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82 OPERATIVE DENTISTRY

varying lengths of the step in plan two of this class. The dotted
lines are the radii of the various circles the arcs of which the point
angles would describe in moving to exit, pivoting on the gingival
margin. The length of the step portion relative to the height of
the filling determines the direction the incisal point angle must take
to exit. With a short proximal portion and a comparatively long
step portion, the first movement of the point angle is almost per-
pendicular. Sec fillings in Fig. 39 {a, x, li; also g, f, n).

Tig. 39.—Drawing to iilustratc the difference in the directions the point angle fillings take in
tipping to exit with various fillings.
Note the difference in the direction the pohit angle would take
to exit with an increased length of filling inciso-gingivally. Also
see 7i, X, a, and then 7i, x, h, and on down until it is li, x, g. It will
1)0 seen that there is a gradation toward the horizontal movement
of the incisal point angle to exit. Again note the change of direc-
tion to exit of the incisal point angles in g, a, i, and then g, h, j, then
n. We see in this series that there is a
g, c, k, and on down to g, f,
gradation toward the perpendicular movement of the incisal point