Dental prophylaxis angle

A dental contra-angle for attachment to a dental handpiece, said contra-angle comprising:

• a body having a generally cylindrical sleeve with an open rear end and a head, a first axial bore in the sleeve and a second axial bore in the head, said first and second bores communicating with each other at an intersection, the second bore being at an angle of from 100.degree. to 120.degree. with respect to the axis of said sleeve at said open rear end;
• a drive gear including a gear and a flexible shaft, said shaft extending rotatably from the open rear end of said sleeve through said first bore;
• means for causing said flexible shaft to be substantially coaxial with said sleeve at said open rear end of said sleeve when said contra-angle is attached to a handpiece and for causing said flexible shaft to form a substantial angle with respect to the axis of said sleeve at said open rear end of said sleeve when said contra-angle is removed from a handpiece, said means including said open rear end of said sleeve's being of sufficiently large diameter that said flexible shaft is flexed when said contra-angle is attached to a handpiece and relatively relaxed when said contra-angle is removed from the handpiece;
• and
• a driven gear rotatably mounted in said head bore and operatively connected to said drive gear, said driven gear including means for retaining a dental bit.

A dental contra-angle for attachment to a dental handpiece, said contra-angle comprising:

• a body having a generally cylindrical sleeve with an one rear end and a head, a first axial bore in the sleeve and a second axial bore in the head, said first and second bores communicating with each other at an intersection, the second bore being at an angle of from 100.degree. to 120.degree. with respect to the axis of said sleeve at said open rear end;
• a drive gear including a gear and a flexible shaft, said shaft extending rotatably from the open rear end of said sleeve through said first bore, said open rear end of said sleeve being of sufficiently large diameter that said flexible shaft is flexed when said contra-angle is attached to a handpiece and relatively relaxed when said contra-angle is removed from a handpiece, said sleeve including a slot into which said shaft extends in said relatively relaxed position;
• and
• a driven gear rotatably mounted in said head bore and operatively connected to said drive gear, said driven gear including means for retaining a dental bit.

In a combination of a dental handpiece and a dental angle mounted on the handpiece,

• the handpiece comprising a nose terminating in a shoulder, the nose including a frustoconical part, a projection on the cylindrical part for angularly aligning the dental angle, and a chuck within the nose part,
• the angle comprising a body including a sleeve part with an open rear end, a neck part, and a head part, a first axial bore extending through the sleeve and neck part, and a second axial bore in the head part, said first and second bores communicating with each other at an angle with respect to each other;
• a drive gear including a gear part and a shaft part, said shaft part extending rotatably through said first bore and being held by said chuck;
• and a driven gear rotatably mounted in said head bore and operatively connected to said drive gear, said driven gear including means for retaining a dental bit;
• the improvement wherein the sleeve part of the angle body is formed of a thin plastic material and includes a generally axial slot at its open end, the slot extending substantially forward of the projection on the handpiece when the angle is mounted on said handpiece with the open rear end of the sleeve against the shoulder on the handpiece nose, the length of the slot and the thinness of the plastic sleeve wall permitting the sleeve to expanse sufficiently when it is forced onto the handpiece to form a size-on-size friction fit with the cylindrical part of the handpiece nose and hold the angle body positioned angularly and axially with respect to the handpiece substantially independent of the shaft part's being held by the chuck.