Teeth are extracted for several reason in orthodontics. The most common reason for extraction is the relief of crowding and to create space to gain good alignment of the teeth. When premolar teeth are extracted for orthodontic treatment this leads to temporomandibular dysfunction (TMD) because of over retracting the upper incisors during space closure, forcing the condyle into a posterior position. It is this posterior position of the condyle within the fossa, which is presumed to cause an anteriorly displaced disc and therefore TMD .The previous study of 42 patients with a Class II division 1 malocclusion treated by the extraction of both upper first premolars and fixed appliances, 70 % showed a forward movements of mandibular basal bone and the changes in condylar position
Orthodontic treatment is needed for those whose occlusion is not functionally optimal to prevent the development of TMD.
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