The Case Analysis Of Dentition Moderate Crowding Of Class Ⅱ Division2Malocclusion With Non-extraction Treatment By Self-ligating Brackets

Objective: This study was designed to observe and evaluate the clinic effect byusing self-ligating brackets in treatment of the patient with class II division2malocclusion, and to investigate mechanism of treatment of dental crowding usingself-ligating brackets.Methods: A female case was selected from the Orthodontic Division of the firstAffiliated Hospital of Dalian Medical University in2012, who was19years and4months old, with class II division2malocclusion, class II skeletal pattern, high anglepattern, bilateral distal cusp-to-cusp molar relationship, moderate flat Spee’s curve,deficiency of maxilla and mandible related to skull base, II degree crowding of upperarch, I degree crowding of lower arch, deep overbite, severe lingual inclination of upperand lower anterior teeth, scissors bite of left maxillary second molar and mandibularsecond molar, profile of mandibular retrusion, discrepancy of midline of face and theone of upper and lower arch, none abnormality of the way to open and close mouth,obvious mentolabial furrow and unsatisfactory lip seal with a tensive upper lip. Thepatient denied her family history and any bad habit except tooth abrasion at night. Thepatient was treated by self-ligating bracket mechanism; teeth aligned and arch leveledby super elastic nickel-titanium arch wire; lingual inclination of upper anterior teeth relieved for the movement and growth of mandible; molar relationship and occlusionadjusted by Multi-loop Edgewise Arch Wire at the later stage of orthodontic treatment.The pre-and post-treatment lateral cephalometric radiograph are measured to comparethe oral and maxillofacial changes of hard and soft tissue, temporomandibular joint,shape of chin and lip seal, and35variables from the cephalometric analyses of BeijingUniversity, Wylie, McNamara, Downs, Merrifield and Burstone are measured andanalyzed. The perimeter and width of dental arch and Bolton’s index are measured byplaster model to analyze the shape of dental arch, inclination of teeth, et cetera. Molarturbo and its discontinuous removal were used to relieve scissors bite of left secondmolars.Results: The course of orthodontic treatment needs17months. The changes ofpre-and post-treatment: The molar relationship and canine relationship changed fromclassⅡ to classⅠ, substantial expansion of maxillary and mandibular dental arch, themost increment of the width between upper and lower second premolars, the widthbetween upper first premolars increased4mm, the width between lower first premolarsincreased3mm, none obvious increment of the width between canines, shape of thedental arch changed from original square to oval, ANB angle changed from9degree to5.5degree, sight increment of arch perimeter, relief of crowding of upper and lowerarches, labial inclination of upper and lower anterior teeth compared with pre-treatmentones, the angulation of first lower incisor (L1/NB) changed from16to30degrees stillin the normal range, the distance from esthetic line to lower lip(EL-LL) increased from-1mm to1mm and instinct improvement of profile. Because of the relief of atresia ofbite, mandible rotated counter-clockwise and chin became more natural. The scissorsbite of left second molars had been relieved and occlusion was nice. The snap oftemporomandibular joint disappeared. The patient and her parents were quite satisfiedwith the curative effect.Conclusions：Class II division2malocclusion can be corrected effectively byself-ligating brackets. The length and width of dental arch get increased, and crowdingof upper and lower arch get relieved, which shows the great effect of arch expansion of self-ligating brackets.