Abstract:
A dental prophy angle adapted to be engaged with a dental handpiece having a nose cone and a low-speed rotary driver within the nose cone. The prophy angle has a proximal end adapted to releasably engage with said nose cone, and a distal end having an implement-mounting member rotatable therein. A flexible shaft extends from the nose cone through the angle to the mounting member and has a diameter which is substantially smaller than the interior wall of the prophy angle. The shaft has a coupling member with a free axial end adapted to engage the rotary driver in the nose cone to be rotated upon rotation of said driver, and an opposite captive end connected to said shaft with a shoulder surrounding said flexible shaft and facing away from said free end to confront an abutment limiting axial displacement of said coupling member within the prophy angle. The flexible shaft is a steel cable comprising a plurality of multi-stranded steel cords twisted together to form a cable and encased in a sheath of polytetrafluoroethylene.

Description:
FIELD OF THE INVENTION 
     The present invention relates to dental equipment, and more particularly to an attachment for a dental handpiece for mounting in a dental cleaning implement for use in prophylaxis procedures. 
     BACKGROUND OF THE INVENTION 
     Dental prophy angles are used in the final step of the dental cleaning visit that practically all patients receive annually. There are marketed various disposable prophy angles, dental prophylaxis angles, that are believed represented by the disclosures of U.S. Pat. Nos. 5,040,978, 5,645,426, 5,352,119, 5,730,595 and 5,156,547. It is recognized that the making of inexpensive prophy angles enables the dental professional or hygienist to discard the prophy angle rather than have to sterilize the unit for re-use. It is further recognized that making a disposable prophy angle (DPA) which is reliable enough to perform complete prophy on a single patient without failure eliminates the time cost and inconvenience associated with refitting the handpiece with a subsequent unit or units during the prophylaxis procedure. 
     Conventional DPA&#39;s are true analogs of the standard Doriot style prophy angle, using the same type of gear geometry. The advantage of this known system is to allow for a “use once and dispose” of a previously high labor cost item (clean, sterilize, and lube between patients). In the past, a number of the units would fail because of poor fit of the gears and their support housing. While a number of companies have engineered better tolerances and materials to overcome these problems, failure of the units still remains as a factor in the field. 
     An additional factor is patient discomfort which results from various degrees of vibration, noise, and heat generated by existing DPA&#39;s while in use. Patient comfort remains a fundamental need for products in this category and improvements are always welcome. 
     An additional factor in the prophylaxis procedure is that the dentition requires the hygienist or dentist to change their handpiece orientation to clean all surfaces. The majority of the presently marketed prophy angles are rigidly fixed at a 90° angle and therefore do not allow adaptability of the DPA to accomplish conformation to various angles of the dentition without manipulating the entire handpiece with the attached DPA. This may become even more important as additional controls are incorporated onto the handpiece itself. 
     SUMMARY OF THE INVENTION 
     A failure-free disposable prophy angle of comparable or lower cost to presently available gear-driven angles for use in the dental field. Alternate embodiments include angle and/or rotational flexibility to the user without changing the handpiece orientation in the user&#39;s hand. 
     The invention provides a dental prophy angle design wherein the rotary force, supplied by a standard low speed dental handset, is transferred directly to the prophy cup eliminating gear transmission. The angle between the axis of rotation of the prophy cup and axis of rotation of said externally supplied force is preferably at a given divergent angle, normally approximately 90°. Alternative embodiments of the invention allow for a variety of angles and rotational orientations between the axis of rotation of the prophy cup and the drive axis of said externally supplied force in a prophy angle housing as required by the user. The entire unit has suitable durability to assuredly perform without failure for the period required to perform the polishing of an entire dentition of a single dental patient. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     All of the objects of the present invention are more fully set forth hereinafter with reference to the accompanying drawings, wherein: 
     FIG. 1 is a longitudinal cross-section illustrating a prophy angle made in accordance with the present invention; 
     FIG. 2 is a side elevation of a second embodiment of the prophy angle with portions broken away illustrating angular adjustability of the distal end part; 
     FIG. 3 is a side elevation, partially in section, of a third embodiment of the prophy angle made in accordance with the present invention with the distal part of the angle shown in section to illustrate the circumferential adjustability thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a preferred embodiment of the prophy angle in accordance with the present invention. The prophy angle  11  shown in FIG. 1 has a generally tubular housing having a proximal end  12  and a distal end  13 . At the proximal end, there is a hollow tubular wall  14  defining within the wall a hollow tubular drive chamber  15 . Preferably, the wall  14  is cylindrical in form to engage and support the prophy angle in the nose cone of a dental handpiece. The outside peripheral surface of the wall  14  has shallow ribs to frictionally engage within the nose cone of the handpiece. The nose cone has a projecting lug which engages in a recess  16  to anchor the prophy angle  11  against inadvertent rotation in the handpiece. The lug may be replaced by other forms of anti-rotation stops. 
