We might be teaching grandma to suck eggs here, but the impression for fabricating your patient’s clear aligners is the foundation of the whole case - so it’s worth getting it right. Even better, if it can be done right the first time around!
We’ve learned some tried and true ways to help with getting that perfect impression that we hope will help you in preventing common errors or manoeuvring tricky scenarios.
- Aligners are made by thermoforming clear aligner plastics over 3D printed models of your patient’s mouth
- These print to an accuracy of <50 microns to ensure the aligners perfectly fit the teeth to enable them to apply forces in exactly the right locations
- A 2 stage putty and wash impression is the best way to capture this level of detail
- Gingival margins are just as important as the anatomy of the teeth to create perfectly fitting aligners
- Room-temperature impression materials perform far better than cold materials
- Move fast when mixing your impression materials - you do not want the setting reaction to be in motion before the tray is placed in the mouth
- Take care to line up the midpoint of the tray with the midlines of the dental arches
- Insert the tray with one hand and use the other hand to grip the lips and pull them well clear so that the impression tray does not trap them
- Maintain the impression in position throughout setting with at least three points of contact
- Never ask the patient to bite down
So now you’ve taken the impression at least, but how do you know if it’s good? Here are a few key features to look out for:
If you look around each tooth within the impression, you should easily be able to detail out the anatomy of the teeth (cusps, fossa) and have clear distinction between the tooth-margin-gingiva.
We call it the vestibular roll! But it’s important to have 2-3 mm of the gingival margin, not only to ensure the trays will be trimmed accurately but also to ensure fit/retention of the aligners.
If trays are trimmed too short due to not having enough height on the impression this can lead to bouncing of the plastic when the patient wears the aligners or even reduce the predictability of the movements planned.
Having incorrectly sized trays can also prevent the ability to fully seat or capture the needed detail for an impression. For that reason, it’s always better to err on the side of “too big” vs. “too small”
The best way to ensure your impression is centred is to line up the handle of the impression tray with the midline of the patient and/or patient’s nose. Without a proper centre, you run the risk of cutting off the molar regions of the mould or obtaining a distorted arch.
If any of the above are seen, it could indicate that the impression was moved prior to complete setting of the impression material. This would lead to an incorrect or skewed representation of the dentition and increase the likelihood that aligners will not be able to be fabricated.
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If you see any parts of the impression tray through the impression, that could be a sign that the tray was over-seated in an area. For example, in the photo below, the upper centrals show the impression tray at the base of the impression. As a result, these teeth could appear “shorter” or chipped compared to actuality if this impression was used.
We are keen to share with you our tips and tricks which you'll get as you use the 32Co platform!
"What if I’m not sure if I’ve taken a good enough impression?" Email a photo and we’ll take a look, or send two impressions and we’ll pick the best one
To book a demo or to learn more about 32Co, please email the team
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