CLINICAL GUIDE
Troubleshooting: Aligners Not Tracking
What to do when a tooth hasn’t tracked as planned. The key principle: diagnose the cause before extending wear. “Wear it longer” only helps when fit, space and movement type are all fine and the real problem is under-wear.
The simple version, run through these
A tooth hasn’t moved as planned by the end of its stage. Before telling the patient to wear it longer, work out why. Fit is the natural first look, but treat these as things to check, not a rigid ranking:
- Does the aligner still fit? A gap at the biting edges means it’s lost tracking. Go back to the last aligner that fully seated, use chewies, then move forward slowly.
- Is there space to move into? If the IPR scheduled for this stage hasn’t been done, the tooth is blocked. Do the IPR, then re-run the stage.
- Is it a movement aligners struggle with? Certain rotations (round-crowned teeth), extrusion, intrusion, root torque. Don’t keep waiting, confirm the attachment is on and intact, and flag for refinement with overcorrection.
- Could the tooth be ankylosed? Rare, but if one tooth won’t move while its neighbours track, especially with a history of trauma or infection, or a high “metallic” note on percussion, it may be fused to bone. Aligners can’t move it; confirm and plan around it.
- Only if 1, 4 are all fine → it’s likely wear time. A few extra days at proper full-time wear can let a compliance gap catch up, a few days, not indefinite. If it still won’t move, refine rather than stretching the stage.
Rule of thumb: “wear it longer” is a compliance fix, not a force fix.
Why “wear it longer” usually doesn’t work
An aligner pushes hardest in the first day or two, then the force fades to a low trickle, testing shows the force decays fastest in the first ~8 hours and plateaus by ~24 hours, so most of the movement happens early in the stage. The randomised trial by Al-Nadawi / Kravitz (Angle Orthodontist, 2021) compared 7-, 10- and 14-day change protocols and found no clinically significant difference in how well teeth moved, shorter intervals simply shortened treatment. Our tri-layer material (firm clear outer layers, soft elastomeric core) gives a gentler, steadier force that holds its shape, but it’s still front-loaded, so once a stage’s force is spent, more days add little.
RUN THE CHECKS
Diagnose the cause, in order
Check 1, Does the aligner still fit?
Look for a gap between the aligner and the biting edges (easiest to see at the front). A gap means the teeth have fallen behind the plan and the aligner no longer fits, “non-tracking”. Pushing on to the next aligner only makes the gap bigger. Step back to the last aligner that seated fully, have the patient use chewies (5 to 10 minutes, a few times a day) until it’s tracking again, then advance, slowing the change interval if needed. This is about fit and geometry, not force.
Check 2, Is there space for the tooth?
Our IPR is staged in the plan on purpose. When a tooth is many degrees of rotation from its final position, you often can’t yet see the contact point that will eventually touch the neighbour, so the IPR is scheduled for the stage where you can see and reach it. A stalled tooth is frequently just sitting at a stage where the scheduled IPR hasn’t been performed yet. Do the scheduled IPR (always gauge-checked), then re-seat or re-run the stage. A frequent, easily-missed cause on crowding and derotation cases.
Check 3, Is it an inherently hard movement?
Some movements barely express even with perfect fit and wear, rotation of round-crowned teeth (canines, premolars), extrusion (especially upper laterals), anterior intrusion and root torque. Across the predictability literature (e.g. Kravitz et al., AJODO 2009) these consistently achieve well under half of what was planned without help. More time won’t fix that, flag for refinement, build in ~20% overcorrection on the next plan, and confirm the attachment is present and intact so the aligner has something to grip.
Check 4, Could the tooth be ankylosed?
Rare but significant, usually only considered once fit, space and movement type are ruled out. Ankylosis is when the tooth root fuses directly to the bone, so the tooth is rigidly fixed and won’t move orthodontically. Signs: one specific tooth not moving while neighbours track; a history of trauma, infection or previous orthodontic difficulty; a distinct high-pitched “metallic” note on percussion; the tooth may sit slightly low. Confirm with percussion and a periapical radiograph and refer to / consult a specialist, forcing it only compromises the adjacent teeth, so plan around it.
Check 5, Compliance / wear habit
Reaching this point means fit, space, movement type and ankylosis are all ruled out, so the likely issue is the patient not wearing the aligner the full 20 to 22 hours a day. A few extra days at proper full-time wear, with chewies, can let a compliance gap catch up, a few days, not indefinite. If it still doesn’t move, escalate to refinement. Backtracking to the last fully-fitting aligner and going slowly is fine; holding a stuck stage indefinitely is not.
Glossary
- Tracking / non-tracking, whether the aligner still fits as designed; non-tracking means a visible gap at the biting edges
- IPR, planned, controlled filing of a tiny amount of enamel between teeth to create space, scheduled at specific stages
- Derotation, turning a rotated tooth back to its correct orientation
- Extrusion / intrusion, moving a tooth further out of, or further into, the gum
- Torque, tilting the root of a tooth, not just tipping the crown
- Attachment, a small tooth-coloured bump bonded to a tooth that gives the aligner something to grip
- Ankylosis, a tooth fused directly to the bone, so it can’t be moved orthodontically
- Refinement, a new scan and fresh aligners to finish or correct movements that didn’t fully express
- Overcorrection, deliberately planning a movement slightly beyond target, so the under-expressed result still lands on target