Patent Publication Number: US-10765491-B2

Title: Dental handpiece and prophy angle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application which claims priority to U.S. patent application Ser. No. 14/736,518, filed Jun. 11, 2015, the entire disclosure of which is incorporated herein. 
    
    
     FIELD 
     The present disclosure relates to a prophy angle and a dental handpiece for connection to and for powering the prophy angle. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Dental prophylaxis angles, generally referred to as “prophy angles”, are commonly used dental instruments providing rotation for dental tools such as brushes, prophy cups, or other receptacles used in polishing teeth. A prophy angle typically includes a housing having a neck and a head portion extending at approximately a 90° angle to the neck, which increases the ability of a dentist to access the varying teeth surfaces of a patient. A drive shaft may be located within the housing and attached to a driven gear in the head of the prophy angle. 
     Prophy angles are generally affixed to a handpiece, for powering and driving the prophy angle drive shaft. The handpiece may be powered by any number of sources, such as pneumatic, electrical, or batteries. Prophy angles are commonly manufactured from lightweight plastic to make them inexpensive enough to be disposable, thereby increasing overall sterility in the dental environment. An issue associated with making the prophy angles, and their constituent elements, such as the driven gear and drive shaft, from plastic is the ability of the handpiece to engage the drive shaft and the driven gear without excessive damage to the prophy angle. 
     A reduction in the number of component parts needed for constructing and assembling a prophy angle is desirable. In addition, designing the component parts to cooperatively operate with other component parts reliably and in an efficient manner is also desirable. 
     A standard well known doriot-style prophy angle includes a generally cylindrical or frustoconical inner wall that mates with a similarly-shaped nosecone of a handpiece. In addition, the doriot-style prophy angle typically includes a notched section that fits with a mating protrusion on the handpiece to key or orient the prophy angle with respect to the handpiece. For a handpiece having an angle-adjustable nosecone, the notched section and frictional forces may provide an unsatisfactory fixation force, between the prophy angle and the nosecone, not allowing the desired angle of the nosecone to be reliably locked and unlocked, during a procedure, because the prophy angle may slip/rotate with respect to the nosecone. Therefore, for a handpiece nosecone having an adjustable angle, providing an easy, quick, and reliable way of adjusting the angle and setting or locking the desired angle is desirable. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     One example disclosed is a combination of a dental handpiece and a prophy angle. The dental handpiece may include a body and a nosecone threadably connected to a distal portion of the dental handpiece. The prophy angle may include a proximal body such that the prophy angle proximal body is matingly attached to the nosecone. A plurality of elongated torque members may be formed on each of the prophy angle proximal body and the nosecone, wherein each of the plurality of elongated torque members is one of a male torque member and a female torque member, such that each male torque member formed on one of the prophy angle proximal body and the nosecone matingly couples with a female torque member formed on the other of the nosecone and the prophy angle proximal body. The prophy angle, including the plurality of elongated torque members formed on the prophy angle, is formed to also be attachable to a known standard doriot-style nosecone. 
     Another example disclosed is a prophy angle having a proximal body for attachment to a dental handpiece nosecone and a head formed on a distal end of the proximal body. A gear assembly may be a combination of a face-gear and a spur-gear. A drive shaft may be rotatably held within the proximal body, including one of the face-gear and the spur-gear formed on a distal end of the drive shaft. A rotor assembly includes a portion rotatably held within the head and the other of the face-gear and the spur-gear may be formed on the rotor assembly such that the rotor assembly is driven by the drive shaft via the gear assembly. A bearing member may form a portion of the rotor assembly and may be rotatably held within the head. The bearing member is symmetrical about a rotation axis of the rotor assembly. A mating bearing member may be attached distally with respect to the drive shaft distal end such that the bearing member matingly couples with the mating bearing member as the drive shaft and the rotor assembly are rotated. The bearing member contacts less than half of the mating bearing member during rotation and structure may form a void radially inward with respect to a plurality of teeth forming the face-gear. 
     A further example disclosed is a dental handpiece for rotatably driving a dental tool including a body and a nosecone connected to a distal portion of the dental handpiece, wherein the nosecone is for coupling with a prophy angle. An engine cartridge may be held within the body and is sized and adapted for containing one of a plurality of engine types. The engine cartridge further may include a drive member extending from an engine cartridge distal end, the drive member being rotatably driven by one of the plurality of engine types and the engine cartridge including a proximal end for connection to one of a plurality of types of power source connectors. A proximal end of the body includes structure for connection to each of the plurality of types of power source connectors. 
