Patent Publication Number: US-2023135224-A1

Title: Dental handpiece and dental handpiece with cleaning adapter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on Japanese Patent Applications No. 2021-178835 filed on Nov. 1, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a dental handpiece and a dental handpiece with a cleaning adapter to which the cleaning adapter for supplying a cleaning liquid into the dental handpiece is connected. 
     BACKGROUND ART 
     There is known a dental handpiece for removing dental calculus and the like by using ultrasonic waves (for example, see JP-A-2012-235979). A dental handpiece disclosed in JP-A-2012-235979 includes an ultrasonic vibrator, a disinfectant flow path, a glass rod serving as an optical path for irradiating an affected area with light from a light source, and the like, and a scaler tip is attached to a tip end of the handpiece during treatment of a patient. 
     In a cleaning treatment including dental calculus removal, protein or the like contained in blood or saliva may splash and remain in a gap between the glass rod and a tip holding portion of the handpiece. Such residues are going to be treated in cleaning, disinfection, and sterilization processes of the dental handpiece after the treatment. 
     However, in the cleaning and sterilization processes described above, it is necessary to disassemble a part of the dental handpiece to facilitate treatment of the residues inside the handpiece, and an operation therefor is complicated. 
     Therefore, an object of the present disclosure is to provide a dental handpiece and a dental handpiece with a cleaning adapter, capable of sufficiently cleaning inside of the handpiece without disassembling the handpiece . 
     SUMMARY OF INVENTION 
     According to an aspect of t the present disclosure, (1) A dental handpiece includes:
     a cylindrical outer body;   an insert body that includes an ultrasonic vibrator, and is configured to be accommodated in the outer body, a front end portion of the insert body closing a front end of the outer body and a rear end portion of the insert body closing a rear end of the outer body;   a tip connection portion that is provided at the front end portion of the insert body and that detachably holds a scale tip to which ultrasonic vibration from the ultrasonic vibrator is transmitted; and   a cleaning liquid flow path that guides a cleaning liquid supplied from a cleaning liquid injection port of the insert body to a front end portion of the outer body,   wherein the cleaning liquid flow path includes an immersion flow path in which the insert body is immersed in the cleaning liquid in the outer body and the cleaning liquid in which the insert body is immersed is discharged from the front end portion of the outer body.   

     According to another aspect of the present disclosure, (2) A dental handpiece with a cleaning adapter includes:
     the dental handpiece according to (1); and   a cleaning adapter that is configured to be detachably connected to a rear end of the dental handpiece and guide the cleaning liquid supplied from an external device into the immersion flow path and the main body side water injection flow path.   

