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Impressions Issues to Avoid - (images to train your staff)
Impressions Issues to Avoid - (images to train your staff)

Train your staff to spot impression issues

Michael Yoon avatar
Written by Michael Yoon
Updated over a week ago

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Impression Problems

Dental impression problems lead to imperfect aligners. This undermines the treatment process and can produce poor results that leave you with an unsatisfied patient. 

There are several reasons OrthoSnap clear aligners are superior to other orthodontic options, and one of the main components of their superiority comes from the perfect fit of our handmade, customized aligners. To achieve a perfect fit, our lab technicians require high-quality, accurate impressions.

In this article, we will discuss the most common impression problems we see, why they happen, and how to avoid them. 

Procedural Errors

The three most common procedural errors include forgetting the light body, using too little material, and performing an improper two-step impression.

  • No light body

Usually, the light and heavy body are different colors. This is so that they can be easily identified. When you forget the light body, the occlusal anatomy and gumlines are not well defined. This produces impressions that appear rounded off and lack sharp detail. To avoid this common issue, be sure to use the light body.

  • Insufficient material

Insufficient material is too thin to make a good impression. The result can include numerous problems, such as the patient biting through the material or lack of details. To avoid this problem, be sure to use plenty of material. Too much material is better than not enough.

  • Improper two-step impression

When performing a two-step impression, it is important to ensure you do it properly. Double imprints can happen and will be discussed below, but the most important thing is to be sure the second step bonds to the first step. The most common reason the two steps don’t bond is using incompatible materials. To avoid this problem, make sure the heavy and light body materials are compatible.


Just what it sounds like, this is an air bubble in the impression. 

There are two common causes of air bubbles. 

  1. Excessive saliva in your patient’s mouth

  2. Lifting the mixing tip out of the material while processing

Avoid this by removing excess saliva and keeping the mixing tip in the material while dispensing it. 


A pulling effect can occur around the gingival margin if the impression is removed before the material fully sets. This can also occur if the impression material sets prematurely before inserting it into the patient’s mouth. 

To avoid this error, set a timer for 60-90 seconds longer than the provided instructions suggest and be sure to insert the tray into the patient’s mouth as soon as you dispense the material.


Voids occur when the full gum line or tooth anatomy is not completely captured by the impression material. This can happen if the tray is too small or there is not enough material. To avoid this, be sure to use the correctly sized tray and plenty of material. Remember, too much material is better than not enough. 

Double Imprints (Shifts)

If you see two teeth imprints or two gumlines on top of or right next to each other, you have a double imprint. 

The two most common reasons for shifts include:

  1. Incorrect two-step procedure

The best way to avoid this issue is to switch to a simpler one-step method. If, however, you prefer the two-step method, you can prevent this by placing a plastic sheet over the first step before performing the second step. 

2. Movement of the tray during the setting process

Ensure the tray remains in place and does not move by educating your patient on the importance of not moving the teeth during the process. 


A tear in the impression material undermines the accuracy of the impression. These usually occur when removing the tray before the material sets completely. They can also occur if the patient has black triangles or sharp undercuts that cause tears when you remove the tray. 

To prevent this from happening, set your timer for 60-90 seconds longer than recommended on the instructions for the material. Also, use wax to avoid tears from sharp undercuts and black triangles. 


Holes occur when the patient bites through the impression material. To avoid this, educate your patient on the importance of not biting down too hard. Also, as already stated several times to avoid other issues, be sure to use a properly sized tray and enough material. 

Thin Walls

This problem can have several causes. The most common is not enough material—or a tray that is too big, which causes the material to spread too thin. Another common cause is pushing the tray too deep.

Prevent this common cause by (again) using plenty of material with properly sized trays. Also, don’t push the trays too hard when placing them on the teeth. 

Related Topics and Information:

Click to learn more about Tips on Taking Impressions and Sending Impressions.

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