The ornamental design for a dentalinstrument handle, as shown and described.
FIG. 1 is a perspective view of a dental instrument handle;
FIG. 2 is a first side view;
FIG. 3 is a second side view;
FIG. 4 is a third side view;
FIG. 5 is a fourth side view;
FIG. 6 is a bottom view;
FIG. 7 is a top view; and,
FIG. 8 is a side cross sectional view taken along line 8-8 of FIG. 1.
The broken lines shown in the drawings are included for the purpose of illustrating portions of the dental instrument handle and form no part of the claimed design.