US 2874470 A
Description (OCR text may contain errors)
J. R. RICHARDS HIGH FREQUENCY DENTAL TOOL Feb. 24, 1959 Filed May 28. 1954 INVENTOR MES R. RICHARDS .um r mw ATTORNEY United States Patent O HIGH FREQUENCY DENTAL TOUL `lames R. Richards, Cheverly, Md., assigner to the United States of America as represented by the Secretary of the Navy The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to a high frequency dental toolkand to a process of high frequency dental clinical wor An object of the invention is the elimination of the slow, cumbersome, heat generating, inaccurate and painful dental drilling with the conventional rotating burr and the provision of a smooth, rapid and efficient excavation method, having no objectionable effects upon the patient and no shock-or-strain-effects upon the tooth drilled.
Another object of the invention is to apply high frequency low amplitude oscillations as the motive tooth excavation actuating power.
A further object of the invention is to employ in dental clinical work the method of motivating abrasives in suspension at a high frequency and acceleration and low amplitude against the tooth under excavation.
Still another object of the inventionis a dental clinical instrument capable of packing a filling into a tooth excavation by high frequency oscillations.
Another object of the invention is to provide a dental excavating tool motivated by high frequency oscillations comprising its own liuid cooling supply and evacuation without damping the high frequency oscillations of the tool.
Another object of the invention comprises the provision of an abrasive and suspension supplying and evacuating means in the excavating tool.
A further object of the invention is to provide linger tip controls of the various supply and evacuation providing conduits, instantly and easily operable during the clinical work and without any interruptions.
Still another object of the invention is the provision of a dental tool, embodying the tooth excavating and flling functions here described, and also capable of accurate, easy performance in the limited working space of the mouth of the patient.
Another object of the invention is to provide a small light pencil-like drill enabling the operator to operate it with an artists ease and fashion to excavate holes and channels of complex shapes with extremely close tolerances desirable for this type of work.
A further object of the invention is to use a premade inlay filling as a tip extension of the dental tool herein described to preform an excavation in the tooth, accurately fitting the inlay without the necessity of any repeated trial and error drillings required up to present.
Another object of the invention is to make it possible for the first time in dental industry to use premade dental inlays of fixed shapes and standardized sizes in filling teeth cavities more efficiently and less expensively than known up to present.
Other objects and advantages of this invention will be- ICC come apparent from the following description and accompanying drawings in which: y
Fig. l represents a longitudinal section ofthe high frequency dental tool showing parts in elevation;
Fig. 2 is a perspective view of the magnetostrictive tube;
Fig. 3 shows a cross-section of the device taken on line 3-3 of Fig. l;
Fig. 4 shows elevations of modifications of the tip;
Fig. 5 is a diagrammatic view showing the valve con-v trois;
Fig. 6 exhibits elevations of' sample inlays correlated' with teeth to be treated.
Referring now to the drawings like reference characters designate like or corresponding parts throughout the severalgures.
The tool'is shown in Fig. 1 'as unit 10 and comprises:
in a preferred embodiment an 4outer tubular jacket 1-6 'of soft iron with its working end closed by plastic cap 11 and its power inlet end closed by plastic cap 12. Inside of the jacket is mounted a concentric magnetostrictive nickel tube 13, over which at its nodal (center) point is attachedV a brass sleeve 14, tightly fitting into the jacket, as shown in Fig. 3. The tube 13 is provided with longitudinal slots 15, shown in Fig. 2. In the space be tween the jacket and the tubeis a low impedance winding 17, shown in Fig. l in two layers wound over a nonconductive spool 20. The spool as shown consists of two sections 20a and 20h, divided by and anchored with their inner ends in radial grooves of the sleeve 14.' The coil is wound uniformly over both sections, and Fig. 1 shows the outer coil sections connected through slot 26e and the inner coil sections through slot 26d in the sleeve 14. This is shown in Figs. 1 and 3. The coil provides a magnetic field through an alternating cur rent input 21, which may be controlled for instance by a finger tip control switch or by a foot switch. Supported thjtkfi'tzdmlmagnet rings 18 and 19 with air gaps between them and the tube. jacket, being made for this purpose of a magnetic material such as soft iron, completes the path of ux bc tween the two magnet rings and the tube. The perma-l nent magnet rings provide the bias necessary to prevent a reversal of the magnetic flux. Without this bias the tube would become alternately magnetized to vibrate at twice the frequency of the sine wave applied. The magnetic field induced must not exceed the bias field. It has been determined empirically that for optimum performance of the embodiment of the invention shown in Fig. 1, the biasing flux density should be about 60% of the saturation value, when appliedV at points of maximum amplitude. The magnetic bias may be provided for by other known means such as a direct current without departure from the scope of the invention. The magnetostriction causes the nickel tube 13 t0 expand and to contract longitudinally from the nodal point in both directions. Lateral expansions and contractions also occur simultaneously. The longitudinal slots 15 in tube 13, shown in Fig. 2 serve to reduce the eddy currents.
