Page 203 - My FlipBook

PORCELAIN INLAYS 187

duces a distinct undercut cavity in the base or
bottom of the inlay. This method is the outcome
of many experiments, made with the object of
improving the retainage of porcelain inlays, and
has given the inventor the greatest satisfaction in
his practice. The procedure, which has been
demonstrated by Mr. Rippon on several occasions
at dental meetings, is as follows A tray filled with
:
dry, finely powdered silex is placed in the furnace,
and heated up until some of the particles of the
silex are found to have formed themselves into small
ball-like masses of various sizes. These little balls
are readily picked up with a small sable brush
that has been brought to a fine point by twisting
it between the lips. The matrix is first thinly
painted over with a thin mix of the inlay body,
which is fused so that the interior of the matrix
is completely covered or lined with a thin
glaze of the body. It is then about half-filled
with a stiffer mix, and a hole is made in the
centre with the brush. In making the hole the
body is swept up to the sides in such a manner
that it goes up to the margins, and the matrix is
thus filled, with the exception of a central round or
oblong cavity, which must extend to the floor, and
leave the thin glaze produced by the first fusing
exposed at the bottom of the hole or cavity. If