Patent ID: 7771197

Claim:
A handpiece for measuring root canal length, comprising: an outer sleeve that is substantially non-insulating and is substantially free of any insulating coating, a connecting device for coupling the handpiece to a control and evaluation unit, to a measuring circuit with a current source for measurement of root canal length and to a drive unit, an instrument carrier configured to receive a dental instrument, at least one transmission element within the outer sleeve that transmits force to move the instrument carrier so that, when received in the instrument carrier, the dental instrument executes a rotating, reciprocating and/or vibrating working movement, a length measuring circuit portion disposed inside the handpiece and operable to transmit measuring signals for measuring length, a contact portion operable to establish a conductive path between the dental instrument serving as an electrode and the length measuring circuit portion, and an insulating portion that insulates the length measurement circuit portion and the contact portion, through which a voltage is applied during measurement, from the outer sleeve, wherein the outer sleeve does not conduct electricity during measurement, and wherein the length measuring circuit portion comprises the at least one transmission element and the insulating portion comprises at least one non-conductive rolling bearing positioned between the at least one transmission element and the outer sleeve.