The ornamental design for the dental instrument delivery unit, as shown and described.
FIG. 1 is a perspective view of a dental instrument delivery unit showing our new design;
FIG. 2 is another perspective view of our new dental instrument delivery unit design, similar to FIG. 1, but with the broken lines removed for clarity;
FIG. 3 is an a front elevation view thereof;
FIG. 4 is a left side elevation thereof, the right side elevation being identical;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is another perspective view thereof.
The broken lines in the figures of the dental instrument delivery unit are for illustrative purposes only and form no part of the claimed design.