الفهرس 
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Abstract
This randomized clinical trial was conducted to evaluate and compare the effects of slow and rapid activation protocols of miniscrew-supported expanders on the skeletal changes, the dento-alveolar changes, and the pain experience.
A total of 30 patients were recruited based on clear eligibility criteria. The patients were randomly and equally allocated to two study groups; slow expansion (group I) and rapid expansion (group II). A miniscrew-supported expander anchored using 4 palatal miniscrews was used in both groups. Patients is group I activated the appliance by turning the expansion screw once every other day, while patients in group II activated the appliance by turning the expansion screw twice daily. After the desired expansion was achieved, the jackscrew was secured using a ligature wire and the appliance was left in place for retention. The appliances were removed 5 months after the initial activation. Digital dental casts were obtained for each patient before expansion (T0), after expansion (T1), and at the end of the retention period after removing the appliance (T2). Cone beam computed tomography (CBCT) scans were obtained at T0 and T2.
The degree of pain, pressure, headache and/or dizziness felt by the patients, in addition to the effect on speech, chewing, and swallowing was quantified using an 11-point numeric rating scale. The scores were recorded by each patient before the appliance insertion (S0), after the first activation of the appliance (S1), after one week of activation (S2) and on the last day after the last activation of the appliance (S3). The data obtained from 24 patients was statistically analyzed in the current study.
A median diastema was evident in all the analyzed patients indicating successful opening of the mid-palatal suture. The transverse discrepancy was corrected in all the analyzed patients in both groups. Measurements made on the digital dental casts in both groups showed
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a significant increase in the maxillary width, inter-molar width and inter-premolar width from T0 to T1, and a non-significant change from T1 to T2. Rapid expansion resulted in significantly larger amount of inter-molar expansion compared to slow expansion.
Slow expansion resulted in a significant increase in all the measured skeletal and dento-alveolar CBCT measurements except the dental inclination of the first molars and left first premolar. On the other hand, rapid expansion resulted in a significant increase in all the measured skeletal and dento-alveolar CBCT measurements. A statistically significant greater mid-palatal suture expansion at the level of the first molar was reported with rapid expansion compared to slow expansion. Slow expansion resulted in significantly lower increase in inter-cusp width and significantly lower increase in molar inclination compared to rapid expansion.
The mid-palatal suture expansion at the level of the first molar amounted to 38.99% and 48.58% of the jackscrew opening in the slow and rapid expansion groups, respectively, which was not significantly different between the two groups. The pattern of expansion in the axial plane in both groups was mostly wider anteriorly.
Multiple miniscrew failures, and miniscrew flexure were observed in the rapid expansion group. In addition, NRS assessment showed significantly higher pain scores at S2 and S3, significantly higher pressure scores at S3, significantly higher difficulty in speech and swallowing at S3, and significantly higher difficulty in chewing at S2 and S3 in the rapid expansion group. Mild headache and dizziness were reported, and they were not significantly different between the two groups.