Page 309 - My FlipBook

PREPARATION OF CAVITIES FOR PORCELAIN INLAYS 305
which should come just short of the dento-enamel junction labially
and lingually. Mesially and distally it should continue to the
cavo-surface angle. A pin hole should then be bored in the ex-
treme ends of this groove not a great distance from the dento-en-
amel junction in the dentine to receive the pins. When the lingual
step is to be added the enamel on the lingual is removed additional-
ly to a distance root-wise at least equal to the labial exposure ; also
an amount of dentine sufficient to make the newly created axial
wall meet the two pulpal walls at right angles. If pins are to be
added the holes should be bored in the floor of the pulpal wall
nearer the labial surface.
In Pulpless Six Anterior Teeth the pulp chamber may be rounded
out and porcelain so baked as to form a post of porcelain for re-
tention.

Fig. 169.—A Class Six cavity using pin anchorage for porcelain inlay, This plan is also
used with the gold inlay.
Pulpless Molars are treated in the same way.
Treatment of Teeth With Malformed Enamel. The major por-
tion or all of the enamel can be successfully replaced with porce-
lain.
The enamel is removed to the desired point resulting in a
gingival wall entirely encircling the tooth. Sufficient dentine is
removed in the incisal region to render the largest girth at the
gingivo-axial line angle which is continuous around the tooth. This
leaves a peg-shaped body of dentine over which the porcelain is
telescoped. The method is termed the jacket crown and the method
of construction and setting is fully described in the writings of
others on crown work.