:

• Very strong (35-50 MPa)
• Used for crown and bridge work
• Has low setting expansion
• Great for detailed work
• Brands include Fujirock® by GC America

Type V – High Expansion

This type is for special cases. It is:

• Used for implant models
• Has high dimensional stability
• Good for large restorations

How Dental Plaster Works

When you mix dental plaster with water, a chemical reaction happens:

1. The powder (calcium sulfate hemihydrate) mixes with water
2. It makes a slurry (thick liquid)
3. It gets warm (exothermic reaction)
4. It gets hard and forms calcium sulfate dihydrate

Mixing Process

The way you mix dental plaster is very important:

A study found that vacuum mixing makes plaster 40% stronger than hand mixing [^1]. This helps make better models.

Step-by-Step Guide to Using Dental Plaster

Here’s how to use dental plaster:

1. Preparation

First, get ready:

• Clean the impression materials
• Disinfect the impression
• Get your mixing bowl and spatula
• Use a dental vibrator

2. Mixing

Now mix the plaster:

• Put water in the bowl first
• Add plaster powder slowly
• Mix for 60 seconds
• Spatulate (stir) well
• Use vacuum mixing if you can

3. Pouring

Pour the mix into the impression:

• Put small bits first in deep parts
• Use the vibrator table to remove bubbles
• Fill the rest of the impression
• Tap gently to release air bubbles

4. Setting

Let it get hard:

• Initial set takes about 10 minutes
• Final set takes 30-45 minutes
• Don’t touch it during setting time

5. Trimming

When it’s hard:

• Remove the model from the impression
• Use model trimmers to shape it
• Make a nice flat bottom
• Shape the sides

Common Issues & Solutions

Sometimes things go wrong. Here’s how to fix them:

Bubbles in the Model

If you see bubbles:

• Use a dental vibrator next time
• Try vacuum mixing
• Pour plaster slowly
• Tap the impression gently

Weak Models

If your models break:

• Use less water in the mix
• Try Type IV stone instead of Type II
• Mix longer (60 seconds)
• Let it set completely before handling

Slow Setting

If it takes too long to get hard:

• The room might be too cold
• Your water might be too cold
• Try adding an accelerator
• Check if your plaster is old

Cracking

If the model cracks:

• You might have used too much water
• It dried too fast
• The model was removed too soon
• Try a different water/powder ratio

Dental Plaster vs. Alternatives

Dental plaster isn’t the only option:

Research shows that plaster models are still the gold standard for accuracy. A study found only 0.08–0.41 mm difference in tooth measurements between plaster and digital methods.

Top Dental Plaster Brands

Some of the best brands are:

• Whip Mix Corporation – Known for consistent quality
• GC America – Makes Fujirock® (Type IV stone)
• Kerr Dental – Affordable options
• Dentsply Sirona – Makes Velmix® stone
• Heraeus Kulzer – High-quality dental materials

Safety & Best Practices

Stay safe when using dental plaster:

• Wear a dust mask when mixing powder
• Use dust extraction in your lab
• Follow ISO 6873 standards
• Wash hands after handling
• Store in a dry place
• Don’t pour plaster waste down drains

How To Choose The Right Dental Plaster

Pick the right type for your job:

• For study models – Use Type II model plaster
• For orthodontic models – Use Type III dental stone
• For crown and bridge work – Use Type IV die stone
• For implant models – Use Type V high expansion stone

Digital vs. Traditional Plaster Models

Digital models are getting popular, but plaster is still important:

• Digital setups reduce lab time by 40%
• Plaster models show 98% accuracy in keeping details for 10 years
• Plaster is still used to check digital model accuracy
• Implant dental laboratory work often needs both digital and plaster models

FAQs About Dental Plaster

Conclusion

Dental plaster is a key material in dentistry. It helps make models of teeth for many treatments. From simple study models to complex crown and bridge work, dental plaster is important.

The right type of plaster makes a big difference. Type II works for basic models, while Type IV die stone is best for detailed work.

Even with new digital tools, dental plaster remains important. It helps orthodontic laboratory technicians make accurate devices that fit well.

By following the right steps for mixing and pouring, you can make strong, bubble-free models every time.