Tech Tip: Impressions FAQ

Despite the increase in intraoral scanners available today, many doctors still prefer to use impressions to submit their cases to ClearCorrect. Here are answers to some of the FAQs about impressions and ClearCorrect. 

Our terms & conditions state: 

"Alginate impressions, stone models, and metal impression trays will be rejected. These and all other submitted materials become the property of ClearCorrect and will not be returned."

no metal trays-1Why doesn't ClearCorrect accept alginate material for impressions?

Alginate dries out and the material itself can shrink or expand depending on environmental factors. This can make the aligner too big or too small, depending on any changes.

Why can't I submit my case with metal trays?

ClearCorrect does not accept metal trays because they're incompatible with our scanning process. 

Why do you need both arch impressions/scans for a single-arch case?

We need both arches for a couple reasons:

  • We need to know where the opposing teeth are located to prevent inter-arch collision or hyper-occlusion when moving teeth to their final position.
  • When improving the overjet, overbite, midlines, canine, premolar, and/or molar relationships, we need to have the opposing arch to setup the correct relationships.

How does the impression tray size and material affect the fit of the aligners?

An impression tray that is too small can have several ramifications:

  • Prevents all teeth from being fully captured in the impression. 
  • The molars may lift from the tray which can ultimately skew the tooth shape and arch form.
  • Can potentially cause the patient to cut through the impression material all the way to the tray and leave holes in the impression.
  • Can prevent capturing the full gingival margin.

impression holes

If a tray is too big, the impression material may be spread too thin, which may make it difficult to fully capture the gingival margins. 

Using too much light-body material, using too little material, or not using light-body at all can also reduce impression accuracy. These procedural errors may cause voids or thin walls, among other issues, which affect the fit of the aligner. 

impression incorrect

Why can't we send stone models?

stone model

Stone models don't always survive the shipping process. There is usually some sort of chipping, especially along the cusps/incisal edges. Sometimes this can be a whole tooth, but most of the time it will be something minor that's hard to detect but can still affect the fit of the aligners. 

Also, with stone models, we can't control the quality of the stone model. The impression might be perfect, but if the pour-up is bad the scan will be compromised. Things like air bubbles can be filled in, but it leaves us guessing at what the shape of the tooth is actually like.

no bite registrationWhy aren't bite registrations required with my ClearCorrect case submission?

Bite registrations are not required to submit your case because our software automatically articulates the arches in maximum intercuspation. For the vast majority of cases, this is as accurate as (or more accurate than) aligning models based on a bite registration. Our technicians also double-check the occlusion against the photos you provide. 

Bite registrations will not be scanned unless specifically requested (either in the prescription form or in response to the technician in a setup decline).

When taking impressions, I have difficulty getting the distal of the last molars. Do you have any suggestions on an easy way to capture these?

Posterior distortion of the most distal teeth in the arch is 3rd on the list of most common impression issues. It can be difficult to get a good impression since it's hard to see back there. There are a couple of ways to avoid this problem:

  1. Make sure that you're using a correctly-sized tray. It should extend past the last tooth in the arch without touching the gums.
  2. Before inserting the tray containing light body, add some light body directly to the occlusal and distal portion of the last tooth in the arch, ensuring that the last tooth is completely covered with impression material.

Check out our Help Center for more information on the topic of impressions:

blog comments powered by Disqus