Patent Abstract:
An electrically heated endodontic syringe for injecting thermoplastic material, such as gutta percha, into a root canal cavity including a handpiece, control box, receiver for receiving a pre-filled cartridge of a thermoplastic material, tapered needle and a foot control peddle. The cartridge is made out of a high temperature plastic material and is indirectly heated by the control box, causing the thermoplastic material inside, preferably gutta percha, to become pliable. The handpiece includes a lead screw that, when activated, slides along the length of the hand piece and contacts a cartridge plunger at an open end of the cartridge, causing the thermoplastic material to travel along a central pathway, through the needle and into the cavity. The plunger is operated by a foot peddle.

Full Description:
RELATED APPLICATIONS  
       [0001]     The present application is related to U.S. Provisional Patent Application, Ser. No. ______, filed on ______, which is incorporated herein by reference and to which priority is claimed pursuant to 35 USC 119. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates generally to the field of dental endodontics and, more particularly, to an endodontic gutta percha placement tool with a disposable gutta percha cartridge, a disposable injection needle and a motor-driven plunger arrangement.  
         [0004]     2. Description of the Prior Art  
         [0005]     In the field of dentistry, filling an inflamed root canal cavity is quite common. One preferred method involves cleaning out the canals and removing the diseased pulp tissue of the damaged tooth with files, drills, and burrs, all the way to the bottom or apex of the tooth. At that point, the tooth is dead. The damaged tooth, however, can be covered with a so-called crown that approximates the features and characteristics of the original tooth. Before the crown can be applied, however, the empty cavity left behind by the root canal operation must be back-filled to prevent bacteria from entering empty cavity and causing infections and to reduce problems with respect to pressure differentials.  
         [0006]     Endodontists traditionally perform this backfill operation by packing a thermo-plastic material known as gutta percha, or GP, which is the milky juice of Malaysian trees and has a semisolid state at a normal temperature, but becomes a hard rubber-like gum when heated.  
         [0007]     The process of filling the vacated canal traditionally begins by down packing the lower ⅓ of the canal with several long “cones” of gutta percha that are selected in size and taper on the basis of the file, drill or burr used to vacate the canal. This down packing process for the lower ⅓ of the canal is well known to those of ordinary skill in the art.  
         [0008]     A gutta percha manual injection gun or many cones of gutta percha is generally used to fill the upper portion of the canal. A conventional gutta percha gun is a manual operated device that heats a slug of gutta percha within a heated barrel and then, using a hand-operated plunger, forces the molten gutta percha out of a needle-like tip. The foregoing device is quite similar to a hot glue gun.  
         [0009]     There are several problems with the just described gutta percha gun. First, the gutta percha slug is in direct contact with the interior of the heated barrel and the face of the plunger that forces the gutta percha out through the needle at the front of the gun. Accordingly, the interior of the gun must be cleaned after each use. Moreover, it is sometimes necessary to replace the plunger periodically because of this direct contact. Second, the hand-operation of the gun interferes with the endodontist&#39;s ability to know that the vacated canal is full through tactile feedback while performing the fill. In particular, because the just-described gun requires the endodontist to squeeze the handle of the tool, it makes it relatively difficult to perceive the upward pressure on the needle tip caused by hydraulic back pressure caused by the gutta percha filling within the cavity.  
         [0010]     There remains a need, therefore, for a gutta percha placement tool that improves upon the just-described device.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art and an object of the present invention Is to provide a gutta percha placement tool that solves one or more of these problems. The present invention is a gutta percha placement tool according to one embodiment of the present invention and includes a handheld tool with a heated chamber that receives a gutta percha cartridge formed from a disposable high temperature plastic cartridge containing gutta percha. For that purpose, the preferred chamber includes a side-loading port through which the gutta percha cartridge may be inserted. The preferred gutta percha cartridge includes a sealing ring (e.g. an o-ring) that engages an interior lumen leading to disposable needle tip to prevent any leakage of gutta percha into the heat chamber. A back end of the gutta percha cartridge is opened to receive a plunger that forces the molten gutta percha out of the gutta percha cartridge and into and through the needle.  
         [0012]     As a result of the use of a gutta percha cartridge according to this embodiment of the invention, there is a significantly reduced need to clean the gutta percha placement tool, if ever.  
         [0013]     Moreover, the preferred gutta percha placement tool of the present invention uses a lead screw that forces the melting gutta percha from the cartridge into the needle tip of the tool. As a result of this unique use of a motor-driven lead screw, the endodontist does not need to squeeze the device and, therefore, is allowed much more ability to sense the back pressure, i.e. to have the tactual feedback described above while placing the gutta percha in the canal.  
