Tech tip: Fitting & tracking issues

How can I tell whether an aligner fits?

A properly fitting aligner should cover the teeth and fit snugly against the patient’s teeth. It will probably feel a little tight at first.

  • The aligner should usually cover the gingival by at least 0–2 millimeters. (Aligners may be trimmed differently to compensate for undercuts, black triangles, recession, bridges, etc.)
  • The incisal edges of the teeth should fit flush against the aligner without any gaps.
  • The aligner should fit snugly over the distal surfaces of the rearmost molars, if the aligner extends that far back.


Properly fitting aligners

Fitting issues

There are a few possible causes for fitting problems:

  • If the first step doesn't fit, the most likely cause is an inaccurate 3D model. This can be caused by distortions in the initial impressions or scans.
  • If the fit of the aligners gets worse over time, the teeth may not be "tracking"—in other words, the aligners are progressing as originally planned in the treatment setup, but the actual teeth aren't keeping up due to lack of space or insufficient pressure.
  • In rare circumstances, an aligner may be distorted due to physical damage or a manufacturing defect.

Some common types of fitting issues are shown below. Click a photo for detailed troubleshooting information.

Incisal gaps 


Aligners that are too big or too small


Aligners that fit on only one side

Tracking issues

Even if the aligners do appear to fit comfortably, that doesn't guarantee that the teeth are actually moving as intended. Here are some tips for identifying unseen tracking issues before the treatment goes too far off the rails:

  • Any patient non-compliance can lead to tracking issues. Educate your patient on the importance of wearing their aligners at least 22 hours per day. Signs of non-compliance include missed appointments, unusually clean aligners, and a persistent tight fit after weeks of wear. Make sure your patients know they should contact you immediately if their aligners no longer fit.
  • Saliva buildup or saliva bubbles inside the aligner often indicates that there is a significant gap between the aligner and the teeth. This will most likely be seen at the trim line.
  • Blanching of tissues indicates soft tissue impingement. This could be the result of inaccurate capture of these areas in the impression or the result of a frenum that extends towards the gingival margins.
  • If the aligners are slightly ill-fitting when you give them to your patient, but the patient calls back a few days later saying that they now fit, don't rely on that self-assessment. Do a follow-up visit to confirm the quality of the fit before advancing to the next step.
  • Even if the aligners are fitting during check-up appointments, you should check the treatment setup and paperwork to see which teeth are moving and if those teeth appear to be on course. If you see that a tooth is not moving as planned, don't wait, take immediate action. If you continue with treatment in hopes that it will correct itself later on, it may get worse.

We hope you found this information helpful!

Looking for something?

We have a great online store filled with useful tools to help you in treating your patients with clear aligners. Everything from IPR Kits and Chewies to Webinars. Check out our store at store.clearcorrect.com.

Until next time…

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