Polishing and Finishing PMMA Temporary Crowns for a Natural Look

A milled PMMA crown is rough straight off the blank. That surface is where plaque and stain live — polishing is clinical, not cosmetic.

The three-stage finish

1. Shape: carbide or diamond at 8,000–12,000 rpm with water.
2. Pre-polish: silicone points to close the surface.
3. High-shine: goat-hair brush + aluminium-oxide paste; aim for <0.2 µm Ra.

Common mistakes

• Dry milling PMMA generates heat that melts the surface — always cool.
• Skipping the pre-polish leaves micro-grooves that stain in a week.
• Over-trimming the margin drops the seat by 50–100 µm.

Start from a closed-surface PMMA disc to make the polish faster and more durable.

The polish ladder

Skipping the 15 µm step leaves a satin finish that stains within a month. A gloss-meter reading above 80 GU at the margin is your pass criterion.