envelop of discrepancy of tooth movement possible by different methods

Presentation on the extent of tooth movement possible in different directions by different methods

1. Envelope of D iscrepency Dr Qurat ul ain Amina

2. Envelope of D iscrepency One of the most important concept in decision making process of orthodontics is the range of tooth movement that can be accomplished within the biological limits. Envelope of discrepancy graphically illustrate how much change can be produced with different treatment modalities It developed from cephalometric data and uses tooth movement relative to the underlying jaw, and jaw relationship with cranial base.

3. Envelope of Discrepency It can be thought of as an elastic 3D, asymmetric closed container Orthodontics alone rearranges the contents of container Growth modification and Surgery change the shape of container

4. For any type of malocclusion, four ranges of correction exist The amount that can be accomplished by orthodontic tooth movement alone A larger amount accomplished by orthodontics aided by absolute anchorage An additional amount can be achieved by growth modification treatment A still larger amount require surgery as a treatment plan

5. If pt has 7mm overjet, correction by retraction is just within the range of orthodontic tooth movement. Maxillary premolar extraction would provide 7-8mm space but 7mm retraction require bone anchors to close ext space Greater overjet require growth modification Even greater overjet more than 12mm require ortho plus orthognathic surgery The same reasoning applies to transverse and vertical possibilities of ortho treatment

6. Retraction of 3mm is within the limits of ortho alone More than 3mm requires orthopedics plus orthodontic tooth movement Orthognathic surgery can correct the sagittal discrepancy of 25mm

7. The envelope in the molar region denotes the ranges of vertical and transverse possibilities of orthodontic treatment The precise dimensions of envelope are less important than the concept

8. The timing of treatment is a factor in a amount of change that can be produced The amount of tooth movement is same in children and adults however the growth modification range diminishes as the child mature and disappear after the adolescent growth spurt Controlling vertical growth in children is difficult and TADs can be useful for this in adults. Thus the concept of range is very imp for stability of orthdodontic treatment