Aligners Don't Fit - Too Big or Too Small

For information regarding aligners that do not fit, refer to the following:

Definition
Causes
Solution

Definition

An aligner is considered too big for the patient when it is obviously too wide or too long for the patient’s arch; there can also be difficulty with the aligner remaining in place while the patient speaks/opens their mouth.

Too Big

An aligner is considered too small when it cannot easily be placed into the patients mouth. For example, the aligner must be trimmed or forcibly seated in order to fit properly.

Too Small

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Causes

Aligners can appear too big/long/wide when:

The impressions used contained minor distortions
Molars have not distalized as expected
The arch in question has not expanded as expected

Aligners can appear too small/short/narrow when:

Mesial translations have not occurred as expected
Bulbous teeth or undesirable undercuts result in too much retention
Excessive crowding results in too much retention
Teeth have not flared and moved lingually as expected

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Solution

For when aligners appear too big/long/wide the following can be done:

Try adding dimples using thermopliers
Try backtracking using the previous aligner
Add engagers (you will need to request a case revision to have more engagers added)

For when aligners appear too small/short/narrow:

Try using Chewies to help the aligners seat properly
Request distal half of the aligner be trimmed when submitting the case
If undercuts are an issue, you can request for undercuts to be blocked at either the beginning of the case (when submitting the case) or in the middle or end of the case (by requesting a case revision). Whether you request at the beginning, middle or at the end of the case, you will need to specify which tooth to block out because we usually leave undercuts alone to allow for retention.
Submit a case revision asking for an adjustment to the trimming, (you can ask us to cut the aligner or shorten the aligner by trimming it at the distal end of the last molar), and if necessary ask for additional engagers. (At this time, other than the above request, we do not do custom trimming of aligners. If there are any other trimming modifications necessary they will need to be done in your office. (Trimming tools to aid you with in-office trimming of aligners can be found in our online store. May or may not be available in your region.)