Abstract:
Method and tool for fracturing the cement interface between a crown and a tooth or a fixture on a tooth and the tooth. The method is accomplished by positioning a clamp having a driven rapid impacting tool against one side portion of a crown or fixture covering the tooth. The working edge of the tool is covered with a first malleable metal cap and is in interfacing abutment with said crown or fixture. The opposed side of the crown or fixture is abutted against an anvil which is part of the clamp. The anvil is covered with a thicker second malleable cap.

Description:
[0001]     This application is a c-i-p of patent application Ser. No. 10/870,612; filed: Jun. 17, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a dental tool and method of use, and more particularly, to a tool for fracturing the interface between two dental structures that have been adhesively secured together.  
       BACKGROUND OF THE PRESENT INVENTION  
       [0003]     Dental structures such as caps, crowns and bridges are bonded to natural tooth roots or implanted posts by well known conventional cements. It is equally well known, that the removal of cemented dental structures may be necessary for one or more of the following reasons: 
        (a) The occurrence of dental decay.     (b) To examine the vitality and pulpal involvement of an underlying tooth     (c) To repair cemented dental structures made defective by the wear of materials.     (d) The loss of selected supporting teeth.        
 
         [0008]     It is also known that natural tooth roots are connected to bone structure by a matrix of connecting fibers. It is stated that the connecting fibers exhibit a resultant vector force which holds the tooth root in place, which vector force operates substantially along a longitudinal axis in the direction of the top to bottom of the tooth. Thus, properly directed impacting forces permit the use of short force magnitude but of high frequency to break or fracture the cement bonds holding the dental structure to the tooth root with a minimal detrimental effect to the fibers or natural tooth roots.  
         [0009]     In the prior art, removal of dental structures such as caps, crowns and bridges was accomplished by often times sacrificing the tooth bearing the caps, crown or bridge or by the application of a rigid grasping means to the structure followed by a manual application of an impacting or leverage force in an attempt to break the cement bonds. However, prior art devices could apply only in exact magnitudes of impacting forces since manual means were used. Such manual means were further limited in that the oral cavity is not large enough to permit easy direct impacting to those dental structures located near the rear of the oral cavity. Other consequences of the use of prior art apparatuses are patient discomfiture, and inconvenience to the dentist occasioned by the cumbersome mechanical apparatus.  
         [0010]     Some recent progress has been made by the use of diminutive ultrasonic probes for application to teeth to remove or loosen orthodontics and other dental structures, such as disclosed in U.S. Pat. Nos. 5,106,302 and 5,320,532 to Farzin-Nia et al.  
         [0011]     Even more recently the art for removal of crowns and the like has been considerably advanced by the invention disclosed in Patent No. 5,547,300 to Goodman, the material therein is incorporated herein in its entirety.  
       SUMMARY OF THE INVENTION  
       [0012]     It is accordingly an object of the present invention to provide a more efficient apparatus for the removal of cemented dental structures.  
         [0013]     It is another object of the invention to provide an apparatus for the removal of a cemented dental structure using precisely impacting forces directed essentially transversely to the longitudinal axis of said structure.  
         [0014]     It is still another object of this invention to provide an apparatus for the removal of a cemented dental structure operable in confined regions of the oral cavity.  
         [0015]     It is an object of this invention to provide an automatic apparatus thereby minimizing manual intervention for effecting the removal of a cemented dental structure.  
         [0016]     It is another object of this invention to provide an apparatus for the removal of a cemented dental structure which apparatus includes a clamping means to hold the dental structure.  
         [0017]     It is still another object of this invention to provide a piezoelectric transducer apparatus for the removal of a cemented structure wherein the piezo crystals are affixed to at least longitudinally extending sides of a steel core.  
         [0018]     It is yet another object of this invention to provide a piezoelectrically driven device in a clamp wherein the steel core terminates in an impacting cone. The said cone has a thin copper cap affixed thereto. An anvil is provided and secured to the clamp and a thicker copper cap is affixed to the anvil. The crown is secured therein between.  
         [0019]     It is yet another object of this invention to provide apparatus for the removal of a cemented dental structure which apparatus may be selectively coupled to any of a plurality of so-called permanent cap, crown or bridge structures.  
         [0020]     The direction of application of impacting must be applied perpendicular to the plane of the cement of the structure. In this way the bond of the cement is fractured by shocking it with numerous low power but nevertheless high frequency shock waves. In use, the piezoelectric device with a cone covered with a thin copper shield is placed perpendicular to the axis of the tooth, at proximate the open end of the cap. The opposite side of the cap must be backed by an anvil. A thicker copper shield is positioned between the cap and the anvil as stated in the foregoing.  
