US2814877A - Abrasive applicator - Google Patents

Description

2 Sheets-Sheet 2 Arron/v5) Dec. 3, 1957 w. F. TILDEN ABRASIVE. APPLICATOR Filed July 11, 1955 new The invention, in general, relates to the art of dentistry.

I atent More particularly, the invention pertains to improved instruments and methods employing abrasive-laden gases for treating teeth, especially for removal of hard tooth structure and for the removal of surface discolorations or of bacterial plaques.

I am aware of certain recent developments in the art wherein abrasive-laden gases are employed to accomplish such corrective procedures as rapid reduction of tooth structure, the removal of stains, and the removal of bacterial plaques in lieu of previously used rotary grinding instruments which involve disagreeable vibration as well as the generation of heat with consequent extreme discomfort to patients. However, the majority of these recently developed devices designed to accomplish such corrective procedures have many disadvantages. Not only are these devices of such complex construction as to be appreciably expensive to manufacture and, perforce, beyond the financial capacity of the average dentist to employ but also they are of such a size that they cannot be accommodated for in the already crowded space allotted to equipment that is mandatory for the practice of dentistry. The present invention has been devised to obviate all of the disadvantages of prior instruments and devices employed to accomplish the aforesaid corrective procedures, and to provide an improved instrument of relatively simple principle and design which can be manufactured at a minimum of expense and which, because of its compactness, will occupy a minimum of space.

A primary object of the invention is to provide an improved self-contained abrasive applicator which affords a controlled even flow of an abrasive-laden gas to the point of application in predetermined proportions of abrasive and the gas vehicle.

Another important object of my invention is to provide an improved abrasive applicator of the indicated nature which is additionally characterized by the provision of a manually operable valve adjacent to the functional end of the applicator to stop and to start the flow of abrasive-laden gas instantly and obviate uneven and uncontrolled flow thereof in the system.

A still further object of my present invention is to provide an improved abrasive applicator of the aforementioned character which can be manufactured inexpensively and which occupies a minimum of space.

Another object of the invention is to provide an improved method and system of treating teeth with an abrasive-laden gas which requires no electrical connections and which functions to effect the removal of hard tooth structure or the removal of surface discoloration from the teeth, or the removal of bacterial plaques in a the advantageous features thereof, will appear from the following description of a preferred embodiment and certain modified embodiments otthe invention which are illustrated in the accompanying drawings. It is to be understood, however, that I am not to be limited to the precise embodiments shown, nor to the precise arrangements of the various parts thereof, as the invention, as defined in the appended claims, can be embodied in a plurality and variety of forms.

Referring to the drawings:

Fig. 1 is a side elevational view, partly broken away and partly in longitudinal section to illustrate the construction, of a preferred embodiment of the invention as exemplified in a self-contained applicator.

Fig. 2 is an enlarged broken longitudinal sectional view of a portion of the embodiment illustrated in Fig. 1.

Fig. 3 is a sectional elevational view of a gas drying element which may be employed in the preferred embodiment of the invention shown in Fig. 1.

Fig. 4 is a sectional elevational view, partly in broken full lines, of a modified embodiment of the present invention.

Fig. 5 is an enlarged cross-sectional detail of the outlet of the hopper employed in the modified embodiment of Fig. 4.

Figs. 6, 7 and 8 are sectional elevational views of various replaceable nozzles for employment with the preferred and modified embodiments of the invention.

In its preferred form, my improved abrasive applicator as exemplified in a self-contained instrument preferably comprises, in combination with a source of dry compressed air, a tubular handle, an enlarged section on said handle defining a chamber for the storage of an abrasive, means for maintaining the abrasive under pressure within said chamber, together with means within said handle and said chamber for conducting a gas under pressure from said source; said means communicating with said chamber for permitting abrasive to be withdrawn therefrom for entrainment with said gas, means for regulating the amount of abrasive withdrawn from said chamber for entrainment in said gas, a manually operable valve on said handle for controlling the flow of abrasiveladen gas therethrough, and a nozzle removably fitted to said handle for directing the abrasive-laden gas against a desired surface. A modified embodiment of the present invention comprises, in combination with a source of compressed air, a tubular handle, a hopper for the storage of an abrasive; said hopper having a restricted out let, a rigid tube supported within said handle for conducting a gas under pressure from said source, means for drying said gas intermediate said source and said tube,