The amplitude of the magnetostriction depends on theV TheA mined as equal to thev evlmcpcityi of soundv propagation through'theparticillaletial used in the tube, divided byt'wo times the length gfthetiibelmspeed of sound propagation in nickel being "16.320 feet per second, the wave length at 25 kilocycles is 0.326'=3.9". At higher frequencies the tube should be shortened, at lower frequencies extended proportionally. A frequency at least above the audible range was selected to prevent undesirable noise productions, which could affect the patient adversely, however higher frequencies of approximately 25,000 cycles per second were found advantageous to the motivation of the present tool at approximately its 4" length with 50 volts at 10 amperes. An acceleration of approximately 5,000 gravitational units is necessary but Nof approximately 10,000 gravitational unitsgis preferable to operate the present tool at high eiciency with an amplitude of about 0.01 mm. The double-layered coil 17 in combination with the magnetic ux path comprised of the jacket 16 the permanent magnet biasing rings 18 and 19 and the magneto-strictive nickel tube 13 serve as the generator of the tool tips reciprocating oscillations in this embodiment when the coil is energized by a conventional power supply having the desired frequency and amplitude characteristics. To prevent damping of the tube 13 at its ends and to allow for free end movements of the tube, the tube is supported within the jacket only by its nodal support and the caps 11 and 12 are spaced free of the tube to prevent any interference with the tubes magnetostrictive movements. The working end of the tube freely protrudes through cap 11 and is provided with an end wall 31. The wall 3l is shown in Fig. 4a at an angle of 90 and in Fig. 4b at an angle of 135 from the tubes longitudinal extension 34. The closure 31 has a hole 32 connecting the tubes interior 28 with the working area 33 of the tooth in the patents mouth. The hole 32 therefore is strategically positioned for optimum results close to the tip of the tube to permit a ow of the fluids from the tubes interior by gravitation and adhesion as shown in Fig. 1. There may be several such holes 32 in the end wall, each providing an outlet for one or more interior conduit lines. One or more lines such as 23 and 24 may be connected from the outside of the jacket. The angle of 135 of the end wall with a tip of la" has been selected as sufficient to provide a freedom of movement of the tool within the patients mouth and simultaneously to permit the hole 32 to function as a conduit of water from area 28 by gravitation upon the tooth. A portion of the wall of the tube may taper off past the end wall 31 into a working tip 34, as shown in Figs. 2 and 4c. When a changeable working tip is desirable an alternative arrangement is to provide the working end of the tube with means to fasten the tip to it, for instance by thread and screw, as shown in Fig. 4d or by soldering or welding. A kit of tips of various shapes and sizes may be made available for every tool. In the alternative the tube itself may be made exchangeable for another with a different tip. The present tool may be used with abrasives such as aluminum oxide or boron-carbide, -of minute particle sizes. Very good results were obtained with abrasives of particle size in the range of approximately 30 microns. Under operating conditions the abrasive is suspended in a fluid such as water or various oils to form in the working area of the tooth a mud of a consistency which may be quickly varied, for instance by the tools fingertip controls, shown in Fig. 5 and hereinafter described. The high frequency and acceleration impact of the tip motivates the abrasive against the tooth area attacked by it and in the direction pointed by the dentist, as the immediate cause of the tooth excavation. The excavation proceeds at extremely close tolerances predetermined by the sizes of the tip and abrasive. The tip may be made of copper, nickel, iron or other metal suficiently soft to permit the abrasive particles to embed themselves loosely in its surface, to be then by magnetostrictive acceleration propelled against the working area of the tooth; or the tip itself may have abrasives such as diamonds pressed in its surface loosely or in a firm contact. The tip, when suciently thin as indicated for instance in Figs. 4b and e may be used as a knife to slice off portions of the tooth laterally. Examples of contra angle types of tips, fiat and edgewise, are shown in Figs. 4b, e and f.