         [0021]     Preferably the anvil and the piezoelectric tool is positioned at the confronting legs of a vise-like device whereby the cap of the tooth is positioned there between in a gripping manner. The vise action results in maintaining constant contact of the piezoelectric tool through the thinner copper shield with the cap or crown which inhibits considerably the production of sound by the piezoelectric tool of the present invention, thereby making it more pleasant for the patient.  
         [0022]     An important feature of the present invention resides in the fact that as the impacts occur from the piezoelectric tool, the copper shields become work hardened but not before it becomes conformed to the surface of the cap or crown that is being impinged.  
         [0023]     The concept is to preferably flex the rim area of the cap or crown very rapidly after work hardening the copper shields but with a minimum of lateral displacement, of the order of approximately five microns whereby the cement is trapped and fractured between the inertia of the root or post on the flexing cap. It has been discovered that the fracture line begins at the point of abutment of the copper sheathed cone of the piezoelectric tool and extends around the tooth, post or root to the other side of the cap or crown. This greatly reduces the energy and time required to break the bond. There is no deleterious pulling force on the tooth, only tiny vibrations. Since there is no pulling or tugging on the tooth and the motion is small, large caps even with multiple posts or roots are loosened by fracturing the cement at each bond individually. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a schematic of the clamp in a side elevation.  
         [0025]      FIG. 2  is a schematic showing the device of the invention employed with the crown in part in cross section.  
         [0026]      FIG. 3  is the same view as in  FIG. 2  with fracture in progress.  
         [0027]      FIG. 4  is a cross sectional and schematic view of another embodiment;  
         [0028]      FIG. 5  is a cross sectional and schematic view of still another embodiment;  
         [0029]      FIGS. 6-9 , are to the embodiment of  FIG. 4  illustrating the action of the tool;  
         [0030]      FIG. 10  is a cross sectional and schematic view of yet another embodiment, showing the operation thereof;  
         [0031]      FIG. 11  is a cross sectional and schematic view of the embodiment of  FIG. 10 , showing the further operation.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]     Attention is now directed to  FIG. 1  where the device is shown, generally, at  11  which is depicted as being clamped about a tooth  12  which has a cap  13  thereon. The device  11  has a housing  14  which has mounted therein a piezoelectric device  15  consisting of an elongated steel four sided bar  16  that terminates in a truncated cone portion  17  at its distal end. The bar  16  has mounted on opposite surfaces piezoelectric crystals  18  and  19 . These crystals are adhesively secured to the bar  16  by a conventional epoxy cement. The bar  16  and the piezoelectric crystals  18  and  19  are mounted in the housing  14  by rubber mounts  20 . The piezoelectric crystals  18  and  19  are electrically connected to a source of electricity by electrically conducting wires  22  and  23 .  
         [0033]     The housing  14  has an elongated linearly spaced channel  25  in which is mounted a reciprocable movable metal flat member  28 . The distal end  26  thereof terminates in an anvil portion  27  which is confrontingly mounted in regard to the truncated cone portion  17  and spaced therefrom detailed to accommodate the to-be treated crown or cap of a tooth.  
         [0034]     The proximate end  30  of flat member  28  is operatively connected to an arm  31  which is arcuately mounted to hub  33 . The hub  33  has an elongated handle  34 . An operator grasps in one hand both the housing  14  and the handle  34 . When the housing  14  and the handle  34  are squeezed together the anvil  27  moves linearly in the direction of the truncated cone  17 . A tooth  12  with a to-be removed cap  13  is grasped between the anvil  27  and the truncated cone  17 .  
         [0035]     Attention is now directed to  FIG. 2  which depicts in fragmentary details a tooth  40  having a crown  41  and a cement  42  there between. Positioned between the crown  42  and the anvil  27  is a cup  45  of relatively thick copper. At the truncated cone  17  is a thinner cup copper interface  46 . Copper is the preferred material as it is very malleable. A combination of the clamping between the anvil and the truncated cone and the vibrations afforded by the piezoelectric device results in the copper surfaces touching the crown  41  conform to the surfaces of the crown  41 . The copper cup  45  being thicker results in good holding characteristics while the thinner copper cup  46  on the truncated cone  17  permits the delivery of vibrations in a manner to spread the peak pressure.  
         [0036]     The vibrations set up in the crown concentrate on the cement pulverizing it in situ with fracturing spreading in a ripple effect throughout the cement resulting in a complete loosening of the crown ready for subsequent removal.  
         [0037]     It is submitted that a similar and applicable piezoelectric tool construction can be seen in U.S. Pat. No. 5,269,291 to Carter. This patent is incorporated herein in its entirety.  
         [0038]     Once the fracturing has been completed the device  10  can be removed, followed by the removal of the cap  41 . In the infrequent event that the fracturing is incomplete the device may be re-positioned for further impact impingement. At no time with the method of the invention is it necessary to apply pulling forces on the crown or tooth which can result in loosening of the tooth per se.  
