Volumetric analysis of external root resorption after clear aligner treatment of open bite cases: a CBCT study

Orthodontically induced external root resorption (OIERR) is a recognized adverse effect of orthodontic treatment. Limited literature exists that reported on volumetric root changes in anterior open bite patients treated with clear aligners. This study aimed to evaluate three-dimensional volumetric changes in anterior teeth roots using cone-beam computed tomography (CBCT) in open-bite patients treated with clear aligners.

Fifty CBCT scans [pre-treatment (T1) and post-treatment (T2)] obtained from 25 adult patients (11 males,14 females; mean age: 32.67 ± 10.67 years) with anterior open bite (1-4 mm) treated using clear aligners were retrospectively analyzed. Semi-automated segmentation of the twelve anterior teeth was performed using Blue Sky Plan software, followed by three-dimensional superimposition in 3-matic software. A reference line at the cementoenamel junction was used to trim the crown, and root volumes were measured at both time points. Percentage changes in root volume between pre-treatment and post-treatment were calculated. The level of significance was set at p ≤ 0.05. Skeletal and dental parameters were assessed before and after treatment. The reproducibility of the measurements was assessed using the intraclass correlation coefficient (ICC).

Both intra-examiner and inter-examiner reliability were excellent (ICC: 0.90-0.94 and 0.92-0.96, respectively; p < 0.001). All anterior teeth demonstrated significant reduction in root volume. Maxillary canines showed the greatest percentage decrease (- 6.33 ± 2.58%), followed by the central (- 5.91 ± 4.93%) and lateral incisors (- 5.50 ± 3.24%). Mandibular canines again showed the largest reduction (- 6.75 ± 2.33%), followed by lateral (- 5.58 ± 3.20%) and central incisors (- 4.86 ± 2.54%). Males exhibited significantly greater root volume reduction across all anterior teeth (p < 0.05), while no significant correlation was found with age.

Patients with anterior open bite who were treated with clear aligners showed mild root volume reduction in all anterior teeth with canines being most affected. This reduction is generally considered to be clinically insignificant. Male patients showed greater volumetric reduction, whereas age and magnitude of incisor movement were not significantly correlated with root volume changes.