A medical or dental handpiece comprises a lighting device for the emission of radiation, in particular of visible light, onto a treatment site, a temperature sensor preferably located in the interior of the handpiece, and at least one shared electrical signal line provided in the handpiece for the lighting device and the temperature sensor. The lighting device and the temperature sensor are both operatively connected to the at least one shared electrical signal line. A medical or dental treatment device comprises such a handpiece and a control and/or regulation device electrically connected to the at least one shared electrical signal line provided in the handpiece, which is designed to emit a first electrical signal assigned to the lighting device and a second electrical signal assigned to the temperature sensor.
