Virtual C-Chain is a treatment plan feature that aims to tighten tooth contacts and to close small residual spaces at the end of treatment through overcorrection.
Overcorrection is the application of additional pressure over added time at the end of treatment to achieve those goals. In traditional braces, this is done with an elastic "power chain", a series of connected elastic bands, each of which fits over a braces attachment. The elastic force pulls the attachments and the teeth to which they are attached closer to one another, closing spaces that may have been difficult to close during active treatment, or further cementing them into place before retention.
With clear aligners, we can perform the same action by including additional aligner steps at the end of a treatment plan. These stages may show additional movement in the digital treatment plan, but that movement may or may not occur depending on how close the contacts already are before the C-Chain steps. Those additional steps are still necessary however, to ensure contact and full correction.
Virtual C-Chain is indicated in cases of residual interproximal spacing, diastema closure, and/or enhancement of contact tightness following treatment.
Virtual C-Chain is contraindicated for significant tooth movements, such as rotations, leveling, alignment, or root positioning. It is also not advised or necessary in areas with already tight contacts, severe crowding, or unresolved occlusal discrepancies, as the additional contact pressure may interfere with planned tooth movements and compromise aligner tracking.
Virtual C-Chain can be requested for your cases either in the Additional Instructions field of the initial intake, or during treatment plan modification. The Virtual C-Chain steps will be applied in the next two stages following the last active stage with a 0.2mm tooth velocity on each. The C-Chain can be applied to the anterior only, or to the anterior and posterior both.
Virtual C-Chain cannot be applied to Retainer cases. These cases never exceed one step, and so cannot include the addition of further, overcorrection steps. A refinement is needed if overcorrection is still indicated at the end of treatment.