Standard or stock impression trays have been used for
over a century in the preliminary stages of the construction
of full dentures, but no comprehensive study of their design
in relation to the size and form of the dentulous and
edentulous jaws could be found in the literature, and none of
the manufacturers of standard impression trays could supply
biometric data on impression tray design.
The present study was undertaken because there appeared
to be a need for further data on the subject.
Following the loss of teeth and the consequent resorption
of supporting bone the facial contour changes, due to collapse
of the lips and cheeks and alteration in the naxillo- mandibul
jaw relationship. One of the objectives when making full
dentures for edentulous persons is to attempt restoration of
this facial contour. For this reason many clinicians have
stressed that not only should the artifical teeth be placed
in the positions formerly occupied by the natural teeth, but
also that an adequate amount of denture base material should
be used to replace the lost supporting bone and soft tissue
(HOOPER 1934; FISH 1948; LANDA 1954.; SWENSON 1959; POUND 1960;
LEE 1962; MARTONE 1963; BALLARD 1963).
In the preliminary stages of full denture construction,
maxillary and mandibular impressions are taken for the
purpose of recording the denture bearing areas of a mouth.
They are taken with an impression material in impression
trays and casts of the region are produced by pouring plaster
of Paris or artificial stone into the impressions.
Many techniques have been described for taking impressions
of the denture bearing areas of edentulous patients. These
techniques have been reviewed by TUCKFIELD (1950), JAEGGI (1960),
WOELFEL (1962) and others. Regardless of the technique
employed, impression trays, known as standard or stock trays,
are a prerequisite to securing a first or primary impression.
It is a common clinical experience that the size of an
impression tray and its shape influences the shape and extent
of the resultant impression taken with the tray. Thus an
impression taken in a tray which is too small will not cover
the denture bearing area, while an impression tray which is
too large may cause an unnatural displacement of the surrounding
lips and cheeks and of the vestibular sulcus which is composed
of loose areolar tissue.
The designs of the impression trays in this study have
been based on the principle that full dentures should replace
lost tissue in such a way that the lips and cheeks are restored as far as possible to their pre -extraction contour,
and that this restoration should begin at the first or
primary impression stage.
AIMS OF THE PRESENT STUDY: i. To devise a method for measuring the size and form
of the maxillary and mandibular denture bearing
areas of the jaws of a selected sample of dentulous
and edentulous human adults; ii. To apply these measurements to the design of standard
impression trays for edentulous human adults.