A practical treatise on the technics and principles of dental orthopedia and prosthetic correction of cleft palate . for which it hasbeen employed in this way, it has accomplished results that the author believeswould have been otherwise impossible. Retention of Bodily Movements In the contemplation of retaining teeth which have been moved bodily, themagnitude and peculiarity of the force of a lever of the third kind, which is theactive mechanical principle in the bodily movement, is equally important toconsider when we come to the retention of this movement. The retaining appliance capable of
A practical treatise on the technics and principles of dental orthopedia and prosthetic correction of cleft palate . for which it hasbeen employed in this way, it has accomplished results that the author believeswould have been otherwise impossible. Retention of Bodily Movements In the contemplation of retaining teeth which have been moved bodily, themagnitude and peculiarity of the force of a lever of the third kind, which is theactive mechanical principle in the bodily movement, is equally important toconsider when we come to the retention of this movement. The retaining appliance capable of fully sustaining this movement must beone that will forcibly combat the great reacting tendency of the elastic bone andtissue fibers to return to equilibrium. As this force is exerted along the entirelength of the root, it must be seen that the stress upon the comparatively narrow zoneof the crown which is grasped by the retaining appliance increases as the force ap-proaches the apical end of the root, on the same principle that the advantage of a CHAPTER LIV. SUPPLEMENTARY RETAINING ATTACHMENTS 399 Fig. lever of the first kind is increased by lengthening the power arm. Therefore, thenecessity is apparent in this character of retention of employing distally extendedarms with stable attachments to the retainer. This is especially true of bodilylabial movement of the front teeth which so commonly carries the entire alveolarridge forward in a manner that could not be accomplished other than by bendingand stretching the cancellous structure of the alveolar process at the apical zoneof its attachments. With bodily retruding movements of the labial teeth, the ob-structing alveolar process in the pathway of the moving roots is to a very largeextent resorbed, and consequently they are far more easily retained. When a bodily protruding or retruding move-ment of the incisors has been produced and hasnot been accompanied by a movement of theroots of the cuspids, the six-band labial
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