For information regarding predictability of movements, refer to the following:
Due to variations between teeth, some are more amenable to certain types of orthodontic tooth movements with clear aligners than others. Here are some rough guidelines to help you choose cases and calibrate expectations.
Clear aligners are particularly-well suited for facial/lingual movements. They excel when there's a broad surface to apply force to, and adjacent retentive surfaces to anchor against.
- Distal/mesial movements - if there is inadequate tooth contact with the aligner with the portion of the clinical crown to "push" the tooth in the desired direction, consider adding an engager for additional surface area
- Most rotations/rotations of lower premolars - ensure there is adequate space to rotate the tooth and consider the position of the tooth root as it is easier to rotate a tooth that is normally inclined. For example, a tooth that is mesially tipped should be uprighted first before attempts to correct its rotation. Conically-shaped teeth, such as mandibular premolars, offer little natural morphology for an aligner to "grip" onto. These teeth commonly require engagers to provide for added morphology.
- Torquing - evaluate the crown morphology, particularly length of the clinical crowns as these are more easily torqued. Short clinical crowns and lack of defined crown morphology (e.g. bulbous shaped crowns) may be assisted with engagers
More challenging movements
These tooth movements require added attention to details such as the crown morphology, position of the tooth root, available space/arch length to perform the movement and can be assisted with engagers and/or auxiliaries such as buttons and elastics.
- Extrusions - most effective with single rooted teeth that have a straight root. Also consider the crown morphology and interproximal areas. Triangular shaped tooth crowns and or interproximal areas that allow for the aligner to engage more of the crown may be extruded without engagers. Short clinical crowns, lack of defined crown morphology and multi-root teeth more commonly require engagers
- Intrusions - consider the morphology and retentiveness of the adjacent anchor teeth. If they do not provide sufficient natural undercut, engagers are often used. ClearCorrect's extended trimline design often provides sufficient retention for intrusion of single rooted teeth without the need for engagers. Intrusion of multi-rooted teeth is extremely rare as this is a very difficult movement and will require engagers on adjacent teeth to assist.