I claim the ornamental design for a dental chair, as shown and described.
FIG. 1 is a perspective view of a dental chair.
FIG. 2 is a front elevational view thereof.
FIG. 3 is a rear elevational view thereof.
FIG. 4 is a right side elevational view thereof.
FIG. 5 is a left side elevational view thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The two pairs of parallel short dashed lines, a first pair extending axially and a second pair extending laterally edge to edge, represent a sewn pattern. The sewn pattern includes portions shown in short dashed lines extending in a perimeter direction at each lateral end. The long dashed lines outside of the dash-dot boundary line form no part of the claimed design.