Dental and Skeletal Changes in the Upper and Lower Jaws after Treatment with Schwarz Appliances Using Cone-Beam Computed Tomography

The purpose of this research was to use cone-beam computed tomography (CBCT) images to evaluate dental and skeletal changes in upper and lower jaws after treatment with Schwarz appliances. Materials and Methods: 28 patients with Angle Class I molar relationships and crowding were randomly divided into two groups – 14 non-expanded and 14 expanded patients. 3D-Rugle CBCT software was used to measure various reference points before treatment (T0) and during the retention period of approximately 9 months after 6 to 12 month expansion (T1). Cephalometric and cast measurements were used to evaluate treatment in both groups. To test whether there were any significant differences between the control and treatment groups at T0 and T1, the Mann-Whitney U-test was used. Results: The dental arch (including tooth root apices) had expanded in the upper and lower jaws. Alveolar bone expansion of up to 2 mm apical to the cementoenamel junction (CEJ) was detected. The midpalatal sutures were separated in some cases and subsequent expansion was observed at the inner surface of the nasal cavity at the inferior turbinates. However, no significant (P > 0.05) difference was observed in the inter-width of the mandibular bodies, zygomatic bones, nasal cavity in the middle turbinate region, condylar heads, or antegonial notches. In mandibular and maxillary cast measurements, arch crowding and arch perimeter showed statistically significant changes in the expansion group. The mandibular width values demonstrated no significant changes as measured from a point 2 mm apical to the CEJ, whereas the maxillary width values demonstrated significant changes as measured from a point 2 mm apical to the CEJ. Conclusions: This study indicates that the Schwarz appliance primarily affects the dento-alveolar complex, while it has little effect on either the mandibular bodies, any associated structures including the maxillary midpalatal suture and the inter-width of the nasal cavity in the middle turbinate region. In addition, the center of rotation of the mandibular and maxillary first molar was observed apical to the root apex.

Three-dimensional (3D) CBCT, multiplanar reconstruction (MPR) image analysis, superimposition, iterative closest point (ICP) method, Schwarz appliances

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