- 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.