Clinical Treatment In Class Ⅱ Maloccusion Subjects Including Mesial Impacted Second Molar

Objective:A study on clinical application of two different methods to upright mesioangular inclined impaction of the second molar.Materials and methods:Two patients with mesioangular inclined impaction of the second molar were selected as objects of study.The first patient was a 24 years old man with permanent teeth.By analyzing models and X-rays,the relationship of the left molar was neutral,while that of the right one was mesio-distal canine-to-canine with local anterior crossbite and mesioangular inclined impaction of tooth 17.The tooth axis of upper anterior teeth was upright,while that of mandibular anterior teeth was inclined to tongue.The crowding degree of maxilla was 16.5mm,while that of mandible was7.5mm.The lower midline was 1 mm to the right and the chin was about 1 mm to the right.According to clinical examinations and diagnosis,orthodontic extraction treatment was adopted with extraction of teeth 14,24,35 and 45.A Nance arch was used to reduce mechanical anchorage loss on maxilla.Alinement and equalization of upper and lower teeth were conducted.After closing the extraction space,a buccal tube was spliced to the buccal side of tooth 17.The orthoaxis spring was applied to erect this tooth which was basically vertical 1 month later.After removing the orthoaxis spring,a NiTi arch wire was used to regulate tooth 17.The second patient was a 12 years old girl with permanent teeth.By analyzing models and X-rays,the relationship of the right molar was neutral,while that of the left one was mesio-distal canine-to-canine with local anterior crossbite and mesioangular inclined impaction of the tooth 37.The tooth axis of upper anterior teeth was upright,while that of mandibular anterior teeth was inclined to lips.The crowding degree of maxilla was 5 mm,while that of mandible was4.5 mm.The lower midline was 1 mm to the left.According to clinical examinations and diagnosis,orthodontic extraction treatment was adopted with extraction of teeth 14,24,34 and 44.Alinement and equalization of upper and lower teeth were conducted.The extraction space was closed.After closing the lower left extraction space,a toothseparation spring was placed between teeth 36 and 37.A month later,effective erection of tooth 37 was observed by panoramic films.Six months later,the tooth was fully healthy.Panoramic films and orofacial images before and after treatment were taken for both patients and the erection efficacy of the second molar was observed.Results: In the first case,tooth 17 was erected successfully by an orthoaxis spring.By comparing conditions before and after treatment,the angle formed by long axes of teeth 16 and 17 was reduced from 45° to 18°;the height of mesioangular alveolar bone of tooth 17 rose;the patient’s facial form maintained well and the proportion of 1/3lower faces was normal.In the second case,tooth 17 was erected successfully by a tooth separation spring.By comparing conditions before and after treatment,the angle formed by long axes of teeth 36 and 37 was reduced from 25° to 6.5°;the height of mesioangular alveolar bone of tooth 37 increase;the patient’s facial form was improved and the proportion of 1/3 lower faces was normal.Conclusions: Both patients suffered from mesioangular inclination or impaction of the second molar.According to different conditions of patients,a method with positive-axis auxiliary-arch and an orthoaxis spring and that with a separator and a tooth separation spring were adopted respectively.The second molars of both patients with mesioangular inclination or impaction were erected effectively.The advantage of the method with a separator and a tooth separation spring was simplicity of operation.The separator was prepared in advance and it is easy to make a tooth separation spring with little foreign body sensation.It had a good curative effect on teenagers whose inclination is within 30°.Its disadvantage was a limited scope of application,so it had a bad effect on patients with great inclination of the second molar or without eruption potential of the second molar.The advantage of the method with positive-axis auxiliary-arch and an orthoaxis spring was a wide range of application,so it could be applied to patients with great inclination of the second molar or space with the first molar after tooth erection or without eruption potential.Its disadvantage was its complex preparation method,which was hard to be mastered,foreign body sensation and froward strength.Clinically,as long as the indication is selected properly,the second molar with mesioangular inclined impaction can be erected by both methods canerect effectively.