Patent Publication Number: US-RE46696-E

Title: Prophy cup for dental handpiece

Description:
RELATED APPLICATIONS 
     The present applicationThis is a reissue application of U.S. patent application Ser. No. 13/247,941 filed Sep. 28, 2011 and issued Jul. 22, 2015, which claims the benefit of priority under 35 USC § 119(e) to U.S. Provisional Application provisional application No. 61/387,467, filed on Sep. 28, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is in the field of prophylactic devices for dental handpieces for remove deposits from surfaces of teeth. 
     2. Description of the Related Art 
     One of the most widely used prophylactic devices in the dental profession is known as a prophy cup. A typical conventional prophy cup has a smooth outer surface. The prophy cup is mounted on a dental handpiece. Prophy paste is picked up in the prophy cup and is applied against the tooth surface to remove the deposits. The prophy paste contains abrasive particles and when mixed with saliva it forms slurry. The slurry almost invariably entrains the patient&#39;s saliva to form an ever-enlarging rope-like mass which migrates along the surfaces of the cup. The rope-like slurry leaves the cup at its narrowest diameter. The slurry is not confined to the patient&#39;s mouth and can be ejected with sufficient velocity to create a contamination area that can be up to 40-50 inches wide and up to 30-40 inches high. The ejected slurry may contain blood-borne pathogens, which can raise the level of contamination. 
     SUMMARY OF THE INVENTION 
     Up until now, the phenomena of how the slurry (blood and saliva and pumice from polishing compound) is picked up by the cup and at what point the slurry leaves the cup was unknown. By using CFD (computation fluid dynamics), Applicants have determined that the saliva is picked up at the largest diameter of the cup (the flared portion of the cup that comes in contact with the tooth and the gums) and is released from the cup at its narrowest diameter. Since the outside of the traditional cup has a smooth surface, the saliva has a laminar flow and is more prone to separation. Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap. 
     The prophy cup disclosed herein in combination with an improved handpiece reduces the discharge of slurry from a patient&#39;s mouth during dental procedures. 
     One aspect of the disclosed embodiments is a prophy cup having an outer surface with dimples, which may be of varying sizes and shapes. The dimples are configured to increase the turbulent flow in the boundary layer to reduce the separation of the boundary layer. The added dimples minimize the quantity of a slurry of saliva, blood and pumice ejected from the surface of the cup. The dimples retain portions of the slurry as the slurry travels in a spiral from the distal portion of the prophy club to the proximal portion of the prophy cup. 
     Another aspect of the disclosed embodiments is a housing configured such that the housing is split longitudinally to allow installation of the shafts and gears to rotate the prophy cup. In addition, the housing includes a wiper to remove a slurry of saliva laden with blood and pumice as the prophy cup rotates proximate to the wiper. The wiper can be an integral part of the housing or added to the housing when the shafts and gears are installed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments in accordance with aspects of the present invention are described below in connection with the attached drawings in which: 
         FIG. 1  illustrates a perspective view of a conventional prophy cup with a smooth outer surface as viewed from the front and top; 
         FIG. 2  illustrates a perspective view of the conventional prophy cup of  FIG. 1  as viewed from bottom; 
         FIG. 3  illustrates a cross-sectional elevational view of the conventional prophy cup of  FIG. 1 ; 
         FIG. 4  illustrates a perspective view of an improved prophy cup in accordance with a dimpled outer surface view from the front and top; 
         FIG. 5  illustrates a perspective view of the improved prophy cup of  FIG. 4  viewed from bottom; 
         FIG. 6  illustrates a cross-sectional elevational view of the improved prophy cup of  FIG. 4 ; 
         FIG. 7  illustrates an enlarged cross-sectional view taken with the dashed circular area  7  in  FIG. 6 ; 
         FIG. 8  illustrates a side elevational view of an improved handpiece with the prophy cup of  FIGS. 4-7  mounted thereon; 
         FIG. 9  illustrates a perspective view of the handpiece and prophy cup of  FIG. 8  viewed from the proximal end of the handpiece; 
         FIG. 10  illustrates a perspective view of the handpiece and prophy cup of  FIG. 8  viewed from the distal end of the handpiece; 
         FIG. 11  illustrates an enlarged elevational side view of the proximal end of the handpiece and mounted prophy cup of  FIG. 8  further showing the flaring of the flareable distal end of the prophy cup when the distal end of the prophy cup is applied to a surface (not shown); 
         FIG. 12  is an elevational view of the housing of the handpiece showing the main housing portion and the hinged housing portion joined by a hinge portion and showing the features that align and interconnect the two housing portions; 
