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CORRF.CTION OF DENTAL I RKl-J ;r I^AkniES. I4I

cxleiuliiii;" from b b. Groox-es arc cut iiiln the antcrioi" and
posterior parts of the plate to correspond with and receive
the points bb and cc. Holes are drilled at these points,
and the wires tied to the rnhher plates. in order that tlie
antericn- teeth may he moved with the greatest force, the
arms are so adjusted that the o-reatest pressure is exerted

on the anterior parts of the plate. This appliance is readily
removed for cleansing and returned to place by the patient.
Dr. Angle's method utilizes the principle of the spring
wdthout the objectionable features of the rubber plate, com-
bined wdth an " expansion arch." Fig. loo show^s a com-
plex case, necessitating force from several directions upon
the badly malposed teeth. The dental arch rec|uires widen-
ing, the centrals and lateral incisors are to be carried for-
ward and outward and rotated. It will be noticed that wdre
ligatures are looped over spurs or pins, w^hich have been
soldered to the lingual sides of the bands, nearly at the
distal angle, thus exerting a pressure as they are occasion-
ally tightened by twdsting or renewal. This tends to rotate
the teeth, as well as move them forward and outw-ard into
harmony with the pattern of the expansion arch. The exact
direction of this force is controlled by little spurs attached