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[Effects of mid-palatal suture opening and midfacial bony structure changes induced by maxillary skeletal expansion in adults].

PURPOSE
To analyze the opening of mid-palatal suture, transverse changes in dental and dentoalveolar measurements and shift of midfacial bony structures induced by maxillary skeletal expansion (MSE) with cone-beam CT (CBCT), and to evaluate the effect of maxillary skeletal expansion and its influence on adjacent bony structures in adults.


METHODS
The study sample consisted of 12 adult patients with maxillary transverse deficiency (4 males, 8 females) at a mean age of (21.17±4.13) years old. All patients were treated with MSE. After treatment, the posterior crossbite was corrected, and the width of the maxillary arch was achieved the optimal width. Pre- and post-treatment CBCT exams were taken before and after MSE treatment. Multiplanar coronal and axial slices obtained from CBCT images were used to measure the changes in transverse widths, angular changes and tooth inclination with Dolphin Imaging 11.9. SPSS 26.0 software package was used for statistical analysis.


RESULTS
After MSE treatment, the anterior nasal spine width increased by (2.38±1.01) mm, posterior nasal spine width increased by (2.25±1.08) mm (P<0.01). The inter-crown and inter-apex distance at the first molar increased by (5.56±1.38) mm and (4.14±1.29) mm, respectively (P<0.01). No significant difference was seen in terms of tooth inclination of the first molar(P>0.05). Pterygoid process angle, pterygoid process width, anterior inter-maxillary distance, upper and lower inter-zygomatic distance were significantly larger after treatment (P<0.01), while the inter-temporal distance and bilateral zygomaticomaxillary angle remained unchanged(P>0.05).


CONCLUSIONS
MSE has a favorable effect in adult patients with parallel skeletal expansion of the mid-palatal suture achieved after expansion. The teeth present with certain buccal inclination but show no significant movement relative to the alveolar bone. The midfacial bony structures also shift in three-dimensional under the effect of the expansion force.