The ornamental design for a dentalhandpiece, as shown and described.
FIG. 1 is a front elevation of a dental handpiece;
FIG. 2 is a right side elevation thereof;
FIG. 3 is a left side elevation thereof;
FIG. 4 is a plan elevation thereof;
FIG. 5 is a bottom elevation thereof;
FIG. 6 is an enlarged right side elevation thereof;
FIG. 7 is an enlarged left side elevation thereof;
FIG. 8 is an enlarged front view thereof leftward of line A-A in FIG. 1;
FIG. 9 is a perspective view thereof; and,
FIG. 10 is a perspective view thereof.
The broken line showing of the controller is included for the purpose of illustrating environment and forms no part of the claimed design. The cord is shown in FIGS. 1, 4, 5, and 9 broken in the middle for ease of illustration.