together with means in the line of flow of said gas and movably supported adjacent said restricted outlet of said enlarged hollow section 12 thereon defining an interior chamber 13 for receiving and holding a quantity of an abrasive powder 14, such as Dolomite or the like. A pistom 16 is movably mounted within the chamber 13 in order to maintain the contained powder under constant pressure and to force the same toward one end of the chamher; the piston 16 being backed up and under the influence of a spring 17 which is confined within the tubular handle 11 between one end of a valve member 18 and the outer end 19 of the head 21 of the piston. Preferably,

the piston 16 comprises an inner generally concave-convexo metal plate 22, an outer generally concavoconvexo metal plate 23, and an intermediate rubber seal 24, which may consist of an O ring; all secured together by a series of screws 26 and each having a central opening therein for the passage of a conduit 27 in which an abrasive-laden gas is conveyed, as hereinafter described. The outer plate 23 of the piston terminates exteriorly in the reduced head 21 extending within the tubular handle at the adjacent end thereof as shown in Fig. 1. The enlarged section 12 is provided with a removable closure 28 to permit ready access to the parts within the chamber 13 when desired; the closure 28 having a threaded hole therethrough which is normally sealed by a screw 29 and rubber washer 31. Removal of screw 29 provides an opening for filling the chamber 13 as well as for the insertion of a rod, or the like, not shown, to hold the piston $356 at the opposite Wall of the chamber against the influence of spring 17 when filling and refilling the chamber 13 with abrasive material.

In accordance with the present invention, as exemplified in a self-contained applicator, means are provided for conveying a gas, such as air, under pressure to and through the chamber 13 as well as to withdraw desired amounts of the abrasive powder 14 from chamber 13 for entrainment in the conveyed gas so .as to provide desired amounts of abrasive-laden gas under pressure at desired surfaces. The source of gas under pressure, not shown, may consist of a tank of pre-dried air held under a pressure head ranging between approximately 65l00 pounds pressure. Such tanks are commercially available but generally occupy too much space for the average practicing dentist and are appreciably expensive. Accordingly, I preferably employ as the source of gas an air compressor, operating at 30-45 pounds per square inch pressure, which is a part of the normal equipment in dental oflices, and combine with the air compressor a drying chamber for thoroughly drying the air prior to conducting the same to the applicator handle 11. To this end, I provide anupright housing 32 having a removable cover 33 thereon and defining a relatively large chamber 34 for holding a quantity of a dehydration substance 36, such as silica gel or the like, which removes moisture from the air passing through the chamber. Secured to the bottom of the cover 33 of the housing 32 and suspended therefrom within the chamber 34 is a rigid tubing 37 which communicates with the air compressor through an inlet passage 38 in the cap or cover 33 and a flexible conduit 39 connected to the outlet of the compressor; the housing cap 33 being also provided with an outlet passage 41 for conducting dried air under pressure through an outlet flexible tubing 42.

In order that the abrasive powder 14 in chamber 13 will be evenly withdrawn for entrainment in the air flowing under pressure, I provide the ported gas conducting conduit or tube 27 with which a needle valve 47 is associated for controlling the admixture of abrasive and conducted air. The tube 27 conveniently is fabricated of a lightweight material, such as aluminum or the like, and is arranged to be supported within and concentrically in relation to the tubular handle 11 with the inner end of the tube 27 securely fitted within a flexible conduit 48 extending through the valve body member 18, which is detachably secured to the outer end of the tubular handle 11. The tube 27 extends through the piston 16 to the outer wall or removable cap 28 of chamber section 12 in alignment with and fitting a central opening 49 in the cover 28. As shown in Fig. 1, the inner wall of cover 28 of the chamber section 12 is formed with a central boss 51 thereon surrounding the opening 49 and projecting inwardly to encompass the outer terminal of the tube 27 and thus fixedly secures the tube in operative position; the tube 27 being flared outwardly at its outer end not only to fit the central opening 49 of cap 28 but also to afford an enlargement thereof defining a mixing chamber 52, and the tube also is formed with an annular port 53 therein which establishes communication between the chamber 13 and H sage 71 of the nozzle.

