Page 119 - My FlipBook

MAKING AND SETTING OF A GOLD INLAY 115

Ideal Conditions Are Obtained when the Avax slightly overlaps
the eavo-surface angle at all points in the outline, about one-tenth
of a millimeter.
This will give sufficient bulk for correct finishing. After the com-
pletion of the pattern it is well to insert the tine of an explorer
to the depth of about one or two millimeters in a convenient posi-
tion for removal.
The tine should be removed and the pattern chilled with cold
water, the tine reinserted into the previously made hole, the pat-
tern gently pushed to exit and then given a cold water bath.
The Placing of the Sprue Wire. While the pattern is still carried
on the tine of the explorer, the sprue wire should be warmed and
inserted.
The sprue wire should be very fine, preferably copper, and in-
troduced deep into the pattern. This use of a fine sprue wire is of

Fig. 7i.—Some of the methods by which inlays may be given retentive form in large decays
and non-vital cases.
advantage from the fact that no considerable body of the wax
melts and runs back up the wire to produce a concavity, close to
where the wire is introduced, which happens when a large sprue
wire is used.
In selecting the position for the wire, care should be taken that
a location is chosen so that the contour of the surface of the pattern
leaves the sprue wire in all directions at an obtuse angle. A neglect
of this point will occasionally result in imperfect casts near the
sprue former. The tine of the explorer should now be withdrawn
and the resulting hole sealed by touching with the Avarm end of
a small instrument.
A good instrument for such work is the flattened end of a large
canal cleaner or broach, mounted on a Avooden handle.
Giving the Wax Pattern Retention Form. Portions of the pat-