Trimming differently to make retention 2x - 4x stronger

by ZenduraDental Team January 18, 2014

Using Zendura material is a great way to get good retention from aligners, but it isn’t the only way. How you trim appliances makes a big difference; and knowing the best ways to trim can get you 2x to 4x better retention with Zendura or even other materials. Read on to see how:

We’re trimming differently to make retention 2x - 4x stronger


As you know, strong retention of aligners on the teeth is key to producing desired tooth movements and tracking of aligners.

In a recent 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.

The difference between the techniques was remarkable.

For clear aligners without attachments, the straight cut 2 mm from the margins was about twice as retentive as the scalloped cut. For clear aligners with attachments, the straight cut 2 mm from the margins was over four times as retentive as the scalloped cut!

Trimming the aligners differently had more of an impact than adding or removing engagers. Scalloping the aligners right at the margin is the technique employed by “the other guys.” Traditionally, we’ve loosely scalloped our aligners slightly over the gumline.

Based on these findings, we’ve decided to start trimming our aligners with a smoother contour and a larger overlap with the margins. This technique should improve the efficiency of the aligners and may reduce the need for engagers in some cases. We expect the new aligners to move teeth more effectively, especially when performing difficult movements like torquing.

We also expect our aligners to be more comfortable than before, because there will be less risk of them impinging on the unattached marginal gingiva. The edge of the aligner will be concealed further under patients’ lips during everyday use, so this should also slightly improve the discreetness of the aligners.

You won’t see a difference right away, but we expect to start rolling out the change over the next few weeks. As always, we welcome your feedback.

 *"The effect of gingival-margin design on the retention of thermoformed aligners" by Daniel P. Cowley, James Mah, and Brendan O'Toole in the Journal of Clinical Orthodontics: JCO 11/2012; 46(11):697-702. Illustration used with permission.

Check the original post HERE.

ZenduraDental Team
ZenduraDental Team