Page 763 - My FlipBook

UPPER PROTRUSION. 761

(d) Thumb-sucking—acquired. (See Fig. 757.)
(e) Lack of development of the lower maxilla (the upper protrusion
is then apparent rather than real)—constitutional.

Fig. 754.

Protrusion—cause (c) (Talbot
(/) Premature loss or injudicious extraction of the first permanent
molars—acquired. Prof. Guilford says of such extraction : " The re-
sult is that the lateral pressure so necessary to proper expansion is lack-
ing in one jaw while in the other normal enlargement continues."

Fig. 751 Fig. 756.

Apparent protrusion due to lack of develop- Dr. Louis Jack's drawing (in Dental Cusmos)
ment of lower maxilla (Talbotj. showing deformity from too early extrac-
tion of first permanent molar.
(g) Weak structure of the upper maxilla, which allows the teeth to
be forced forward by occlusion with a large lower maxilla of hard and
dense structure with short rami—acquired. (See Fig. 757.)