the mixing chamber 52. Needle valve 47 slidably fits the central opening 49 of the chamber section cover 28 and is sealed and retained in operative position by means of a packing gland consisting of a rubber gasket 54, a threaded nipple 56 on the outer wall of the cover 28, and a knurled cap 57 threadedly engaging the nipple and encompassing the gasket 54. As shown, the needle valve 47 is provided with a constricted inner tip 58 having a relatively small outlet orifice 59 therein which terminates in the mixing chamber 52. The dried air under pressure is delivered from the drying chamber 34 through flexible tube 42 to and through needle valve 47 which is variably positioned with respect to the port 53 of the conveyor tube 27 as well as mixing chamber 52 to draw the desired amount of abrasive 14 from the chamber 13 for entrainment in the air stream; adjustment of the needle valve 47 being readily made manually by drawing out or pushing in the same relative to the cap or cover 28 of the abrasive chamber section 12.

In accordance with the invention, as exemplified in the self-contained applicator, valve body member 18 is provided with a transverse bore 61 for the reception of a push-button pinch valve member 62 as well as a coil spring 63 which normally urges a shoulder 64 of the valve member 62 against the flexible conduit 48 and pinches the same together so as to cut off gas flow therethrough. Pressure of the thumb upon a thumb-piece 66 of the valve member 62 depresses spring 63 to open the conduit 48 for full or partial gas flow therethrough, as desired. As shown, a short rigid outlet tube 67 is telescopically fitted to the outlet of flexible tube 48 to maintain the flexible tube open at its outlet end at all times, as is the case of the inlet end of the tube 48 which is held open at all times by the inner end of rigid tube 27. Abrasive-laden gas under pressure emanating from the outlet tube 67 of the valve body member 18 is delivered through any selected one of a plurality of applicator nozzles 68 which are readily removably fitted by means of a bayonet clutch fit to the outer end of valve body member 18.

As shown in Figs. 1, 4, 68, inclusive, the applicator nozzle 68 may be any one of several various types, such as a straight tip type, as shown in Fig. 6, wherein the nozzle tip 69 extends in a straight line from the outlet of the nozzle and is coaxial with the narrow discharge pas- Or, the nozzle 68 may take the form shown in Fig. 7, which is provided with a tip 69a disposed in right angle relationship to the axis of the discharge passage 71a thereof; the nose of the nozzle, likewise, being formed to the same right angle to accommodate the right angle tip. Again, the nozzle 68 may be formed with a back-angle tip 69]) in relation to the axis of the discharge passage 71b, as shown in Fig. 8, with the nose of such type nozzle similarly disposed to accommodate this disposition of the tip. Or, the nozzle 68 may take the form shown in Figs. 1, 2 and 4, wherein its tip 690 is at a contra-angle to the axis of the discharge passage 71c, and the nose of such type nozzle being similarly disposed to present the tip at such an angle. These various types of nozzles are, of course, interchangeable and each is sealed by means of a rubber gasket 72, see Figs. 2 and 4, to prevent gas leakage. As indicated, the various nozzles may be detachably secured by any suitable means, such :as screw threads or by a bayonet-type locking means, as shown.

In order to retain the piston 16 in a compressed position against the inner wall of the chamber 13 when filling and refilling the chamber with a supply of abrasive powder, I provide a latching means for the piston comprising apin 7 6 which includes an integral thumb-knob 77; the pin being movably seated in a small casing 78 and held normally in unlatching position by means of a spring 79 confined between the inner bottom of the casing, which may be an enlarged portion of the tubular handle 11, and a collar 81 fixedly secured to the pin 76. The pin pierces the bottom of casing 78 and extends within the tubular handle 11,

when depressed by pressing down on the thumb knob 77, to engage a notch 82 formed in the head 19 of the piston 16, thus holding the piston in its ultimate compressed position. Naturally, the pin is held in the notch 82 during the filling of the chamber 13 and only released after the screw 29 has been replaced after the completion of a filling operation.