         [0039]     It will be appreciated that other drivers may be substituted for the pizeoelectric ultra sonic vibratory motor described in the foregoing. As a matter of fact it is not necessary that the driver be operable at an ultra sonic speed. In the following, there are disclosed two alternate drivers which comprise an air driven piston impact tool that is employed to loosen a conventional cap from a tooth and alternatively an air driven ball impact hammer. Both are useful in a dentist&#39;s office where compressed air is available at the patient&#39;s chair.  
         [0040]     Accordingly,  FIGS. 4 and 5  pertain to an air driven piston impact tool wherein, reference numeral,  51 , generally, illustrates the air driven impact tool  51 . The air driven impact tool  51  is shown in cross-section and is essentially schematic, thereby presenting the air driven motor with clarity. The two figures also show the air driven impact tool  51  is in an enlarged fashion so the drawings are not to scale.  
         [0041]     The main body portion of the air driven motor has a tubular housing  52  which has therein an elongated centrally located tubular chamber  53  which consists of a first section  54  and a second section  55  which are axially disposed and interconnected so that one runs into the other. The first section  54  is rearward of the housing  52 . The second section  55  is located forward of the first section  54 , that is, the second section  55  which is to the right of the first section  54 , as detailed in the accompanying drawings. The second section  55  has a larger diameter than the first section  54 . The first section  54  is fitted with a piston  56  that consists of a tubular stem portion  57  and extending therefrom and forwardly a hammer portion  58  which extends into the second section  55 . The second section  55  has resiliently mounted therein a chisel  59  that extends axially outwardly out of the second section  55 . The housing  52  has a conduit  49  which is perpendicular to the first section  54  and is supplied with conventional fitting (not shown) by means of which air under pressure is introduced. The chisel  58  has a rearward portion  60  and a forward portion  61  which is to the right with respect to the drawings.  
         [0042]     A helical spring  62  is concentrically located in said second section  55 . The helical spring  62  is mounted at its end  63  thereof about the rear portion  60  of the chisel  58 . The other end  64  of the helical spring  62  is mounted around the hammer portion  58 . The said end of which abuts against the underside the of an annular flange  66  of the hammer  58 . Section  55  has a front piston vent  67  through which air is vented. The first section  54  has a valve  65  which consists of a relatively small tube. The tube of the valve is concentric with respect to a major portion of the stem  57  of the piston. The stem of the piston  57  has located therein a conduit  68  which extends from near the backside of the piston to an opening  70  near the most rearward end of the stem  68 . The portion of the tube covers that opening  70  to close egress to the ambient. The valve functions by being slid closed in one position thereby permits the air pressure to be built on the backside of the piston-hammer combination  56  &amp;  58  which results in the latter being driven to the right. The surface  69  of the hammer  58  impinges on the surface  71  of the top of the chisel  61 .  
         [0043]     The air under pressure received through conduit  49  and the fitments thereof pressurizes the first section  54 . The piston  56  and hammer  58  are driven to the right and against the top of the chisel at portion  60 ; the other end of which has a chisel edge  72  which is impacted against a side of a cap of a tooth, the latter which is be removed. Any build up of air pressure in the second section  55  and ahead of the front of the hammer is vented through perpendicularly disposed conduit  67 . Inertia drives valve  65  axially concentrically to the right along the stem portion  57  of the piston  56 . This motion uncovers the end opening  70  of the conduit located in the stem portion  57  of the piston  56  whereby the pressurized air build up in the first section  54  is vented out the backside of said first section  54 . The relief of air under pressure permits the helical spring to operate to drive the piston-hammer combination back to its original position. When the stroke to the left is completed the air venting position to the rear is closed by tube valve  65  which completes its travel to the left under the aegis of inertia and the first section  54  is open again to the conduit  49  and its source of air under pressure to again cycle the piston-hammer combination to the right as before.  
         [0044]     The air under pressure drives the piston-hammer combination  56  &amp;  58  in one direction while opening of venting valve  65  which is opened under the aegis of inertia. The helical spring  62  operates to return the piston-hammer combination  56  &amp;  58  to the left with the concomitant closure of venting opening  70 .  
