Page 84 - My FlipBook

34 THE technic.Uj procedtjees in filling teeth.

until after he had learned to keep his cutting instruments sharp.
It is simply imiDossible to etfectively prepare cavities for filling
without sharp instruments. The student who can not, or will
not, learn this should abandon the study of dentistry.
A good Arkansas stone is a necessity and is one of the best
pieces of property in the outfit of a dentist. If properly cared
for, it will serve for a lifetime. It is therefore well worth while
to be careful in its selection and to pay a price that will command
a stone of the best quality. It is of first importance that the
stone be very hard. Dental instruments are very small, and if
the attempt is made to use a soft stone, the point will catch and
ruin both the edge of the instrument and the surface of the
stone. The quickness of cutting, or the so-called "sharpness"
of the stone is certainly a very desirable quality, but should be
for, if the surface of the stone
held as secondary to hardness ;
easily becomes roughened or uneven, it becomes ineffective. A
v^ery hard stone that will cut with only medium quickness is
much more desirable than a quicker cutting stone that is con-
tinually losing the evenness of its surface. Dental instruments
do not need much grinding but do need accurate grinding.
The size of the stone should not be less than one and one-half
by five inches. A little larger stone is better, but a dentist should
not use a smaller one. The stone should be cared for method-
ically and carefully. It should be kex^t in a light l)ut strong case
or box that will protect it from breakage in any ordinary fall.
The stone should be thoroughly soaked in oil and then wiped off
as dry as possible. It may then be used with oil or used dry,
but however used the surface should be cleaned after using with
a woolen cloth and oil. In grinding steel, the steel cuttings fill
up the "teeth of the stone" and soon the stone becomes dulled
and will not cut well. The oil on the woolen cloth removes these
cuttings and serves to keep the face of the stone sharp and other-
wise in good condition. It is well to keep such a cloth in the box
with the stone and always clean the stone after using, before it
is put away. In operating at the chair, the stone should always
be conveniently at hand for correcting the edge of anj^ instru-
ment that is not just right. If, in time, the surface of the stone
becomes in any way marred or is worn unevenly, it may be
refaced by rubbing it on a sheet of emery paper laid flat on a
smooth table or level board. The facing should be finished on
the finest grade of emery paper.
In grinding the cutting edges of excavators, the correct
bevel should be carefully maintained. The bevel wanted on each