         FIG. 13  is a perspective view of the housing of  FIG. 13  after installing the shafts, the prophy cup and the wiper and before rotating the hinged housing portion to interconnect the two portion; 
         FIG. 14  is an enlarged perspective view of the proximal end of the hinged housing portion taken within the dashed circular area  14  of  FIG. 13  to show the openings that receive the tabs to interlock the two housing portions; 
         FIG. 15  is an enlarged perspective view of the main housing portion taken within the dashed circular area  15  of  FIG. 13  to show the tabs that interlock with the openings in  FIG. 14 ; 
         FIG. 16  is an enlarged perspective view of the hinged housing portion taken within the dashed circular area  16  of  FIG. 13  to show the alignment recesses; and 
         FIG. 17  is an enlarged perspective view of the main housing portion taken within the dashed circular area  17  of  FIG. 13  to show the alignment protrusions that engage the alignment recesses of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1, 2 and 3  illustrate a typical conventional prophy cup  100  used for polishing the surfaces of teeth during a dental procedure. The prophy cup is generally cylindrical but has a flareable distal portion  102  that transitions to a tapered middle portion  104  that extends from the flareable distal portion to an enlarged proximal portion  106 . The diameter of the prophy cup increases rapidly in a transition portion  108  between the tapered middle portion and the enlarged proximal portion. The proximal portion includes an engagement cavity  110  formed in an upper surface  112 . The engagement cavity is connectable to a shaft (not shown) of a conventional dental handpiece (not shown). The shaft is rotatable by a conventional power source to cause the prophy cup to rotate at a high angular velocity (e.g., 2,500 RPM) during a dental procedure. 
     As shown in more detail in the bottom view of  FIG. 2  and the cross-sectional view in  FIG. 3 , the flareable distal portion  102  and the tapered middle portion  104  of the conventional prophy cup  100  have a tapered distal bore  120  formed therein. The tapered distal bore in the illustrated prophy cup has a plurality of flutes  122  formed therein so that when pressure is applied to the prophy cup to force the distal end of the prophy cup against the surface of a tooth, the distal portion flares outward to expose the flutes to the surface of the tooth. In the illustrated prophy cup, the tapered distal bore includes a plurality of ribs  124  that provide internal support to the tapered middle portion for structural stability. Although illustrated with a fluted distal bore with ribs, it should be understood that the distal bore may have other configurations. Dental pumice applied to the distal portion of the prophy cup is transferred to the surfaces of teeth in a patient&#39;s mouth when the prophy cup is rotated during a dental procedure. 
     The conventional prophy cup  100  shown in  FIGS. 1, 2 and 3  has a smooth outer surface  130  that extends from the flared distal portion  102  to the enlarged proximal portion  106  via the tapered middle portion  104  and the transition portion  108 . 
     Applicants have discovered that that the pumice mixes with the patient&#39;s saliva, and in many cases mixes with the patient&#39;s blood, to create a slurry that forms on the surfaces of the flared distal portion  102  of the conventional prophy cup  100 . The slurry rapidly migrates in the proximal direction away from the flared distal portion to the tapered middle portion  104  and then to the enlarged proximal portion  106  via the transition portion  108 . Applicants have investigated the fluid flow characteristics of the conventional prophy cup and have determined that the smooth outer surface  130  causes the slurry to have a laminar flow, which causes the slurry to be prone to separation from the outer surface of the cup. In addition, the conventional prophy cup has a relatively abrupt diameter change in the transition portion between the tapered middle portion and the enlarged proximal portion, which causes an abrupt increase in surface velocity. The abrupt increase in surface velocity also contributes to the separation of the slurry from the outer surface of the prophy cup. 
     An improved prophy cup  200  shown in  FIGS. 4, 5 and 6  reduces the ejection of the rope-like slurry from the prophy cup during a dental cleaning procedure. The general structure of the improved prophy cup may be similar to the conventional prophy cup  100  of  FIGS. 1, 2 and 3  and is illustrated accordingly. In particular, the improved prophy cup of  FIGS. 4, 5 and 6  has a flared distal portion  202 , a tapered middle portion  204 , an enlarged proximal portion  206  and a transition portion  208  between the tapered middle portion and the enlarged proximal portion. The enlarged proximal portion includes a central cavity  210  that is engageable with a dental handpiece that rotates the prophy cup during a dental cleaning procedure. The improved prophy cup of  FIGS. 4, 5 and 6  further includes a tapered distal bore  220  with flutes  222  and ribs  224  similar to the flutes and ribs described above. 