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a side view showing an external appearance of a dental handpiece to which a scaler tip and a cleaning adapter are connected. 
         FIG.  2    is a schematic side view of an insert body. 
         FIG.  3    is a schematic exploded perspective view of the insert body. 
         FIG.  4    is a schematic cross-sectional view taken along a line IV-IV in  FIG.  2   . 
         FIG.  5    is a schematic cross-sectional view taken along a line V-V in  FIG.  2   . 
         FIG.  6    is an end view of a rear end side of the dental handpiece. 
         FIG.  7    is an end view of a front end side of the dental handpiece. 
         FIG.  8    is an explanatory view schematically showing an internal structure of the dental handpiece and a flow path of a cleaning liquid. 
         FIG.  9 A  is a schematic perspective view showing a flow path of the cleaning liquid formed in a connector portion. 
         FIG.  9 B  is a schematic perspective view showing the flow path of the cleaning liquid formed in the connector portion. 
         FIG.  10 A  is a schematic perspective view of one collar half body of a rear end side collar. 
         FIG.  10 B  is a schematic perspective view of the other collar half body of the rear end side collar. 
         FIG.  11    is a schematic perspective view of the rear end side collar in which collar half bodies are combined. 
         FIG.  12 A  is a schematic perspective view of a front end side collar as viewed from the front end side. 
         FIG.  12 B  is a schematic perspective view of the front end side collar as viewed from the rear end side. 
         FIG.  13    is an explanatory view showing a flow of the cleaning liquid in the front end side collar. 
         FIG.  14    is a cross-sectional view showing the cleaning adapter according to a first configuration example. 
         FIG.  15    is an exploded view of the cleaning adapter shown in  FIG.  14   . 
         FIG.  16    is a partial cross-sectional perspective view showing a connection state between the cleaning adapter and the dental handpiece. 
         FIG.  17    is an end view of the cleaning adapter on the front end side. 
         FIG.  18    is an explanatory view showing a state in which the cleaning adapter is connected to a nozzle of a spray can. 
         FIG.  19    is an explanatory view showing a state in which the cleaning adapter is connected to a handpiece holder of a hot water cleaner. 
         FIG.  20    is a cross-sectional view showing a configuration of the cleaning adapter connected to an autoclave device dedicated to a handpiece. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of a dental handpiece according to the present disclosure will be described in detail with reference to the drawings. 
       FIG.  1    is a side view showing an external appearance of a dental handpiece  100  to which a scaler tip  13  and a cleaning adapter  200  are connected. 
     The dental handpiece  100  includes a cylindrical outer body  11 . The scaler tip  13  is detachably held at a front end portion of the outer body  11 , and the cleaning adapter  200  to be described in detail later is connectable to a rear end portion of the outer body  11 . 
     In the present specification, a connection side of the scaler tip  13  to the dental handpiece  100  is referred to as “forward”, a “front end side”, and “front”, a connection side of the cleaning adapter  200  thereto is referred to as “rear” and a “rear end side”, and a longitudinal direction of the dental handpiece  100  is referred to as an “axial direction”. 
     Configuration of Dental Handpiece 
       FIG.  2    is a schematic side view of an insert body  15 . 
     The insert body  15  is accommodated in the outer body  11  of the dental handpiece  100 .  FIG.  3    is a schematic exploded perspective view of the insert body  15 . A shape of each member shown here is an example for explaining the embodiment, and the present disclosure is not limited thereto. 
     As shown in  FIG.  2   , the insert body  15  includes an ultrasonic vibrator  17  and a tip connection portion  19  provided at a front end portion thereof, and a cleaning liquid injection port to be described later is provided at a rear end portion thereof. In this configuration, the cleaning liquid injection port is provided in a connector portion  21  of the insert body  15 , which is connected to a hose or a cleaning device connected to a handpiece control device (not shown). The front end portion of the insert body  15  closes a front end of the outer body  11 , and the rear end portion of the insert body  15  closes a rear end of the outer body  11 , whereby the insert body  15  seals an internal space of the outer body  11 . A housing portion  23  that covers a front end side and a rear end side of the ultrasonic vibrator  17  is provided outside the ultrasonic vibrator  17 . A pair of glass rods  25  (only a front side is indicated by a dotted line in  FIG.  2   ) are disposed along an axial direction of the insert body  15  outside the housing portion  23 . The glass rod  25  guides laser light or the like supplied from an optical connector (not shown) connected to the connector portion  21  to the front end portion of the insert body  15 . The dental handpiece  100  may not include the glass rod  25 . 
     As shown in  FIG.  3   , the ultrasonic vibrator  17  includes an ultrasonic vibration source  27  that generates ultrasonic vibration, a front horn  28 , and a rear horn  29 . The front horn  28  is a vibration transmission member that is connected to a front end side of the ultrasonic vibration source  27  and transmits the generated ultrasonic vibration to the scaler tip  13  ( FIG.  1   ), and a front end of the front horn  28  serves as the tip connection portion  19 . The rear horn  29  is connected to a rear end side of the ultrasonic vibration source  27 . 
     The housing portion  23  includes a front end side collar  31  that covers a region from the ultrasonic vibration source  27  to the front end of the front horn  28 , and a rear end side collar  33  that covers a region from the ultrasonic vibration source  27  to a rear end of the rear horn  29 . The rear end side collar  33  is preferably formed of a pair of collar half bodies  33 A,  33 B each having a half cylindrical shape. In this case, the pair of collar half bodies  33 A,  33 B include engagement portions  35  that engage with each other in a case where the pair of collar half bodies  33 A,  33 B are combined with each other. In the engagement portions  35 , a claw portion  35 A provided on one of the collar half bodies  33 A,  33 B is engaged with a receiving portion  35 B provided on the other of the collar half bodies  33 A,  33 B, whereby the collar half bodies  33 A,  33 B are integrally combined. The collar half body  33 A and the collar half body  33 B have the same shape, and the claw portion  35 A and the receiving portion  35 B are engaged with the corresponding receiving portion  35 B and claw portion  35 A, respectively. Only the rear end side collar  33  is limited to the half cylindrical shape, and the front end side collar  31  may have a half cylindrical shape, or both may have a half cylindrical shape. 
       FIG.  4    is a schematic cross-sectional view taken along a line IV-IV in  FIG.  2   .  FIG.  5    is a schematic cross-sectional view taken along a line V-V in  FIG.  2    (also see  FIG.  6    to be described later for the line IV-IV and the line V-V). In the following description, the same members or portions are denoted by the same reference numerals, and description thereof will be simplified or omitted. 
     As shown in  FIGS.  4  and  5   , the front horn  28  and the rear horn  29  of the ultrasonic vibrator  17  are connected to each other via a connection member  37 , and a vibrating body  39  is disposed on an outer periphery of the connection member  37 . The front horn  28 , the connection member  37 , and the rear horn  29  respectively have through holes  28   a ,  37   a ,  29   a  penetrating in the axial direction. The through holes  28   a ,  37   a ,  29   a  and a connection flow path  30  that allows a central connection port  41  of the connector portion  21  to communicate with the rear horn  29  form a main body side water injection flow path  43 . The main body side water injection flow path  43  is formed so as to penetrate a central axis of the insert body  15  from the central connection port  41  to the tip connection portion  19 , and is used for water supply to an affected area or the like during treatment of a patient. 
     An outer periphery of the ultrasonic vibration source  27  is liquid-tightly covered with an elastic cover  45  made of silicon rubber or the like having insulating properties and chemical resistance. A cable (not shown) connected to an electrode terminal  47  shown in  FIG.  5    is connected to the vibrating body  39 . 
       FIG.  6    is an end view of a rear end side of the dental handpiece  100 . 
     As shown in  FIG.  6   , the central connection port  41  is disposed on a central axis of the connector portion  21 . Liquid may be sent from the central connection port  41  to the main body side water injection flow path  43 . A pair of electrode terminals  47  are disposed in a bottomed recess  21   a  of the connector portion  21 . End portions of the pair of glass rods  25  are fixed to the connector portion  21  so as to be disposed on both sides of the central connection port  41 . 
     A gap in a circumferential direction between the glass rod  25  and the bottomed recess  21   a  in the connector portion  21  is a cleaning liquid injection port  49  (indicated by hatching in  FIG.  6   ) for injecting a cleaning liquid to be described later. At the rear end of the outer body  11 , only the cleaning liquid injection port  49  of the connector portion  21  communicates with inside of the outer body  11 , and the other portions have an airtight and watertight structure. That is, gas and liquid do not enter the inside of the outer body  11  from a portion other than the cleaning liquid injection port  49 . 
       FIG.  7    is an end view of a front end side of the dental handpiece  100 . 
     As shown in  FIG.  7   , a discharge port  91  of the main body side water injection flow path  43  is provided in a center of the tip connection portion  19 . Light emitting ends of the pair of glass rods  25  are fixed to the front end side collar  31  on an outer side of the tip connection portion  19 . An annular gap between the tip connection portion  19  and the front end side collar  31  is a cleaning liquid discharge port  93  to be described in detail later, and an arc-shaped gap between the glass rod  25  and the front end side collar  31  is a cleaning liquid discharge port  95  to be described in detail later. In a case where the dental handpiece  100  does not include the glass rod  25 , a light emitting end of the front end side collar  31  is sealed together with the discharge port  95 , and the cleaning liquid is discharged from the discharge ports  91 ,  95 . 
     Cleaning Liquid Flow Path 
     Next, a flow path of the cleaning liquid that cleans inside of the dental handpiece  100  having the above configuration will be described. 
       FIG.  8    is an explanatory view schematically showing an internal structure of the dental handpiece  100  and the flow path of the cleaning liquid. 
     As shown in  FIG.  8   , the flow path through which the cleaning liquid is supplied from the connector part  21  into the handpiece includes a central flow path FC through which the cleaning liquid is supplied from the central connection port  41  and a peripheral flow path FS through which the cleaning liquid is supplied from the cleaning liquid injection port  49 . The cleaning liquid supplied to the central flow path FC is sent from the central connection port  41  to the tip connection portion  19  through the main body side water injection flow path  43 . Thereby, the main body side water injection flow path  43  is cleaned. 