The handling and use of the self-contained abrasive applicator, hereinabove described, is relatively simple. Assuming that a nozzle 68 has been selected for treating a desired surface and condition, and has been secured to the outer end of the valve body member 18 of tubular handle 11, and further assuming a full supply of abrasive powder in chamber 13, the air compressor is started causing air under pressure to be delivered through the flexible conduit 39 to and through the drying chamber 34 for delivery of dry air under pressure through flexible tube 42 to and through the passage of needle valve 47 which has been adjusted with relation to the mixing chamber 52 and the port 53 of the rigid tube 27 so as to withdraw desired amounts of the powder for entrainment in the air stream. Because of the expansion of the air when entering the mixing chamber 52 from the passage of the needlevalve, a Venturi action takes place permitting effective and thorough mixing of the powder with the air. Due to the continuing pressure of the piston 16 on the contained powder in chamber 13, an even withdrawal of the powder therefrom is always had. The abrasive-laden gas under a pressure head passes through tube 27 and reaches the flexible hose 48 in the valve body member 18 of the tubular handle where it is retained under such pressure head. The dentist, or operator, then depresses valve member 62 by pressing down on the thumb-piece 66 thereof to open the conduit 48 for full or partial flow of the abrasive-laden gas, as desired, to and through the nozzle 68 and tip 69 thereof and against the surface or tooth being treated. Preferably, a tungsten-carbide nozzle tip is used in all of the nozzles 68 in order to increase longevity of use thereof. The flow of the abrasive-laden gas is continued to the extent necessary and then the thumb removed from the thumb-piece 66 causing the valve member 62 to return to its initial position under the influence of its associated spring 63 to pinch the rubber hose 48 and cut ofl the flow. For convenience in handling, the outer surface of the tubular handle 11 is knurled as is, likewise, the outer surfaces of the screw 29 and the adjusting cap 57 for the needle valve 47.

It may be observezd that in order to utilize my improved abrasive applicator for the removal of hard tooth structure, the dry compressed vehicle, such as air, for carrying the abrasive powder should be under a pressure ranging from approximately 65 to approximately 100 pounds per square inch. For such operations, therefore, it is desirable to combine the hand instrument embodiment of my improved self-contained applicator, as above described, with a tank, not shown, of dry compressed air which is held under the stated pressure head, and to connect the outlet of such a tank by means of suitable tubing to the inlet end of the passage of needle valve 47. The stream of abrasive-laden air under the increased pressure indicated is directed by nozzle 68 to the area of the tooth to be abraded, and the spent abrasive removed by a suitable vacuum cleaner means, not shown, since the amount of abrasive to perform such a function is considerable and a collecting device is essential. However, for normal and prophylaxis, including removal of discoloration and bacterial plaques, the relatively small volume of abrasive powder used in most cases makes it unnecessary to include a clean-up device as the moist tissue areas will hold the spent powder. As indicated above, therefore, the gas pressure required for oral prophylactic work may be delivered from an ordinary air compressor operating under approximately 30-45 pounds pressure which is nor- .mally available in all dental ofiices. In order to remove undue moisture present in the air delivered from the air compressor, it isrecommended that the compressed air be first directed through a drying chamber, such as the drying chamber 34 described above, for all of such oral prophylactic work.

A modified embodiment of my present invention is illustrated in Fig. 4 of the annexed drawings. In this modification, I provide a relatively short hand-piece or tubular handle 111 to which is detachably connected by threaded engagement therewith a valve body 118 and in which is supported a relatively narrow rigid tube 127 through which abrasive-laden gas is caused to flow for application to a desired surface. The tube 127 is supported between valve body member 118, at one end, and by a screwclosure cap 128, having a central opening therethrough in which the other end of tube 127 is fitted and from which it projects.

