Screw for securing a dental prosthesis
View Patent ↗A screw ( 10 ) for securing a dental prosthesis directly to a dental abutment includes a threaded portion ( 12 ) lying within a virtual cylinder ( 14 ) of a first diameter D 1 , and a head portion ( 16 ) having a shaped recess ( 18 ) for receiving a driver. The head portion ( 16 ) has a second diameter D 2 greater than first diameter D 1 . A conical clamping surface ( 20 ) lies between threaded portion ( 12 ) and head portion ( 16 ) and forms a conical angle α to a central axis ( 22 ) of the virtual cylinder, where α is between 25 and 35 degrees, and preferably around 30 degrees. The conical clamping surface may be provided with a number of anti-rotation grooves ( 26 ).
1 . A screw for securing a dental prosthesis directly to a dental abutment, the screw comprising:
(a) a threaded portion for engaging a female thread of an abutment, said threaded portion lying within a virtual cylinder of a first diameter;
(b) a head portion having a shaped recess for receiving a driver, said head portion having a second diameter greater than said first diameter;
(c) a conical clamping surface between said threaded portion and said head portion, said conical clamping surface forming a conical angle α to a central axis of said virtual cylinder, where a is between 25 and 35 degrees, said conical clamping surface including a plurality of anti-rotation grooves, each of said anti-rotation grooves defining a step oriented to oppose a loosening rotation of said threaded portion; and
(d) an un-threaded cylindrical portion having said first diameter interposed between said threaded portion and said conical clamping surface.
2 . The screw of claim 1 , wherein said conical angle α is 30 degrees±5%.
3 . The screw of claim 1 , wherein said second diameter is between 2.1 mm and 3 mm, and wherein said first diameter is at least 1 mm smaller than said second diameter.
4 . The screw of claim 1 , wherein each of said anti-rotation grooves is formed as a partial-cylindrical groove intersecting said conical clamping surface and terminating at said step.
5 . The screw of claim 1 , wherein said plurality of anti-rotation grooves are implemented as at least three anti-rotation grooves angularly spaced around said central axis.
6 . The screw of claim 1 , wherein an extent of said conical clamping surface along said central axis is at least half of a length of said threaded portion along said central axis.
7 . The screw of claim 1 , wherein said shaped recess is a star socket.