     Another example disclosed is a dental prophy cup having a body with a proximal portion and a distal portion. A cup may be formed on the body distal portion. A rotor cavity may be formed within the body proximal portion. A rotor contact surface may form a portion of the rotor cavity and have a profile for matingly coupling with a rotor surface. 
     Still another example disclosed is a dental prophy angle having proximal body for attachment to a dental handpiece nosecone. A drive shaft may be rotatably held within the proximal body and extend beyond a proximal end of the prophy angle. A retainer may be held within the proximal body and surround a portion of the drive shaft, a distal end of the retainer may form a bearing surface for a gear attached to a distal end of the drive shaft. A retention boss may be formed on and surround the retainer. A cross-section of the retention boss may taper to an outer edge. A retention groove may be formed in the proximal body for mating attachment with the retention boss such that a portion of the retention boss is compressed within the retention groove. 
     Yet another example disclosed is a dental prophy angle having a proximal body for attachment to a dental handpiece nosecone and a head formed on a distal end of the proximal body. A rotor assembly may include a portion rotatably held within the head and a retention flange extending radially from the rotor assembly. A retention boss may extend from an interior surface of the head and be located above the rotor assembly retention flange. The retention boss forms an arc of less than three hundred sixty degrees. 
     A yet further example disclosed is a dental handpiece having a body; and a nosecone assembly attached to a distal end of the body. The nosecone assembly may include a proximal base section for attachment to the handpiece body distal end. A ball nose may be pivotally engaged with the proximal base section. A ball lock may surround a portion of the proximal base section and a portion of the ball nose. A flexible ring seal may surround a portion of the ball nose and may be positioned between the ball nose and an interior surface of the ball lock. A nosecone may be threadably coupled with the ball nose. A locking seal may surround a distal portion of the ball lock and a proximal portion of the nosecone. As the nosecone is increasingly threaded onto the ball nose, a frictional contact force is increased between the ball lock and each of the proximal base section, the ball nose, and the locking seal. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a modified exploded perspective of an example dental handpiece and a prophy angle; 
         FIG. 2  is a partial cross section of the handpiece of  FIG. 1 ; 
         FIG. 3  is an exploded perspective of a portion of the handpiece of  FIG. 1 ; 
         FIG. 4  is a perspective of a portion of the handpiece of  FIG. 1 ; 
         FIG. 5  is a perspective of a body portion of the handpiece of  FIG. 1 ; 
         FIG. 6  is an exploded perspective of  FIG. 4 ; 
         FIG. 7  is another example of a portion of  FIG. 6 ; 
         FIG. 8  is yet another example of a portion of  FIG. 6 ; 
         FIG. 9  is a modified exploded view of the example prophy angle of  FIG. 1 ; 
         FIG. 10  is a partial perspective of a portion of  FIG. 9 ; 
         FIG. 11  is a partial perspective of a portion of the example prophy angle; 
         FIG. 12  is a partial perspective detailing a connection between to components of  FIG. 9 ; 
         FIG. 13  is a partial perspective of a portion of the example prophy angle; 
         FIG. 14  is a perspective of an example prophy cup; 
         FIG. 15  is a partial cut-away elevation of the example prophy cup; 
         FIG. 16  is a partial perspective of an example prophy angle with an attached prophy cup; 
         FIGS. 17A and 17B  illustrate example hand grips of a user for an example handpiece; and 
         FIG. 17C  is a distal end elevation showing example finger recesses of an example handpiece. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     An example combination of a dental handpiece  10  and a prophy angle  12  are shown in  FIG. 1 . The dental handpiece  10  may include a body  14  and a nosecone  16  threadably connected to a distal portion  18  of the dental handpiece  10 . The prophy angle  12  may include a proximal body  20  such that the prophy angle proximal body  12  may be matingly attached to the nosecone  16 . The operation of the example nosecone  16  and similar nosecones are known and therefore not described in detail. Generally, in the example disclosed, the nosecone  16  may be pivoted with respect to the handpiece  10  and locked at the desired angle by increasingly threading the nosecone onto the handpiece  10  until the nosecone is locked in place. More detailed explanations of similar nosecones, particularly details of the pivot structure, are provided in at least U.S. Pat. No. 8,834,159. 