     Unlike the conventional prophy cup  100  described above, the improved prophy cup  200  of  FIGS. 4, 5 and 6  has a dimpled outer surface  230 . In particular, substantially all of the outer surface of the improved prophy cup from the flareable distal portion  202  to the enlarged proximal portion  206 , except for a first undimpled band  240  and a second undimpled band  242 , has dimples formed into the surface. The first undimpled band lies between the enlarged proximal portion and the transition portion  208 . The second undimpled band lies between the transition portion and the tapered middle portion  204 . In alternative embodiments, the entire outer surface may be dimpled. 
     In the illustrated embodiment, the plurality of dimples include a first set of dimples  250  and a second set of dimples  252 . As shown in more detail in an enlarged portion of the dimpled outer surface  230  in  FIG. 7 , the dimples in the first set have larger diameters that the dimples in the second set. For example, in the illustrated embodiment, the dimples in the first set advantageously have diameters at the outer surface of approximately 0.41 millimeter, and the dimples in the second set advantageously have diameters of approximately 0.15 millimeter. The smaller-diameter dimples of the second set are interleaved with the larger-diameter dimples of the first set to provide a larger area of the outer surface that is covered by dimples. In the illustrated embodiment, each dimple extends into the outer surface of the prophy cup to a depth that is less than the spherical radius of the respective dimple. For example, the larger diameter dimples advantageously have a depth of approximately 0.1 millimeter, and the smaller dimples advantageously have a depth of approximately 0.03 millimeters. The diameters and depths of the dimples can be varied. 
     The dimples  250 ,  252  on the outer surface  230  of the improved prophy cup  200  introduce turbulent flow in the boundary layer on the outer surface. The turbulent flow reduces the separation of the slurry from the outer surface. The deeper the dimples and more the dimples on the surface, the more the saliva flow becomes turbulent. Even though dimples increase drag slightly when the lifting force experienced by rotating bodies are travelling through a medium, Applicants have determined that the dimples reduce the chances of saliva separation from the outer surface. 
     The dimples  222 ,  224  formed into the outer surface  220  of the improved prophy cup  200  introduces turbulent flow to the slurry on the outer surface. Furthermore, portions of the slurry enter the dimples while flowing over the dimples, which minimizes the chances of separation. Although the turbulent flow has more drag initially, turbulent flow provides better adhesion of the slurry to the outer surface, which causes the slurry to be less prone to separation. Turbulent flow also breaks the surface tension, etc. The drag coefficient on the outer surface of the prophy cup increases with dimple depth. The high drag coefficient reduces fluid velocities. 
       FIG. 8  illustrates a side elevational view of an improved handpiece  300  with the improved prophy cup  200  of  FIGS. 4-7  mounted thereon.  FIG. 9  illustrates a perspective view of the handpiece and prophy cup of  FIG. 8  viewed from the proximal end of the handpiece.  FIG. 10  illustrates a perspective view of the handpiece and prophy cup of  FIG. 8  viewed from the distal end of the handpiece.  FIG. 11  illustrates an enlarged elevational side view of the proximal end of the handpiece and mounted prophy cup of  FIG. 8  further showing the flaring of the flareable distal end  202  of the prophy cup when pressure is applied to the handpiece to force the distal end of the prophy cup against the surface of a tooth (not shown). 
     The improved dental handpiece  300  of  FIGS. 8-11  is useable in combination with the improved prophy cup  200  to further reduce the ejection of slurry from a patient&#39;s mouth. The dental handpiece includes a housing  310 , which has a proximal end  312  having a cavity  314  that is configured to be mountable to a conventional rotating power source (not shown). A notch  316  in the housing assures that the handpiece is aligned with the power source. 
