Page 189 - My FlipBook

SEPARATION OF THE TEETH. 187
Caoutchouc—India-rubber.—When a strip of india-rubber is
drawn into a close interspace the middle portion is constricted to g-reat
tenuity. The action is by the resilience determining the Im^o exposed
ends toward the middle, Avith the result that at length the space attains
the size of the thickness of the strip. It will be perceived that the
physical force is that of two opposed wedges acting with constant
power. The effect is such that it overcomes the greatest resistance to
separation of the parts and therefore is the most effective means which
we have.
Caution is required in the use of this material both as to the thick-
ness of the rubber and as to its purity. The pronounced resilience of
pure rubber is generally painful, and in most instances greatly so.
The resilience can be reduced by employing adulterated sjjecimens
of the material. The white-rubber tubing of the shops cut longi-
tudinally into various widths effects the object with less rapidity but
surely, and generally without pain. The strip is drawn into position
by a sliding motion, care being taken not to force the piece into contact
with the gum. To prevent the rubber being conveyed to the gum as
the space enlarges, a small portion should extend slightiv beyond the
occlusal surface. As this kind of rubber is more difficult to introduce
when the contact is close and firm, a previous partial opening should be
made with a piece of rubber dam. This method has the value of pain-
lessness, and also does not usually necessitate a period of rest after the
separation has been effected.
Red Base-plate Gutta-percha.—When it is desirable to gradually
effect considerable spacing between teeth, where the carious cavities are
deep w'ith well-defined boundaries but not involving the pulp, the method
of Dr. Bonwill, of packing the cavities and the existing space with a
sufficient mass of this form of gutta-percha, produces expansion by the
continued force of mastication driving the material upward. This
method also has value in some instances where it is desired to force
the gum beyond the cervical margins, and may be an acceptable sub-
stitute for aseptic cotton for this purpose.
Securement of the Space.—Should soreness of the teeth have been
caused by the separation, a period of rest should be given the parts until
the distress has passed over. It is, however, important that large spaces
should not be long retained, since in some instances alveolar resorption
may be induced by the continuation of the changed position. An inter-
val of two days usually suffices for the pericementum to recover from
the disturbance, when the restorative procedures may be conducted.
The retention of the space may be effected with gutta-percha or -with
the plastic cements,—the first being suitable when an open cavity
appears ; zinc phosphate when from the smallness of the cavity gutta-