As in the preferred embodiment, a drying chamber containing a dehydration substance is preferably included in the modification for removing moisture from the delivered gas before entrainment of the abrasive powder into the gas stream. Parenthetically, it may be observed that if an air compressor is the source of the compressed gas then the dehydration substance is used in the drying chamber but if the source of compressed air is a tank of dry compressed air it is unnecessary to fill the drying chamber with the dehydration substance. To this end, I provide a drying chamber housing 132 which preferably is constructed to a size that will conveniently be accommodated in the conventional medicine bottle-holder, not shown, that is found in practically all dental units, thereby to conserve space as well as effectively to place the applicator Within a short distance of the patient. The housing 132 is provided wtih a specially formed removable top 133 and defines a relatively large drying chamber 134 in which a quantity of a dehydration substance 136, such a silica gel, may be contained. Suspended from the bottom of the top 133 of housing 132 within the chamber 134 is a vertically disposed small metal tube 137 for carrying the delivered gas under pressure to the bottom of the chamber 134 from which it filters upwardly through the silica gel for moisture removal; the metal tube 137 being in communication with an inlet passage 138 of cap 133 and, in turn, with a flexible conduit 139 leading from the outlet of the source of compressed air or gas, not shown. The dried gas leaves the drying chamber through an outlet passage 141 opening to a variable size transverse passage formed in the upper portion of the removable top 133 of the drying chamber housing 132, and communicating with a flexible tube 142 for conducting the abrasiveladen gas to the rigid tube 127 of the tubular handpiece 111. As shown, a needle valve 147 is movably mounted within passage 140; that portion of the passage 140 in which the needle valve is movably disposed being of larger diameter than the restricted outlet in the passage which communicates with the flexible conduit or tube 142, thus defining a mixing chamber 152 wherein the abrasive powder is mixed with the compressed dried gas by a Venturi action and is entrained in the gas for delivery to the rigid tube 127 of the hand-piece 111. The needle valve 147 is sealed against gas leakage outwardly of transverse passage 140, yet permitting axial movement of the needle valve, by a suitable packing gland consisting of an exteriorly threaded apertured nipple 154, a rubber gasket 156, and a screw-cap 157, as shown.

In accordance with my present invention, as exemplified in the modification of Fig. 4, I provide a hopper 212 defining a large interior chamber 213 for holding a quantity of a suitable abrasive powder 214; the hopper having an exteriorly threaded outer end for threaded engagement with an interiorly threaded upper extension of the drying chamber housing 132 so that the hopper may be removably seated upon such housing. The hopper is provided with a threaded closure cap 215, upon removal of which the chamber 213 may be filled and refilled with the abra sive powder. The bottom of chamber 213 preferably is bounded by a converging wall having a centrally arranged opening therein communicating with an outlet passage 216 which, in turn, communicates with an axially aligned passage 217 formed in the upper portion of the top 133 of housing 132; the passage 217 terminating in a transversely arranged narrow slot 218, see Fig. of the drawings, which communicates with the enlarged portion of transverse passage 140 and which is controlled by the needle valve to regulate the volume of abrasive powder withdrawn from the chamber 213 for entrainment in the stream of compressed gas flowing through the passage 140.

Substantially the same type of pinch valve is provided in the modified embodiment of the invention as that included in the preferred embodiment of the invention shown in Figs. 1 and 2.. However, a slight modification is made in the modified embodiment, in that the abrasiveladen gas passing through rigid metal tube 127 enters a flexible hose 148 contained in a longitudinal bore of the valve body member 118; the flexible hose 148 being pinched when the applicator is not in use by a valve member 162 which is held in a pinching operative position by means of a spring 163 as well as an overlying tip 164 of a manually operable pivoted lever 166 including a thumb piece 167. Pressure of a thumb upon thumb-piece 167 of the lever 166 causes the overlying tip 164 of the lever to disengage the valve member 162 and, under the influence of the spring 163 the valve rises to open the flexible hose 148 for full or partial flow of the abrasive-laden gas therethrough. As in the case of the preferred embodiment of the invention, 1 provide in this modification a nozzle 168 provided with a tungsten-carbide tip 169; the nozzle being detachably secured to the hand-piece 111 by any suitable means, such as by a bayonet clutch connection. It is understood, of course, that any selected one of the nozzles illustrated in Figs. l, 4, and 6-8, inclusive, may be detachably connected to the hand-piece, as desired,

'to accomplish the abrasion of the tooth surface being treated.

