The ornamental design for a dental drillguide, substantially as shown and described.
FIG. 1 is a perspective view of a dental drill guide showing my new design;
FIG. 2 is a front view thereof, the rear view thereof being a mirror image;
FIG. 3 is a right side view thereof, the left side view thereof being a mirror image;
FIG. 4 is a top view thereof; and,
FIG. 5 is a bottom view thereof.
The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only; the broken lines form no part of the claimed design.