US2643456A - Dental hand instrument - Google Patents

Description

June 30, 1953 J. MAURER ETAL DENTAL HAND INSTRUMENT File'd Feb. 23, 1951 3 Sheets-Sheet l Ilm- IN VEN TORS ./A/fos MA1/RER w Ross/Tr MA1/RER THE/l? A 7' T ORNE Y June 30, 1953 J. MAURER ET AL DENTAL HAND INSTRUMENT 5 Sheets-Sheet 2 Filed Feb. 25, 1951 llllllllllllllllllilUI INVENTORS. JAKOB MAI/RER AND ROBERT MAURER THEIR ATTORNEY June 30, 1953 J. MAURER ETAL DENTAL HAND INSTRUMENT 5 Sheets-Sheet 5 Filed Feb. 25, 1951 INVENTORS. JA/(0B MAURER AND HUBERT MAI/RER 7' HE IR ATT OHNE Y Patented June 30, 1953 2,643,456 A DENTAL HAND INSTRUMENT Jakob Maurer, Kilchberg, and Robert Maurer,

Zurich, Switzerland, assignors to Ritter Company, Inc., Rochester, N. Y., a corporation of Delaware Application February 23, 1951,*Serial'No. 212,222 In Switzerland February 25, 1950 2.0 Claims.

This invention relates to dental hand instruments or tools for operating on tooth surfaces to cut and shape the same. It has been proposed, in the patent to Jakob Maurer, No. 1,664,369, to employ a blast of fluid under pressure containing abrasive particles and operating in a manner analogous to the known sand blast, to accomplish the Work previously done by burrs, drills and the like, in a more painless and rapid `manner. The said patent discloses means for lapplying the abrasive material through one `hand tool and for withdrawing'the abrasive material through'another tool, such as a hollow perforated ring surrounding the mouth yof the patient and subjected to a sub-atmospheric pressure. In our copending application for Letters Patent of the United States, Serial No. 205,302, filed January 10, 1951, We have disclosed an improved hand tool of the abovecharacter in Awhich the conducting means for projecting and withdrawing the abrasive mixture are unitarily and concentrically combined in a single hand tool and provided With self-illuminating and heating means to facilitate the Work. One object of the present invention is to provide still further improvements inthe tool for generally facilitating its use, eifecting more precise shaping of tooth cavities and increasing the speed of operation and the like, as hereinafter more particularly described.

Another object of the invention is to provide a tool of the above character having practical and effective means for varying and precisely controlling the shape and direction of the blast of abrasive material, to suit different operating conditions and requirements.

Another object is the provision of such a tool having an interchangeable variety of suction nozzles to suit various operating conditions and so constructed as to facilitate visibility of the work.

A further object is tosupply a tool of the character described having resiliently and adjustably mounted blast and suction nozzles for promoting the flexible application of the tool to the work.

Still a further object is to afford a tool having the above advantages in a simple and practical type of construction capable of being readily manufactured at relatively W cost.

To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings:

Fig. 1 is alongitudinal sectional viewof a dental f hand instrument embodying the present invention;

Fig. 2 is anenlarged longitudinal sectional View of conducting and nozzle means thereof detached;

Fig. 3 is a side elevation, partly broken away, of suction conducting and nozzle means shown in Fig. 1;

Fig. 4 is a vview of the same means, as seen from the right in Fig. 3;

Fig. 5 is a view similar to Fig. 3 but showing a modified construction;

Fig. 6 is a `sectional view on the line 6 6 in Fig. 5;

Fig. 7 is a view similar to Fig. 6 but shows a modied construction;

Fig. 8 is a view similar to Fig. 3 but showing a vmodified construction;

Fig. 9 is a view ofthe same parts as seen from `the right in Fig. 8;

Fig. 10 is a view similar to Fig. 8 but showing a modified construction;

Fig. 11 is a view similar .to Fig. 3 but showing -in section a modified construction;

Fig. 12 is an enlarged elevation of nozzle means shown in Fig. 1;

Fig. 13 is a sectional view on the line |3-I3 in Fig. 12;

Fig. 14 is a View similar to Fig. l2 but showing a modified construction;

Fig. v15 is a sectional view on the line I5-I5 in Fig. 14;

Fig. 16 is a sectional View on the line It-I6 in Fig. 14;

Fig. 17 is a, view similar to Fig. 12 but showing a modified construction;

Fig. 18 is a sectional view on the line l8--I8 in Fig. 1'7; Fig. 19 is a View similar to Fig. l2 but showing a .modified construction;

Fig. 210 isa sectional view on the line :2D-20 in Fig. 19:

