Page 22 - My FlipBook
P. 22
8 METHODS OF FILLING TEETH.
cavity shaped as seen in Fig. 10, we should have^", a weak point, as
shown in Fig. 8, where we view the same thing from another aspect.
Extension toward the as shown in this would
cutting-edge figure
make possible a fracture in the direction of a, which would result in
the loss of the corner.
Until I take up special cavities in detail, it is not necessary to say
more of approximal cavities, there being only a few points in con-
nection with the incisor region which do not apply to bicuspids and
molars, and vice versa.
FIG. 9. FIG. ro. FIG. 12.
In the of what are crown cavities there is little
preparation strictly
to be said here beyond emphasizing the necessity already pointed out,
not to leave too undercuts. If the be left as in 1 1
great cavity Fig.
after the removal of decay, an attempt to insert gold would probably
result as figured, spaces occurring at a, a. Subsequent mastication
would crush the weak enamel, and leaky borders would ensue. Fig.
12 shows how such a should be formed, the dentine left
cavity being
as thick as possible (a) over the pulp.
FIG.
FIG. 13. FIG. 15
The consideration of crown and
compound cavities, involving approx-
imal surfaces, may be better discussed when I come to special cases.
Festoon cavities are those which, of all surface cavities, require
most thought. Fig. 13 is a section through an incisor and filling.
Grooves for retention have been made at points a, a, equidistant
between the central line and the approximal surfaces. These being
directed toward the downward where the is
pulp, or straight pulp
closely approached, offer .counterbalancing resistance and are all-
sufficient, especially because the position is one where there will be
little, if any, mechanical force exerted to dislodge the filling. In this
form of cavity we obtain strong edges, whereas if shaped as in P'ig. 14
cavity shaped as seen in Fig. 10, we should have^", a weak point, as
shown in Fig. 8, where we view the same thing from another aspect.
Extension toward the as shown in this would
cutting-edge figure
make possible a fracture in the direction of a, which would result in
the loss of the corner.
Until I take up special cavities in detail, it is not necessary to say
more of approximal cavities, there being only a few points in con-
nection with the incisor region which do not apply to bicuspids and
molars, and vice versa.
FIG. 9. FIG. ro. FIG. 12.
In the of what are crown cavities there is little
preparation strictly
to be said here beyond emphasizing the necessity already pointed out,
not to leave too undercuts. If the be left as in 1 1
great cavity Fig.
after the removal of decay, an attempt to insert gold would probably
result as figured, spaces occurring at a, a. Subsequent mastication
would crush the weak enamel, and leaky borders would ensue. Fig.
12 shows how such a should be formed, the dentine left
cavity being
as thick as possible (a) over the pulp.
FIG.
FIG. 13. FIG. 15
The consideration of crown and
compound cavities, involving approx-
imal surfaces, may be better discussed when I come to special cases.
Festoon cavities are those which, of all surface cavities, require
most thought. Fig. 13 is a section through an incisor and filling.
Grooves for retention have been made at points a, a, equidistant
between the central line and the approximal surfaces. These being
directed toward the downward where the is
pulp, or straight pulp
closely approached, offer .counterbalancing resistance and are all-
sufficient, especially because the position is one where there will be
little, if any, mechanical force exerted to dislodge the filling. In this
form of cavity we obtain strong edges, whereas if shaped as in P'ig. 14