     The distal end  13  of the prophy angle has an axial passage  18  with a peripheral internal groove  19 . An implement-mounting member  21  is mounted in the passageway  18  and the member has a flange  22  which engages in the groove  19 . The axial passage  18  provides a bearing surface affording rotation of the member  21 , the groove  19  capturing the flange  22  so as to prevent inadvertent axial displacement of the member  21 . The member  21  is preferably formed of a non-friction material so as to freely rotate within the passage  18 . At the open end of the passage  18 , the member  21  is provided with a deflector  23  which serves to limit the infiltration of particles and droplets generated during the use of the cleaning implement. Beyond the deflector  23 , a button  24  is provided to releasably mount the prophy cleaning tool shown in broken lines at  25 . In the present embodiment of the invention, the distal end of the prophy angle is disposed at a right angle to the axis of the nose cone and the drive chamber  15 . In the present embodiment, the right angular projection of the distal end is positioned to diverge from the extended axis of the chamber  15  in the same downward direction as the circumferential position of the recess  16  about the axis. 
     In accordance with the invention, the mounting member  21  is coupled to the rotary driver within the nose cone of the handpiece by a flexible shaft  31  extending from the member  21  at the distal end of the prophy angle through the hollow tubular housing and terminating in the chamber  15 . The housing of the prophy angle  11  provides a continuous channel from the distal end to the proximal end and, as shown in FIG. 1, the channel  41  has a narrow mid-portion which flares outwardly towards the chamber  15  at the proximal end and towards the passageway  18  at the distal end  13 . The minimum width of the channel  41  is at least twice the thickness of the flexible shaft  31  so as to allow the shaft to accommodate flexure by lateral displacement toward and away from the internal walls of the channel. 
     At the proximal end, the flexible shaft  31  has a connector  35  which is operable to be engaged within the rotary driver which is located centrally within the nose cone of the handpiece. As shown, the connector  35  comprises a free end with a cylindrical stub  36  which is adapted to be frictionally engaged in the rotary driver of the nose cone. At the other end, the connector  35  has a flange  37  which fits loosely within the interior wall  14  of the chamber  15 . At the inner end of the chamber  15 , the interior wall  14  terminates in an abutment  38  which serves as a barrier between the chamber  15  and the channel  41 . The abutment  38  provides a continuation of the passage  41  into the chamber  15 , but the internal perimeter of the abutment  38  is smaller than the outer perimeter of the flange  37  so that the abutment  38  serves to provide a support for positioning the stub  36  concentrically within the chamber  15  during initial engagement of the stub  36  with the rotary driver of the nose cone. When the flange  37  engages the abutment  38 , the flexible shaft  31  is flexed towards the wall of the channel at  42  where the channel is curved to accommodate the angular position of the passage  18  in the distal end of the prophy angle relative to the axis of the chamber  15 . When the shaft  31  is flexed towards the outside wall  42  of the curve, it also is flexed away from the inside wall  43  of the curve. 
     In order to have a prolonged effective life of the flexible shaft  31 , it is desirable to support the shaft  31  at a single location within the prophy angle during use and rotation of the flexible shaft. To this end, the mounting member  21  provides the sole support for the flexible shaft at the distal end, the shaft being supported by the connector  35  at the proximal end within the rotary driver of the nose cone. When supported at these points, the flange  37  is separated from the abutment  38  and the mounting member  21  is freely rotatable in the passageway  18 . Preferably, the material of the member  21  is of anti-friction material, but it is also contemplated that if the member  21  is subject to friction, the passageway  18  and groove  19  may be lined with anti-friction material. 
     Prior attempts to employ a flexible shaft in a prophy angle have led to premature failure of the shaft. In accordance with the present invention, the flexible shaft of the present invention comprises a stainless steel cable sheathed in polytetrafluoroethylene (Teflon), for example supplied by McMaster-Carr Part No. 3423T29, which is a {fraction (1/16)}″ stainless steel wire rope having nine cords twisted together, each cord comprising  19  strands of stainless steel wire. The {fraction (1/16)}″ diameter of the sheathed wire rope fits loosely within the {fraction (3/16)}″ width of the channel  41  at its narrowest point. Since the rope occupies one-third of the width of the channel, there is little tendency for the rope to engage the walls of the channel and generate friction which would cause deterioration of the cable drive. A wire rope of this character is effective to rotationally drive the member  21  with a minimum generation of friction and heat. 