     The cleaning liquid supplied to the peripheral flow path FS is an in-case immersion flow path in which the insert body  15  is immersed in the cleaning liquid in the outer body  11  and the cleaning liquid in which the insert body  15  is immersed is discharged from a front end portion of the outer body. The peripheral flow path FS is divided into an inner flow path FS r   1  passing through a center side close to the central connection port  41  and an outer flow path FS r   2  passing through a outer body  11  side during flowing through the connector portion  21 . 
       FIGS.  9 A and  9 B  are schematic perspective views showing the flow path of the cleaning liquid formed in the connector portion  21 .  FIGS.  9 A and  9 B  representatively show the flow path of a part of the cleaning liquid supplied from a pair of cleaning liquid injection ports  49 . 
     As shown in  FIGS.  9 A and  9 B , the cleaning liquid supplied from the cleaning liquid injection port  49  flows forward in the flow path while being stirred by unevenness formed by the glass rods  25 , glass rod rear end holding portions  51  that fix the glass rods  25  by a snap-fit structure, and the like. The connector portion  21  is connected to the rear end side collar  33  in the outer body  11  shown in  FIG.  8   , and the inner flow path FS r   1  and the outer flow path FS r   2  each extend to the front end side along an axial direction of the rear end side collar  33  and become an inner flow path FS t   1  and an outer flow path FS t   2  to be described later. Although the connector portion  21  is formed separately from the rear end side collar  33 , the present disclosure is not limited thereto, and the connector portion  21  may be formed integrally with the rear end side collar  33 . 
       FIG.  10 A  is a schematic perspective view of one collar half body  33 A of the rear end side collar  33 .  FIG.  10 B  is a schematic perspective view of the other collar half body  33 B of the rear end side collar  33 . 
     As shown in  FIGS.  10 A and  10 B , a pair of collar half bodies  33 A,  33 B constituting the rear end side collar  33  has a plurality of claw portions  35 A and receiving portions  35 B that engage with each other. The claw portion  35 A may be a protruding piece defined by a slit formed on the collar half bodies  33 A,  33 B, or a protruding piece formed by protruding from a part of the collar half bodies  33 A,  33 B. 
     The slit formed around the claw portion  35 A in the hollowed state is a through hole  55  penetrating the collar half bodies  33 A,  33 B in a thickness direction. The receiving portion  35 B is provided with a through hole  57  into which a tip end portion of the claw portion  35 A is inserted. A protrusion  59  including a rib protruding in the thickness direction and various grooves recessed in the thickness direction are formed on outer peripheral surfaces of the collar half bodies  33 A,  33 B. Glass rod holding portions  61  that fix the glass rods by a snap-fit structure and a notch  63  are also formed, and a through hole  65  is formed around the glass rod holding portion  61 . In this way, the rear end side collar  33  is provided with a large number of through holes  55 ,  57 ,  65 , the protrusion  59 , the notch  63 , and recesses including the grooves. 
     In a region of the rear end side collar  33  shown in  FIG.  8   , the cleaning liquid flows toward the front end side along the inner flow path FS t   1  flowing on an inner peripheral side of the rear end side collar  33  and the outer flow path FS t   2  passing through a space between an outer peripheral side of the rear end side collar  33  and the outer body  11 . 
       FIG.  11    is a schematic perspective view of the rear end side collar  33  in which the collar half bodies  33 A,  33 B are combined. 
     During passage of the cleaning liquid through the region of the rear end side collar  33 , as indicated by arrows in  FIG.  11   , the cleaning liquid flows from the inner flow path FS t   1  to the outer flow path FS t   2  or from the outer flow path FS t   2  to the inner flow path FS t   1  through through holes formed in the rear end side collar  33 , and diffusion of the cleaning liquid is promoted. An effect of stirring the cleaning liquid is enhanced by unevenness formed in the rear end side collar  33 . 
     Even in a case where the glass rod  25  indicated by a dotted line in  FIG.  11    is assembled, the cleaning liquid is stirred while changing a flow direction in a gap between the glass rod  25  and the rear end side collar  33  and a gap between the rear end side collar  33  and an inner peripheral surface of the outer body  11  (not shown). 
     The cleaning liquid flowing through the inner flow path FS t   1  is guided to the outer flow path FS t   2  through a through hole as indicated by an arrow FSt on a connection end side of the rear end side collar  33  with the ultrasonic vibration source  27 . Then, the cleaning liquid in which the cleaning liquid from the inner flow path FS t   1  of the rear end side collar  33  and the cleaning liquid from the outer flow path FS t   2  merge with each other becomes a flow path FSv flowing outside the ultrasonic vibration source  27 , that is, outside the elastic cover  45  shown in  FIG.  8   , and is directed toward the front end side collar  31 . 
       FIG.  12 A  is a schematic perspective view of the front end side collar  31  as viewed from the front end side.  FIG.  12 B  is a schematic perspective view of the front end side collar  31  as viewed from the rear end side. 
     The front end side collar  31  includes a large diameter portion  71  on the rear end side and a small diameter portion  73  extending from the large diameter portion  71  to the front end side. Substantially half of the large diameter portion  71  in the circumferential direction is formed in a cylindrical shape, and a remaining substantially half of the large diameter portion  71  is formed as a pair of notches  75  that accommodate the glass rods  25  (not shown). The pair of notches  75  are formed to face each other in a radial direction. Opening holes  77 ,  79  communicating with an inner space of the cylindrical large diameter portion  71  are formed in a bottom portion of the notch  75  on a radially inner side. A flange portion  81  facing the ultrasonic vibration source  27  is provided at a rear end of the large diameter portion  71 , and an edge portion  83  abutting on the inner peripheral surface of the outer body  11  is provided at a front end of the large diameter portion  71 . As shown in  FIG.  12 B , slit grooves  87  extending in the axial direction are formed in an inner peripheral surface of the cylindrical large diameter portion  71 . 
     The small diameter portion  73  has a multistage, substantially cylindrical shape whose diameter decreases toward the front end side, and glass rod front end holding portions  85  that fix the glass rods  25  by a snap-fit structure are provided at a front end portion of the small diameter portion  73  so as to correspond to the pair of notches  75 . The glass rod front end holding portions  85  are provided so as to protrude radially outward from an outer peripheral surface of the small diameter portion  73 , and are in contact with the inner peripheral surface of the outer body  11  (not shown). 
     In the front end side collar  31 , a flow path reduction portion As in which a flow path cross-sectional area of an outer flow path gradually decreases is formed from the flange portion  81  to the edge portion  83  shown in  FIG.  8   . In the flow path reduction portion As, the cleaning liquid flowing through the outer flow path is divided into an inner flow path and an outer flow path of the front end side collar  31 . 
     As shown in  FIG.  12 A , the cleaning liquid from the outer flow path FSv reaching the front end side collar  31  flows along a flow path FSwa flowing forward over the flange portion  81  and a flow path FSwb flowing forward through a gap between the outer body  11  and the front end side collar  31  at a position where the glass rod  25  (not shown) is held between the notch  75 . 
       FIG.  13    is an explanatory view showing a flow of the cleaning liquid in the front end side collar  31 . 
     A flow of the flow path FSwb is mainly divided into a flow path FSwc that flows into inside of the front end side collar  31  from the opening hole  79  that opens to the notch  75  of the large diameter portion  71 , a flow path FSwd that flows into the inside of the front end side collar  31  from the opening hole  77 , and a flow path FSwe that leads to outside of the small diameter portion  73  over the opening holes  77 ,  79 . The cleaning liquid in the flow path FSwc flows forward inside the front end side collar  31  while being rectified along the slit grooves  87  shown in  FIG.  12 B . The cleaning liquid in the flow path FSwd also merges with the flow path FSwc inside the front end side collar  31  and flows forward. 
     On the other hand, since an outer flow path of the flow path FSwa is closed by the edge portion  83  of the large diameter portion  71 , the flow path FSwa becomes a flow path FSwf extending from the notch  75  toward an outer periphery of the small diameter portion  73 , merges with the flow path FSwe, and flows outside the front end side collar  31 . 
     A connection portion of the small diameter portion  73  with the large diameter portion  71  has a tapered shape whose outer diameter gradually decreases. Thereby, as shown in  FIG.  8   , an outer flow path ahead of the edge portion  83  becomes a flow path enlargement portion A E  in which a flow path cross-sectional area gradually increases. In the flow path enlargement portion A E , since a flow path width is narrowed by the edge portion  83  and then widened, changes in a flow direction and a flow velocity of the cleaning liquid become large, and stirring of the cleaning liquid is promoted. 
     Then, as shown in  FIG.  12 A , at a front end portion of the front end side collar  31 , the flow path cross-sectional area of the outer flow path is narrowed by the glass rod front end holding portions  85 , and at front end edges  85   a  of the glass rod front end holding portions  85 , the front end edges  85   a  come into contact with the inner peripheral surface of the outer body  11  and a part of the outer flow path in the circumferential direction is closed. Thereby, in the outer flow path, the flow of the cleaning liquid is concentrated on the glass rod front end holding portions  85 . In this way, a portion closer to the front end side than the flow path enlargement portion A E  shown in  FIG.  8    is a re-reduction portion A RS  in which the flow path cross-sectional area of the outer flow path gradually decreases again. The re-reduction portion A RS  is an outer flow path regulation portion, and regulates a part of the cleaning liquid in the outer flow path passing through the re-reduction portion A RS . Thereby, the cleaning liquid is stirred in a turbulent flow and discharged from a discharge port of the outer flow path. The inner flow path of the front end side collar  31  is connected to a periphery of the tip connection portion  19  of the front horn  28  through a space between the front end side collar  31  and an outer peripheral surface of the front horn  28 . 