     A plurality of elongated torque members may be formed on each of the prophy angle proximal body  20  and the nosecone  16 . Each of the plurality of elongated torque members may be one of a male torque member and a female torque member, such that each male torque member formed on one of the prophy angle proximal body  20  and the nosecone  16  matingly couples with a female torque member formed on the other of the nosecone  16  and the prophy angle proximal body  20 . In the example of  FIG. 1 , the nosecone  16  has a plurality of male torque members  22  (one torque member  22  is not seen in the  FIG. 1  view) and the proximal body  20  may have a corresponding number of female torque members  24 . In other examples the male torque members may be formed on the proximal body  20  with corresponding female torque members formed on the nosecone  16 . As explained in more detail below, when in use, the mated torque members  22  and  24  provide a user grasping the proximal body with significant leverage to tighten and loosen the nosecone with respect to the handpiece  10  to select and set a desired angle of the nosecone with respect to the handpiece  10 . Without the torque members, attempting to tighten or loosen the nosecone  16 , during a procedure, may easily result in the prophy angle slipping and rotating about the nosecone; consequently, attaining the proper amount of leverage to loosen or tighten the nosecone may not be possible. 
     In addition, the prophy angle  12 , including the plurality of elongated torque members  24  formed on the prophy angle  12 , may be formed to also be attachable to a known standard doriot-style nosecone. This is accomplished, in the example of  FIG. 1 , by forming the inner wall  26  to have a diameter that mates with a standard doriot-style nosecone. Said another way, a portion of the proximal body forming inner wall  26 , not including structure forming the three female torque members  24 , frictionally attaches to the known standard doriot-style nosecone (not shown). For example, a standard doriot-style nosecone and a standard doriot-style prophy angle have dimensions as described in the American National Standard Institute/American Dental Association (ANSI/ADA) Specification No. 85—Part 1 (Aug. 25, 2004). All references, in the disclosed examples, to standard doriot-style nosecones and prophy angles and their respective parts should comply with this ANSI/ADA specification. Therefore, the inner wall  26  should have a diameter slightly larger to allow the prophy angle to be pushed on and pulled off of the standard doriot-style nosecone; yet, sized so that the proximal body is matingly coupled to the nosecone via a frictional interference. Additionally, the notch shown at  28  allows the prophy angle  12  to fit around mating structure of a standard doriot-style handpiece. It is also noted that, for clarity, the prophy angle  12  of  FIG. 1  does not show any of the drive shaft, a rotary assembly, or a prophy cup. 
     In the example shown, the nosecone  16  includes three male torque members  22  and the prophy angle  12  includes three female torque members  24 , though other configurations and numbers of torque members  22 ,  24  may be used, depending on the design and specification requirements. Further, the nosecone  16 , including the plurality of elongated torque members  22  formed on nosecone, may be formed to prevent attachment to a known standard doriot-style prophy angle. That is to say a circumference defined by a top surface of each of the three male torque members  22  is sufficiently large to prevent the attachment of the nosecone  16  to the known standard doriot-style prophy angle. In this way only prophy angles  12  with mating torque members may be attached to nosecone  16  to ensure that a sufficient amount of force may be transferred to the nosecone  16  to ensure that the nosecone is locked relative to the body  14  during use. 
     It is noted that in another example (not shown) the mating torque members may be switched; such that the male torque members may be formed on the prophy angle proximal body and the female torque members may be formed on the nosecone or a combination of male and female torque members may be formed on each of the prophy angle proximal body and the nosecone. Said another way, a plurality of elongated torque members may be formed on the nosecone, wherein each of the plurality of elongated torque members is one of a male torque member and a female torque member, such that each male torque member formed on the nosecone is for matingly coupling with a female torque member formed on a mating prophy angle proximal body. In this example, similar to the  FIG. 1  example, a circumference of an outermost top surface of the nosecone may be sufficiently large to prevent the attachment of the nosecone to the known standard doriot-style prophy angle. 
