Treatment Of Severe Crowding Malocclusion In Adults With Self-ligating Appliances

Objective: To discuss the clinical effect of straight-wire technique with self-ligating brackets applied to adult malocclusion with severe dental crowding.Method: An adult patient enrolled to Dr. Dalian dental Clinic in 2011 was selected. This patient was 25 years old male diagnosed with Angle’s class II, skeletal class II malocclusion and severe dental crowding. She had Class I molar relationship on the left, class II molar relationship on the right and Class II canine relationship on the both left and right. Total crowding in both upper and lower arch was 12 mm. She exhibited large overjet of 5mm and normal overbite of 3 mm. The lower arch was with 4mm curve of spee on the left and 2mm on the right. Midline shift was 1 mm towards right on lower arch when comparing with the facial midline. The patient’s facial profile was straight, but the soft tissue of chin was a little tight. The results of cephalometric tracing was almost normal. Treatment plan was drawn according to analysis result: Extraction of first premolar on upper arch and second premolar on lower arch. Straight wire technique was used with self-ligating brackets to align and level the dentition. Extraction spaces was closed by sliding mechanics without anchorage reinforcement. Clinical records and cephalometric analysis was done to evaluate pre and post treatment changes in dentoalveolar structures and soft tissue.Result: Total duration of treatment was 27 months. Dentition was well aligned and extraction spaces were closed. Canine relationship and molar relationship was both Class I on the left, but was both Class II on the right. Midline shift was 1 mm towardsright on lower arch yet. Antero-posterior relationship was good with normal overbite and overjet. There were significant increase not only in anterior arch width of upper arch but also in anterior and middle arch of lower arch. The facial profile of the patient was pleasing. Comparison of pre and post treatment cephalometric tracing indicated following changes: SNA decreased by 1.3°. SNB decreased by 0.2°. ANB angle decreased by 1.1°. The skeletal pattern turned to Class I skeletal. Go Gn-SN, FMA angle change were negligible. OP-SN angle increased by 2.9°, indicating the occlusion plane rotate clockwise. The U1-SN angle, U1-NA angle and U1-NA distance were both reduced. L1-NB angle, U1-L1 angle were increased. Pos Bs-FH angle and FCA angle were decreased, FH-Ns-Pos angle was increased. The pleasing facial profile was achieved. After each visit while increasing the force, patient didn’t feel painful basically, just feel a little uncomfortable sometimes. The brackets were easy to clean because of the absence of wire ligatures. It could protect the gingiva health.Conclusion: For the adult malocclusion with severe dental crowding, straight wire technique with self-ligating brackets could align and level the arches as quickly as possible, expanse the arches modestly. At the same time, moving teeth with a light, continuous force was better to the periodontal condition.