It will be readily appreciated that these contra angle tips make it possible for the first time in the history of dentistry to drill a tooth at any angle required by its usually twisted channels of decay and to follow them. Up to the present it was necessary to drill away large healthy portions of the tooth to gain access to the decayed tissues not otherwise accessible by the rotating burr. The contra-angle tips shown also are able to fill the irregular cavities by their magnetostrictively created impacts. The angle of the end wall 31 and the length of the tip `34 are selected to cooperate in providing optimum access and clinical working freedom in the patients mouth. The length of the elongation 34 including any working tip attached thereto must be `considered in the determination of the length of the tube at the particular frequency selected. The magnetostriction subjects the tube to lateral and longitudinal vibrations controlling the multivibrational directions of the tip.
Without the abrasive the tool may be used as an impact tool, for instance to fill an excavated tooth with gold foil. The foil is built up and packed into the cavity as a hardened mass by the continuous impacts of the tool.
The tool makes it possible to employ an unprecedented method of tooth filling with ready made inlays. According to the present invention an inlay of non-brittle material may be used at the end of the tip as the tip itself and will imbed itself into the tooth to be excavated, if abrasive is applied between it and the tooth. The inlay may be held in place against the tooth simply by the pressure of the tip, or the tool may include a conventional grasping mechanism. For instance the inlay may be held firmly in position on the tooth together with the tools tip with a jig. The jig may rest on or be clamped to the surrounding teeth. Thus the inlay itself will be countersunk in the tooth to preform there a perfectly fitting cavity for itself with the closest possible tolerance. The inlay itself may be used to excavate the tooth and simultaneously form its own bed. It will be thereafter taken out, the cavity cleaned and the inlay reinserted and cemented in. Such a method is possible in a great percentage of tooth fillings. According to the present invention the inlays are to be mass produced in several standardized sizes corresponding to the most frequently encountered sizes of cavities to be filled. The inlay may be shaped with a larger bottom than top area, such as a frustated cone or 'pyramid and may be dovetailed into the tooth to anchor it more firmly. An example of such an inlay is indicated in Fig. 4a showing at the end of tip 34 a triangular prism. A body of any other geometrical shape may be utilized as an inlay. ,X
An altrenative arrangement is to provide the np 34 itself with a premade extension of the same predetermined size and shape as an inlay to be inserted into the tooth, of which again Fig. 4a is a demonstration.
In Fig. 6 are shown examples of unconventionally shaped inlays and how they may be fitted over teeth cavities with the present tool. Fig. 6a represents a crown 43 which differs from the thin-shelled crowns used up to the present in that it is a combination of a crown and inlay. The conventional thin-shelled crown must be tailor made individually for each tooth, and even then its interior does not correspond to the surface of the tooth and does not repalce the excavated area. A brittle filler is used to build up the tooth within the shell. Often air cavities remain behind after the crown is cemented on and within a short interval the top of the crown, not having a solid support. is bitten through and must be replaced. The crown of the present invention shown in Fig. 6a is a solid body having the conventional outer shape and a solid in ner area replacing the excavated tooth portion. Up to present it would be almost impossible to t a tooth with a premade crown of this type, since the dentist cannot see inside it, when fitting it over the tooth. It would be also impractical to individually make a crown body lilling the excavated tooth area. The present invention makes it possible for the first time to use a premade crown of a standard predetermined size and shape comprising a solid inner body and an outer shell to countersink it over and into the tooth in one simple operation. Fig. 6B shows in front view the example of another type of an inlay 44 in the form of a U-shaped band as it tits over a tooth and Fig. 6C exhibits a side view of a similar inlay with its prong ends sharp and tapered like staples to take a rm grip in the tooths body.