     As a result, a front end of the dental handpiece  100  shown in  FIG.  7    is provided with the discharge port  91  of the main body side water injection flow path  43  opened at a center of the tip connection portion  19 , the discharge port  93  of the inner flow path that is an annular gap between the outer peripheral surface of the tip connection portion  19  and an inner peripheral surface of the front end side collar  31 , and the discharge port  95  of the outer flow path that is an arc-shaped gap between a radially outer side of the glass rod  25  and the outer body  11 . The cleaning liquid supplied from the central flow path FC shown in  FIG.  8    is discharged from the discharge port  91 , and the cleaning liquid supplied from the peripheral flow path FS is discharged from the discharge ports  93 ,  95 . 
     That is, the cleaning liquid supplied from the connector portion  21  to the central connection port  41  in the central flow path FC cleans the main body side water injection flow path  43  and is discharged from the discharge port  91 . The cleaning liquid supplied from the connector portion  21  to the cleaning liquid injection port  49  in the peripheral flow path FS flows between the inner peripheral surface of the outer body  11  and an outer peripheral surface of the ultrasonic vibrator  17  on an inner peripheral side and an outer peripheral side of the rear end side collar  33 , passes through outside of the ultrasonic vibration source  27 , flows on an inner peripheral side and an outer peripheral side of the front end side collar  31 , and is discharged from the discharge ports  93 ,  95 . 
     In this way, in the peripheral flow path FS, the insert body  15  disposed inside the dental handpiece  100  is immersed in the cleaning liquid, and the cleaning liquid in which the insert body  15  is immersed is discharged from the discharge ports  93 ,  95 . Therefore, even in a case where the dental handpiece  100  is used for the treatment of the patient and a residue is generated due to intrusion of foreign matter or the like into the handpiece, the cleaning liquid flows in the handpiece in a cleaning process of the dental handpiece  100 , and thus the residue may be reliably treated. In a case where an electrical component is built in the insert body  15 , foreign matter including dust adhering due to, for example, static electricity may also be washed away with the cleaning liquid. 
     In general, since the residue is likely to adhere to a narrow gap, it is difficult to reliably remove the residue by a general method of cleaning from outside of the handpiece, and disassembly cleaning is required. However, according to the dental handpiece  100  having the above configuration, inside of the handpiece may be easily cleaned without being disassembled. That is, in a case where the inside of the handpiece is filled with the cleaning liquid, the insert body  15  is immersed in the cleaning liquid, and dirt attached to the insert body  15  floats. Then, by discharging the cleaning liquid in which the insert body  15  is immersed, the floating dirt is discharged. In addition, since the cleaning liquid flows into every corner inside the handpiece while being stirred by various types of unevenness, through holes, and the like inside the handpiece, an cleaning effect is improved by a momentum of the liquid flow. That is, the inside of the handpiece has an uneven structure using a large number of engagement portions (claw portions and receiving portions) having the snap-fit structure in addition to the through holes, the protrusions, and the grooves of the respective portions of the insert body  15 . As a result, an effect of treating the residue by the cleaning liquid is improved. 
     In the dental handpiece  100 , since the flow path of the cleaning liquid is a flow path along one direction, the cleaning liquid is smoothly discharged from the inside of the handpiece to the outside, and liquid accumulation inside the handpiece is less likely to occur. 
     The ultrasonic vibration source  27 , which is an electrical component disposed inside the handpiece, is liquid-tightly covered with the elastic cover  45 , thereby preventing water from entering inside of the electrical component. Since the elastic cover  45  has insulating properties and chemical resistance, the electrical component is protected from the cleaning process. Therefore, even in a case where the inside of the handpiece is filled with the cleaning liquid, the electric component is not affected. 
     According to the above configuration, a high cleaning effect may be obtained without complicating the cleaning process, and determination of a guideline for a dental handpiece cleaning process defined in each country may be reliably cleared. 
     Cleaning Adapter 
     Next, the cleaning adapter  200  will be described. 
     As shown in  FIG.  1   , the cleaning adapter  200  is configured to be connected to the rear end portion of the dental handpiece  100 , and supply the cleaning liquid to the dental handpiece  100 . In general, the dental handpiece  100  is connectable to a cleaning device that includes various external devices for cleaning and disinfecting the handpiece, and a user of the dental handpiece connects the dental handpiece to the cleaning device via a cleaning adapter corresponding to the dental handpiece to perform cleaning and disinfecting treatment. 
     First Configuration Example of Cleaning Adapter 
       FIG.  14    is a cross-sectional view showing the cleaning adapter  200  according to a first configuration example.  FIG.  15    is an exploded view of the cleaning adapter  200  shown in  FIG.  14   .  FIG.  16    is a partial cross-sectional perspective view showing a connection state between the cleaning adapter  200  and the dental handpiece  100 .  FIG.  17    is an end view of the cleaning adapter  200  on the front end side. 
     As shown in  FIGS.  14  and  15   , the cleaning adapter  200  includes a connector main body  111 , a water injection flow path connection portion  113 , and a cleaning device connection portion  115 . As shown in  FIG.  16   , the connector main body  111  includes a flange portion  119   that forms a recess  117  on the front end side. The flange portion  119  is fitted to an outer peripheral surface of the connector portion  21  and is connected to the dental handpiece  100 . A male screw  121  that fixes the cleaning device connection portion  115  is formed on an outer peripheral surface of the connector main body  111  on the rear end side. The connector body  111  is provided with a through hole  123  along a central axis Lc shown in  FIG.  14    and a plurality of peripheral holes  125  on a radially outer side around the through hole  123 . A female screw  127  is formed on an inner peripheral surface of the through hole  123 . A counterbore portion  129  having a diameter smaller than that of an inner peripheral surface of the flange portion  119  is formed on a bottom surface of the recess  117 , and a plurality of peripheral holes  125  are opened in the counterbore portion  129 . 
     As shown in  FIG.  17   , the plurality of peripheral holes  125  are provided at, for example, four positions at equal intervals in the circumferential direction, but the number of peripheral holes  125  is not limited thereto. 
     The water injection flow path connection portion  113  is disposed on the central axis Lc of the connector main body  111  shown in  FIG.  14   , and a male screw  131  formed on the rear end side is fastened to the female screw  127  of the connector main body  111 . A connection end  133  of the water injection flow path connection portion  113  on the front end side protrudes from the bottom surface of the recess  117  and is connected to the central connection port  41  of the dental handpiece  100  (see  FIG.  16   ). A through hole  134  penetrating along the axial direction is formed in the water injection flow path connection portion  113 . 
     A plurality of thin flexible springs  136  obtained by dividing a thin cylindrical body by slits in the axial direction are provided on an outer periphery of the connection end  133 . The thin flexible spring  136  presses the central connection port  41  inserted into the connection end  133  from the outside to the inside by its own elasticity to sandwich the central connection port  41 . The thin flexible spring  136  improves sealability between the connection end  133  and the central connection port  41 . An O-ring  138  is disposed on an outer peripheral surface of a front end of the connection end  133 . The O-ring  138  is pressed against an inner peripheral surface of the central connection port  41  to improve liquid tightness. At the same time, a frictional force is generated in an insertion/removal direction of the central connection port  41 . This frictional force prevents the dental handpiece  100  from falling off due to a pressure of the cleaning liquid during cleaning. In this way, a connection structure between the water injection flow path connection portion  113  and the central connection port  41  may more stably hold the dental handpiece  100  while withstanding an internal pressure of the cleaning liquid. 
     As shown in  FIG.  15   , the cleaning device connection portion  115  has a flange portion  137  that forms a recess  135  on the front end side. A female screw  139  to be fastened to the male screw  121  of the connector main body  111  shown in  FIG.  14    is formed on an inner peripheral surface of the flange portion  137 . A shaft portion  141  connected to the cleaning device is provided on a rear end side of the cleaning device connection portion  115 . A through hole  143  is provided in the shaft portion  141  along the central axis Lc, and a female screw  145  is formed on an inner peripheral surface of the through hole  143 . A counterbore portion  147  is formed between the recess  135  and the through hole  143 . 
     In the cleaning adapter  200  having the above configuration, as shown in  FIG.  14   , a space serving as a liquid injection side storage portion  151  is defined on the rear end side between the counterbore portion  147  communicating with the through hole  143  and the connector main body  111 . In the liquid injection side storage portion  151 , rear ends of the plurality of peripheral holes  125  and a rear end of the through hole  134  of the water injection flow path connection portion  113  are both opened. The counterbore portion  129  communicating with the plurality of peripheral holes  125  is formed on a connection side of the connector main body  111  to the connector portion  21 . A liquid delivery side storage portion  153  is defined between the counterbore portion  129  and the connector portion  21 . The liquid delivery side storage portion  153  does not communicate with the through hole  134  of the water injection flow path connection portion  113 . 
     Connection to Cleaning Device 
     Next, a flow of the cleaning liquid when connected to the cleaning adapter  200  and the cleaning device having the above configuration will be described. 
     Examples of a connection form with the cleaning device include the following forms.
     (1) The cleaning adapter  200  is connected to a nozzle of a spray can (for example, WL-clean manufactured by ALPRO MEDICAL GmbH) that store a cleaning liquid or a nozzle of a spray gun that sprays a cleaning liquid. The cleaning liquid may by disinfectant or dry air.   (2) The cleaning adapter  200  is connected to a handpiece holder that holds a handpiece and supplies a cleaning liquid to inside of the handpiece in a hot water cleaner in which the handpiece is disposed in a sealed cleaning container and the cleaning liquid flows into the disposed handpiece. For example, the hot water cleaner may be SOKUSEN which is a registered trademark by Takara Belmont.   (3) A dedicated cleaning adapter is connected to an autoclave device dedicated to a handpiece. For example, the autoclave device may be DAC UNIVERSAL 2 GUI manufactured by Dentsply Sirona.   

