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34 THE TECHNICAL PROCEDURES IN FILLING TEETH.
Use of the Dental Engine.
The dental engine has in recent years become an important
instrument in operative dentistry. It is used for certain parts of
the work of excavating cavities, for trimming fiUings to form
after they have been inserted, and a large amount of the work
of polishing is best done with it. For these several purposes
engines should be equipped with certain sizes and forms of
excavating burs, a few sizes and forms of finishing burs, stones
for grinding and sandpaper disks of different grades of fineness,
rubber disks for carrying polishing powders, etc.
In excavating, the bur is nowadays indispensable, and yet but
a small part of the excavating should be done with burs. The
tendency among students is to continually use the bur too much
and to use it in improper places.
The forms of bur most useful are what are known as the
inverted cone bur and the fissure bur. Round burs are not
often used to advantage, and yet there are certain definite pur-
poses requiring round burs.
The sizes of burs are very important. With the dental
engines with which we are supplied no large burs can be used to
advantage for the reason that the motion is conveyed by a cable
which allows large burs to jump and chatter. Cord engines
give to the bur a much smoother motion and better cutting
power, but are not regarded as so convenient. Practically none
of them have sufficient power to run a large bur to advantage.
For our use, then, burs for excavating that are over one and
one-half millimeters in diameter should not be used at all. The
most useful burs are one millimeter and less in diameter. The
round bur is used only for the one purpose of opening pit cavi-
ties in which decay has only just begun. For this purpose
round burs, from a little less than one millimeter to one and a
half millimeters in diameter, should be used by placing them in
the pit while in motion and swaying the hand-piece to and fro so
as to rotate the bur laterally while it is rapidly turning upon its
axis. This lateral motion of the hand-piece will cause the bur
to cut much more rapidly than when held simply against the
work. Use the smaller size first, and when it has entered the
pit change it for a larger, using this in a similar way and follow
this again with a larger size. Then the round bur should be
34 THE TECHNICAL PROCEDURES IN FILLING TEETH.
Use of the Dental Engine.
The dental engine has in recent years become an important
instrument in operative dentistry. It is used for certain parts of
the work of excavating cavities, for trimming fiUings to form
after they have been inserted, and a large amount of the work
of polishing is best done with it. For these several purposes
engines should be equipped with certain sizes and forms of
excavating burs, a few sizes and forms of finishing burs, stones
for grinding and sandpaper disks of different grades of fineness,
rubber disks for carrying polishing powders, etc.
In excavating, the bur is nowadays indispensable, and yet but
a small part of the excavating should be done with burs. The
tendency among students is to continually use the bur too much
and to use it in improper places.
The forms of bur most useful are what are known as the
inverted cone bur and the fissure bur. Round burs are not
often used to advantage, and yet there are certain definite pur-
poses requiring round burs.
The sizes of burs are very important. With the dental
engines with which we are supplied no large burs can be used to
advantage for the reason that the motion is conveyed by a cable
which allows large burs to jump and chatter. Cord engines
give to the bur a much smoother motion and better cutting
power, but are not regarded as so convenient. Practically none
of them have sufficient power to run a large bur to advantage.
For our use, then, burs for excavating that are over one and
one-half millimeters in diameter should not be used at all. The
most useful burs are one millimeter and less in diameter. The
round bur is used only for the one purpose of opening pit cavi-
ties in which decay has only just begun. For this purpose
round burs, from a little less than one millimeter to one and a
half millimeters in diameter, should be used by placing them in
the pit while in motion and swaying the hand-piece to and fro so
as to rotate the bur laterally while it is rapidly turning upon its
axis. This lateral motion of the hand-piece will cause the bur
to cut much more rapidly than when held simply against the
work. Use the smaller size first, and when it has entered the
pit change it for a larger, using this in a similar way and follow
this again with a larger size. Then the round bur should be