     A first shaft  320  is centered within the cavity  314  of the housing  310  to receive the rotational power provided by the power source. The shaft rotates about a first axis (horizontal in  FIG. 8 ) and communicates the rotational power through the housing to a drive head  330  at the distal end of the housing. The drive head includes internal gears (described below) that drives a second shaft  332 , which rotates about a second axis (vertical in  FIG. 8 ). The distal end of the second shaft is coupled to the prophy cup  200  to rotate the prophy cup about the second axis. In the illustrated embodiment, the distal end of the second shaft includes a pair of barbs (or teeth) that extend outward from the second shaft. Preferably, the distal end of the second shaft is inserted into the mold when the prophy cup is formed so that the medical-grade silicone material forming the prophy cup flows around the barbs and engages the barbs. Accordingly, the completed prophy cup is securely attached to the second shaft and cannot slip with respect to the shaft when the shaft is rotated. 
     The improved dental handpiece  300  of  FIGS. 8-11  includes a wiper  340 , which is positioned below the housing  310  proximal to the drive head  330  and which extends downward proximal to the transition portion  208  and the tapered middle portion  204  of the prophy cup  200 . As shown in  FIGS. 8 and 11 , the wiper includes a first blade edge  342  that is positioned along the outer surface  230  of the prophy cup next to the transition portion of the prophy cup, and includes a second blade edge  344  that is positioned along the outer surface of the prophy cup next to the tapered middle portion of the prophy cup. The clearance between the first and second blade edges of the wiper and the outer surface of the prophy cup is minimized to enable the wiper to remove fluid from the outer surface of the prophy cup as the prophy cup rotates. For example, in certain embodiments, the clearance between the second blade edge and the tapered middle portion of the prophy cup varies from touching (or almost touching) at the proximal (upper in  FIGS. 8 and 11 ) portion of the second blade edge, which is juxtaposed with the undimpled band  242  in  FIG. 5 , to approximately 0.4 millimeter at the distal lower part of the second blade edge. Similarly, the clearance between the first blade edge and the transition portion of the prophy cup varies from touching (or almost touching) at the distal part of the first blade edge to approximately 0.1 millimeter at the proximal part of the first blade edge. The wiper causes the slurry to be removed from the outer surface of the prophy cup along the smaller outer diameter of the middle portion of the prophy cup before the slurry migrates proximally to the enlarged proximal portion of the prophy cup where the ejection forces are greater. The tighter clearance between the blade edges and the prophy cup near the proximal part of the tapered middle portion of the outer surface assures that substantially all of the slurry is removed prior to reaching the transition portion where the surface velocity increases as the diameter increases. Although the first blade edge and the second blade edge are shown as being relatively blunt in the illustrated embodiment, the wiper can be tapered so that one or both blade edges is thinner and thereby more flexible proximate to the outer surface of the prophy cup. In such embodiments, the blade edges of the wiper can positioned closer to the outer surface of the prophy cup. 
     The housing  310  of the improved handpiece  300  is preferably formed as a single molded structure similar to a “clam shell” configuration. In particular, as shown in  FIGS. 9 and 10 , and as shown in more detail in  FIGS. 12-17 , the housing comprises a main housing portion  400  and a hinged housing portion  410 . The two housing portions are joined at a longitudinal seam  420  and a semicircular transverse seam  422 . As illustrated the transverse seam is displaced from the proximal end  312  of the housing such that a proximal portion  424  of the housing surrounding the cavity  314  that engages the power source (not shown) is formed as a single molded, generally cylindrical, part that does not have any seams. Accordingly, the dimensions of the cavity in the proximal portion of the housing can be manufactured with close tolerances such that when the handpiece is mounted on the power source, the handpiece is held snugly on the power source and does not move with respect to the power source. 
     The main housing portion  400  and the hinged housing portion  410  are permanently joined together at a flexible hinge portion  430 , which allows the hinged housing portion to rotate from an open position (discussed below) to the closed position shown in  FIGS. 9 and 10 . In the position, the two housing portions are held together by a pair of tabs  432  (one shown in  FIGS. 9 and 10 ) formed as part of the main housing portion that engage a pair of openings  434  (one shown in  FIGS. 9 and 10 ) formed in the hinged housing portion. 