     A sheathed cable of this type withstands a severe radius of curvature while under the rotational forces generated by rotation of a standard low-speed dental handpiece in the range of 0-50,000 rpm and under loads equal to those found while polishing the dentition utilizing a standard dental prophy cup. The wire will perform without fracture, splitting, seizing or other forms of failure that would interfere with the rotation of the mounting member  21 . Other cables of similar nature which may vary in materials composed thereof of geometries employed in the assemblage, or relative sizes utilized may be found to achieve the same or similar end results. 
     In order to accommodate the desire to use prophy angles with angles other than 90°, as shown in FIG. 1, several prophy angles may be supplied in which the housings  11  are formed to provide different angles as requested by the dental technician, hygienist or dentist. 
     Instead of providing a plurality of prophy angles in which the projection of the distal end from the chamber axis is fixed, the prophy angle may be made in two parts, as shown in FIG.  2 . In this embodiment of the invention, a prophy angle  51  has a proximal end part  52  and a distal end part  53 . The proximal end part has a drive chamber  55  with a recess  56  for engagement with the nose cone of the handpiece. At the remote end of the proximal part  52 , a yoke  60  mounts the distal end part  53  for angular adjustment. Like the distal end  23  of the embodiment shown in FIG. 1, the distal end part  53  has an axial passage  58  with an annular recess  59  to provide a bearing for a mounting member  21  of a flexible drive assembly which may be identical to the assembly shown in FIG.  1 . The member  21  serves as the sole rotary support for the flexible drive shaft  31  which extends rearwardly through the channel  61  in the housing of the prophy angle  51 . The flexible shaft  31  has a connector  35  with a stub  36  for engagement with the rotary drive of the nose cone, similarly to the engagement provided in the embodiment of FIG.  1 . As shown, the angle of the axis of the passage  58  diverges from the extended axis of the chamber  55  at an adjustable angle which, in FIG. 2, is 90°. The yoke is frictionally engaged with the remote end of the proximal end part  52  with a friction coupling to enable adjustment of the yoke  60  to varying angles between 0-90°. As in the embodiment of FIG. 1, the flexible cable  31  preferably comprises a multi-stranded stainless steel cable having a teflon coating. 
     The embodiment of FIG. 2 provides for adjustment of the angle of the passage axis relative to the axis of the chamber  55 , with the passage axis diverging from the chamber axis at a position corresponding to the position of the recess  56  circumferentially in the chamber  55 . Where it is desired to adjust the position of divergence circumferentially of the chamber  55 , an alternate embodiment may be provided, as shown in FIG.  3 . In this embodiment of the invention, the prophy angle is made with a proximal part  72  and a distal part  73 . The embodiment of FIG. 3 is designed to cooperate with a flexible drive assembly identical to the drive assembly shown in FIGS. 1 and 2. To this end, the distal part  73  has an axial passageway  78  with a recess  79  to serve as a bearing for the mounting member  21  of the flexible shaft assembly shown in the previous figures. The assembly includes the member  21 , the flexible shaft  31  and the connector  35 . In the present instance, the near end of the distal part  73  has an enlarged cylindrical socket  81  which telescopically engages a hollow cylindrical plug portion  82  at the remote end of the proximal part  72 . The free end of the plug part  82  has axially-projecting teeth  84  which cooperate with corresponding teeth  85  in the socket part  81 . The socket part  81  is frictionally engaged with the plug part  82  and when fully engaged, the teeth  84  mesh with the teeth  85  to anchor the socket part against rotation about the common axis of the plug and socket. When it is desired to adjust the circumferential position of the divergence of the passage axis, the plug and socket are separated sufficiently to disengage the teeth and enable rotation of the socket  81  on the plug  82  to reposition the passage at a different position relative to the circumference of the chamber  75 . The prophy angle of FIG. 3 may be provided with different angles of divergence between 0° and 90°, according to the desires of the dental technician, hygienist or dentist and may also be provided with an adjustable yoke as described in connection with the embodiment shown in FIG.  2 . 
     While particular embodiments of the invention has been herein illustrated and described, it is not intended to limit the invention to such disclosures, but changes and modifications may be made therein and thereto within the scope of the following claims.