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778 ORTHonoyTfA as an operative procedure.

In some, lower protrusion from this cause is apparent only when
the patient masticates. Figs. 785 and 786 will illustrate this condition.

Fig. 785. Fig. 786.

Apparent lower protrusion—during mastication. The patient's natural occlusion.
If the npper incisors erupt slightly back of their proper position the
cutting edges will occlude with the cutting edges of the lower incisors.
As eruption continues they will open the bite (Fig. 786) so that the
patient must throw the lower jaw forward in order to occlude the bicus-

FiG. 787.

The same denture after treatment.
pids and molars. (See Fig. 785.) It is quite possible that this will
result in a permanent protrusion of the lower jaw. The case shown in
Figs. 785 and 786 was an argument against that, however, and against
the possibility of "jumping the bite" (see page 770), for the patient
was thirty years old, and never protruded his lower jaw except when
masticating. For many years mastication had been attended with
neuralgia in the temporo-maxillary articulation, caused by the unnatural
strain, yet this neuralgia disappeared entirely after the upper incisors
and canines had been moved forward enough to close in front of the
lower. The teeth were moved by the split plate shown in Fig. 717.
In moving forward the upper anterior teeth in cases of " apparent
lower protrusion," such as shown in Fig. 785, or those due to lack of
development of the upper maxilla, it sometimes occurs that when the
cutting edges overlap the lower incisors the crowns have a very
unnatural slant forward, and the roots need to be moved forward.