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ME THODS OF KEEPING CA V1TIES DR \ '.
27
extend the gold beyond the true the
cavity- edge, partly obliterating
natural depressions. If a rilling so placed is well burnished and
any ragged edges trimmed off, the form of the margin need give
little concern, since it is entirely covered. Overlapping in masticating
surfaces is not objectionable, because, whilst the gold may spread nut,
here as elsewhere, it is in such a position that all the force exerted
it more
simply presses tightly against the tooth-substance which it is
intended to cover and protect.

CHAPTER II.
GENERAL PRINCIPLES INVOLVED IN THE FILLING OF TEETH METHODS
OF KEEPING CAVITIES DRY THE RUBBER-DAM LIGATURES CLAMPS
LEAKAGE THE NAPKIN CHLORO-PERCHA WEDGES vs. SEPARATORS
THE USES AND DANGERS OF MATRICES.

METHODS OF KEEPING CAVITIES DRY.
DURING the insertion of any kind of filling-material, all cavities
should be unless this is which
kept dry absolutely impossible, rarely
occurs. It does not follow from this axiom that the rubber-dam is
There are occasions when a dexter-
invariably necessary. very many
ous operator can dispense with the dam, which is always annoying to
the patient, and yet insert as good afilling. As a conspicuous illus-
tration of this, I need but to cite cavities, occurring in the anterior sulci
of superior sixth-year molars. Where the patient is a child, and the
cavity small, it is unwarrantable to force a clamp over a short tooth-
crown, crowding painfully against sensitive gum-tissue, with the risk
of a the This would necessitate the removal cf
slip during operation.
the half-finished and it anew, with the
filling, beginning gum bleeding,
thus to the difficulties of an which could have been
adding operation
performed with little trouble by using a napkin. Another condition
where the dam is sometimes contraindicated is where the cavity in
an approximal surface extends below the gum line. In order to ex-
pose the gingival margin, various methods have been advised, to
which I need not allude at this time. Where the depredation has
been meet a condition where
quite extensive, we not infrequently
the gum about the edge of the cavity is soft, yielding readily under
pressure, but is firm and unyielding around the rest of the circumfer-
ence at the neck of the tooth. This is especially true of molars. In
these cases, though we may succeed in forcing the gum away from
the gingival border of the cavity, we have a condition similar to that
shown in Fig. 48. Here it is noticeable that while the cavity border