Abstract: A medical/dental handpiece comprises a housing having distal portion, the head portion having a bottom surface defining an opening. A motor and a light source are positioned with the handpiece, and the handpiece removably receives a light guide in alignment with the light source, to receive light from the light source. The light guide includes a probe which can be positioned adjacent or within a treatment area. The handpiece can be operated to activate only the light source, such that light is directed through the probe to or into the treatment area, to activate only the motor to rotationally or reciprocatingly drive the light guide, or to activate both the light source and the motor.