الفهرس 
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Abstract
The aim of this study was to evaluate mandibular distal force system assisted with miniscrew anchorage three dimensionally. CBCT images were used to evaluate the effect of miniscrew anchorage in distalization of mandibular molars.
A sample of 15 subjects that required mandibular distalization was selected from the outpatient clinic of the Orthodontic Department in the Faculty of Dentistry, Ain Shams University. from those patients; 12 patients completed the study and 3 patients dropped out. Among these 12 patients, 6 patients required unilateral distalization and 6 patients required bilateral distalization in the mandibular arch.
After taking the standard orthodontic records, prior to the insertion of the distalizing appliance and the miniscrew, patients were referred for extraction of lower right and left third molars, if present. Molar bands were selected and cemented for both lower first and second molars. Self-drilling titanium miniscrews with collar diameter of 1.4 mm and a length of 6 mm were selected for insertion in the buccal interradicular bone between lower canine and first premolar.
DPMD was tailored to the insertion site and was fabricated from .017” × .025” TMA wire. A section of .019” × .025” TMA wire was inserted in the main tube of the first and second molars bands to held them together buccally and a three unit power chain held them together lingually through the molar bands cleats. The distal end of the distalizer was inserted in the first molar band auxiliary tube.
A NiTi open coil spring was placed at the mesial end of the appliance which was then fitted within the miniscrew slot head and secured in place using stainless steel ligature wire.
Patients were checked every 3 weeks for cooperation and treatment progress. The spring was replaced every 6 weeks. Distalization was continued until Class I molar relationship and the space required for correction of mandibular arch deficiency were achieved.
Each patient received a cone beam computed tomography (CBCT) using PLANMECA CBCT scanner before the beginning of treatment and after the completion of molar distalization. DICOM images were imported in the InVivo5 software. Linear and angular measurements were done to assess the distalization effects. Also, superimpositions were done to visualize treatment results.
Results showed a statistically significant increase in the amount of centroid, furcation and mesial root distalization of the mandibular first molars with a mean of 3.09 mm, 2.73 mm and 0.82 mm respectively. Distal molar tipping was evident after distalization and the mean tipping was 8.69 degrees. Most of the distalized molars showed a significant mesiobuccal rotations and lingual crown tipping after distalization. Molars tipping ratio showed an average of 27.6 %. Regarding the rate of molar distalization, an average of 0.45 mm distalization per month was achieved. The overall success rate of miniscrews in this study was 88.8 %