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P. 177
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CROWN- AND BRIDGE-WORK. 165
can be used in the same manner. It also affords the great-
est facihty f(^r the sHght touches required to abrade the
tliin cer\ical Ijorders of the crown (Fig. 128), which may
\)v this means l)c done withtnit encroachment on the post.
THE FERRULE OR COLLAR CROWN.
This crown was originally brought to the notice of the
profession by Dr. C. M. Richmond, of New York, and is
therefore ordinarily known as the Richmond Crown. Nu-
merous modifications have been made, however, which en-
hance its value. The process of constructing the improved
crown is as follows :
Facing the Root.—The root must be trimmed down to
about the gum-line, except the labial portion, which should
be cut nearly a sixteenth of an inch below the gum margin.
For this purpose, carborundum stones or the Ottolengui
root- facers are employed, as described on page 160.
Removing the Enamel Ledge.—The ring of enamel re-
maining upon the root should be carefully and thoroughly
removed (see Fig. 129), making the sides
of the root parallel, so that the band, when ^"^^
JJ'^'
applied, may fit closely its entire zuidtJi. If
this is not done, the band, even if a narrow
one, instead of fitting closely will form a
pocket beneath the gum margin, and will,
in consequence of its irritating effect upon
the surrounding tissues, cause more or less inflammation
and possibly the loss of the root.
Numerous instruments have been devised for the removal
of this enamel among the most efficient are those invented
;
by Dr. Calvin S. Case and Dr. Geo. M. Weirich. Fig. 130
illustrates Dr. Case's enamel cleavers. These are so shaped
that they can be partially rotated under the margin of the
gum, presenting a sharp point toward portions of the enamel
CROWN- AND BRIDGE-WORK. 165
can be used in the same manner. It also affords the great-
est facihty f(^r the sHght touches required to abrade the
tliin cer\ical Ijorders of the crown (Fig. 128), which may
\)v this means l)c done withtnit encroachment on the post.
THE FERRULE OR COLLAR CROWN.
This crown was originally brought to the notice of the
profession by Dr. C. M. Richmond, of New York, and is
therefore ordinarily known as the Richmond Crown. Nu-
merous modifications have been made, however, which en-
hance its value. The process of constructing the improved
crown is as follows :
Facing the Root.—The root must be trimmed down to
about the gum-line, except the labial portion, which should
be cut nearly a sixteenth of an inch below the gum margin.
For this purpose, carborundum stones or the Ottolengui
root- facers are employed, as described on page 160.
Removing the Enamel Ledge.—The ring of enamel re-
maining upon the root should be carefully and thoroughly
removed (see Fig. 129), making the sides
of the root parallel, so that the band, when ^"^^
JJ'^'
applied, may fit closely its entire zuidtJi. If
this is not done, the band, even if a narrow
one, instead of fitting closely will form a
pocket beneath the gum margin, and will,
in consequence of its irritating effect upon
the surrounding tissues, cause more or less inflammation
and possibly the loss of the root.
Numerous instruments have been devised for the removal
of this enamel among the most efficient are those invented
;
by Dr. Calvin S. Case and Dr. Geo. M. Weirich. Fig. 130
illustrates Dr. Case's enamel cleavers. These are so shaped
that they can be partially rotated under the margin of the
gum, presenting a sharp point toward portions of the enamel