     The distal portion  18  may include a locking seal  30  and a ball lock  32  and related components contained within the locking seal  30  and the ball lock  32 , as shown in  FIG. 2 . Of course, distal portion  18  may include other structure; for example, if the handpiece  10  does not have the capability of adjusting the angle of the nosecone  16  relative to the body  14 , then much of the structure shown in  FIG. 2  is not necessary, as those skilled in the art will appreciate. The example of  FIG. 2  shows nosecone  16  threadably connected to distal portion  18  at  34 . In this example, the distal portion  18  includes a ball nose  36  for the threaded attachment of nosecone  16 . 
     The example of  FIG. 2  may be described as a nosecone assembly attached to the body  14 , where the nosecone assembly includes a proximal base section  38  for attachment to the handpiece body  14 , the ball nose  36  pivotally engaged with the proximal base section  38 , the ball lock  32  surrounding a portion of the proximal base section  38  and a portion of the ball nose  36 , a flexible ring seal  40  surrounding a portion of the ball nose  36 , wherein the flexible ring seal  40  is positioned between the ball nose  36  and an interior surface of the ball lock  32 , the nosecone  16  threadably coupled with the ball nose  36 , the locking seal  30  for surrounding a distal portion of the ball lock  32  and a proximal portion of the nosecone  16 . In this example, as the nosecone  16  is increasingly threaded onto the ball nose  36 , a frictional contact force is increased between the ball lock  32  and each of the proximal base section  38 , the ball nose  36 , and the locking seal  30 . This allows a desired angle of the nosecone  16  to be set relative to the body  14  of handpiece  10  in a quick, efficient manner. 
       FIG. 2  shows further structure, not referenced, that is used to drive a prophy angle  12  attached to the nosecone  16 . 
       FIG. 3  is an exploded view of a portion of the components of  FIG. 2 . The proximal base section  38  may be formed of aluminum to provide light weight, durable construction. The ball nose  36  may be formed of aluminum, including at least a partially anodized exterior surface  42 . By anodizing the exterior surface  42  (generally the spherical portion of ball nose  36 ) a useful life of ball nose  36  may be extended by increasing the resistance to wear compared to a non-anodized part. The ball lock  32  may be formed of aluminum, including at least a partially anodized exterior surface  44 . Anodizing ball lock  32 , at least at surface  44  may increase the useful life of ball lock  32  by increasing the wear resistance of surface  44  compared to a non-anodized surface. The nosecone  16  may be formed of aluminum, including at least a partially anodized exterior surface such as the surface that frictionally contacts a mating prophy angle (not shown in  FIG. 3 ). Again, anodizing the exterior surface of nosecone  16  may extend the useful life of nosecone  16 . The locking seal  30  may be formed of a suitable plastic and may have a portion of an interior surface  46  roughened. The roughened interior surface  46  is in frictional contact with anodized surface  44  of ball lock  32  and the roughened interior surface  46  may increase the effective locking force when a user applies torque to the nosecone  16  to lock-in a desired angle. In this manner, at least a frictional contact surface of each of the ball nose  36 , the ball lock  32 , and the locking seal  30  may be roughened for enhancing the frictional contact force. In the example of  FIG. 3 , the roughened frictional contact surfaces may include  42 ,  44 , and  46 . The interior surface (not shown in  FIG. 3 ) of base portion  38  that contacts surface  42 , may also be roughened. 
       FIG. 3  also shows threads  48  on ball nose  36  and threads  50  on nosecone  16  that together form the threaded connection  34  shown in  FIG. 2 . 
       FIG. 3  further shows that a plurality of finger recesses  52  and  54  equally spaced and formed around a periphery of each of the ball lock  32  and the locking seal  30 . Interestingly, during development of handpiece  10 , it was discovered that handpieces where a number of finger recesses  52 ,  54  are an integer multiple of three provides a user with a comfortable, stable grip as explained in detail below. The example shown includes nine finger recesses  52  and  54 , though other integer multiples of three may also be acceptable, such as 3, 6, 12, or the like. 
     In addition to the dental handpiece  10  including body  14  and the nosecone  16  connected to a distal portion  18 , the dental handpiece  10  may also include an engine cartridge held within the body  14 . The engine cartridge may be sized and adapted for containing one of a plurality of engine types. An example engine cartridge  56  is shown in  FIG. 4 . The engine cartridge  56  may further include a drive member  58  extending from an engine cartridge distal end  60 . The drive member  58  may be rotatably driven by one of the plurality of engine types, as explained further below. The engine cartridge  56  also includes a proximal end  62  for connection to one of a plurality of types of power source connectors  64  (and  78 ,  82  described below). A proximal end of the body  14  includes structure, such as threads  65  shown in  FIG. 5 , for connection to each of the plurality of types of power source connectors  64 . In the example shown in  FIG. 4 , the base portion of power source connector  64  may be formed with threads  66  to mate to threads  65  formed in body  14 . However, in other examples different structure for connection between the power source connectors  64  and body  14  may be used. For example, the boss or raised edge  68  may form a part of a snap-fit with body  14 . 
