Tips for taking a good impression

Follow these tips to ensure you take a perfect impression every time.

1. The anatomy of a good impression

2. Use the proper impression material

To begin manufacturing aligners, we must receive VPS, PVS, or polyether impressions. Plaster models can chip or break, and alginate can dry out and distort. Therefore, while plaster models or alginate impressions allow us to evaluate a case, we cannot produce aligners with these molds.

Also, use plenty of material. Remember, too much is better than not enough.

We recommend using a top wash (light body) on top of a base. Please reach out to [e-mail] if you would like some recommendations for materials or some of our favorite techniques.

Please note it is important NOT to use alginate, or to send us plaster models. We will need PVS impressions in order to start manufacturing.

3. Send all the necessary impressions

Make sure to send impressions of both arches, even if you are only treating one. In addition, we need a bite registration. The lab tech needs to know the location of opposing teeth to prevent hyper-occlusion or inter-arch collision. Bite registration also allows us to create the correct relationship between upper and lower aligners for correcting bite issues.

4. Use the correct trays

When it comes to trays, proper sizing is the most important factor. The tray must extend 4 mm beyond the gingival margin and fit all the teeth. It should also extend beyond the terminal teeth. If the tray is too large or too small, it can cause issues that may require a re-make.

If the teeth touch the edges of the tray, it is too small.

As far as the type of tray, you can use whichever you prefer. Please be aware, however, that we will not return trays. Therefore, disposable trays are the best option.

5. Remove engagers

To make accurate molds, the impressions must be free of engagers. If your patient has engagers on any teeth, be sure to remove them before taking impressions.

6. Fill in undercuts

Use wax to fill in undesirable undercuts. Neglecting this step can cause distortions or tears when removing the impression material.

7. Don't forget the light body material

Be sure to add the light body material before the heavy body or putty dries.

8. Avoid the most common mistakes

Some of the most common problems we see with dental impressions for orthodontic aligners include:

Using trays that are too small

If the tray is not big enough, all teeth may not be properly captured. It can also miss the gingival margins. This is important, because we design the aligners to go beyond the gingiva for improved retention. In addition, if the tray is too small, it can lead to holes in the impression when the patient’s teeth can cut through the material.

Using trays that are too big

The impression material can spread too thin with trays that are too large. This can cause tears and distortions and can also make it difficult to fully capture the gingival margins. It also increases the risk of the patient cutting through the material, causing holes in the impression.

Not allowing the material to set fully

To ensure the best impressions, make sure the materials fully set. Here’s a tip: Discard the first inch of material from each new mixing tip. Then, be sure to set a timer based on the instructions for your material. As a safeguard, wait an additional 60-90 seconds beyond what the instructions advise before removing the tray.

Double impression

When using a two-step impression method, the most common error is a double impression. To avoid this mistake, consider switching to the simpler and more reliable one-step method. If you prefer the two-step method, we will accept them. Just be sure to cover the putty for the first impression with a plastic sheet and begin the second step before the first one fully sets.

Posterior distortion

Don’t allow distal teeth to get shortchanged. The most important factor is to use properly sized trays (as mentioned twice before). Make sure the tray extends beyond the most distal tooth without touching the gums. Add some light body on the distal and occlusal portion of the last teeth before inserting the tray. This ensures complete coverage.