Abstract:
A disposable dental contra-angle comprising a plastic housing having a sleeve, a tapered neck, a head and a disposable bur. The bur being removably coupled to a driven rotating mandrel located in the head section. The rotating mandrel having an integral axis pole member extending through and outwardly from its top and bottom portions wherein the bur is maintained in a 1:1 rotational luted connection, with virtually no slippage. The sleeve section having an elongated opening for receiving a power drive from a dental handpiece. A gear ratio mechanism located in the sleeve section rather than the head section, for either increasing or decreasing the shaft speed. 
     A gear to gear arrangement in the head section for translating rotation from the drive shaft to the bur. In addition to having a flat surface for a luted non-slippage connection within the rotating mandrel, the bur further has a plurality of semi-circular grooves for connecting with a plurality of O-ring connections disposed within the chamber of the axis pole for prevention of axial displacement of the bur from the mandrel.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on Provisional Patent Application Ser. No. 60/163,040 filed Nov. 2, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     My U.S. Pat. No. 6,099,309, relates generally to a disposable prophy angle. Structure of this prophy angle is utilized to contain and support the present invention. 
     1. Field of the Invention 
     The present invention relates generally to an improved disposable contra-angle. More particularly, the present invention relates to disposable burs that can be placed into rotation for high speed drive. 
     2. Description of the Prior Art 
     Dental drill burs are well known in the art. At present, they are removably placed into the contra-angle by the dentist or the dental assistant. The standard procedure is for the dentist to place the bur into the contra-angle, and after the procedure it is removed manually to be brushed and sterilized. Often, it is discarded because of wear or inability to properly clean. Because the contra-angle is subject to contamination and infection from saliva and blood of the patient, it needs to be brushed; placed into ultrasonic; sterilized; and then lubricated before it can be used again. The lubrication is very critical due to the variable speeds generated by contra-angles. Extra care must be taken to prevent any oil from escaping into the patient&#39;s mouth or on the cavity itself. Occasionally the contra-angle must be taken apart because the gears have smudge accumulation and thereby have difficulty operating. This along with normal cleaning creates a substantial time loss leading to lower productivity of the entire dental office. All of this makes the use of reasonably priced contra-angles very practical. But beyond cost, the most important reason for using disposable contra-angles is to reduce the danger from incomplete sterilization, whereby the bacteria and infection are then transferred from one patient to another. 
     The main problems associated with the prior art is that the retained bur has a tendency to rattle and be generally noisy. This is primarily due to the fact that they are only connected at the superior end. There definitely is too much play between the cylinder of the bur and the core of the rotating mandrel. This results in energy loss, fatigue, loss of cutting efficiency. The patients feel all of this, and thus there can be an increase in anxiety in an already very stressful environment. 
     U.S. Pat. No. 5,766,008 issued to Hughes on Jun. 16, 1998, teaches what is the standard method of inserting a dental bit into the dental handpiece. One end of the shank&#39;s superior end being luted. 
     U.S. Pat. No. 5,749,728 issued to Bailey on May 12, 1998, teaches the use of a disposable dental angle. He uses a latch on the cap to lock the angle together. This latch is typical of the method employed in the prior art to contain the driving and driven gears and to retain a bur that is held therein. 
     U.S. Pat. No. 5,718,582 issued to Quinn et al. on Feb. 17, 1998, is illustrative of a patent that has a solution for the one of the most common problem encountered in dental handpieces, especially those that reach speeds of 400,000 rpm. This problem is rotation and axial slippage within the mandrel (chuck). 
     None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the above problems and difficulties are obviated by the present invention which provides for a disposable contra-angle to be used in association with motorized dental handpieces. 
     More particularly, the present invention is comprised of four major sections: a sleeve, a neck, a head and a bur attachment. The main inventive concept of the present invention being the utilization of a gear system at a relative distance from the head. This gear ratio taking place in the sleeve section, which has the largest cross sectional area. A secondary shaft, leading from the location of the gear ratio, needs to be only a fraction of the size of the main drive shaft. This allows the neck section to be thinner, thereby allowing greater visibility for the dentist. Also, by having the gear ratio take place in the sleeve section, the heaviest portion of the contra-angle is in the handle. This will create a more balanced contra-angle, one that will be easier for the dentist to control, cause less fatigue, give better access, and it will also help to keep the hands of the dentist out of and away from the patient&#39;s mouth. 
