Making Midsagittal diagrams
order to obtain a precise diagram of the shape of the speaker's palate,
the palatal impression must be accurately sectioned in three dimensions.
The first cut will be through the center of the impression to provide an
datum line for further measurement. To get the most information on the
shape of the soft tissues, the impression should be cut mid-sagittally
before trimming around the teeth (Fig.7). Next trace an outline of the
palate, upper teeth, and upper lip on a sheet of paper (Fig. 8). Use
a ruler and your fingers to brace the impression (Fig. 9).
Alternatively, put one of the halves on the glass of a copy machine, and
copy. Either way, make several copies of the tracing just in case.
7: The impression is now sectioned along the saggital plane. Use the central
fissure as a guide.
8: One of the resulting halves is used as a pattern to create a paper tracing.
9: The flexible nature of the alginate requires careful support so as not
to distort the shape of the palate.
bisect the impression halves in the coronal plane, at a point about the
middle of the impression (usually between the second premolar and first
molar). The intersection of these mid-sagittal and coronal cuts can be
used to define x and y axes and an origin on a piece of graph paper.