In the modification of Fig. 4, a by-pass tube 221 is supported within the hopper chamber 213 by fitting the same in a through opening in the bottom of the hopper; the bypass tube 221 communicating with an axially aligned passage 222 formed in the upper portion of the drying chamber housing 132 which, in turn, communicates with the transverse passage 149 therein, as well as with a transverse opening 223 formed in the needle valve 167, thus allowing a part of the dried gas to pass up to the top of the abrasive chamber 213 to equalize the pressure throughout the combination of drying chamber and housing, as well as the entire system.

By reason of the units and system thus described, the modification of the present invention is highly effective causing the emanation of desired amounts of abrasiveladen gas under pressure at a desired surface. The provision of the relatively narrow slot 218 as the outlet of the abrasive chamber 213 not only prevents the passage of abrasive when gas is not flowing but also allows the abrasive powder to be drawn down from the mixing chamber when the air stream is flowing into the mixing chamber 152 under a Venturi eflect to insure not only proper mixing of the abrasive with the air but also that the powder is properly proportioned. As the needle valve 147 is advanced inwardly, less of the opening 218 is open to the passage 14% and less abrasive powder is admitted into the air stream. As the needle valve is withdrawn, the maximum opening and the maximum amount or" powder is obtained. The transverse, restricted outlet orifice 218 of the hopper 212 is a special feature of this modification.

It is to be understood that the appended claims are to be accorded a range of equivalents commensurate in scope with the advance made over the prior art.

I claim:

1. A self-contained dental abrasive applicator comprising, in combination with a source of compressed gas, a tubular handle, an enlarged section on said handle defining a chamber for the storage of an abrasive, means for maintaining the abrasive in said chamber under pressure, a tube extending through said handle and said chamber; said tube having a port therein establishing communication between said tube and said chamber; said tube having a flaring end adjacent to said port defining a mixing chamber, a needle valve movably disposed in said tube adjacent to said port and said mixing chamber for regulating the amount of abrasive passing from said chamber into said tube and said mixing chamber through said port; said needle valve having a passage therethrough, means connected with the outlet of said source of compressed gas for conveying a stream of gas under perssure to and through the passage of said needle valve to eifect withdrawal of a predetermined amount of abrasive from said chamber into said mixing. chamber under Venturi action for entrainment in said stream of gas in predetermined proportion thereto and to cause abrasive-laden gas to flow through said tube and out of the same, a nozzle on said handle and in communication with said tube for directing jets of abrasive-laden gas to a desired surface, and a manually operable valve disposed adjacent to said nozzle for controlling the flow of abrasive-laden gas from said nozzle.

2. A self-contained dental abrasive applicator for emitting a stream of abrasive-laden gas under pressure; said applicator comprising, in combination with a source of compressed gas, a tubular hand-piece, an enlarged hollow section integral with and having its axis in alignment with the axis of said hand-piece and defining a compartment for holding a quantity of an abrasive, means in communication with the outlet of said source of compressed air for conveying a stream of gas under pressure therefrom and for eflecting the withdrawal of abrasive from said compartment for entrainment in the stream of gas, a nozzle on said tubular hand-piece for directing a jet of the abrasive-laden gas to a desired surface, means for conveying the stream of gas with entrained abrasive through said hand-piece to the outlet of said nozzle, and a valve on said hand-piece adjacent to said nozzle for controlling the flow of abrasive-laden gas from said nozzle.