         [0014]     The hollow needle used with the gutta percha tool is preferably made of a metal having high thermal conductivity such as a silver alloy or a copper alloy. That way, the hollow needle is sufficiently hot so that the melting gutta percha does not solidify as it is pushed through and nears the far end of the hollow needle. The preferred needle has a continuous taper, free of joints. In the preferred embodiment, a foot pedal would be used to allow the endodontist to conveniently operate the motor that drives the lead screw.  
         [0015]     While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 USC 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 USC 112 are to be accorded full statutory equivalents under 35 USC 112. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a partially see through view of a first embodiment of the present invention.  
         [0017]      FIG. 2  is a side view of the injector element of a first embodiment of the present invention.  
         [0018]      FIGS. 2   a - 2   d  show a more detailed view of a first embodiment of the present invention.  
         [0019]      FIG. 3  is a partially see through view of the distal end of a first embodiment of the present invention.  
         [0020]      FIG. 4  is a side view of the cartridge element of a first embodiment of the present invention.  
         [0021]      FIG. 5  is an exploded side view of a second embodiment of the present invention.  
         [0022]      FIG. 6  is a see through view of a second embodiment of the present invention.  
         [0023]      FIG. 7  is a side view of a second embodiment of the cartridge element of the present invention.  
         [0024]      FIG. 8  is a side view of a preferred embodiment of a needle. 
     
    
       [0025]     The invention and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the invention defined in the claims. It is expressly understood that the invention as defined by the claims may be broader than the illustrated embodiments described below.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Referring initially to  FIG. 1 , a first preferred embodiment of an endodontic injection apparatus  10  for injecting material in to a prepared root canal according to the present invention is shown. The injection apparatus  10  comprises a handpiece  11  that is directly connected to a power control box  14 . The handpiece defines a longitudinal axis L 1  that extends there through from a proximal end  12  to a distal end  13  thereof. A chamber  16  is defined within the handpiece  11  and defines a hollow cavity  28  therein. In a preferred embodiment the handpiece  11  is a pen-like injector.  
         [0027]     The proximal end  12  of the handpiece  10  includes a lead screw  22  that is axially aligned with the longitudinal axis L 1 . The lead screw  22  travels on the longitudinal axis L 1  when it is actuated. In a preferred embodiment, an electrical power control box electronically actuates the lead screw  22 . In another embodiment, the lead screw  22  is electronically actuated by a foot pedal. As shown best in  FIGS. 1 and 2 , a pre-filled cartridge  26  is loaded into the handpiece  11  via a side loading port  24  that the cartridge  26  drops into. The side loading port  24  leads to the chamber  16  within the handpiece  11  and the chamber receives the cartridge  16  when it is dropped into the side loading port  24 . When the cartridge  26  is loaded into the chamber  16 , and the lead screw  22  is actuated, the electrical control box  14  provides power to a heating element  29  that is disposed around the chamber  16 . The chamber  16  heats up and the cartridge  26  is thereby indirectly heated causing the thermoplastic material within the cavity  44  to become pliable. This allows the thermoplastic material to travel through the needle  20  when the lead screw  22  is actuated and forces the thermoplastic material out of the cartridge opening  46 . In a preferred embodiment, the cartridge is disposable and the thermoplastic material is gutta percha.  FIG. 2   a  shows the lead screw  22  retracted so that the cartridge  26  may be loaded into the side loading port  24 .  FIG. 2   b  shows the cartridge  26  within the chamber  16 .  
         [0028]     In a preferred embodiment, an insulating sleeve  36  is removably inserted over the chamber  16  after the cartridge  26  is inserted into the side loading port  24 .  
         [0029]     As shown best in  FIG. 3 , the distal end  13  of the needle nut  52  has mating threads  32  that thread into the chamber  16  and comprises a central passageway  30  that extends from the cartridge  26  to a needle  20 . The needle extends through a plastic flange  38  that is connected to the needle nut  52  with threading  32  or any other fastening device that connects the needle  20  directly to the needle nut  52 . In a preferred embodiment the needle is jointless and made of a high thermal conductive material i.e. a silver or copper alloy.  
         [0030]     As is best seen in  FIG. 2 , the needle  20  and nut  52  assembly is separate from the cartridge  26 , and therefore the needle  20  and nut  52  assembly, at the discretion of the operating endodontist, does not need to be replaced every time the cartridge  26  is emptied. This gives the endodontist the option of reusing the needle  20  and nut  52  assembly with multiple cartridges  26 . The option of the needle  20  and nut  52  assembly being reusable saves the user money because otherwise he would have to constantly replace the needle  20  and nut  52  assembly and order more, and he would have to spend the time properly disposing of it and changing them.  