Fig. 21 is a View similar to Fig. 12 but showing a modied construction;

Fig. 22 is a sectional View on the line 22-22 in Fig. 21;

Fig. 23 is a View similar to Fig. 12 but showing a modified construction;

Fig. 24 is a sectional View on the line ZIi-Zll in Fig. 23;

Fig. 25 is an enlarged bottom View of the nozzle shown in Fig. 23;

Fig. 26 -is a view similar to Fig. 23 but showing 4a modified construction;

Fig. 27 is a `sectional View on the line .2l-2l irl-Fig. 26;

Fig. 28 is a bottom plan view of the nozzle shown in Fig. 26;

Fig. 29 is a View similar to Fig. 28 but showing a modified construction;

Fig. 30 is a View similar to Fig. 23 but showing a modied construction;

Fig. 31 is a similar View but showing a modified construction;

Fig. 32 is a sectional view on the line 32--32 in Fig. 31;

Fig. 33 is a View similar to Fig. 23 but showing a modified construction, and

Fig. 34 is a view similar to Fig. 33 but showing the nozzle as viewed from the right.

In the use of the invention, it has been found desirable and feasible to provide the conducting means for discharging the abrasive material with detachably interchangeable and adjustable nozzles of different kinds, for differentially shaping and discharging the abrasive stream in different directions and at different inclinations to the general longitudinal axis of the tube. For this purpose, the present improvements, in the preferred embodiments herein disclosed by way of illustration, are combined with a handtool of the general character disclosed in ourl said pending application, comprising a tool having a body portion 46 (Fig. 1) suitably formed of metal, plastic material, or the like, carrying inner and outer tubular members 4l and 42 for projecting and withdrawing the abrasive material, respectively. These tubular members are mounted in concentric relation, as shown, so as to provide separate inner and outer passageways in the respective tubes which terminate in juxtaposed working nozzles, as hereafter described. Means are provided at the opposite end of the inner tubular member 4i for connection with a source of fluid under pressure (not shown) containing known and suitable abrasive materials or particles for projection against a tooth surface, to shape it by abrasion, as described in said patent, while the opposite end of the tubular member 42 is branched laterally and provided with means for connection with a source of sub-atmospheric pressure (not shown) for withdrawing by suction the pressure iluid and abraded material, as hereafter further described.

The tool body 4U preferably comprises a tubular portion 43 formed with a tubular end 44 for the detachable reception of the outer tubular conductor 42, the opposite end portion 43 being branched to form tubular terminals 45 .and 46, the one being provided with means for connection with the abrasive material supply and the other with means for connection with the low The inner tubular member 4I for supplying the abrasive material, is carried in the branch 45 of the tool and extends through the outer tubular suction member 42, as shown. The tubular portion 45 of the body of the tool has tightly fitted or otherwise fixed therein a cylindrical plug 4l, of rubber or similar insulating material, having a center bore slidably receiving a tube 48. Tube 4S is fixed to and supports tube 4| (Fig. 2) and carries a collar 49. A compression spring 58 is coiled about tube 48 between the collar and plug 4l and tends to move both tubes longitudinally in a resilient and yieldable manner, while an elongated collar l, adjustably fixed to the outer end of tube 48 by a set screw 52, adjustably limits the action of the spring in sliding tube 48 and advancing tube 4l and its discharge nozzle. Collar 5I has a nger piece or knob 53 by means of which the collar may be manipulated during adjustment and by means of Which the tubes 48 and 4l may be adjustably rotated in situ, to adjustably position the discharge nozzle. Tube 48 has tted to its outer end a flexible tube 54 of rubber or the like, forming part of the means for supplying the abrasive pressure stream to the instrument, which may be of any known and suitable construction, such, for example, as disclosed in said patent. The conductor tube 4I is preferably provided with heating means, as described in our copending application to which reference may be had for` further description thereof, the electrical connections for which, indicated generally at 55, are preferably carred in a self-contained manner through branch 46 of the tool to the power source.

The other or nozzle end of the inner conductor 4l is preferably provided with an enlargement or head 56 (Fig. 2) having a threaded end 51, as shown., Screwed on this head is a sleeve 58 and the ends of the head and sleeve are shaped to form a partly spherical socket for a substantially ball-shaped element 59, as shown. This element is extended at one side to provide a tubular discharge nozzle 60, the bore of which extends through the element 59 and is enlarged to maintain communication between the nozzle and conductor 4|. Nozzle 60 is thus readily detachable from its conductor by unscrewing sleeve 58- and is mounted on the conductor for `adjustment by rotation about its own axis as well as adjustment universally to different inclinations to the axis of the conductor. The nozzle is universally adjustable to project the abrasive material in various lateral directions andat various inclinations, to facilitate the formation of various surfaces in a tooth cavity. The nozzle is thus readily detachable and replaceable to substitute different nozzles for different purposes, as hereafter more fully described, and the nozzle is frictonally retained in adjusted position upon the conductor by screwing up the sleeve 58.

