Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Orthodontics

Objectives: The aim of the present study was to investigate whether low intensity laser could have an effect on orthodontic mini-screws stability using CBCT. Subjects and Methods: This study was carried out on thirty mini-screws in fifteen subjects with a mean age of 20 years by using split mouth design for the patients who required therapeutic extraction of maxillary first premolars, the mini-screws were placed bilaterally between the maxillary second premolar and the first molar. A direct force using closed nickel-titanium coil spring extending from the mini-screw to the hook of maxillary canines was applied, It delivered a force of 150 gm per side to retract the maxillary canine. The subjects were referred to take the Pre-CBCT.. Low intensity laser was applied without contact over and perpendicular to mini-screws of the laser sides on days (0, 7, 14, and 21). After six months of canine retraction, The subjects were referred to take the Post-CBCT. Results: The overall success rate of mini-screws in this study was approximately 85.7% and It was found that movements of the mini-screws in the Laser side was lesser than the control side. The mini-screws were moved anteriorly in mesial direction from the (axial) view and inferiorly in occlusal direction from the (coronal) view, and Its Movement in mesial direction was greater than its occlusal one. The angular difference between the laser and control groups in mesial movement of mini-screws was 0.91{u00B0} and in occlusal movement of mini-screws was 0.53{u00B0}

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