For most clear aligner cases, a lab wants one upper impression, one lower impression and if the Angles class is anything other than one, a PVS bite. So let’s address the steps involved in preventing delays, costs, and embarrassment.
For most clear aligner cases, a lab wants one upper impression, one lower impression and if the Angles class is anything other than one, a PVS bite.
“But which impression material should I use? –
There are no good or bad impression materials – only compatible materials.
All too often, a lab will receive 4 different impression materials combined to make one set of impressions for no other reason than
“That’s all I had laying around.” –
Or they’ll receive three upper impressions and two lower impressions with a soaking wet note stating
“I’ve taken a few, pick the best one.” –
Statistically none of them will be acceptable and this little gem will come out
“My other lab has never asked for a new impression!” –
They have, you know they have, and we know they have. So let’s address the steps involved in preventing delays, costs, and embarrassment. Tray Selection
Use disposable impression trays.
Use the upper tray for the upper arch and the lower tray for the lower arch.
Despite popular belief, lower trays are not for both arches.
Select a tray that fits, if the nearest-fitting tray doesn’t fit, make it fit. If you can’t make it fit, make a custom tray.
Customising a stock tray.
If you’re stuck between two stock trays and need to make a minor adjustment, heat the edge of the tray with a brush flame or Bunsen burner, bend it with your fingers, then run it under cold water to set the new position.
Without adhesive, you can’t take an impression. The putty will separate from the tray and distort the impression. If the laboratory sees there is a separation, they’ll usually reject the impression.
Putty impression | Stage 1.
Mix the putty carefully and ensure there are no streaks of material.
Fill the tray level with the edge of the tray – No more, no less.
When taking the putty impression, apply constant pressure over the premolars of the lower and the centre of the palate during the first stage of setting.
Prior to the putty setting, create space for the wash material by ‘wiggling’ the tray laterally.
Interim quality control.
If your putty impression doesn’t look good – retake it.
Wash impression | Stage 2
Apply a single stripe of wash material to the dentate void.
It’s also likely that there will be some deficient areas around the periphery of the putty impression, you can add some additional wash material to these areas. Don’t overload the tray with wash material.
When taking the wash impression, apply constant pressure over the premolars of the lower and the centre of the palate for the full duration of setting.
Never touch the tray handle during the wash phase of the impression.
Final quality control.
Your final impression should look perfect, if it doesn’t
– retake it.
Distal surfaces of the most posterior tooth is clear to the margin and beyond.
Occlusal surfaces are clear, well defined and free from bubbles.
All gingival margins are clear and well defined.
At least 3-5mm of buccal and lingual soft tissue is recorded outside of the gingival margin.
Impression material is intact and there is no damage, warping, delamination, bubbles, voids, or double imprints.
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