       FIG.  18    is an explanatory view showing a state in which the cleaning adapter  200  is connected to a nozzle of a spray can. 
     In a case of the above (1), a nozzle attachment  163  is attached to a spray port of a spray can  161 . A male screw  165  that may be fastened to the female screw  145  of the cleaning adapter  200  is formed at a front end of the nozzle attachment  163 . The nozzle attachment  163  is attached to the cleaning adapter  200  by fastening the male screw  165  to the female screw  145 . 
     Then, in a case where the cleaning liquid is sprayed from the spray can  161 , the cleaning liquid is supplied to the liquid injection side storage portion  151 . The liquid injection side storage portion  151  is filled with the supplied cleaning liquid, and the cleaning liquid is sent from the liquid injection side storage portion  151  to the main body side water injection flow path  43  (see  FIG.  8   ) through the through hole  134  of the water injection flow path connection portion  113 . This flow path serves as the central flow path FC described above. 
     The cleaning liquid is sent from the liquid injection side storage portion  151  to the cleaning liquid injection port  49  (see  FIG.  8   ) through the plurality of peripheral holes  125 . This flow path serves as the peripheral flow path FS described above. Here, the cleaning liquid that has passed through openings of the peripheral holes  125  on the front end side is temporarily accumulated in the liquid delivery side storage portion  153 . The liquid delivery side storage portion  153  is a sealed space between a rear end of the connector part  21  connected to the recess  117  and the counterbore portion  129 , and may stably supply the cleaning liquid to the cleaning liquid injection port  49  of the connector portion  21  by an internal pressure of the cleaning liquid filled in this space. 
     Even in a case where circumferential positions of the peripheral holes  125  and the cleaning liquid injection port  49  do not overlap with each other and are shifted from each other, the liquid delivery side storage portion  153  may uniformly supply the cleaning liquid from each cleaning liquid injection port  49 . A supply amount of the cleaning liquid may be easily increased. 
       FIG.  19    is an explanatory view showing a state in which the cleaning adapter  200  is connected to a handpiece holder  167  of a hot water cleaner. 
     The handpiece holder  167  of the hot water cleaner is a flexible elastic body including silicon rubber, and the cleaning liquid is supplied from a cleaning liquid supply port  171  at a bottom portion of a holder recess  169 . 
     In a case of the above (2), the dental handpiece may be fixed to the hot water cleaner by a simple operation of merely inserting the shaft portion  141  of the cleaning adapter  200  into the holder recess  169 . A flow of the cleaning liquid in this case is the same as that in a case of  FIG.  18    described above. 
     Second Configuration Example of Cleaning Adapter 
       FIG.  20    is a cross-sectional view showing a configuration of a cleaning adapter  210  connected to an autoclave device dedicated to a handpiece. 
     The cleaning adapter  210  in a case of the above (3) is different from a structure in which the connector main body  111  and the cleaning device connection portion  115  shown in  FIG.  14    are separated from each other, and includes a connector main body  173  and the water injection flow path connection portion  113 . 
     A pedestal  177  having a groove  175  to be fixed to the autoclave device is provided at a rear end of the connector main body  173 . injection holes  179 A,  179 B into which the cleaning liquid is injected are formed in a bottom surface of the groove  175 , and one of the injection holes  179 A,  179 B is selectively used depending on a type of the autoclave device. Front end side of the injection holes  179 A,  179 B are connected to a through hole  181  communicating with the plurality of peripheral holes  125  and the through hole  134  of the water injection flow path connection portion  113 . Both end portions of the through hole  181  are closed by appropriate plug bodies  183  to define a space serving as the liquid injection side storage portion 151described above. 
     According to the cleaning adapter  210 , the cleaning liquid injected from one of the injection holes  179 A,  179 B is sent to the main body side water injection flow path  43  through the through hole  134  (see  FIG.  8   ) and is supplied to the central flow path FC. The cleaning liquid is sent to the cleaning liquid injection port  49  through the peripheral holes  125  (see  FIG.  8   ), and is sent to the peripheral flow path FS. A space serving as the liquid delivery side storage portion  153  is defined on the front end side of the peripheral holes  125 , and the cleaning liquid may be stably supplied to the cleaning liquid injection port  49 . 
     The present disclosure is not limited to the embodiment described above, and modifications, improvements, and the like may be made as appropriate. In addition, materials, shapes, sizes, numerical values, forms, numbers, arrangement positions, and the like of components in the embodiment described above are optional and are not limited as long as the present disclosure may be achieved. 
     As described above, the following matters are disclosed in the present specification. (1) A dental handpiece comprising:
     a cylindrical outer body;   an insert body that is configured to include an ultrasonic vibrator, and is accommodated in the outer body with a front end portion thereof closing a case front end of the outer body and a rear end portion thereof closing a case rear end of the outer body;   a tip connection portion that is provided at the front end portion of the insert body and that detachably holds a scale tip to which ultrasonic vibration from the ultrasonic vibrator is transmitted; and   a cleaning liquid flow path that guides a cleaning liquid supplied from a cleaning liquid injection port provided in the rear end portion of the insert body to a front end portion of the outer body,   wherein the cleaning liquid flow path includes an immersion flow path in which the insert body is immersed in the cleaning liquid in the outer body and the cleaning liquid in which the insert body is immersed is discharged from the front end portion of the outer body.   

