The ornamental design for a dual headbatterytoothbrush with prophy cup, as shown and described.
FIG. 1 is a top perspective view of a dual head battery toothbrush with prophy cup showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left side elevation view thereof, the right side being a mirror image;
FIG. 5 is a front elevation view thereof;
FIG. 6 is a rear elevation view thereof; and,
FIG. 7 is a top perspective view with the phantom bristles on the forward section removed for clarity of illustration.
The broken lines showing bristles, the central area of the gapped region in FIG. 2, and a handle illustrate portions of the toothbrush that form no part of the claimed design.