Digital scanning has become the standard for clear aligners, but many practices still take physical impressions for some or all cases. Aligners need an accurate full-arch model, so impression quality directly affects tray fit. These steps help avoid the most common problems.
Choose the right material
Polyvinyl siloxane (PVS) is the material of choice for aligner impressions because of its accuracy and dimensional stability. Alginate is generally not recommended for aligner cases: it loses accuracy quickly as it gains or loses water and must be poured almost immediately.
Tray selection
- Use a rigid tray that covers all teeth, including the distal surfaces of the last molars.
- Allow even space for material around the teeth; a tray that's too tight distorts the impression.
- Apply tray adhesive and let it dry according to the manufacturer's instructions.
Technique
- Clean and dry the teeth; remove any debris or excess saliva.
- Use the technique your material is designed for, such as putty-wash or monophase.
- Seat the tray evenly and hold it still without rocking until the material has fully set.
- Remove the tray with a single firm motion along the long axis of the teeth to reduce distortion.
Inspect before the patient leaves
| Defect | Why it matters |
|---|---|
| Voids or bubbles on tooth surfaces | Create bumps on the model that the aligner will copy |
| Drags or tears | Distort the shape of teeth, especially at contacts |
| Tray showing through the material | Indicates pressure spots and likely distortion |
| Incomplete distal molars | Leads to trays that don't seat on the last teeth |
| Separation from the tray | Distorts the whole arch |
Retake any impression with defects on tooth surfaces. It's much faster than troubleshooting a tray that doesn't fit weeks later.
Bite registration
Record the bite in maximum intercuspation with a registration material, and confirm it seats accurately on both impressions.
Disinfection, pouring and shipping
- Disinfect impressions following your infection-control protocol and the material manufacturer's guidance.
- Follow the manufacturer's recommended pour window if models are poured in-house.
- Protect impressions from heat and pressure during shipping, and label them clearly.
Consider going digital
Infinity Aligner accepts both digital scans and PVS impressions. Many practices find that scanning reduces retakes and shipping time; our team can help you evaluate the transition.
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