     As shown in  FIGS. 12-17 , the housing  310  in the illustrated embodiment is formed as a single molded structure with the main housing portion  400  and the hinged housing portion  410  interconnected by the flexible hinge portion  430 . For example, the two housing portions and the flexible hinge portion are injection molded with a medical-grade plastic material in a conventional manner. As discussed above, the proximal end portion  424  of the main housing portion has the cavity  130  314 formed therein as part of the injection process. The main housing portion includes the pair of tabs  432 , which are spaced apart from the hinge portion by substantially the same distance as the pair of openings  434  formed in the hinged housing portion. The main housing portion also includes a pair of generally oval-shaped protrusions  450 , and the hinged housing portion includes a pair of generally oval-shaped recesses  452  that are sized to receive the protrusions. The protrusions are spaced apart from the hinge portion by substantially the same distance as the recesses. 
     When the hinged housing portion  410  is rotated about the flexible hinge portion  430 , the pair of protrusions  450  on the main housing portion are inserted into the pair or recesses  452  in the hinged housing portion to align the hinged housing portion with the main housing portion. In addition, the tabs  432  on the main housing portion enter into and engage with the openings  434  in the hinged housing portion to fixedly secure the two housing portions together. Thus, the tabs and the openings operate as snap joints. 
     As further shown in  FIG. 12 , the main housing portion  400  includes first half  470  of a first channel that extends to the drive head  330 . A corresponding second half  472  of the first channel extends to the drive head in the hinged housing portion  410 . When the two housing portions are secured together the two halves of the first channel form a cylindrical channel that supports the first shaft  320 . As shown in  FIG. 13 , the first shaft advantageously includes a pair of enlarged cylindrical portions  474  that act as bearings for the first shaft and that center the first shaft in the cylindrical channel. The first shaft is relatively long with respect to the diameter. By providing the enlarged cylindrical portions at spaced apart locations on the first shaft, the cross section of the first shaft varies along the length of the first shaft. The varying cross section reduces harmonics that might otherwise be produced on the first shaft. 
     As further shown in  FIG. 12 , the main housing portion  400  includes an first half  480  of an enlarged cavity in the drive head  330 , a first half  482  of an upper bearing chamber and a first half  484  of a lower bearing channel. The hinged housing portion  410  includes a respective second half  490  of the enlarged cavity, a respective second half  492  of the upper bearing chamber and a respective second half  494  of the lower bearing channel. 
     As shown in  FIG. 13 , prior to rotating the hinged housing portion  410  and interconnecting the hinged housing portion with the main housing portion  400 , the first shaft  320  is positioned in the first half  470  of the first channel. A first bevel gear  500  attached to the first shaft is positioned in the first half  480  of the enlarged cavity in the drive head  330 . The second shaft  332  is positioned in the first half  484  of the lower bearing channel. A second bevel gear  510  attached to the second shaft is positioned in the first half of the enlarged cavity with its respective teeth engaged with the respective teeth of the first bevel gear. An extended portion  512  of the second shaft is centered within the first half  482  of the upper bearing channel. When the hinged housing portion is engaged with the main housing portion, the respective second halves of the cavity and the channels are aligned with the respective first halves of the cavity and the channels maintain the proper alignment of the two shafts so that rotation of the first shaft results in rotation of the second shaft via the two bevel gears. 
     As further shown in  FIG. 12 , the main housing portion  400  includes a first half  530  of a recessed channel positioned proximal to the drive head  330 . An oval-shaped protrusion  532  extends from the first half of the recessed channel. As shown in  FIG. 13 , the proximal portion of the wiper  340  includes an oval-shaped through-bore  534  that is sized and shaped to receive the third protrusion when the proximal portion of the wiper is positioned in the recessed channel. The proximal portion of the wiper fits snugly within the recessed channel. When the hinged housing portion  410  is engaged with the main housing portion, a second half  540  of the recessed channel in the hinged housing portion also constrains the upper portion of the wiper. The combined effects of the two halves of the recessed channel and the third protrusion prevent the wiper from moving in any direction. Thus, the wiper is properly positioned with respect to the prophy cup  200  as described above. 
     In an alternative embodiment (not shown), the wiper  340  may be formed as an integral part of either the main housing portion  400  or the hinged housing portion. 
     In an alternative embodiment (not shown) of the housing  310 , the main housing portion  400  and the hinged housing portion  410  are secured together by ultrasonic welding of the medical-grade plastic material. The ultrasonic welding may be used instead of the tabs and openings described above or in addition to the tabs and openings. 
     In certain embodiments (not shown) of the housing  310 , the outer surfaces of the main housing portion  400  and the hinged housing portion may be knurled to enhance a user&#39;s ability to grip the handpiece. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all the matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.