Nozzle 6U may have a variety of forms, as illustrated in Figs. 12 to 34, inclusive. Its discharge end may have the form of a plain straight tube, as shown in Figs. 2, l2 and 13. This form may be varied to control the shape and direction of the discharged abrasive blast, as by reducing the size and shape of the bore of a similar nozzle BI, by the insertion of a ller strip 62 of generally elliptical cross-section, as shown in Figs. 14, l5 and 16. Strip 62 is frictionally or otherwise secured in the nozzle and the end of the strip and one side wall of the nozzle may be notched or cut away, as at 63. The nozzle bore is thus shaped to produce an abrasive stream of greater width than thickness and generally of curved or crescent shape and to discharge the same in a direction extending more or less laterally to the nozzle and the concave width of the stream, as may be desired for operating in a corner or other cavity shape.

Another nozzle form is shown in Figs. 17 and 18 in which the end of nozzle 64 is closed by an end wall 65 and the adjacent side wall is apertured by a circular discharge opening 66, to direct a circular abrasive stream laterally, substantially at right angles to the axis of the nozzle. A somewhat similar nozzle form is shown vin Figs. 19 and 20 in which the nozzle 61 has a closed lower end 68 as before but has a lateral opening in theshape of a slot 69 extending longitudinally on the side Wall to project a correspondingly shapedlateral blast of abrasive material against a more extensive .side l,wall vof 'fa cavity. Figs. 21 and 22 show `a further variation of this general nozzle form in which 'the nozzle 'lil has its lower end closed only partially, as by a wall and the remainder cutaway along with a portion of the adjacent side wall, to form a substantially semi-circular opening i2 for projecting an abrasive Istream yof -corresponding shape in a downward and lateral idirection, as sometimes found desirable.

Figs. 24 to 34 inclusive illustrate another variety of nozzle having a discharge opening of generally ilattened or slot-like shape. In Figs.

Y23, 24 and 25, the nozzle '|3 has its discharge end flattened and extended laterally, as at 74 to produce a slot-like discharge opening -'|5 adapted to discharge a flattened Vabrasive stream of greater width than thickness and in -a v*plane parallel with the longitudinal axis of the nozzle, -for vforming portions of a tooth cavity for which this shape is suited.

Figs. 26 to 29, inclusive, show similar forms of nozzles with flattened discharge openings fexcept that the nozzle 'i6 of Figs. 26, 27 and 28 has its ilattened discharge end formed to an angular, substantially V-shape, as shown, while Fig. 29 shows another form in which the discharge opening Tl is curved Vfrom end to end of the slot, as shown, to produce flattened abrasive streams of correspondingly angular or Vcurved shape from side to side thereof.

Fig. 30 illustrates a nozzle A.18 generally similar to that shown in Fig. 23 except that `the nozzle end is inclined to its longitudinal axis, as at 19, and ,one side wall is slightly cut away `or shortened as at 8D, to produce a flattened abrasive stream extending in a downward and lateral direction. Figs. 31 and 32 show a nozzle 8| of a form generally similar to that of Fig. 23, with the discharge slot 82 extending normally to the axis of the nozzle, except that one side wall is slightly cut away, as at 83 to produce a attened abrasive stream having its sides at the same elevation but extending in a generally downward and lateral direction.

Figs. 33 and 34 show a further modification in which the nozzle 84 has its discharge end curved to extend in a lateral direction, as at 85, with its extremity attened, as at 86, to produce slotlike discharge opening 8l, one side of which may be slightly out away, as at 38, to produce a flattened stream lying generally in a plane parallel to the longitudinal axis of the nozzle.

The outer tubular conductor 42 is preferably formed of moldable transparent plastic material such, for example, as Lucite, although it may be made, in part or in whole, of a harder transparent material such as a hard glass, -quartz or the like. This conductor is of substantially larger diameter than the inner conductor 4|, so as to leave therebetween apassageway of `substantial volume for withdrawing air and waste products by suction. Its inner end is slidably fitted in the tubular end 44 of the tool body 4D and a coiled compression spring 9i) is interposed between the inner end of tube 42 and a shoulder 9| of the body, to resiliently advance the tube and its terminal nozzle. A collar 92 fixed .about the tube is arranged to engage an inwardly turned flange at the end ofa sleeve 93 which iS threadedly secured to the end of the portion 44 of the tube body, so as to provide Va stop for limiting the outward movement of thefconductor tube-42 by the spring.

