# Root resorption: braces or aligners?

From SMILE-FX® · Prepared 30 October 2026

Orthodontically induced external apical root resorption is loss of hard tissue at a tooth's root tip. It concerns the root, not simply how straight the visible teeth look. Other forms and causes of resorption need separate assessment.

Root shortening occurred with both appliances in a small randomized study of selected adults. It found no statistically significant difference between Invisalign® and fixed appliances. That does not prove equal risk or predict a rare severe outcome.

The adult comparison excluded prior orthodontic treatment, upper-incisor trauma and pre-existing resorption. Its averages cannot simply predict outcomes for people with those histories or for children.

A separate six-month adult open-bite trial found less shortening with an in-house aligner-plus-exercise protocol, alongside less achieved molar intrusion than miniscrew-assisted fixed treatment. This does not establish a general aligner safety advantage.

![Diagram distinguishing the crown, root and root tip.](assets/root-structure.svg)

Root-tip tissue loss concerns the root, not the visible crown.

Conceptual illustration · unscaled

| Study observation | Direction |
| --- | --- |
| Root shortening. | Less |
| Achieved intrusion. | Less |

In this trial, less measured root shortening accompanied less achieved molar intrusion.

[Continue to Decisions](root-findings-and-treatment-decisions.html)

## Sources

- [2025 randomized trial](https://pmc.ncbi.nlm.nih.gov/articles/PMC12972252/)
- [2023 open-bite trial](https://pmc.ncbi.nlm.nih.gov/articles/PMC10633803/)
- [2020 retrospective study](https://pmc.ncbi.nlm.nih.gov/articles/PMC6943096/)

Related guides: [Imaging](https://orthodonticimagingguide.com/) · [Retreatment](https://orthodonticretreatmentguide.com/)

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