Page 297 - My FlipBook

FILLING WITH TIN. 295

rations are simplified by the use of a matrix upon the distal surface.
A band matrix could be employed, but it obstructs the light somewhat
and the operator will more frequently confine himself to a matrix upon
but one side of the tooth. The filling should be commenced at the
disto-cervical border, and after inserting a few mats or cylinders of
non-cohesive foil proceed as in cavities described under class Q
(Fig. 250).
If these cavities be of considerable size the buccal and linijual walls
are weakened and there is danger of their being broken away in the act
of mastication. It is often well to truncate the cusps somewhat and
build the gold well across the occlusal surface, allowing the strain to
come directly u[)()n the gold instead of upon the tooth structure.
Filling with Tin.
It is not definitely known when tin was first employed for filling
carious teeth, but it has been used for at least a century and has found
great favor with many. Prior to the improvement in the formulas of
dental amalgams, tin was used more generally than at the present time.
Tin possesses certain inherent characteristics which make it valuable
as a filling material. Among these are great malleability, non-conduc-
tivity, and it is thought by many to possess antiseptic properties. But
while it has desirable qualities it has also some undesirable ones, such
as softness, and when exposed to the secretions of the mouth it discolors,
—which facts render it unfit for surfaces exposed to great wear in the
act of mastication and upon surfaces exposed to view. The discolora-
tion, however, is confined to the surface, and teeth filled with tin are not
discolored in consequence of its presence.
There are various methods of preparing tin for dental pui-poses.
That which has found greatest favor in the past is in the form of foil.
The tin used should be chemically pure. An ingot of the metal is
rolled into ribbon and then beaten, after the same manner as gold foil,
into sheets of the desired thickness. As a rule it is not beaten as thin
as the former. The foil best suited for most fillings is No. 10.
Pure tin, like pure gold, is cohesive, and fillings of great solidity
can be made if the operator will exercise care in packing it. The best
results are obtained by taking a third of a leaf of No. 10 foil and roll-
ing it into a loose rope, then cutting it into lengths of half an inch or
less and packing each piece with a view of making each part of the
filling solid. Some prefer folding the sheet with a spatula after the
same manner as gold foil, and then cutting into narrow tape. Equally
good results are obtainable by either method.
A more rapid but less satisfactory manner of introducing the fillings
is to use the tin in the form of cylinders, not relying so much upon the