The various conduits of fluid supplies and exhausts may be valve-controlled by fingertips of the same hand holding the tool during its operation. Fig. 5 shows the unit 10 provided on the outside of jacket 16 with valve control knobs 35, 36, 37 slidable by linger tip control, each between a pair of rails 38, 39 and 40. Each conduit is shown provided with a valve; the exhaust with valve 23a, the air line with valve 29a and the water line with valve 22a, each connected to its respective slidable' knob by a control wire 41. Each control wire is protected by a tubular control wire guide 42. As an example buttery valves may be used comprising a diaphragm inside the valve housing with a spring loaded shaft controlled by the slidable knob to force the return of the valve into its original position upon release.
While magneto-striction has been utilized in the preferred embodiment of the invention shown, other sources of high frequency vibrations, such as mechanical, electrical, electromagnetic, piezoelectric or sonic may be employed as equivalent motive powers of the present dental tool, without departing from the spirit and scope of the invention.
The alternating current input lines 21 and various iluid conduit lines are admitted into the jacket either through cap 12 or through orifices in the jacket such as 25. The coil 17 is shown in Fig. l cooled through conduit 24 circulating water through inlet 25, slots 26e and 27 as indicated by arrows, into the interior 28 of tube 13. There the water cools the tube and is dispersed by the magnetostn'ctive motions and by gravity partially through slots (shown in Fig. 2) into the air space 30 and partially through hole 32 into the working area 33 to cool the tooth under excavation and to keep the abrasive in liquid suspension. Lines 22, 29 and 23 are shown entering the interior of the tube through orifices in cap 12'. Lines 22, supplying air, and 29, supplying water, extend to the working end 31 of the tube and produce there by combined function and air-water spray penetrating through hole 32 upon the excavated tooth 33 to cool it. An additional line such as 29, may be incorporated to supply the tooth with the abrasive either dry or in solution with water. An additional vacuum exhaust line such as 23b, may be extended to the area 33 tovwithdraw excess moisture and used up abrasive from the tooth excavated. The water which penetrates through slots 15 into the air space 30 and any excess of water in the interior 28 of the tube is withdrawn through the vacuum exhaust line 23 which eliiciently increases the cooling of both the exterior and interior walls of the tube.
The advantages of the invention as here outlined are best realized when all of its features and instrumentalities are combined in the respective structures, but useful devices may be produced embodying less than the whole.
While the tool has been illustrated operable as a dental tool it isby no means limited to such purposes, but may be used for instance by artists, in sculpture, diamond setting, in providing artificial dentures with inlays to simulate teeth appearing convincingly true, etc.
It should be understood that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifica tions of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.
l. A pencil like shaped dental tool comprising in combi. nation an outer longitudinal jacket, an inner high frequency oscillating tube suspended within said jacket with a clearance at its working end, and protruding through it at its working end with an extended working tip for endwise free reciprocating oscillations of said tip, a generator of said oscillations, a power supply to said generator, and at least one iluid conduit and fluid supply and exhaust means connected with the interior of said tube.
2. A pencil like shaped dental tool comprising in combination an outer cylindrical jacket of magnetic material, an inner tube of magnetostrictive material protruding through said jacket at its working end with an extended working tip, said tube being centered within said jacket by a sleeve support for otherwise free magnetostrictive movements, a high frequency magnetostrictive oscillations exciting electric winding on a spool spaced within said jacket and over said tube, an alternating current supply exibly connected through the conduit end of said jacket to said winding and two permanent magnet rings, each mounted inside one end of said jacket and spaced from the adjoining longitudinal portions of said tube.