     According to this dental handpiece, the insert body is immersed in the cleaning liquid supplied from a connector portion in the outer body, and the cleaning liquid in which the insert body is immersed is discharged from the front end portion of the outer body. Therefore, a residue accumulated in the outer body may be reliably treated with the cleaning liquid without disassembling the dental handpiece. 
     (2) The dental handpiece according to (1), further comprising:
     a housing member that is disposed inside the outer body and covers an outer side of the ultrasonic vibrator,   wherein the immersion flow path includes an inner flow path between the insert body and the housing member and an outer flow path between the housing member and the outer body.   

     According to this dental handpiece, the cleaning liquid flows in each of the inner flow path and the outer flow path of the housing member in the outer body, whereby the cleaning liquid is stirred, and dirt in the outer body may be efficiently treated. 
     (3) The dental handpiece according to (2), wherein the housing member is provided with a through hole that allows the inner flow path and the outer flow path to communicate with each other. 
     According to this dental handpiece, since the cleaning liquid flows from inside to outside and from the outside to the inside of the housing member through the through hole, the cleaning liquid may flow over the entire housing member, and stagnation is less likely to occur. 
     (4) The dental handpiece according to (2) or (3), wherein at least one of an inner peripheral surface and an outer peripheral surface of the housing member is provided with a protrusion protruding in a thickness direction of the housing member or a recess recessed in the thickness direction. 
     According to this dental handpiece, an effect of stirring the cleaning liquid is enhanced by the protrusion or the recess. 
     (5) The dental handpiece according to any one of (2) to (4), 
     wherein the ultrasonic vibrator includes an ultrasonic vibration source and a vibration transmission member that transmits ultrasonic vibration generated from the ultrasonic vibration source to the scaler tip, and   wherein the housing member includes a front end side collar that covers a region from the ultrasonic vibration source to a front end portion of the vibration transmission member, and a rear end side collar that covers a region from the ultrasonic vibration source to the cleaning liquid injection port and has an injection port for the cleaning liquid to be supplied to the cleaning liquid flow path.   