         [0031]     As seen in  FIG. 4 , the pre-filled cartridge  26  comprises a proximal end  41  and a distal end  42  and defines a cavity  44  within. The distal end  42  of the cartridge  26  comprises grooves  47  for an O-ring to be placed in order to assure that when the thermoplastic material is discharged from the cartridge  26 , it does not leak into the chamber  16 . In a preferred embodiment, the thermoplastic material is gutta percha. The distal end  42  of the pre-filled cartridge  26  comprises an opening  46  for discharging the thermoplastic material that is held within the cavity  44 .  
         [0032]     In a first embodiment, the pre-filled cartridge  26  comprises at least one stop  40  that abuts against the chamber  16 , and prevents the cartridge  26  from moving within the chamber  16 . In a preferred emodiment, there are two adjacent stops  40  that create a space between them and allows the heated cartridge  26  to be pulled out of the chamber  16  with a tool after use. During activation, a lead screw  22  travels on the longitudinal axis L 1  towards the distal end of the injection apparatus  10  and contacts a plunger  45  located within the cavity  44  causing the plunger  45  to move towards the distal end  13  of the handpiece  11 . The thermoplastic material is then forced to the distal end  42  of the cartridge  26 , through the opening  46  of the cartridge  26  and into a central passageway  30  that leads to the needle  20 . The thermoplastic material is smoothly pushed out of the cartridge  26  in a continuous and uniform motion, causing very little movement of the injection apparatus while in the root canal. This makes it relatively easy to perceive the upward pressure on the needle tip within the cavity. In a preferred embodiment, the plunger  45  has two sealing rings that contact the walls of the cavity  44 . This ensures that the gutta percha will not leak out of the cartridge  26  when the plunger  45  is sliding within the cavity  44 .  
         [0033]     In a second embodiment, shown in  FIG. 5 , the pre-filled cartridge  26  is loaded into a front aperture  56  on the chamber  16  and abuts against a lead screw (not shown) that is in a fixed position. Having the lead screw be in a fixed position eliminates the loading and waiting time. Once the cartridge  26  is inserted into the front aperture  56 , a needle hub  50  fits onto the nozzle  58  of the cartridge and puts the needle  20  in fluid communication with the cartridge  26  via a central passageway  30 . A nut  52  is then strattled over the needle  20  and has mating threads  32  that thread onto the mating threads  27  of the chamber  16 . In a preferred embodiment, the nut  52  is made out of copper, so that the heat from the heating element  29  transfers through the nut  52  and to the needle  20 . In a preferred embodiment, the nut  52  is hexagonal so that a wrench can be used to tighten the nut  52  onto the chamber  16 .  
         [0034]      FIGS. 5 and 6  show a second embodiment of the invention assembled, wherein the cartridge  26  is front loaded into the chamber  16 .  
         [0035]     In a second embodiment, best shown in  FIG. 7 , the distal end  42  of the cartridge  26  comprises at least one stop  54  i.e. O-ring, that sealingly engages the interior lumen of the cartridge. In the second preferred embodiment, there are two stops  54  located on the distal end  42  of the cartridge  26 . On the nozzle  58  of the cartridge  26 , is a groove  47  adapted to hold a sealing ring (not shown). The proximal end  41  of the cartridge  26  is open to receive a lead screw  22 .  
         [0036]      FIG. 8  shows a preferred embodiment of the needle  20  being joint free and tapered from a proximal end  81  to a distal end  82 . In the preferred embodiment the needle  20  is made from a silver or copper alloy.  
         [0037]     A root canal is back filled with a thermoplastic material by providing an endodontic injection apparatus  10  having a handpiece  11 , a cylindrical chamber  16  defined within the handpiece  11 , a side-loading port  24  adapted to receive a disposable cartridge  26 , wherein the cartridge  26  defines a cavity  28  within, has a proximal end  41  and a distal end  42  and is pre-filled with gutta percha. A lead screw  22  aligned on a longitudinal axis L 1 ; and a reusable needle  20  coupled to the handpiece  11 , wherein the needle  20  can be reused with multiple cartridges  26 . A heating element  29  directly connected to a electrical power control box  24  is supplied to heat the chamber  16 . The proximal end of the cartridge  26  comprises at least one stop  40  and is open to receive a lead screw  22 , and the distal end comprises a discharge aperture  46 . The lead screw  22  is electronically actuated by a foot control peddle  18  and smoothly and uniformly pushes a plunger  45  located within the cavity  44  towards the distal end  13  of the handpiece  11 .  
         [0038]     Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. For example,  
         [0039]     Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.  
         [0040]     The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.  
         [0041]     The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination.  
         [0042]     Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.  
         [0043]     The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.

Technology Classification (CPC): 0