     Each of the power source connectors  64  may include appropriate connections between the particular engine type and the power source for that engine type. The example, shown in  FIG. 4 , includes a pneumatically-driven motor and the connections to the power source (not shown) include an air supply line  70  for supplying pressurized air to drive the motor and an exhaust line  72  for routing exhausted air to a muffler (not shown) or other remote location.  FIG. 6  shows the engine cartridge of FIG.  4  in exploded form.  FIG. 6  shows an example engine  74  that rotatably drives drive member  58  via a drive assembly  76 . The example drive assembly  76  includes a planetary gear assembly that is driven by a mating gear (not shown) on the engine  74 . Of course, other appropriate drive arrangements may be utilized. The plurality of engine types may include an AC electrical motor, a battery-powered electrical motor, a pneumatically-driven motor, or any other appropriate type of engine to drive a prophy angle. Each engine type requires a corresponding power source connector. In the example of  FIGS. 4 and 5 , power source connector  64  is for a pneumatically-driven motor  74 . For an AC electrical motor, a corresponding power source connector  78  is shown in  FIG. 7  and includes an electrical cable  80  for connection to an electrical power source (not shown) such as a wall outlet. For a battery-powered electrical motor, a corresponding power source connector  82  is shown in  FIG. 8  and includes a cap  84  that may be removed to insert batteries within connector  82 . Example engines  74  may include any appropriate engine including motors specially designed for the example dental handpiece or commercially available engines from a variety of manufacturers. The use of off-the-shelf commercially produced engines is likely to be the most cost-effective, as these engines are typically produce in large quantities, thus reducing individual engine cost. It is also noted that each engine may include associated engine controller circuitry (not shown) for controlling the speed and other characteristics depending on the type of engine used. 
     The modular construction of the engine cartridge  56  and its associated component parts allows a manufacturer to reuse many components and reuse component parts even while providing customers with a range of power sources for handpiece  10 . For example, through careful design and component selection it may be possible to make and sell a pneumatic, AC electrical, and a battery powered handpiece where all three different power options use the same body  14 , engine cartridge  56 , and drive assembly  76 . Only the power source connectors need be different for each corresponding engine type. Compared to designs where each type of power source is individually designed, the disclosed modular engine cartridge designs allows for a significant reduction in the number of components needed to be held in inventory and because of the significant reuse of components across power source options the reuse components may be built and purchase in significantly greater volumes further reducing the per piece component cost. 
     The prophy angle  12  of  FIG. 1  is shown in cross section in  FIG. 9  in a modified exploded view of an example prophy angle  12 . Prophy angle  12  includes the proximal body  20 . A plurality of elongated torque members  24  may be formed on the prophy angle proximal body  20 . Each of the plurality of torque members  24  may be one of a male torque member and a female torque member, such that each male torque member formed on the prophy angle proximal body is for matingly coupling with a female torque member formed on a mating dental handpiece nosecone. In the example shown in  FIG. 9 , each of the three torque members  24  is a female torque member and mates with a corresponding male torque member on nosecone  16 ; however, each female torque member does not necessarily need to mate with a male torque member. As stated above, the prophy angle  12 , including the plurality of elongated torque members  24  formed on the prophy angle, is formed to also be attachable to a known standard doriot-style dental handpiece nosecone. This is accomplished in the example shown, by having the diameter of inner wall  26  mate with the known standard doriot-style dental handpiece nosecone via a frictional interference. 
     The prophy angle  12  may also include a head  86  formed on a distal end of the proximal body  20  as shown. The prophy angle  12  may further include a gear assembly comprising a combination of a face-gear and a spur-gear, comprised of component parts described below. 