3. A pencil like shaped dental tool comprising in combination an outer cylindrical jacket of'magnetic material, an inner tube of magneto-strictive material protruding through said jacket at its working end with an extended working tip, said tube being centered within said jacket by a sleevesupport for otherwise free magneto-strictive movements, a high frequency magneto-strictiveoscill tions exciting electric winding on a spool spaced within said jacket and over said tube, an alternating current supply liexibly connected through the conduit end of said jacket to said winding, two permanent magnet rings, each mounted inside one end of said jacket and spaced from the adjoining longitudinal portions of said tube, a plu rality of fluid conduits of abrasive, abrasive suspending medium, and cooling and flushing uid, said conduits connected with the interior of' said tool for supply and withdrawal of said iluids, and an end wall at the working end of said tube provided with a hole connecting the working area of the tool with theinterior of said tube.
4. A pencil like shaped dental tool comprising in combination an outer cylindrical jacket of magnetic material, an inner tube of magneto-strictive material protruding through said jacketI at its working end with an extended working tip, said tube being centered within said jacket by a sleeve support for otherwise free magneto-strictive movements with clearance from the ends of the jacket at both ends, a high frequency magneto-strictive oscillations exciting electric winding on a spool spaced within said jacket and over said tube, an alternating current supply flexibly connected through the conduit end of said jacket to said winding, two permanent magnet rings, each mounted inside one end of said jacket and spaced from the adjoining longitudinal portions of said tube, a plurality of uid conduits of abrasive, abrasive suspending medium, cooling and flushing uids and air, said conduits connected with the interior of said tool for supply and withdrawal of said uids, an end wall at the working end of said tube provided with a hole connecting the working area of the tooth with the interior of said tube, each of said conduits equipped with fingertip controls of said valves mounted on said jacket.
5. A pencil like shaped dental tool comprising in combination an outer cylindrical jacket of magnetic materiaL. an inner tube of magneto-strictive material protruding through said jacket at its working end with an extended working tip, said tube being centered within said jacket by a sleeve support for otherway free magneto-strictivo movements, a high frequency magneto-strictive oscillations exciting winding on a spool spaced within said jacket and over said tube, an alternating current supply flexibly connected through the conduit end of said jacket to said winding, two permanent magnet rings, each mounted inside one end of said jacket and spaced from the adjoining longitudinal portions of said tube, a plurality of uid conduits of abrasive, abrasive suspending medium, cooling and ushing uid, said conduits connected with the interior of said tool for supply and withdrawal of said fluids, an engLwall at the working end of said tube provided with a hole connecting the working area of the tooth with the interior of said tube, each of said conduits equipped with a valve and finger tip control of said valves mounted on said jacket, said end wall of said tube being tapered ot toward the root of the working tip at an angle of less than 90.
6. In a dental tool, a generator of magneto-strictive oscillations comprised of a coil member wound upon a spool of non-conductive material and fiexibly connected to an alternating current supply, and a ux path consisting of a jacket member of conductive material concentrically disposed around said coil, a tubular tool holder element of conductive material having a plurality of longitudinal slots concentrically located within said coil, and a plurality of permanent magnet biasing rings mounted within said jacket and separated from the tool holder by air gaps; the magnetic bias of the permanent magnet rings, the size of said air gaps, and the length of the tubular tool holder being deterrninative of the frequency and amplitude ratings required of the alternating current supply.
7. In a dental tool, a generator of magneto-strictivc oscillations comprising a double-layered coil wound upon a spool of non-conductive material and flexibly connected to an alternating current supply, a ux path consisting of a jacket of conductive material concentrically xed about said coil, a tool holder of conductive tubular material having a plurality of longitudinal slots therein, said tool holder being concentrically located within said coil and tixed at its midpoint for symmetrical oscillations, and a plurality of permanent magnet rings mounted within said jacket so as to form air gaps between the jacket and tool holder, said permanent magnet rings providing a bias for the magnetic field setup by the coil when it is energized.
References Cited in the le of this patent UNTIED STATES PATENTS 1,118,301 Magill Nov.' 24, 1914 1,882,393 Pierce Oct.l l1, 1932 1,966,446 Hayes July 17, 1934 2,490,273 Kean Dec. 6, 1949