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Objective To compare the transverse dental and skeletal changes in patients treated with bone‐anchored palatal expander (bone‐borne, BB) compared to patients treated with tooth and bone‐anchored palatal expanders (tooth‐bone‐borne, TBB) using cone‐beam computer tomography (CBCT) and 3D image analysis. Methods The sample comprised 30 patients with transverse maxillary discrepancy treated with two different types of appliances: bone‐borne (Group BB) and tooth‐bone‐borne (Group TBB) expanders. CBCT scans were acquired before (T1) and after completion of maxillary expansion (T2); the interval was 5.4 ± 3.4 and 6.2 ± 2.1 months between the T1 and the T2 scans of Group TBB (tooth‐bone‐borne) and Group BB (bone‐borne), respectively. Transverse, anteroposterior and vertical linear and angular three‐dimensional dentoskeletal changes were assessed after cranial base superimposition. Results Both groups displayed marked transverse skeletal expansion with a greater ratio of skeletal to dental changes. Greater changes at the nasal cavity, zygoma and orbital levels were found in Group BB. A relatively parallel sutural opening in an anterior–posterior direction was observed in Group TBB; however, the Group BB presented a somewhat triangular (V‐shaped) opening of the suture that was wider anteriorly. Small downward‐forward displacements were observed in both groups. Asymmetric expansion occurred in approximately 50% of the patients in both groups. Conclusion Greater skeletal vs dental expansion ratio and expansion of the circummaxillary regions were found in Group BB, the group in which a bone‐borne expander was used. Both groups presented skeletal and dental changes, with a similar amount of posterior palate expansion. Asymmetric expansion was observed in both groups.

Introduction Maxillary expansion in patients at the end of their growth relies on the possibility to use miniscrew supported expanders to apply expansion forces directly to the midpalatal suture. Although miniscrews provide a stable anchorage unit, several studies have reported that they do not remain in exactly the same position during treatment. The aim of the present study was to analyze miniscrew position changes after the expansion using bone-borne appliances in late adolescent patients. Methods Nineteen patients (13 females, 6 males), with a mean age of 17.81 (SD = 4.66), were treated with a Bone-Borne Expander Device. The appliance was designed with 4 miniscrews: 2 in the anterior palatal area, at the third rugae level; 2 in the posterior area. A CBCT and an intraoral scan were obtained before treatment (T0), and then, a second CBCT was obtained after the expansion (T1). Data on peri-suture bone thickness were collected at T0, then the CBCTs were superimposed, and changes between mini-screws position on T0 and T1 were evaluated, both by linear and angular displacements. Results Significant longitudinal differences were found in the distance of the head and the tip of miniscrews measured at the occlusal plane, as well as angular changes. Correlations between displacement measurements and peri-suture bone thickness and height measurements were found as well. Conclusions While acting as bone anchor units, miniscrews do not remain in the same position during bone-borne expansion. The amount of displacement was related to peri-sutural total bone height and cortical thickness, especially in the anterior area of the naso-frontal maxillary complex.

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