     A drive shaft  88  may be rotatably held within the proximal body  20  and may include one of the face-gear and the spur-gear formed on a distal end  90  of the drive shaft  88 . In the example shown, distal end  90  has a face-gear  92  attached. A rotor assembly  94  may include a portion, shown generally at  95 , rotatably held within the head  86 . The rotor assembly  94  may further include the other of the face-gear and the spur-gear formed on the rotor assembly such that the rotor assembly  94  is driven by the drive shaft via the gear assembly. In the example shown, rotor assembly  94  includes the spur-gear  96 . 
     A bearing member  98  may form a portion of the rotor assembly  94  and is rotatably held within the head  86 . The bearing member  98  is symmetrical about a rotation axis  100  of the rotor assembly  94 . A mating bearing member  102  may be attached distally with respect to the drive shaft distal end  90  such that the bearing member  98  matingly couples with the mating bearing member  102  (a concave surface shown below that mates with the curved convex surface of bearing member  98 ) as the drive shaft  88  and the rotor assembly  94  are rotated. The bearing member  98  contacts less than half of the mating bearing member  102  during rotation and is shown in more detail below. In the example shown, only the semi-spherical bearing member  98  contacts the mating bearing member  102  during rotation. The flat portion  104  and the tapered portion  106  are formed to not contact mating bearing member  102  during rotation. This ensures that the no opposing rotational forces are encountered between bearing member  98  and mating bearing member  102 . If bearing member  98  contacted more than half of mating bearing member  102 , the other half of mating bearing member  102  would be rotating in an opposite direction of bearing member  98  causing unwanted resistance to the desired rotation of rotor assembly. Such unwanted resistance may require a greater driving force from handpiece  10  and could create undesirable heat build-up in the gear assembly. In addition, structure may form a void  108  radially inward with respect to a plurality of teeth  110  forming the face-gear  92 , as shown in  FIG. 10 . The void  108  provides space for the insertion of lubricant that is well-placed to lubricate the gears  92  and  96  to further assist in smooth, easy rotation of the rotor assembly  94 . 
     The bearing member  98  of the disclosed example may include a convex bearing surface as shown and the mating bearing member  102  may include a mating concave bearing surface  112 , shown in  FIG. 10 . Other mating bearing configurations may be used; for example, the bearing member could be formed from a flat, chamfered surface and mate with a corresponding flat, chamfered surface of the mating bearing member. The mating bearing member  102  may further include structure defining a central void  114  extending below the concave bearing surface  112 . The central void  114  further reduces the contact surface between the bearing member  98  and the mating bearing member  102 . In addition, the central void  114  has a benefit during manufacturing of providing a gate release location for injection molding the drive shaft  88 , face-gear  92 , and the mating bearing member  102  as a single unit. The central void  114  accommodates any material remnants from the gate release, thus reducing potential labor needed post-injection to knock-off remnant material and smooth the bearing surface  112 . This assists in enabling the manufacture of reliable components at a reduced cost, compared to a bearing surface  112  formed without central void  114 . 
       FIG. 11  shows the gear assembly of face-gear  92  and spur-gear  96  without head  86 . This view illustrates the relationship between bearing member  98  and mating bearing member  102  where bearing member  98  contacts less than half of the mating bearing member  102  during rotation. 
     Referring back to  FIG. 9 , dental prophy angle  12  may include the proximal body  20  for attachment to a dental handpiece nosecone  16  and the drive shaft  88  rotatably held within the proximal body  20 . The drive shaft  88  may also extend beyond a proximal end of the prophy angle  12 . A retainer  116  (shown in cross section) may be held within the proximal body  20  surrounding a portion of the drive shaft  88 . A distal end  118  of the retainer  116  may form a bearing surface for the gear  92  attached to the distal end  90  of the drive shaft  88 . A retention boss  120  may be formed on and surrounding the retainer  116 , wherein a cross-section of the retention boss tapers to an outer edge  122 , as shown. A retention groove  124  may be formed in the proximal body  20  for mating attachment with the retention boss  120  such that a portion of the retention boss  120  is compressed within the retention groove  124 . This is best shown in  FIG. 12  that illustrates the connection between the retention boss  120  and the retention groove  124  in detail. The dashed line illustrates where outer edge  122  would lie in an uncompressed state compared to the compressed state shown. This compression of retention boss  120  within retention groove  124  provides a robust connection and ensures that drive shaft  88  aligns face-gear  92  and mating bearing member  102  properly with spur-gear  96  and bearing member  98  during use, as force is applied to the prophy angle  12  against a patient&#39;s teeth. An exterior of the retainer  116  may also include at least one raised annular rib  126  for frictional contact with the proximal body  20 . The annular rib  126  is shown as a dashed line because it is optional. The raised annular rib  126  may provide additional frictional contact with the proximal body  20 . 