The =outer or `nozzle end A of ftubular conductor 6 .42 Vis slightly :enlarged as ,at 94 and has an open' nozzle end 95, .as shown. This nozzle end iS preferably dared `outwardly on the one side, as at `96, to produce `an open shoulder portion Q1 covered by a plate 98 .of hard transparent material, such as quartz, capable of resisting cutting .by the abrasive material and through which the voperator may vobserve the inner discharge nozzle and work. The edges of the opening in `shoulder 97|, `under the window plate v98, arev preferably notched, as at 99 (Figs. 3 and 4), to permit the inflow of air and deflect and reduce the impact of abrasive vparticles against the underside of the window plate. The side wal-l kof the :nozzle is preferably provided, as at Vits rear portion, with a suitable reiiecting or mirror surface '|00 for reflecting light toward theoperating area.

Suction conductor v42 communicates through end 44 of the tool -body with branch 46 of the body, the outer end -of which is adapted for the attachment of a flexible conductor ||l|, of rub- 'ber or the like, for connection with a suitable source of sub-atmospheric pressure for producing a suction in member 42 and its nozzle 95, for withdrawing and -discharging the air, abra- "sive and waste -materials from the operating area. It will thus be seen that the concentric conductors -4| and 42 and associated parts thus provide separate passageways for Vsupplying the abrasive material in a blast against the tooth surface'and for withdrawing the air and abraded materials, as more fully described in our said copending application.

The tool is also provided with self-contained means `for illuminating the -nozzles and working area, for which purposeplug 41 of `the tool body is formed with a plurality of sockets |02 (Fig. 1) 'for receiving and holding the terminal posts |33 of a'plu-rality of electric lamps |64, the terminal casings ofwhich are in contact with an electrical vconducting plate |05 onthe inner endof plug 4T.

This plate is connected with Aone wire |06 of an velectrical circuit having its other Wire |971 carried through and insulated from .plate |65 and connected through plug Y4l with-the terminal posts |03 of the lamps. These circuit wires are also preferably carried in self-contained fashion through the branch 46 of the body, as shown.

The flamps |04 are preferably provided in a sufiicient number to outline substantially a circle or Tring in tubular portion-43 of the body, substantially opposite the `inner end of the outer or suction conductor 42, so that the light from the -lamps is reflected from the inner surfaces of the `tubular portion 43 and enters the passageway within conductor .42, aswell as within the transparent walls of the conductor, being thus transzmitted -through :the conductor and its walls to and ybeyond tube nozzle 95. The tool is thus equipped with self-contained lamp means and for means for vprojecting 'the light on the working surface, to aid the vision and vto facilitate the Work'of the operator.

The outeror suction conductor 42 is preferably suppliedin a'variety of forms for interchangeable association with the 'tool socket 44, to suit the particular conditions and Vrequirements of the work to be performed. Thus, a conductor |418 may be provided (Figs. 5 and 6'), which, in addition to anobservation window plate 49, as previously described, is formed with a plurality of lateral windowopenings |||l in its side walls adjacent the nozzle opening, through which thefoperatorimaylinspectthetooth cavityandtheposition and operation of the inner blast nozzle 0. The suction within the conductor tends to draw air in these inspection openings, thus preventing the escape of the abrasive materials and the openings may be positioned so that the incoming air tends to carry the abrasive material away from the under side of the inspection plate |09, so as to reduce the abrasive action thereon. A similar suction conductor and nozzle HI (Fig. 7) maybe provided in which such lateral Window openings as lli] may be closed by inserts H2 of hard glass, quartz or the like, adapted to resist cutting by the abrasive materials.

Similar suction conductors and nozzles may also be provided in which the nozzle opening, instead of lying in a plane normal to the nozzle axis, may be inclined thereto in different directions. Thus, a similar nozzle l I3 may be provided (Figs. 8 and 9) in which the nozzle opening H4 is inclined inwardly tov/ard the side of the nozzle having the observation window plate H5, as shown. A similar nozzle H6 may be provided (Fig. 10) in which the nozzle opening Il? is inclined inwardly toward the side of the nozzle opposite the observation window IIS. These various suction nozzle forms have been described in an exemplary way and it is contemplated thatv still other forms may be provided for interchangeable association with the tool as conditions may be found to require.

