Tech Tip: Trim Lines

We've been getting some questions about trimming recently, so we're revisiting some of our older tech tips on the subject.

As you know, aligners need strong retention in order to move the teeth as desired.

In a 2012 study, doctors from the University of Nevada compared the retentive strength of three trimming techniques:

  • A) a scalloped margin,
  • B) a straight cut at the gingival zenith, and
  • C) a straight cut at 2 mm above the gingival zenith.

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The difference between the techniques was remarkable. For clear aligners without engagers, the straight cut 2 mm from the margins was about twice as retentive as the scalloped cut. For clear aligners with engagers, the straight cut 2 mm from the margins was over four times as retentive as the scalloped cut!

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Trimming the aligners differently had more of an impact than adding or removing engagers.

Based on these findings, we started trimming our aligners with a smoother contour and a larger overlap with the margins in 2013.

Because there is less risk of the aligners impinging on the unattached marginal gingiva, our aligners are more comfortable with this technique. The edge of the aligner is concealed further under patients’ lips during everyday use, so they're also a bit more discreet.

Here are answers to a couple of common questions:

Can I make custom trimming requests?

At this time, we are not able to accept custom trimming requests. We trim all aligners using the same standard protocol. If you want to customize your aligners, you can do so fairly easily in your office with a buffing wheel (like the ones available in our online store).

What should I look for if my patient complains of sore gums?

ClearCorrect aligners go through a multi-stage polishing process, so actual rough or sharp edges should be quite rare. It is fairly common, however, to experience some discomfort for the first few days wearing an aligner. This often indicates that the soft tissue is getting used to having foreign material present in the mouth. Changes to the mucosa eventually fade away when the patient stops wearing aligners.

If the gums are being impinged, one possibility is that the gingiva were not captured accurately in the impression. We prefer 4-5 millimeters of gum to be included. Incomplete impressions will affect our production models.

You may also want to look for frenum pulls.

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These can be difficult to detect because the aligner may feel comfortable at first, but as the patient speaks and moves around, the frenum becomes irritated and ulcerated. Unfortunately this dynamic movement is not captured in the impression. Clear photographs can help to identify these. Gingival frenum pulls are rare, but when they occur, they are typically found in the maxillary premolar and midline areas. If this proves to be a problem, you may want to trim the aligner shorter in the affected areas.

We hope you found this information helpful. Don't forget—you can always visit our Help Center, which has loads of useful articles, and of course, feel free to contact any of our knowledgeable support representatives.

Until next time…

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