     The dental prophy angle  12  may include the proximal body  20  for attachment to a dental handpiece nosecone  16 , the head  86  may be formed on a distal end of the proximal body  20  and the rotor assembly  94 , including the portion  95  rotatably held within the head  86 . The rotor assembly may further include a retention flange  128  extending radially from the rotor assembly  94  as shown in  FIG. 9 . A corresponding retention boss  130  may extending from an interior surface of the head  86  and is located above the rotor assembly retention flange  128  when the rotor assembly  94  is mounted within head  86 . The retention boss  130  may form an arc of less than three hundred sixty degrees. Forming the retention boss  130  at less than a full, complete, three hundred sixty degree ring allows room for an injection molding form to be pulled from head  86  without stressing and deforming the shape of the opening in head  86 . The retention boss  130  is best seen in  FIG. 13 . 
     The prophy angle  12  and rotor assembly  94  may further include a button  132  with a plurality of radial protrusions  134 . The button  132  and radial protrusions  134  are for frictional contact with a dental prophy cup. The button  132  and protrusions  134  are only one example and they may have any appropriate form factor for non-slip engagement with a prophy cup during use. 
     The dental prophy cup  136  may include a body  138  having a proximal portion  140  and a distal portion  142 , as shown in  FIGS. 14 and 15 . A cup  144  may be formed on the body distal portion  142 . A rotor cavity  146  may be formed within the body proximal portion  140 . A rotor contact surface  148  forms a portion of the rotor cavity  146  including a profile for matingly coupling with a rotor surface (such as the button  132  and radial protrusions  134  shown in  FIG. 9 ). The rotor contact surface  148  profile may include a plurality of radial recesses  150  for matingly coupling with the plurality of radial protrusions  134  formed on a top surface of the prophy angle rotor  94 . Providing mating surfaces between the prophy cup  136  and the rotor assembly  94  including the mating radial recesses  150  and radial protrusions  134  positive, robust, non-slip contact is achieved, even as the rotor assembly is rotated at a high rate and force is applied against a patient&#39;s teeth. 
     The dental prophy cup  136  may further include a proximal end  152  of the body  138  forming a skirt  154  for surrounding a flange  156  (shown in  FIG. 9 ) of the prophy angle rotor  94 . The flange  156  is held externally with respect to the head  86  of the prophy angle  12  when the rotor assembly  94  is mounted within the head  86 . The skirt  154  acts as a rotating seal to reduce the amount and likelihood of moisture and debris entering inside head  86  during use, thus helping to provide reliable, stable, smooth rotation of the prophy cup  136 .  FIG. 16  shows a partial perspective view of prophy angle  12  with prophy cup  136  mounted on the rotor assembly  94  (not seen) that is held within head  86 . Prophy cup  136  may be formed of silicone or other appropriate pliable resilient material that will stretch to be placed over the button  132  and flange  156  and that will deform against a patient&#39;s teeth under pressure during use. 
       FIGS. 17A, 17B, and 17C  are examples showing the benefits of providing handpieces  10  with an integer multiple of three number of finger recesses  52 ,  54 . Such an integer multiple of three number provides a user with a comfortable, stable grip because a typical position of a user&#39;s fingers  158  gripping a handpiece  10  will be as shown in  FIG. 17A . This position may be described as creating an equilateral triangle between the contact points of each finger  158  and the handpiece  10 . The equilateral triangle is shown in  FIG. 17B , where a user&#39;s fingers  158  are shown without handpiece  10  so that equilateral triangle  160  may be clearly shown. It is also noted that the hand grip of  FIG. 17A  is slightly different from the hand grip of  FIG. 17B , yet the equilateral triangle is still formed.  FIG. 17C  shows an end view of an example handpiece  10 , with finger recesses  52 ,  54 , and with the equilateral triangle  160  showing a typical hand grip contact points. The example shown is with respect to finger recesses  52  but the same explanation applies to finger recesses  54 . It was discovered that providing an integer multiple of three number of finger recesses spaced about the periphery of handpiece  10  provides a user with a comfortable, reliable, and consistent hand grip location. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.