     The working member of the contra-angle is a bur which differs from the prior art in that it is disposable and has a new and improved means for retention within the head of the contra-angle. The present invention allows for the bur to be either placed manually by the dentist or by the manufacturer. The manufacturer would use a luting process and the bur and contra-angle would be disposed of together. The advantage of having the dentist place the bur is that it would be possible, in cases of improved materials, for the dentist to only remove the bur and thereby reuse the contra-angle a plurality of times. 
     Two primary considerations in designing a contra-angle system is the retention of the bur without rotation or slippage. Also the ability of the angle to deliver true spin to the working bur. Most systems today use a manually extending latch to retain the bur within the housing. The per cost of most of the burs used today is approximately $1.00. The time required to sterilize and lubricate is far in excess of that cost. Also to brush the flutes and cross cut patterns of a bur is not economical. Therefore, it is aim of the present invention to have a disposable unit. 
     The present invention provides a redesign of the bur shaft and the seating area within the mandrel to provide for the disposability of the bur and/or contra-angle. The aim of the present invention is to have superior retentive characteristics. Also the majority of the parts for the contra-angle can be manufactured out of plastic materials. Most prior art burs are made from a highly polished circular rod having a flat section and a circular notch for the manual latch means. The flat surface is for rotation of the bur more so than the latch. The latch is strictly a retentive feature. 
     The present invention utilizes a more extensive flat slot along the longitudinal suface of the bur shaft and abuts the inner chamber of the mandrel. This extension of the flat slot will resolve the problem created by too much play between bur and cylinder. 
     The flat side of the bur shaft is luted to a flat surface in the chamber. This aids in retention, rotation, less wobble, less noise and greater efficiency. With the present invention, the rotation of the bur will be equal to the rotation of the mandrel, thereby causing less fatigue to the hands of the dentist, less pressure, less energy expenditure, more efficiency, less friction, less heat and subsequently more comfort for the patient. 
     Although the present inventon can utilize the conventional latch retention system, their failure due to inadvertent opening due to vibration has prompted the present invention to replace the external manual latch with an internal “O” ring that is contained within a recess area of the contra-angle shell. The top end of the chamber having a circular depression about its entire circumference which corresponds to the “O” ring within the recess. Within the mandrel chamber are a plurality of semi-circular protrusions which are in a cooperating relationship to a plurality of semi-circular grooves disposed in the outer surface of the bur shaft. These “O” rings and protrusions could be metal or hard plastic. Hard plastic would have more give and allow an easier insertion of the bur. An alternate embodiment to the concentric bur shaft would be to have a shaft made in in a triangular, rectangular, hexagonal or some other non-rounded shape. This would increase the rotational retention towards the idealistic 1:1 rotation. 
     The present invention will provide a cover over an outer boss that in itself rotates at a variable speed. This cover would be a safety feature. It being a circular piece that would either snap into place or else have means for screwing into place. The cover would also help to maintain true spin, because it would engage part of the tapered shank of the bur, thereby serving as a deterrent against the bur being dislodged. 
     The present invention provides an improved design feature for protection against the bur flying out of its position within the mandrel and possibly into the patient&#39;s mouth. The bur in its functional state is pushed down with some force to engage the tooth. Although the present design is for relatively low variable speeds (15-45,000 rpm), the functional force aids in retaining the bur in its housing. With the contra-angle spinning at 30,000 rpms, if the dentist inadvertently lifts the bur up, there would be the danger of the bur spinning out into the mouth of the patient. This has been seen with latching types of contra-angles. The vibration and multi-use wear loosens the latch and because this was the only retentive feature, the bur at times would slip out of the angle. 
     Another embodiment in the design of the present invention is the placement of a depressible ball in the chamber wall of the mandrel. This will engage within a groove about the shaft to prevent axial movement between mandrel and bur. The spring ball will spin with the shaft in the scored section. 
     An important object of the present invention is to prove a contra-angle that is inexpensive to manufacture and that is totally disposable. 
