A clinical evaluation of the differential force concept as applied to the edgewise bracket.

When the Siamese edgewise bracket with continuous arch wires is used, it does not always follow that with 100 to 150 Gm. of applied force only the canine and not the buccal segment or anchor unit will move. Conversely, it does not always follow that with 400 to 500 Gm. of applied force only the buccal segment or anchor unit will move forward and the canine will not move. With the sliding mechanics of this study, the percentage of greater rates of tooth movement happening coincident with greater forces was found to be 0.86. With the edgewise bracket and sliding mechanics, the curves showed that, in general, reciprocal forces cause reciprocal tooth movement with varying and relative rates of space closure. Subjectively, no relationship was found between pain and increased forces; that is, pain in this study was found just as often on the side with 100 to 150 Gm. of applied force as on the side with 400 to 500 Gm. of applied force. This is not to say that there is not more tissue damage found with the use of heavier forces.