The ornamental design for a palatalexpansionappliance, as shown and described.
FIG. 1 is a top perspective view of a palatal expansion appliance illustrating an embodiment of my new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 depicts the alternate position thereof.
The contrast in shading (line shading) represents a contrast in appearance only and does not represent any particular color, material, texture, or finish.