Assessment of Maxillary Molar Tooth Changes Caused by Class III Elastics in Hybrid Hyrax-Mentoplate Treatments: A Pilot Study.

Objective: This study aimed to investigate the positional changes of maxillary first molars in patients treated with the hybrid hyrax-mentoplate and Cl III elastics combination using cone-beam computed tomography (CBCT).

Methods: Ten patients (7 females-3 males, mean age: 11.66±0.83 years) treated with hybrid hyrax-mentoplate at Marmara University Department of Orthodontics were included. Angular and linear measurements were taken from pre-treatment and post-treatment CBCT images, and changes in maxillary first molar teeth were examined using 3D SLICER version 5.0.2 (www.slicer.org). Statistical significance was set at p≤0.05.

Results: Significant increases were observed in all distance measurements except C16p-C26p in the coronal plane, and significant decreases were observed in angular measurements only at 16mb and 26mb (p≤0.05). All measurements in the sagittal plane significantly increased compared to the vertical and horizontal reference lines (p≤0.001). Angular measurements relative to the palatal reference line significantly increased only in P-16p, P-26mb, and P-26p (p≤0.05). In skeletal measurements, significant changes were observed only in V-A, V-ANS, H-PNS, and V-PNS measurements (p≤0.05). The expansion at the apical level was significantly higher than that at the coronal level (p≤0.05). Compared to the V line, more mesial movement was observed at the coronal level than at the apical level (p≤0.001).

Conclusion: The use of Class III elastics causes greater expansion at the apical level than the coronal. Molar teeth exhibit a mesial movement, but there could be multiple contributing factors. In molars connected to Class III elastics, extrusion occurs. When vertical control is important, appropriate safety measures are advised.