Dental instrument

Claim 2

A dental instrument for treating nonlinear root canals of teeth comprising a handpiece, a broach having a slender shaft with a tip at one end and a shank at the opposite end, said shaft having sharp barbs projecting therefrom including barbs near the tip, said shaft being resiliently flexible within the elastic limit of the material of the shaft to permit lateral flexing to follow nonlinear root canals and being torsionally flexible to permit rotation of said shank about its longitudinal axis through a predetermined limiting angle of not less than 90* of torsional flexion relative to said tip within the elastic limit of said material, socket means for holding said broach by its shank, bearing means rotatably supporting said socket means in said handpiece while holding it against axial movement, and drive means for rotationally oscillating said socket means about its longitudinal axis through a predetermined angle which is at least of the order of 90* and at the most equal to said limiting angle of torsional flexion of said broach shank, whereby if the tip of said broach becomes fast in a root canal continued rotational oscillation of the shank of said broach by said socket means will not break the broach, lengthwise penetration of said broach into a root canal being effected solely by manipulation of said handpiece by an operator.

Claim 3

A dental instrument according to claim 1, in which said broach shank has a plurality of said barbs equally spaced around its circumference and in which the angle of oscillation of said socket means is not less than 360* divided by the number of barbs around the circumference of said broach shank.

Claim 4

A dental instrument according to claim 1 in which said socket means comprises a hollow circular cylinder in which said broach shank is received, said cylinder having a longitudinal slot in its outer surface, and in which said drive means comprises a rotating shaft in said handpiece with an axis normal to the axis of said cylinder, an arm fixed on an end of said shaft adjacent said cylinder and a pinion lug carried by said arm eccentric of the axis of said shaft and engaging in said slot to oscillate said cylinder upon rotation of said shaft, said slot having a length at least equal to twice the eccentricity of said pinion lug.

Claim 5

A dental instrument according to claim 3, in which said shank comprises a mandrel integral at one end with the shank of said broach and having a circumferentially extending groove near its free end, and in which a manually operable spring loaded locking plate slidably mounted on said handpiece has a bore engageable in said groove to hold said shank releasably in said hollow cylinder.

Claim 6

A dental instrument for treating nonlinear root canals of teeth comprising a handpiece, a broach having a slender shaft with a tip at one end and a shank at the opposite end, said shaft having shaft barbs projecting therefrom including barbs near the tip, said shaft being resiliently flexible within the elastic limit of the material of the shaft to permit lateral flexing to follow nonlinear root canals and being torsionally flexible to permit rotation of said shank through a predetermined limiting angle of torsional flexion relative to said tip within the elastic limit of said material, socket means for holding said broach by its shank, bearing means rotatably supporting said socket means in said handpiece while holding it against axial movement, and drive means for rotationally oscillating said socket means through a predetermined angle which is at the most equal to said limiting angle of torsional flexion of said broach shank, whereby if the tip of said broach becomes fast in a root canal continued rotational oscillation of the shank of said broach by said socket means will not break the broach, penetration of said broach into a root canal being effected solely by manipulation of said handpiece by an operator said drive means comprising a driving spindle, a first plate fixed on one end thereof, a first crankpin carried by said plate and extending parallel to but offset from said driving spindle, a driven spindle coaxial with said driving spindle and in driving connection with said socket means, a second plate fixed on an end of said driven spindle and facing said first plate, a second crankpin carried by said second plate and extending parallel to the axes of said spindles but offset from said axes a distance less than the offset of said first crankpin, said crankpins overlapping one another in an axial direction and a fork-shaped member pivotally mounted to swing about a fixed pivot parallel to said spindle axes and offset from said axes a distance greater than the offset of said first crankpin, said fork-shaped member having a slot receiving both of said crankpins whereby rotation of said driving spindle produces oscillation of said fork-shaped member about its pivot which in turn produces oscillation of said driven spindle, the angle of oscillation of said driven spindle being determined by the respective offsets of said crankpins.

Claim 7

A dental instrument for treating nonlinear root canals of teeth comprising a handpiece, a broach having a slender shaft with a tip at one end and a shank at the opposite end, said shaft having shaft barbs projecting therefrom including barbs near the tip, said shaft being resiliently flexible within the elastic limit of the material of the shaft to permit lateral flexing to follow nonlinear root canals and being torsionally flexible to permit rotation of said shank through a predetermined limiting angle of torsional flexion relative to said tip within the elastic limit of said material, socket means for holding said broach by its shank, bearing means rotatably supporting said socket means in said handpiece while holding it against axial movement, and drive means for rotationally oscillating said socket means through a predetermined angle which is at the most equal to said limiting angle of torsional flexion of said broach shank, whereby if the tip of said broach becomes fast in a root canal continued rotational oscillation of the shank of said broach by said socket means will not break the broach, penetration of said broach into a root canal being effected solely by manipulation of said handpiece by an operator said drive means comprising a driving spindle, a first plate fixed on one end thereof, a first crankpin carried by said plate and extending parallel to but offset from said driving spindle, a driven spindle coaxial with said driving spindle and in driving connection with said socket means, a second plate fixed on an end of said driven spindle and facing said first plate, a second crankpin carried by said second plate and extending parallel to the axes of said spindles but offset from said axes a distance less than the offset of said first crankpin, said crankpins overlapping one another in an axial direction and a fork-shaped member pivotally mounted to swing about a fixed pivot parallel to said spindle axes and offset from said axes a distance greater than the offset of said first crankpin, said fork-shaped member having a slot receiving both of said crankpins whereby rotation of said driving spindle produces oscillation of said fork-shaped member about its pivot which in turn produces oscillation of said driven spindle, the angle of oscillation of said driven spindle being determined by the respective offsets of said crankpins.