         [0045]     The air driven impact tool of the above discussed tool comprises one side of an U-shaped tool as disclosed in issued patent No. 5,547,380 which is incorporated herein by reference. Instead of an ultra-sonic driver as taught in the patent, the air driven impact producing tool is now taught. The other side of the U-shaped tool comprises an anvil carrying member  73 , shown in cross section in  FIGS. 4 &amp; 5  discussed in the immediate foregoing. By way of further clarification, one leg of the U-shaped tool carries the air driven impact device while the other leg carries the anvil  73 . While it is contemplated that the applicable anvil can have different surface configurations, an exemplary anvil is shown in the  FIGS. 4 &amp; 5 . It is shown to have a shoulder or notch into which the top edge of a cap  74  a toot  69  is fitted. The working surface of the anvil is covered with removable copper cap  79  which is configured to follow the outline of the notch. The copper cap  79  should have a thickness of about 0.045 inches and should be work hardened. The notch configuration shown assists to retain the tooth and its to be removed cap  74  in a substantially rigid condition there against so that vibratory causing stress on the tooth itself is minimized. The leading edge of the chisel  72  is in abutment with the opposite side of the cap  74  of the tooth. This embodiment of  FIG. 4  is useful in removing the caps on teeth wherein the caps are more firmly adhered due to the use of improved newer cements which do not readily fracture at the interface of the tooth and cap thereon. In such a situation the cap  74  is disintegrated and can not be used again.  
         [0046]      FIG. 5  is illustrative of another embodiment. The leading edge  72  of the chisel is covered with a removable hard metal insert  75  having a cap configuration thereby giving the leading edge  72  a harder secondary leading edge  76 . The secondary leading edge  76  is covered by a soft copper sheath or cap  77 , said cap having preferably a thickness of about 0.016 inches. The copper cap  77  is bonded to the hard metal insert. This embodiment has been found to be particularly useful with regard to older crowns that are cemented with less adherent cements and are subject to fractioning under the aegis of vibratory action of the herein disclosed air driven motor.  
         [0047]     Attention is now directed to FIGS.  6  to  9  for a detailed consideration of the operation of the novel air driven impact tool of the present invention. In  FIG. 6  the piston-hammer is to the left and the valve is to the left covering the air escape opening  70  and simultaneously opening the air under pressure conduit whereby air is admitted into first section  54  and behind the piston  56  of the hammer  58 . In  FIG. 7  the pressurized air drives the hammer  58  to the right to impact the top of the chisel. Then in  FIG. 8  the valve  65  is carried on the stem  57  of the piston  56  and under inertia progresses independently to open up section  54  to the ambient air through conduit  68  in the stem  57  of the piston  56 , thereby relieving the air pressure so that the helical spring  62  can drive the piston-hammer  56  &amp; 58  combination to the left. The valve  65  in  FIG. 9  moves under inertia to the left to again close the opening  70  at the end of the conduit  68  in the stem of the piston thus to stop the venting of air, as in  FIG. 6 , while at the same time opening first section  54  to the flow of air under pressure through conduit  68 . In the course of the reciprocation conduit  67  remains open to provide relief on the non pressurized side of the piston.  
         [0048]     It is incumbent to become acquainted with an additional drive means to impact on the impact receiving end of a chisel with the working end or leading edge thereof in confronting relationship with one side of the cap of a tooth, which is to be removed. With this view, attention is now directed to  FIGS. 10 and 11 .  
         [0049]     The actual impact treatment of  FIG. 4  corresponds to the impact treatment area of  FIG. 10 . Likewise the impact treatment area of  FIG. 5  corresponds to the treatment are of  FIG. 11 . However the impact drive means in both  FIGS. 10 and 11  are the same, while the drive means is uniquely different in that it can be economically constructed and requires very few moving parts while still able to deliver good impact to the working chisel.  
         [0050]     The drive means is an air driven hammer wherein the impact means is a steel ball  79  that is driven along a confining oval track  81  by suitably positioned jets of air along the perimeter of the track. The ball is thrust against the top or rear portion of the chisel and approaches the top of the chisel at an angle of 25 degrees to the axis of the chisel. Then the ball bounces away from the surface of the top of the chisel at an angle of 25 degrees to the axis of the chisel.  
         [0051]     In  FIGS. 10 and 11 , a housing  80  is provided which has a substantially oval track  81  in the housing  80 . A steel ball  82  transverses the track. The housing  80  has a concentric arcuate channel  82  radially displaced from said track opposite the position at which the chisel is mounted. The channel  82  is positioned around the track for only a portion thereof. The channel  82  has ingress port  85  for air under pressure which is distributed into the confines of the track  81  through a plurality of nozzles  83  detailed to deliver the blasts of air tangentially to the track whereby each nozzle delivers the air against the ball as it passes a nozzle. The track  81  of the housing  80  has a plurality of egress ports  84  which connect centrally radially inwardly with an egress collection conduit whereby the air under pressure is exhausted to ambient. The chisel is mounted through an opening  86  of the housing  80  which is opposite the ingress port  85 . The chisel is mounted resiliently by an elastic mount  87 .  
         [0052]     It is to be understood that various other changes and modifications may me made without departing from the scope of the invention. The present invention being only limited by the claims which are appended hereto.