Page 298 - My FlipBook

cases where a more effective cleaning of an interproximate
space by the process of mastication seems desirable the form
of the part of the occlusal surface formed by the filling may
be so modified that in the crushing of food a greater amount
of it will be directed into the embrasure and effect a more
thorough cleaning of the marginal lines of a filling. This
may usually be done by cutting away some portion of the
marginal ridge and so sloping the surface toward the em-
brasure that when the food is crushed upon it, it will tend
to slide into and through the embrasure.
A change in the form of the proximate surface can often
be made that will improve the cleaning of the parts, especially
in broad proximate cavities in the molars and bicuspids.
The distal surface of the first molar, particularly when the
distal cusp is large and protrudes to the distal so that the
lingual embrasure is much narrowed, will not have its disto-
lingual angle well cleaned by the excursions of food, and
on this account decay is especially liable to occur along the
gingival portion of the lingual wall after the filling is made,
if the original form is preserved or reproduced. In this
case it is much better to carry the cutting somewhat beyond
the disto-lingual angle of the tooth, and in finishing the
filling reduce the distal protrusion of this cusp and widen
the embrasure. If at the same time the distal marginal
ridge is left low, or the occlusal surface sloped a little toward
the embrasure, so as to direct the crush of food into the
embrasure, the cleaning of the lingual margin of the filling
will be so improved as to prevent this tendency to recurrence
of decay at this point.
In the bicuspids there are great differences among dif-
ferent individuals in the mesio-distal breadth of the lingual
cusps as compared with the buccal. When the lingual cusps
are broad in this direction the lingual embrasures are very
narrow, so that the cleaning of the lingual marginal lines
of fillings will be very imperfect, these embrasures should
be broadened by narrowing the lingual cusps wherever prac-
ticable, and the occlusal surface so finished as to direct the
excursions of food into and through these embrasures so
that they will be continually cleaned by the act of mastica-
tion. In making these form changes every care must be
had to retain, or even slightly increase when practicable^
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