3. A self-contained dental abrasive applicator comprising, in combination with a source of compressed gas, a tubular hand-piece, a tube supported within said hand-piece, an abrasive holder integral with said hand-piece; said holder having an outlet communicating with said tube, means in communication with said source of compressed gas for conveying a stream of gas under pressure from said source past said outlet of said abrasive holder to draw a predetermined amount of abrasive from said holder into said stream of gas and for conducting the abrasive-laden gas through said tube, a nozzle on said hand-piece communicating with said tube, a manually operable valve in the path of said abrasive-laden gas intermediate said tube and said nozzle for controlling the flow of the abrasive-laden gas through said tube and said nozzle, and a lever movably mounted on said hand-piece adjacent to said nozzle and connected to said valve for actuating the same.

4. A self-contained dental abrasive applicator for directing a jet of abrasive-laden gas upon a desired surface; said applicator comprising, in combination with a source of compressed gas, a hand-piece, a tube within said handpiece, a chamber on said hand-piece for holding a quantity of an abrasive; said chamber having an outlet communicating with said tube, a needle valve movably disposed in said tube and controlling the outlet of said chamber for regulating the amount of abrasive drawn from said chamber; said needle valve having a passage therethrough communicating with said tube, means between said source of compressed gas and the passage of said needle valve to convey a stream of gas under pressure from said source to and through said needle valve past said outlet to effect entrainment of a predetermined amount of abrasive in said stream and to conduct abrasive-laden gas through said tube, a valve containing said stream of abrasive-laden gas within said tube under a pressure head, a nozzle on said hand-piece in communication with said tube, and a lever movably mounted on said hand-piece adjacent to said nozzle and connected to said valve for opening said valve at will and for causing a jet of abrasive-laden gas to be emitted from said nozzle.

5. A self-contained abrasive applicator as defined in claim 4, and including means in said chamber for maintaining the abrasive therein under constant pressure in diminishing supply whereby the abrasive is uniformly withdrawn therefrom by the stream of gas under pressure for entrainment therein.

6. A self-contained abrasive applicator as defined in claim 4, and including a spring-urged piston in said chamber for constantly forcing the abrasive therein against one end thereof whereby uniform amounts of the abrasive are Withdrawn from the chamber by the stream of gas under pressure for entrainment therein, and means for holding said piston at one side of said chamber against the action of the spring while filling the chamber with an abrasive.

7. A self-contained abrasive applicator as defined in claim 4, and means for drying the gas during its conveyance from said source to said needle valve.

8. A self-contained dental abrasive applicator for removing hard tooth structure; said applicator comprising, in combination with a source of dry compressed gas held under a pressure head ranging between approximately 65 to approximately 100 pounds per square inch, a handpiece, a tube supported within said hand-piece, an enlarged section on said hand-piece defining a chamber for holding a quantity of an abrasive; said chamber having an outlet communicating with said tube, means for conducting a stream of said dry compressed gas to said tube piece in communication with said tube, a valve between said jet nozzle and said tube for containing the stream of abrasive-laden gas within said tube under said pressure head, and a lever movably mounted on said hand-piece adjacent to said nozzle and connected to said valve for opening the same at will to cause a jet of the abrasiveladen gas to issue from said nozzle against a desired tooth structure.

9. A dental abrasive applicator comprising, in combination with an air compressor for delivering air under pressure, a handle, a tube secured Within said handle, a housing having a relatively large chamber therein, a dehydration material in said chamber, a removable cap on said housing; said cap having an inlet, an outlet, and a transverse passage communicating with said outlet, means establishing communication between said inlet and said air compressor for conducting a stream of air under pressure into said chamber through said dehydration material to remove moisture therefrom and for conducting the dried air stream through said outlet into and through said transverse passage under pressure, means establishing communication between the outlet of said transverse passage and said tube in said handle, a hopper removably mounted on said housing and containing a quantity of an abrasive; said hopper having a restricted outlet communicating with said transverse passage, a needle valve movably mounted in said transverse passage and controlling said restricted outlet of said hopepr to regulate the amount of abrasive drawn therefrom for entrainment in said stream of air flowing in said transverse passage, a nozzle on said handle communicating with said tube, a valve between said nozzle and said tube to contain abrasive-laden dry air under a presure head, and means movably mounted on said handle adjacent to said nozzle for opening said valve at will to cause a jet of abrasive-laden gas to be emitted from said nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 2,725,684 Crowe Dec. 6, 1955

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