Page 92 - My FlipBook

-^6 THE TREATMENT OF TEETH
and the angles niade sharp with an inverted cone
bur, or suitable excavator, and this bur can be used
in these cavities easily and with safety.
In incisors and canines the older method is to
remove the decay, and cut to hard dentine with
excavators and round burs. A groove is then cut
along the cervical wall with a small round bur,
taking care to avoid, on the one hand, cutting too
close to the enamel margin, and, on the other, too
close to the pulp. The ends of" the groove are then
deepened slightly, by drilling upwards and outwards
at the cervico -labial, and upwards and backwards at
the cervico-palatal parts. One or both of these de-
pressions is deepened into a starting pit, if desired. An
opposing retainage is made by drilling a little pit in
the dentine at the cutting edge whenever the cavity
will admit of this being done without weakening the
cutting edge ; and whenever the labial and palatal
walls will admit of it, a fine groove is made along them
with a fine round bur, or an excavator, at the line of
junction of these Avails and the floor of the cavity.
Whenever, as often happens, the enamel is not
supported Avith a sufficient thickness of dentine to
admit of this, the cervical retainage is deepened and
broadened, particularly at the ends of the cervical
groove ; and whenever the near approach of the
cavity to the cutting edge renders the drilling of a