     Another object of the present invention is to provide a contra-angle that will give the dentist greater range of visibility during the procedure and also reduce vibration to the hands. 
     Still another object of the present invention is to provide a gear ratio closer to the hands for greater balance, thereby causing less fatigue and stress to the hands of the dentist. The major benefit of this gear ratio is that less air will be required to drive the system. Beyond economical considerations, less air means less vibration and increased frequency of rotation at the head end of the angle, thereby less auxiliary movement (non-functional) of the bur. 
     An object of the invention is to impart true spin to the bur which will minimize wobbling. 
     Another object of the invention is to redesign the bur to make the insertion and removal of the disposable bur easier for the dentist. 
     Yet another object of the invention is to eliminate much of the time required to brush and sterilize burs and contra-angles. 
     Another object of the present invention is to increase productivity of the dental office. 
     And the most important object of the present invention is to prevent cross infection, whereby bacteria can be transported from patient to patient or to a member of the dental staff. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view showing the disposable contra-angle with bur mounted therein. 
     FIG. 2 is a front elevational view of the main drive gear and secondary gear taken along lines A—A of FIG.  1 . 
     FIG. 3 is a longitudinal cross sectional view of the neck section. 
     FIG. 4 is a cross sectional view of the neck section taken on lines B—B of FIG.  3 . 
     FIG. 5 is a cross sectional view of the head section and the relationship of the driving gear and the driven gear located on the mandrel. 
     FIG. 6 is an elevational view of mandrel and chamber therein. 
     FIG. 7 ia an elevational view of the bur. 
     FIG. 7 a  is an elevational right side view of FIG.  7 . 
     FIG. 7 b  is an elevational left side view of FIG.  7 . 
     FIG. 7 c  is a top view of the bur. 
     FIG. 8 is an elevational view of another embodiment having a depressed spring ball in mandrel wall. 
     FIG. 8 a  is an elevational view of bur having means for cooperating with depressed spring ball of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and in particular to FIG. 1, reference numeral  20  indicates a disposable contra-angle of the present invention which is designed to operate at variable speeds (15-45,000 plus rpms). The angle  20  includes a body  27 , a head section  23  and a bur member  24  that can be either removable or permanently integral within the head section  23 . The body  27  includes a sleeve section  21  and a tapered neck section  22 . Sleeve section  21 , having means  79  for snap-fitting into neck section  22 , while neck section  22  has similar means for snap-fitting into head section  23 . Conventional means for connecting the sections are well known in the art. These connections can also be made by bonding the mating surfaces by suitable adhesives, fusion welding or other well known techniques. Sleeve section  21 , neck section  22  and parts of the head section  23  are preferably made according to my U.S. Pat. No. 6,099,309, which was issued on Aug. 8, 2000. 
     Sleeve section  21  is comprised of a thin outer shell made from a disposable plastic material, a plastic that is F.D.A. approved such as a polycarbonate resin like that marketed under the General Electric trademark LEXAN. Sleeve section  21  has a generally cylindrical elongated passageway  25  therein, and an opening  26  of sufficient diameter to accept the nose portion of a conventional dental handpiece (not shown). The handpiece is usually air or electrically driven and connected to a dental unit. The dentist can control the speed of the handpiece by pressing upon a foot pedal (rheostat). Located in close proximity to opening  26  is a standard “T” shaped keyslot (not shown) for securing the dental handpiece in place. It is presumed that this mounting means can be adapted to accept a variety of handpieces without deviating from the intent of the present invention. Integrally interposed within passageway  25  are support struts  28 . Struts  28  provide stability to sleeve  21 , thereby eliminating the need for a thicker shell. Each strut  28  will have an orifice  63  leading to a conduit  64 , allowing the dentist/hygienist to periodicaly add dental oil for lubrication. This will be important on units designed to be used more than once and thereby requiring autoclaving, however even on disposable angles  20  it may be desired to decrease friction from time to time. An integrally interposed 360° stop  29  is positioned to orient the dental handpiece and insure that it will be properly inserted within sleeve section  21 . Extending longitudinally through passageway  25  is a drive shaft  30 , which has a proximal end  31  and a distal end  32 . Proximal end  31  has a drive gear  33  integrally connected to it. As shown in FIG. 2, drive gear  33  has internal teeth. Distal end  32  of drive shaft  30  connects with the drive input of the dental handpiece. Struts  28  and stop  29  provide support, stabilization and alignment for drive shaft  30 . Struts  28  and stop  29  being molded from the same type of plastic as sleeve section  21 . Drive shaft  30  and drive gear  33  are generally made from a different grade of plastic, which is generally dependent upon the speeds of the gears and the inherent amounts of heat thereby generated. Gears usually require more flexibility and therefore a plastic such as acetal copolymer (available under the Celanese trademark CELCON) as well as many others can be used. The exterior surface of sleeve section  21  can have rubber soft pads  42  dispersed to help reduce vibration to the hands of the dentist. These pads  42  can be manufactured as part of the contra-angle  20  or else can be removably passed over sleeve section  21 . 
