Evaluation of bony changes observed in mid-palatal suture after rapid maxillary expansion using fractal analysis

Introduction
Transverse deficiency of maxilla is one of the common reasons of malocclusion. This anomaly is treated with rapid maxillary expansion (RME) in children and adolescents. Evaluation of mid-palatal suture using cone-beam computed tomography (CBCT) allows for accurate assessment of mid-palatal suture, and with this technique, surgical treatment can be avoided in late adolescent and young adult patients.

Objectives
This study aimed to evaluate the new bone formed in mid-palatal suture after retention period in patients treated with RME using fractal analysis (FA).

Material and methods
A total of 30 patients (18 females and 12 males) were included in the study, with mean age of 14.29 ± 1.62 years. Mid-palatal suture was identified, and imaging area was designed as a 40 × 120 pixel rectangle at T0 and T1 on axial CBCT image, extending from posterior border of incisive canal to anterior border of posterior nasal spine. Fractal dimension (FD) was compared between before treatment (T0) and after retention pe­riod (T1). FD analysis was calculated with box-counting method using ImageJ software.

Results
The mean FD value of pre-operative period was 1.24 ± 0.05, and the mean FD value after retention period was 1.10 ± 0.09. Statistically significant difference was found when the FD value was compared before treatment and after retention period (p < 0.001).

Conclusions
Evaluating mid-palatal suture ossification in patients who underwent RME using FA is reliable method. It can be used confidently to determine the duration of retention period.