     According to this dental handpiece, a flow path of the cleaning liquid is formed along the front end side collar and the rear end side collar. 
     (6) The dental handpiece according to (5), wherein at least one of the front end side collar and the rear end side collar is formed of a pair of collar half bodies each having a half cylindrical shape, and includes an engagement portion in which a claw portion provided in one collar half body and a receiving portion provided in the other collar half body are engaged with each other in a case where the half collar bodies are combined with each other. 
     According to this dental handpiece, the effect of stirring the cleaning liquid is enhanced by unevenness formed by the claw portion and the receiving portion of the engagement portion. 
     (7) The dental handpiece according to (6), wherein the claw portion is formed so as to be surrounded by a slit formed in the collar half body. 
     According to this dental handpiece, since the claw portion is formed by being surrounded by the slit, a through hole is formed around the claw portion. The cleaning liquid flows to the inside and the outside of the housing member through the through hole. 
     (8) The dental handpiece according to any one of (2) to (7), wherein the immersion flow path includes:
     a flow path reduction portion in which a flow path cross-sectional area of the outer flow path gradually decreases from the rear end portion side toward the front end portion side of the outer body;   a flow path regulation portion that regulates a part of a flow of the cleaning liquid in the outer flow path by bringing the housing member and a part of the outer body into contact with each other at a front end of the flow path reduction portion, and   a flow path enlargement portion in which a flow path cross-sectional area of the outer flow path gradually increases from the flow path regulation portion toward the front end portion side.   

