Overview
Pouring the dental master cast is where impression accuracy either transfers faithfully to the working model or degrades into positional error. The dental master cast serves as the foundation for all dental framework design and fabrication—dental analog positions in stone must exactly mirror clinical dental implant positions. Proper stone selection, mixing technique, and pouring protocol preserve the accuracy achieved during impression taking.
What You'll Need
- Verified impression with embedded copings and splint
- Implant analogs compatible with your system
- Type IV dental stone (high-strength, low-expansion)
- Vacuum mixer and mixing bowl
- Vibrator for bubble elimination
- Boxing wax or silicone mold frame
- Calibrated scale and graduated cylinder
Step-by-Step
Verify Impression Integrity
Before pouring, inspect the impression. Confirm all copings remain embedded and rigidly splinted. Check for tears, pulls, or distortion around coping bases.
Attach Implant Analogs
Thread analogs onto each embedded impression coping. Engage the anti-rotational feature fully and apply specified torque. Verify absolute seating with an explorer.
Box the Impression
Create a containment boundary using boxing wax or a silicone mold form. Provide at least 10mm clearance around all analogs and extend 15-20mm below the deepest analog point.
Select Appropriate Stone
Use Type IV dental stone for implant master casts. This material offers the best combination of accuracy, strength, and dimensional stability.
Proportion Accurately
Weigh powder and measure water according to manufacturer's exact specifications. Water/powder ratio directly affects setting expansion and final strength.
Mix Under Vacuum
Combine water and powder in a clean mixing bowl. Mix under vacuum to eliminate air incorporation. The final mix should be smooth and creamy.
Pour Initial Increment
Place the impression on a vibrator. Flow stone carefully around each analog, filling the coping-analog interface completely. Build up slowly, avoiding air entrapment.
Complete the Pour
Add remaining stone to achieve desired base thickness (minimum 15mm). Continue vibrating until stone begins to set.
Allow Complete Set
Let the stone cure undisturbed for the full manufacturer-recommended time—typically 45-60 minutes minimum for Type IV products.
Separate and Inspect
Carefully separate the cast from the impression. Inspect each analog for voids, bubbles, or incomplete stone coverage. Verify analogs are firmly embedded.
Verify Transfer Accuracy
Test the dental verification jig on the new dental master cast. The jig should seat passively with Sheffield testing showing no gaps.
Tips & Best Practices
- Pour the cast within one hour of impression taking to minimize material relaxation
- Store poured casts in humid environments for the first 24 hours
- Label casts immediately with patient name, date, and dental implant system
- Consider pouring duplicate casts for complex cases as insurance against damage
Common Mistakes to Avoid
Inaccurate water/powder ratio
Even small deviations affect expansion and strength. Measure precisely.
Air incorporation
Bubbles at analog interfaces create positional errors. Vacuum mix and vibrate consistently.
Premature separation
Removing the cast before complete stone set risks distortion. Wait the full cure time.