     As depicted in FIGS. 3 and 4, neck section  22  is elongated and tapered quite significantly (in respect to prior art contra-angles) and has a cross sectional shape that is flat on the top  65  and bottom  66  surfaces, while having elliptical side surfaces  67 . Neck section  22  is made from the same plastic as sleeve section  21 . The tapering shape allows the dentist to have greater visibility and also increases the comfort level of the patient. A circular body is also feasible with slight modification that would be known to those in the art. Neck section  22  having a bore  34  defined therein. Interposed within bore  34  are neck struts  68  which are integral with neck section  22 . In addition to supporting neck section  22 , they also provide support for an optional stability tube  74  which will further eliminate vibration in the system. Stability tube  74  passes longitudinally through bore  34  and provides support and alignment for a secondary shaft  37 . This secondary shaft  37  moves longitudinally through tube  74  and has a first end  38  integrally connected to a secondary gear  39 . Secondary gear  39  having externally mounted teeth for meshing with drive gear  33  (as shown in FIGS.  1  and  2 ), whereby secondary shaft  37  will have the same rotational direction as drive shaft  33 . One of the inventive concepts of the present invention is in providing the gear ratio away from head section  23 . Another is having on the second end  40  of secondary shaft  37  a spirally shaped driving gear  41 , including gear teeth that although they gradually narrow from the outer extremity to the inner core, they also may vary in numbers and in widths and depths. The advantages of this will be stated later. Shown in the preferred embodiment but possibly eliminated for cost effective units are orifices  63 , located in the neck section  22  for introducing oil which would flow through conduits  64  to lubricate the secondary shaft  37 . It is to be appreciated that the slim and elongated shape of neck section  22 , along with the main drive gear  33  being in the sleeve section  21 , allows for a more balanced contra-angle  20 , with the weight closer to the dentist&#39;s hands. This will also help to reduce stress and fatigue. 
     Head section  23  and its relationship to neck section  22  and dental bur  24  are best described by FIG.  5 . Head section  23  is made from the same disposable plastic as sleeve section  21 . It is critical for the exterior surface of head  23  to be extremely smooth so as to eliminate possible irritations with the inner membranes of the mouth and tongue. The design of the present invention enhances this concept as rounded head  23  and neck  22  are not only smooth but smaller than conventional disposable contra-angles. Within head section  23  is a cavity  43 . The bottom of head section  23  having snap-fitting means  79  to allow access. A rotating mandrel  45  is seated within cavity  43 . Mandrel  45 , as shown in FIGS. 6, has an elongated axis pole  71  integral with it. Axis pole  71  having a top end  84  extending from the top surface of mandrel  45  and a bottom end  86  extending downwardly from mandrel  45  through a round opening  44  defined by a wall surface  55  in the bottom portion of the head section. The outer surface  90  of axis pole  71  having a concentric shape. The inner surface  92  of axis pole  71  defining a chamber  73  therein. The chamber  73  having a flat luted surface  72  on one side. Upper outer surface  90  of axis pole  71  having a concentric depression  60  defined therein. The upper shell portion of head section  23  having a recess  48  for rotatively accepting top end  84  of axis pole  71 . Insuring proper alignment and spatial positioning of mandrel  45  is a hollow cylindrical sheath  97  that extends downwardly to the upper portion of mandrel  45 . Recess  48  having a circular O-Ring  46  for cooperatively mating with concentric depression  60  of axis pole  71 . Axis pole  71 , being integral with mandrel  45 , therefore will rotate at same speed as mandrel  45 . The inner surface  92  of axis pole  71  will have defined at least one semi-circular flexible protrusion  70  therein. FIG. 5 shows that the preferred embodiment has three such protrusions  70 . The bottom end  86  of axis pole  71  having an aperture  