Page 83 - My FlipBook

MATERIALS FOR FILLING. 79 ;

admissible to employ a softer material for filling cavi-
ties in the proximal surfaces of the teeth, provided
it perfectly excluded all foreign substances.
Again, a material should be as nearly as possible a
non-conductor of heat, particularly for filling sensitive
teeth, or those liable to become so under the influence

of slight causes. Great variations of temperature will,
in most instances, aggravate sensitiveness, and, in
susceptible cases, produce it; and, if the irritation is
continued, the result may be necrosis. Gold, which
possesses the largest number of desirable qualities as
a material for filling, is in this respect very defective,
being one of the best conductors of heat. To obvi-

ate this defect, some non-conducting material is em-
ployed between the gold and the sensitive portion of
the tooth. The nerve is liable to. be affected by sud-
den and great changes of temperature, transmitted to
it through a gold plug.
In the next place, a material should be susceptible
of being welded, or united into a solid mass. The
permanency of an operation depends very much upon
this quality. A filling having the different pieces
which compose it perfectly united, will be much more

durable than if effected with a material in which this
cohesive property is lacking, it can be made with
greater facility, and will be better and longer retained
and mainly because such a filling cannot be destroyed