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7- Busy patients need not spend so nuich time in the dental chair.
After the cavity is prepared the matrix may be burnished to the cavity,
or an impression of the cavity may be taken, and then the patient dis-
missed until the inlay is completed.
8. Faulty fillings are easily dislodged. While porcelain has the
advantage over gold in making a filling that more nearly harmonizes
with the natural teeth, and one that is a non-conductor of thermal and
electrical changes, it has still another advantage, which should appeal to
all conscientious operators, in that imperfect fillings made of this material
are easily dislodged. A large number of faulty gold fillings, which do
not preserve the teeth, are retained by deep grooves, so that it is almost
impossible to dislodge them : such fillings deceive the patient, and many
times even the dentist. If a porcelain filling is faulty, it is displaced, and
the patient knows immediately that the services of a dentist are required.
The disadvantages of porcelain as a filling mate-
Disaduantagcs of 'ial are :
i- The friability of porcelain causes it to frac-
Porcelain.
ture readily, thereby excluding it from any form of
cavity that can not be so prepared that frail margins of the filling mate-
rial can be avoided or else protected from stress.
2. It is impossible to bevel the cavity margins to protect the enamel.
The relative strength of the porcelain and the enamel are approximately
the same so that one can not protect the other.
3. It is difficult to match the color of the natural teeth. This alway.s
has been and always will be one of the most serious disadvantages of
porcelain as a filling material ; and until we understand more thoroughly
the general phenomena of color formation, we may expect to be disap-
pointed with many of our inlays.
4. The cement used as a retaining material may cause a change in
the color of the tooth or of the inlay. This, however, may be largely
overcome by the application of correct principles in cavity preparation.
5. The cement will dissolve unless there is only a thin film used as the
retaining medium. This is not so much a disadvantage to the skilful,
painstaking operator ; for, if the margins are defective, he will remove
the defect by making a new inlay. But to the incompetent or careless
operator, this will always be a disadvantage, because any cement now
produced will dissolve from the margins of an ill-fitting inlay.
Porcelain is not applicable to all forms of fill-
higs, and will never entirely displace gold or
flpplicabilitv of it
Porcelain. amalgam as filling materials. It has taken its place.
however, along with these materials, and, when
properly applied and judiciously used where indicated, porcelain should

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