Oral cavity is acceptable

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Jamie L. Somers - Global T&E Director
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Arguably the most important aspect of submitting a case to ClearCorrect is to ensure clear, precise impressions or intraoral scans. We figured we should cover some basics about taking impressions.

From the technique used to the material used and the impression trays used, there are a few important aspects that you should consider when taking impressions.

Best practices

  • We accept all silicone-based impression materials, including PVS, VPS and polyether. Alginate is not acceptable as it dries out and the material itself can shrink or expand depending on the environmental conditions. Plaster models are also not acceptable. Please read our article on impression materials for more information.
  • Be sure to,Disposable spoon and not to use metal or perforated spoons. We do not give back spoons, even if metal spoonsreceived by us, the impression must be processed manually, which can open the door to potential problems with the aligners. Perforated trays (sometimes referred to as "triple trays") are often too shallow to capture sufficient gingival margin of 2-3 mm, and incisal detail is often lost when teeth hit the grid. The scanning software also does not recognize several dental arches at the same time.
  • We recommend,Heavy body and light bodymaterial to use. Impression techniques with heavy-body and light-body material seem to produce the best results.
  • Perform cleaningbefore taking impressions. This removes deposits, which means that better impressions can be achieved and remaining gaps can be reduced at the end of the treatment.
  • Dry the teeth with the air syringeto prevent saliva bubbles from affecting the details of the impression.
  • Make sure,remove all attachmentsbefore taking impressions. If impressions are taken with attachments still attached to the patient's teeth, there is a possibility that the attachment will tear the shape when the impression tray is removed, which can damage the impression.
  • One-step molding techniques seem to get the best results (though we also accepttwo-stage impressions).
  • If you are applying the light body material on top of the heavy body material, you should be bestavoid lifting the tip of the applicator. This will prevent bubbles from forming in the impression.
  • The most common mistake impression-taking occurs when the trays are removed before the material is fully cured.
    • Set a timer and be sure to carefully follow the directions for your material.
    • Discard the first 2-3 inches of material that comes out of each new mixing tip.
    • We recommend,additional Wait 60-90 seconds longer than specified before removing the spoons from the patient's mouth.
  • Another common problem when taking impressions, it is important to capture the distal part of the last molars. It can be difficult to get a good impression because this part of the dentition is difficult to see.
    • Make sure you use the correct size impression tray. It should reach over the last tooth in the arch without touching the gums.
    • Before inserting the impression tray with the light body material, apply some of the light body material directly to the occlusal and distal part of the last tooth in the arch to ensure that the last tooth is completely covered with the impression material.
  • After taking the impressions, examine the impressions,before You send them in, andcheck the following:
    1. Make sure the occlusal surfaces are detailed and precise. This will ensure that the aligners will be tight.
    2. Make sure that all gum margins are defined and clear. (Including at least 3-4 mm of the buccal and lingual surfaces outside the gingival margin.) This ensures sufficient retention points for effective tooth movement.
    3. Make sure the impression material is intact. Damaged or thin impression material will affect the accuracy of the molds and the resulting aligners.
    4. Make sure there are no imperfections in the impression material. (Make sure there are no voids, bubbles, thin walls, displacements, duplicate marks, streaks, or cracks.) Imperfections or duplicate marks in the impression can affect the effectiveness of treatment with the resulting aligners.

Main reasons for rejection of impressions

The following are the top reasons for impression rejection that are featured here at ClearCorrect. Check your impressions for these mistakes before sending your patient home!

Cavities

Insufficient material creates a cavity in the impression and prevents us from capturing the actual tooth contour.

 

Vesicles

As the impression material is distributed, bubbles form when the tip is lifted out of the material. Pulling out the tip creates a cavity which, as more material is spread on it, creates a bubble.

Thin walls

Thin walls are created in different ways: insufficient material, impression trays that are too small or too deeply inserted. The material itself captures most of the tooth anatomy, but the scanning process (performed by ClearCorrect) does not pick up the impression well (where the tray shows through as shown in the picture below), so much of the tooth anatomy is incomplete or distorted.

 

Shifts

The impression tray was moved before the impression material hardened, creating a double edge on some teeth.

  

Duplicate prints

When the entire jaw or quadrant has been moved; this problem usually occurs with a two-stage impression.

 

Streaks

If the impression material hardens prematurely before it is inserted into the patient's mouth, this leads to a "streak" effect around the gumline.

Cracks

Cracks occur when the patient has extreme undercuts or black triangles that cause the impression material to jam in the proximal area and tear when the impression is removed (to avoid this, use wax to fill in the undercuts before taking the impression) .

Following these best practices can make all the difference between getting you good case planning with properly fitting aligners, or getting a difficult case where the teeth don't follow the planned movement. Make sure you send in good impressions for your cases and get everything right the first time!

Just a reminder: We accept digital impressions (scans) from CEREC, Ormco Lythos, 3M True Defintion, Carestream, iTero, 3Shape TRIOS, E4D PlanScan and Motion View Ortho Insight 3D scanners.

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