In order to assist with the scaling it is also advisable to draw round the base of the teeth. Check with your local biology or physical anthropology departments for a tomograph with which to make the 5 mm horizontal slices. Otherwise, it is relatively easy to make a tool to cut the alginate mold parallel to the plane of the teeth. On a flat, smooth, 190 x 125 mm wooden board paste heavy cardboard strips parallel to each other, 70 mm apart, resulting in a two “walls” of height 5mm. On top of, and perpendicular to the cardboard walls place an 80 mm long razor blade, creating a wide slicing area. Push each quadrant of the dental impression through this tool so as to cut off the bottom 5 mm of impression material in the occlusal plane. Place the quadrants back together at the origin on the graph paper, trace them, and repeat the process until all of the impression material is drawn in this way.
Alternatively, you can use a cast to get the contour lines: fill the cast with liquid to depths of 5, 10, and 15 mm, photographing each depth.
a detailed illustration of this process please refer to Ladefoged’s chapter
on static palatography in his 2003 book, Phonetic Data Analysis.