Page 122 - My FlipBook

118 OPERATIVE DENTISTRY

To Restore Occlusal and Incisal Surfaces lost from abrasion
Avith inlays where the tooth is vital, nothing answers the purpose
better than the following method. The outline of the surface to
be covered is established. Small holes are drilled to convenient
depths in safe locations of sufficient size to receive a 20 gauge
iridio-platinum or tungsten pin. Three or four pins are required
for molars and two or three for bicuspids or incisors. A pure gold
matrix, 32 or 34 gauge, is then burnished to an approximate fit.
The positions of the holes in the tooth will be outlined in the gold.
The matrix should be pricked at these points with a sharp pointed
instrument smaller than the ijins. One pin is inserted and should
protrude occlusally through the matrix for a short distance, and
be bent at right angles.
It is good practice when using tungsten to make a loop which
goes to the full depth of two of the holes and lies along the gold
surface in the body of the loop, thus establishing the alignment of
tAvo of the pins at once. This also places the exposed end of these
tungsten pins, to which gold will not cast, entirely away from a
position which might result in shoAving the exposed ends in the
completed case.
This pin and matrix are then removed and attached Avith solder,
applying the solder to the occlusal side of the matrix. The matrix
should be returned to the tooth and another pin placed and at-
tached in the same Avay, repeating until all pins are in position,
Avhen the matrix should receive a final burnishing. The Avax con-
tour is then added as before described, the pattern replaced and
articulation secured in the mouth and finally trimmed to desired
contour. The Avax should then be chilled and the entire pattern
remoA'ed and iuA'Csted.
Method of SAveating- the Contour.—Advantages. The advan-
tages of this older method of making an inlay still exist Avhere the
inlay is to cover considerable surface and is very shalloAV. Such
inlays are generally termed "onlays." This method is advised
from the fact that models of such nature Avill seldom maintain ex-
act form during the process of removing and investment unless a
gold matrix is used.
If the gold matrix is used it is difficult to cast a thin layer of
gold over the entire surface of this matrix and get good margins
unless a large quantity of gold is melted to make the cast in Avhich
case the gold matrix is very liable to be entirely fused, AA-hich Avill
not give the best results. Speed is also a factor in this instance.