Surgery – Truss – Pad
Patent
1978-06-07
1980-03-18
Cohen, Lee S.
Surgery
Truss
Pad
128776, 433 27, A61B 505
Patent
active
041934083
ABSTRACT:
An endodontic device for measuring and indicating the depth of penetration of a probe in a root canal of a tooth during a root canal operation includes a meter having a pair of juxtaposed, graduated scales for respectively indicating probe penetration depth in a first broad range of penetration within the root canal, and a second, relatively narrow range of penetration therein, adjacent the apex of the canal, and further includes a bidirectional indicator pointer to provide a precise, accurate visual indication of the probe penetration depth, particularly when such probe is immediately adjacent the apex of the canal. An a.c. measurement signal derived from a d.c. powered oscillator circuit is passed through the probe to a bridge circuit which measures the probe resistance, and thus the position of the probe relative to the canal apex, and also inverts the phase of the measurement signal when the probe reaches a prescribed penetration depth close to the canal apex. A pair of parallel coupled discriminator circuits sense the phase of the measurement signal and are respectively operative to selectively swing the indicator pointer in one direction when the probe is in the first broad penetration range thereof to produce a reading on one of the scales, and reverse the swing direction of the indicator pointer upon sensing a phase change in the measurement signal to produce a reading on the second, expanded scale associated with the second narrow probe penetration range immediately adjacent the canal apex.
REFERENCES:
patent: 2736313 (1956-02-01), Mathison
patent: 3660901 (1972-05-01), Inoue
patent: 3753434 (1973-08-01), Pike et al.
patent: 3859983 (1975-01-01), Dohring et al.
patent: 3894532 (1975-07-01), Morey
patent: 3901216 (1975-08-01), Felger
patent: 3916529 (1975-11-01), Mousseau
patent: 3993044 (1976-11-01), McGuffin
patent: 4016870 (1977-04-01), Lock
Cohen Lee S.
Shirota Electric Furnace Material Co., Ltd.
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