Patent ID: 8092457

Claim:
A medical drilling device for drilling of human or animal bone tissue, said medical drilling device comprising: a bore electrode for transmitting electrical current; a drill bit having an exterior surface and an interior portion, said drill bit including: a drill bit tip for penetrating human or animal bone tissue, the drill bit tip being non-insulated and able to conduct electricity; and an annular area on said exterior surface of said drill bit and placeable in electrical contact with said bore electrode, said annular area being non-insulated and able to conduct electricity; said exterior surface being surface treated with a surface treatment except at said drill bit tip and said annular area, said surface treatment provides electrical insulation such that said exterior surface is unable to conduct electricity except at said drill bit tip and said annular area, said drill bit tip, said annular area and said interior portion of said drill bit being able to conduct electricity; a bore drive for driving the drill bit, a backing electrode, which is directed in a way, that the tissue to be drilled substantially lies between the backing electrode and the drill bit, a resistance measuring device connected with the bore electrode and with the backing electrode, the two electrodes being exposable to a current for creating an electrical resistance between the drill bit tip and the backing electrode, said bore electrode being in electrical contact with the backing electrode, the resistance between the drill bit tip and the backing electrode being precisely measurable, and a monitoring device operatively connected to said resistance measuring device for indicating information delivered from said resistance measuring device, wherein electrical current is transmittable on said annular area through said interior portion and through said drill bit tip, said resistance measuring device creating the electrical resistance between said drill bit tip and said backing electrode indicative of the type of tissue being drilled and the depth of the drilling, and said monitoring device yielding information about the type of tissue being drilled and a precise measurement of the depth of the drilling, wherein said exterior surface of the drill bit allows electrical contacts only at said drill bit tip and said annular area, said surface treatment provides electrical insulation which prevents errors in resistance measurements and enabling the simultaneous measurement of the type of tissue being drilled and the precise measurement of the depth of the drilling without interruption in the drilling.