Page 292 - My FlipBook

290 thp: operation of filling cavttiks.

as iiuicli dopcml.s upon this for holding the filling in place. Great hard-
ness is also essential to ])revent l)att('rina- in the
Fig. 250.
act of mastication (Fig. 250).
Class Q. — Disfo-occ/u.^a/ va\]Uc^ may he lillcd
in ])recisely the same mainier as those situated
u))(>n the mesio-occlusal surfiice. The dilHculties
Approximo-occlnsnl
are slightly greater because these cavities are not
cavities.
so accessible. ( avities ol' this description can be
greatly simpliiied by the use of the matrix. This little device converts
compound cavities into simple ones, and when used with care and judg-
ment fiicilitates the o])eration of filling to a wonderful degree. It will
be observed in the Jack matrices (as shown in Fig. 251) that jirovision
Fig. 2.")1.

The matrices of Dr. Louis Jack.
has been made for contouring the filling. If this style be employed the
operator must study the outline which he desires his filling to assume
and select his matrix accordingly. He must have previously obtained
ample space between the teeth for the placement of the matrix.
When put in place the matrix should be thoroughly fixed against the
tooth to be filled, with wedges of orange wood previously dipped in
Fig 252.

'^iidJ ^ W W
Kiy vi>' v?.'
Loop matrices.
moderately thick sandarac varnish. This will keep the wedges from
slipping. A very good way of fixing the matrix is to pack between it
and the adjoining tooth some quick-setting oxyphosphate of zinc. If
the part be thoroughly dry the cement will become adherent to the
matrix and the adjoining tooth and the matrix will thus be made secure.