Page 74 - My FlipBook

Because of the irregular formation of some approximo-mcisal, and
the inaccessibility of many approximo-occlusal cavities, the method of
first swaging the foil into a model of the cavity is particularly indicated.
Although many porcelain workers construct all inlays by swaging matrices
into models of cavities, the author believes it is possible to construct more
accurately fitting inlays for simple approximal and most of the approximo-
incisal cavities by burnishing the foil directly into the cavity or by swaging
first into the model and then burnishing the foil into the cavity. How-
ever, ho believes more accurately fitting matrices may be constructed for

Fig. 8o. Fig. 8i.

large approximo-occlusal cavities by relying wholly on swaging into
models because of the difficulty with which matrices are burnished into
such cavities in the mouth. Still, he admits that it is almost impossible
for him to construct absolutely accurate models unless they are made
under pressure, and he believes that, with few exceptions, the models
not constructed under pressure, as made by most dentists, are not absolute
positives of the cavities which they represent.
There are many materials used for taking im-
Imprcssion pressions of cavities. Those which have received
methods. the most consideration are : Dental lac, modeling
compound, Klewe & Company's impression ma-
terial, gutta percha and the oxyphosphate cements. Dental lac and
modeling compound are used probabh' more than all of the other ma-
terials. They have the advantage in that they are more easily manipu-
lated and require less time for taking the impression. Modeling compound
should be made plastic by moist, and the other materials by dry heat.
An impression tray, the design of (Fig. 82) makes a valuable adjunct

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