The ornamental design for a teethwhiteninglight, as shown and described.
FIG. 1 is a front perspective view of a teeth whitening light showing my design;
FIG. 2 is a back perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof; and,
FIG. 9 is a front exploded perspective view thereof.
The broken lines shown in the drawings depict portions of the teeth whitening light in which the design is embodied that form no part of the claimed design.