88  for receiving bur member  24 . Mandrel  45  having an upper surface defining spirally shaped bevel gear  49  therein. Gear  49  is put into direct engagement with driving gear  41  which is actuated by secondary shaft  37 . The result being a greater contact area between gear teeth  41  and  49 . The greater gear surface area means a reduction in weight, more spin and less energy expenditure. Driving gear  41  approaches driven gear  49  at a right angle but maintains a 360° groove, whereby the gears  41 ,  49 , are locked throughout the rotation. A concentric slot portion  69  integrally connects bottom surface of mandrel  45  to a circular boss  36 , while maintaining a generally parallel spatial relationship between them. Boss  36  having a diameter larger than round opening  44 , thereby forms a seal with the opening  44 . Slot  69  is in a friction fit with the perimeter of round opening  44 . The present invention is designed to eliminate harmful vibration. Embedded in the wall surface  55  are a plurality of ball bearings  52  dispersed therein for enhancing frictionless spin. Heat, caused by friction, when combined with vibration is a major factor of wobbling. Disposed on the lower outer surface of head section  23  are snap-fitting means  53 . With boss  36  rotating at the variable speeds of mandrel  45 , it is imperative that boss  36  be encapsulated by a non-rotating cover  47 . Cover  47  is snap-fitted onto buttons  53 , however many well known means are available for connecting cover  47  to head  23 , such as having threaded sections for screwing cover  47  to head  23 . 
     FIGS. 7,  7   a ,  7   b  and  7   c  depict a bur member  24  of the preferred embodiment. Bur member  24  is comprised of a top shaft section  56 , a tapered shank section  58 , and the working end or bit  59 . Bit  59  can take many shapes and forms comprising but not limited to round, inverted cone, cylindrical, oval etc. Bur member  24  of the present invention will have a flat face  61  extending along part of its length. In the manufactured units, the flat surface face  61  will juxtapose along the lute surface  72  of in chamber  73 , to prevent slippage of bur  24  while it is engaged within chamber  73 . To retain bur member  24  from axial movement within chamber  73 , there is at least one semi-circular groove  78  defined about the exterior surface of bur  24  for meshing with flexible protrusions  70  of chamber  73 . Bur member  24  can be in itself a disposable item, whereby the dentist can simply remove it for another type of bit. However, bur member  24  can also be factory installed to mandrel  45 , thereby rendering the combination disposable. Factory installation would be relatively simple with all the conventional bonding agents available on the market today. Regardless of whether bur member  24  is inserted by dentist or factory installed, the elongated surface should be scored rather than highly polished. This will aid retention and reduce unwanted slippage within chamber  73 . 
     FIGS. 8 and 8 a  disclose another embodiment of the present invention which would provide a means for preventing axial movement of bur  24 , whereby surface  92  of chamber  73  would in lieu of at least one semi-spherical protrusion  70 , would have a depressed spring ball  80 . Bur member  24  would then have only one semi-spherical cavity  96  to ingress ball  80 . 
     In the embodiments of the present invention it is appreciated that the retention of bur member  24  within recess  48  can also by the conventional latching means of the prior art without deviating from the inventive concept of having disposable bur members  24  and disposable contra-angles  20 . 
     It is illustrated above in FIGS. 1 and 2, a gear mechanism whereby a larger drive gear  33  drives a smaller secondary gear  39 . However, it is to be appreciated that the present invention is not to be limited to this type of gear relationship. It is possible that under some conditions it would be more advantageous to have almost a reverse relationship, whereby a smaller gear is driving a larger gear, without deviating from the inventive concept of the invention. 
     It is to be understood that the present invention is not limited to the sole embodiment described above, but encompasses all embodiments within the scope of the following claims.