     According to this dental handpiece, stirring of the cleaning liquid is promoted by reduction and enlargement of the flow path cross-sectional area due to the outer flow path of the cleaning liquid being narrowed by the flow path reduction portion, a part of the flow path being regulated by the flow path regulation portion, and the outer flow path being widened by the flow path enlargement portion. 
     (9) The dental handpiece according to (8), further comprising:
     a flow path re-reduction portion in which a flow path cross-sectional area of the outer flow path gradually decreases from the flow path enlargement portion toward the front end portion side; and   an outer flow path regulation portion that regulates a part of the flow in the outer flow path by bringing the housing member and a part of the outer body into contact with each other on the front end portion side of the flow path re-reduction portion,   wherein the cleaning liquid from the inner flow path and the outer flow path is respectively discharged from mutually different discharge ports around the tip connection portion.   

     According to this dental handpiece, a part of the cleaning liquid in the outer flow path passing through the re-reduction portion is regulated by the outer flow path regulation portion, whereby the cleaning liquid is stirred in a turbulent flow on the front end portion side having the largest amount of residue, and the cleaning liquid is discharged from a discharge port of the outer flow path. 
     (10) The dental handpiece according to any one of (1) to (9), wherein the cleaning liquid flow path includes a main body side water injection flow path connected to a tip side water injection flow path of the scaler tip through a through hole along a central axis of the insert body. 
     According to this dental handpiece, inside of the main body side water injection flow path may be cleaned by the cleaning liquid flowing through the main body side water injection flow path. 
     (11) A dental handpiece with a cleaning adapter comprising:
     the dental handpiece according to the configuration (10); and   a cleaning adapter that is detachably connectable to a rear end of the dental handpiece and injects the cleaning liquid supplied from an external device into the immersion flow path and the main body side water injection flow path.   

     According to the dental handpiece with the cleaning adapter, the cleaning liquid from the external device may be supplied to the immersion flow path and the main body side water injection flow path. 
     (12) The dental handpiece with the cleaning adapter according to (11), wherein the cleaning adapter includes:
     an external connection portion that is connected to the external device that supplies the cleaning liquid;   a liquid injection side storage portion that stores the cleaning liquid supplied from the external connection portion;   a central flow path that communicates with the liquid injection side storage portion and is connected to the main body side water injection flow path of the dental handpiece; and   a plurality of peripheral flow paths that communicate with the liquid injection side storage portion and are connected to the immersion flow path of the dental handpiece.   

     According to the dental handpiece with the cleaning adapter, the cleaning liquid from the external connection portion may be stably injected into both the central flow path and the peripheral flow paths through the liquid injection side storage portion. 
     (13) The dental handpiece with the cleaning adapter according to (11), wherein the cleaning adapter includes:
     an external connection portion that is connected to the external device that supplies the cleaning liquid;   a central flow path that is connected to the main body side water injection flow path of the dental handpiece and a plurality of peripheral flow paths that are connected to the immersion flow path of the dental handpiece, both communicating with the external connection portion; and   a liquid delivery side storage portion that is provided between the plurality of peripheral flow paths and the immersion flow path of the dental handpiece, stores the cleaning liquid sent from the plurality of peripheral flow paths and supplies the cleaning liquid to the immersion flow path.   

     According to the dental handpiece with the cleaning adapter, the cleaning liquid supplied from the plurality of peripheral flow paths is accumulated in a liquid delivery and diffusion portion, and the cleaning liquid is supplied to the immersion flow path by an internal pressure of the cleaning liquid filled in the liquid delivery and diffusion portion. Therefore, the cleaning liquid may be stably supplied to the immersion flow path regardless of formation positions of the plurality of peripheral flow paths. 
     (14) The dental handpiece with the cleaning adapter according to (12) or (13),
     wherein the external connection portion includes a recess communicating with the central flow path and the peripheral flow paths, and   wherein a female screw connected to a cleaning liquid supply port of the external device is formed on an inner peripheral surface of the recess.   

     According to the dental handpiece with the cleaning adapter, the female screw is fastened to a male screw of the cleaning liquid supply port of the external device, and the cleaning liquid may be sent from the external device to a dental handpiece side. 
     (15) The dental handpiece with the cleaning adapter according to (12) or (13),
     wherein the external connection portion includes a cylindrical protrusion protruding in an axial direction, and   wherein inside of the cylindrical protrusion communicates with the central flow path and the peripheral flow paths.   

     According to the dental handpiece with the cleaning adapter, by inserting the cylindrical protrusion into a holder recess of a handpiece holder including the cleaning liquid supply port of the external device, an inner peripheral surface of the handpiece holder and an outer peripheral surface of the cylindrical protrusion are brought into close contact with each other, and the cleaning liquid may be sent from the external device to the dental handpiece side. 
     (16) The dental handpiece with the cleaning adapter according to (12) or (13),
     wherein the external connection portion includes a cleaning liquid injection hole communicating with the central flow path and the peripheral flow paths, and   wherein an outer opening of the cleaning liquid injection hole is formed in a groove bottom surface of a groove to be engaged with the external device.   

     According to the dental handpiece with the cleaning adapter, the cleaning liquid may be sent from the external device to the dental handpiece side through the cleaning liquid injection hole in a state where the groove of the external connection portion is engaged with the external device.