Question:

For refinement movement - closing left over gaps, are there any specific instructions we provide to invisalign tech? Like add power chain etc?

Answer:

In this clinical analysis, several experts provide insights into effective methods for managing tooth rotation and spacing in aligner therapy. Contributions from Kelly, Sadaf, and Hubert are discussed to highlight techniques for achieving consistent tracking and optimal results with aligner treatments.

Staging and Space Management

In the initial ClinCheck review, as Kelly noted, the staging sequence presents an issue. The process begins by creating space around the tooth, enabling rotation, after which the tooth is intended to move lingually. However, if space is lost at any point in this sequence, as in this case, it undermines the process. This likely indicates a tracking issue that may have halted progress. At this stage, if space loss occurs, treatment consistency becomes difficult to maintain.

Adjusting Attachment Orientation for Effective Rotation

A significant adjustment in this case involves altering the orientation of the attachment to enhance rotational movement. Typically, when trying to create rotation, force is applied from the mesial point towards the distal. By re-orienting the attachment in the opposite direction, it allows for pushing under the attachment from the gingival side, optimizing force application for rotation. This method increases the surface area for applied force, which can improve tracking and consistency in treatment.

Surface Area and Anatomical Considerations

In agreement with Kelly's observations, even in refined alignments, the tooth appears to have adequate surface area for the attachment to grip and push against. The anatomy of this specific tooth, with prominent line angles, presents more options for effective force application compared to other, more circular teeth. However, premolars, whether lower or upper, can be particularly challenging for rotation due to their complex anatomy. Often, using a c-chain for rotating these teeth is a more efficient option.

Using C-Chains for Tooth Rotation

To further illustrate, the analysis describes a case of a lower premolar in crossbite that caused a fraction and recession in the opposing arch. Addressing this issue involved rotating the premolar, as leaving it rotated would exacerbate the patient’s concerns. Initial attempts to rotate the tooth by creating space and adding attachments were unsuccessful. The next step involved attaching buttons to both the buccal and lingual sides and applying a c-chain, as advised by Sadaf and Hubert.

The process of attaching a c-chain involves connecting it between two buttons using hemostats, which makes it easy to adjust for the required tension. In most cases, a single loop is sufficient; any additional loops can be trimmed. Although lingual attachment is possible, it is often avoided due to accessibility challenges.

Clinical Tips for Patients Using C-Chains

When applying c-chains, trimming the aligner trays may be necessary to prevent interference with the c-chain during insertion. Regular monthly appointments are recommended to change the c-chain. In cases where the tray contacts the c-chain, minor adjustments can be made with scissors. Patients can be instructed to check tray fit by pulling down the lip and ensuring the tray does not make contact with the tooth or c-chain.

If patients are uncomfortable trimming the aligners themselves, practitioners can perform this adjustment during follow-up visits.