Tech Tip: Taking impressions with undercuts

If you've ever tried to pull your feet swiftly out of a giant puddle of mud, you've experienced the frustration associated with making impressions of teeth with undercuts.

We asked our chief technical officer, Paul Dinh, to give us some tips on taking quality impressions from patients with undercuts.

The impression material gets locked in the patient's mouth because the material fills in between the teeth. When the impression hardens, there isn't enough flex to remove the impression. 

To save you from having to physically cut out the impression material from the patient's mouth, Paul gave us two great solutions:

  • Fill the area between the undercut teeth with a material that will not bond to the impression (like wax). The impression will be able to glide right out from between the teeth, while still making a quality impression that we can use to make your patient's treatment setup.
  • Try a two-step impression. Once the first step is done, get a knife and remove the gums 2 mm past the gingival in the medium body material. Then, when the light body gets added onto the medium body, the second step light body material will be the only material that will be covering the gums with the undercuts. The light body will flex easily to allow removal of the impression.

You can view our step-by-step video on taking two-step impressions here.

Thanks again to our chief technical officer. If you have any tips or experiences you'd like to share, please let us know!

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