Duration-Dependent Caries Risk During Clear Aligner Therapy: A Retrospective Analysis

TL;DR

This study found that longer clear aligner therapy is linked to a small but significant increase in tooth decay, suggesting the need for preventive dental care during treatment.

Contribution

The study identifies treatment duration as a key risk factor for caries progression during clear aligner therapy.

Findings

Longer treatment duration was independently associated with caries progression (β = +0.0088 per tray, p = 0.0037).

Each 10-tray increment increased the odds of new decay by 55% (OR = 1.55, 95% CI: 1.26–1.90).

A threshold of ≥42 trays was identified as clinically relevant for caries risk (AUC = 0.67).

Abstract

Background: Clear aligner therapy (CAT) represents a biomimetic orthodontic approach that uses flexible thermoplastic materials to reproduce the physiological tooth movement and mechanical load distribution of natural tissues. While these materials promote oral hygiene and aesthetic comfort, their long-term biological impact on the caries process remains uncertain. This retrospective study aimed to evaluate changes in the number of decayed teeth (ΔD) before and after clear aligner treatment and to identify duration-dependent risk factors. Methods: This retrospective study included 362 patients (279 females, 83 males) treated with Invisalign® aligners between 2020 and 2024. Baseline and post-treatment panoramic radiographs were analyzed to determine decayed tooth counts. Age, sex, and total aligner count were recorded. Non-parametric tests, multivariable regression, and ROC analysis were used to assess predictors of ΔD. Results: The mean number of decayed teeth increased slightly from 3.54 ± 2.76 to 3.83 ± 2.93 (p < 0.001). Longer treatment duration was independently associated with caries progression (β = +0.0088 per tray, p = 0.0037), and each 10-tray increment increased the odds of new decay by 55% (OR = 1.55, 95% CI: 1.26–1.90). ROC analysis identified ≥42 trays as a clinically relevant threshold (AUC = 0.67). Conclusions: Clear aligner therapy demonstrated a statistically significant yet clinically small increase in caries incidence, primarily related to treatment duration. As a biomimetic orthodontic approach that integrates mechanical and biological dynamics, extended clear aligner use may alter biofilm–surface interactions and salivary conditions over time. Therefore, preventive strategies–such as professional fluoride applications, strict cleaning protocols, and shorter recall intervals–should be emphasized for long-duration treatments to preserve the biological benefits of this biomimetic system.

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