For information regarding the 2 basic principles for clear aligner treatment, refer to the following:

• Overview
• Principle 1: Teeth need space to move
• Principle 2: Teeth need pressure to move

Overview

Clear aligners have a lot of advantages over metal braces—most obviously, they're clear and they're removable. There is a trade-off, though. Because they aren't attached to the teeth, some movements can be more difficult to achieve than they are with traditional braces.

For this reason, it’s important for you to know the limitations of clear aligners so that you can properly assess whether they can achieve the treatment outcomes that you and your patient desire. There are two key principles to keep in mind.

Principle 1: Teeth need space to move

When you prescribe your case, you can plan to create space with extraction, arch expansion, or IPR, depending on how much space is required. However, despite prediction and planning, there may be some instances where insufficient space will still be an issue.

For example, when teeth crowd each other there may be tight contacts between them. Tight contacts between teeth are common and exist naturally due to the patient's dentition. The teeth are so crowded, they press up against each other, and literally put each other under pressure. You can try to relieve this pressure by creating space (for instance, by performing IPR).

If there's enough pressure, the surrounding teeth may just move in to fill the space you’ve created. If this happens, you may need to create more space than originally intended. If this is not caught and addressed, it can prevent treatment from going forward as planned because the rest of the movements no longer have sufficient space to straighten out. This can result in treatment going off track and the aligners no longer fitting.

You can check for tight contacts by running floss between the teeth. If the floss has a hard time popping in and out, then you know that you have a tight contact. (If the floss pops in and out easily, then you have light to moderate contact.)

Conversely, you don't want too much space left between the teeth. Compliance Checkpoints can also help you to tell if the space you made is closing as planned.

Solutions for creating more space

• Hand stripping/IPR
• Revise treatment to request expansion or IPR

TIP: Always track the amount of IPR being done. We offer an IPR tracking chart for this purpose.

Principle 2: Teeth need pressure to move

Most teeth will move with a little bit of consistent pressure on them. However, some types of teeth, some movement, and some other factors are more prone to issues than others. These include:

• Maxillary laterals
• Premolars
• Short clinical crowns
• Molars
• Age and health of teeth
• Intrusions
• Extrusions
• Rotations

Solutions for increasing pressure

• Engagers
• Dimples
• Overcorrection
• Digital power chains
• Extruding with auxiliaries
• Rotating with auxiliaries

Each of these solutions can increase pressure. The key is knowing when to apply each one.

Engagers may be included in the treatment plan based on your prescription and/or the technician’s recommendation. Engager preferences and timing can be adjusted according to the needs of the patient—just let us know when submitting the case or in a revision.

Dimples can be created in office with dimple pliers. These can be used to slightly increase pressure to assist with difficult movements. They are best used to increase the retention of an aligner when needed, such as with short clinical crowns.

Buttons and elastics can be used to help with extrusions. See our technique for extruding with auxiliaries.

Buttons and elastics can also be used to help with rotations. See our technique for rotating with auxiliaries.

Overcorrection is when the technician adds 2-3 more stages of movement beyond the desired finished position to ensure the teeth move into their final position. Overcorrection can be requested in your case submission form at the start of treatment, or in a revision.

Digital power chains can be used to close residual spacing, which can occur if too much IPR was done. Or some cases start with spacing, and you just want to ensure all spaces have closed.

General solutions

Here are some techniques that can assist with both insufficient space and insufficient pressure:

Backtracking is used to get the teeth back on track by having the patient wear an earlier aligner longer before advancing to the next step. You can get best results by requesting a fresh replacement. You can combine this with other solutions, like adding dimples, extruding with auxiliaries, IPR or hand stripping, all designed to get the teeth back on track without requiring a revision.

Longer wear schedules may help with patients that you suspect are non-compliant or need more time to achieve planned tooth movements.

Increasing patient compliance can be achieved with incentives according to what you want to offer. Here are some incentives used by doctors:

• Educating the patient that by wearing their aligners 22 hours a day, they can avoid delays and added costs, and will be more likely to complete treatment within the expected time frame.
• Explaining the alternative (traditional braces) if aligners are not worn 22 hours a day.
• Using the treatment setup as an incentive to be compliant – reminding them of what their teeth could look like if they keep to their wear schedule.

Consequences

The consequences for not monitoring or addressing insufficient space and/or insufficient pressure can include:

• Tracking issues
• Aligners that don’t fit
• Case revisions that prolong treatment time
• Expected results not attained
• Unhappy patients
• Refund requests
• Frustration and stress (for you and your patient)

We hope this article helps you to understand how treatment can go off track, how you can prevent this and how to achieve your desired treatment outcomes.