ARTICLE II.
Taking Upper Impressions of the Mouth.
BY GEO. S. FOUKE, WESTMINSTER, MD.
It is admitted that taking impressions of the mouth, par-
ticularly of the upper jaw, for dental purposes, is an opera-
tion attended with no little uncertainty as to certain and en-
tirely satisfactory results. Therefore, anything tending to
simplify and improve the means of performing this very im-
portant operation, will not be lightly esteemed by those en-
gaged in supplying artificial dentures.
We propose to consider the practicability of taking upper
impressions after a method based upon scientific principles,
and which method when rigidly carried out must result in
a perfectly successful result. Yery little has been done as
yet to reduce this operation to a strictly scientific basis. It
has been hitherto treated as a purely art operation, and as
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such it seems to be regarded as an operation dependent en-
tirely upon the skill and experience of the practitioner.
We believe the operation of taking a practically correct
impression for an upper denture, is an operation dependent
for its successful performance upon science more than upon
art ; and it shall be our object to elucidate the fact in this
article.
In considering this operation from a stand-point we have
thus assumed, we will first inquire, what is a practically or
philosophically correct upper impression f Is it the Plas-
ter-of-Paris impression which the profession now so gener-
ally rely upon as the " perfection," par excellence of such
impression ? We say emphatically, no, it is not.
This plaster theory of " perfection " would seem to be self-
condemned from this consideration alone, namely, that up-
per dentures made from the most correctly taken plaster im-
pressions, often result in mere approximations to true suc-
tion plates, and sometimes terminate in the most disastrous
failures.
Plaster impressions of upper cases are only in the main
ideally " perfect," and may be, for all that is known when
taken, a very incorrect form of impression for the require-
ments of the case. Now the reason why the ordinary plas-
ter impression as taken for the upper jaw is deceptive and
essentially incorrect in many cases, is simply this: the un-
certainty there is in the proper and requisite distribution of
pressure against the membranes of the alveolar ridges and
the palatine arch. The whole secret of this matter of what
constitutes a scientifically correct upper impression, liesjust
in this simple proposition, namely, distribute the pressure
as it should be in taking the impression, and the impression
will be practically correct. Such is our experience.
Now that this matter may be better understood, we will
consider a moment. It is said that a perfect upper impress
ion consists in this, to wit: a correct representation of all
the parts to be covered by the plate in their normal condi
tion." Plaster has held a long pre-eminence as the best
2
18 Original A rticles.
material for taking impressions, mainly for the reason that
pressure is avoided in the performance of the operation,
and the "parts" are not disturbed in their "normal condi-
tion.
Fatal error! What an immensity of perplexing trials
has resulted from this fallacious theory! We look back
upon our own twenty years of experience with piaster upper
impressions with a sensibly felt shudder! But science?
truth has lifted the veil, and our burden is lightened.
Experimentvm docet! It teaches what a practically cor-
rect upper impression is, and lays it down as a fundamental
principle in the science of taking such impression, that an
intelligent distribution of pressure over the surfaces of the
ridge and arch of the mouth are an absolute pre-requisite
to absolute certainty of practical result. We have exhausted
experiment in our own practice, and we feel entirely con-
vinced of the fact, that just in proportion as all the " parts "
of the roof of the mouth are perfectly reduced by compress-
ion, or intelligently directed manipulative pressure will be
the completeness and practical efficiency of the impression.
Pressure so applied as to force down all "soft parts" as firmly
as possible against the subjacent bones, reduces the entire
surfaces to something approximating a uniform, consistent,
or equally balanced basis or foundation for the resting place
of the dental plate. A careful and thorough compression
as thus indicated, secures most effectually all that is desira-
ble and necessary in an upper impression. It relieves un-
due pressure upon the hard raphce of the palatine arch ; it
sustains the contact of the plate to the " soft" parts ; the
palatine cavity (so to speak,) is filled by the properly formed
plate to its utmost capacity, and as a necessary consequence,
the highest degree of usefulness is achieved.
Having endeavored to define what we regard a correct
upper impression, we would inquire next how is it to be taken
in the simplest and most reliable way?
From the nature of the case it is apparent that the ordi-
nary upper impression cups, as made of solid metal, are not
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adapted to the taking of the kind of impressions we have
described. The cups in use, including even Dr. Thomas
Wardle's movable palate plate tray* do not afford the opera-
tor the means of directing the necessary pressure against the
palate. The pressure as made by the metal cups, is made
only in one direction, perpendicular to the apex of the arch,
and consequently there is great uncertainty in the distribu-
tion of the pressure against the soft sides of the palate.
With plaster there is simply no pressure at all; and with
wax or gutta-percha, the pressure may be but imperfectly
made; especially the lateral compression which is so essen-
tially necessary to a correct impression, it istiext to impossi-
ble to effect.
Finding it simply impossible to carry out our theory with
any trays or cups we could find, we devised the upper im-
pression cup for which letters patent were granted us on the
20th of January, 1874.
It is presumed that the profession are aware somewhat of
the nature of our new combination impression cup, and it
certainly is no part of our design to speak here of its merits
for any personal advantage that may accrue to ourself, but
solely for the purpose of promoting the interests of the art
and science in which we are engaged.
The cup we have devised is a simple, elegant and sure
mode of operating. It allows of direct manipulative press-
ure to be applied to the soft parts of the roof of the mouth
after the ordinary perpendicular pressure has been applied.
This after manipulative pressure is made against the flexible#
bottom of the cup directly with the index finger, and in the
most certain manner; leaving no possible uncertainty in
regard to the intelligent distribution of the requisite press-
ure. The cup is suited to the use of plaster, wax or gutta-
percha, although we confine ourselves almost exclusively
to the use of gutta-percha. Wax is very good, and excel-
lent impressions are taken by this process with it.
The mode of manipulating in the use of our cup is readily
suggested by the appearance of the tray ; but we have some
20 Selected Articles.
peculiarities in our own use of the cup for the different ma-
terials, which we regard as important, and which we pro-
pose to give in a future recurrence to this subject.


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