Such suction nozzles may be provided with flexible tips for sealing the nozzle to the surfaces around the cavity or" the tooth under treatment, so as to prevent the escape of the abrasive and abraded materials. Such a flexible tip may be made of rubber, soft plastic or similar materials and may have the form, for example, shown in Fig. 11 in which a nozzle [I9 is equipped with a sleeve-like rubber tip i2!) one end of which is frictionally or otherwise secured over the nozzle eX- tremity, while its other end I2I is adapted to be pressed against the surfaces of a tooth around the cavity under treatment to seal the joint between the nozzle and the tooth as described above. It is also contemplated that the tooth under treatment may be protected by the application thereto of a template of rubber or other elastic material formed with a suitable work opening. The inner surface of the template may consist of material of an adhesive nature so that the template may be applied to cover and protect the tooth except at the work opening through which the dentist may operate the tool. Such a template aiords a yielding surface around the Work opening against which the suction nozzle may be pressed to eiect a tight seal for the purpose described. Similar templates may be fitted over the adjacent teeth to protect them against abrasion.

It is apparent from the above description that the invention provides the unitary illuminated hand piece or tool of our said application with a series of fully adjustable and readily interchangeable pressure and suction nozzles of various forms and shapes for facilitating the work of the dental operator in meeting the various conditions and requirements encountered in the preparation of a tooth cavity. Such interchangeable suction nozzles, while maintaining the described illumination, provide increased visibility of the nozzle for projecting the abrasive material and of the work area. rlhe conducting tubes with their nozzles are mounted in the tool body in a way which provides for adjustment of their relative lengths and either or both nozzles are yieldably supported to enable the operator to apply them effectively for cutting the tooth and for sealing the suction nozzle to the cutting area. Such improvements facilitate the precise formation of the desired cavity shapes, reduce the escape of the abrasive and abraded material into the mouth and increase the speed and comfort with which such operations may be performed.

Parts of the construction herein disclosed are disclosed and claimed in our copending patent application, Serial No. 205,302.

It will thus be seen that the invention accomplishes its objects and while it has been herein disclosed by reference to the details of preferred embodiments, it is to be understood that such disclosure is intended in an illustrative, rather than a limiting sense, as it is contemplated that various modiiications in the construction and arrangement of the parts will readily occur to those skilled in the art, within the spirit of the invention and the scope of the appended claims.

We claim:

1. A unitary dental hand tool comprising an elongated body of relatively small size in cross section adapted for insertion in the mouth and provided with conductors terminating in juxtaposed nozzles, means connected with one of said conductors and adapted for connection with a source of fluid under pressure containing abrasive material for projecting the same through said conductor and the nozzle thereof against a tooth surface, said nozzle for abrasive material having a relatively small opening for confining a jet of said material to particular portions of said tooth area, means connected with the other of said conductors and adapted for connection with a source of sub-atmospheric pressure for w'ithdrawing said fluid and material through said other conductor and the nozzle thereof by suction after abrading contact with said tooth surface and means for detachably connecting said pressure conductor with the nozzle thereof for detaching and replacing said nozzle.

2. A dental hand tool as specified in claim 1 in which the nozzle of said pressure conductor is provided with an adjustable connection with said conductor by which the longitudinal axis of said nozzle may `be adjustably inclined to the axis of said conductor for projecting the abrasive material at a desired inclination against a tooth surfalce to be shaped.

3. A dental hand tool as specified in claim 1 in which the nozzle of said pressure conductor is connected to said conductor for rotary adjustment about the nozzle axis and for universally adjusting the inclination of said nozzle axis to the axis of said conductor to project said material in various lateral directions and at various inclinations.

4. A dental hand tool as specified in claim l in which the nozzle of said pressure Iconductor is connected to said conductor by a ball and socket joint for universally adjusting the direction in which said material is projected.

5. A dental hand tool as specified in claim 1 in which the nozzle of said pressure conductor has a discharge outlet opening laterally through a side wall of said nozzle for projecting said abrasive material laterally against an upstanding side wall of a tooth cavity.

6. A dental hand tool as specified in `claim l in which the nozzle of said pressure conductor has its longitudinal axis curved laterally with a laterally opening outlet of slot-like shape elongated in a direction lying in the plane of said nozzle, for projecting said abrasive material laterally against an upstanding side wall of a tooth cavity.

7. A dental hand tool as specified in claim 1 in which the nozzle of said pressure conductor has a discharge opening of slot-like shape for projecting said abrasive material in a flattened stream of greater width than thickness.

8. A dental hand tool as speciiied in claim i in which the nozzle of said pressure conductor has a discharge opening in the shape of a curved slot for projecting said abrasive material in a thin wide stream of curved shape from side to side thereof to eiect corresponding shaping of a tooth surface.

9. A dental hand tool as specified in claim 1 in which the nozzle of said pressure conductor has a discharge opening of slot-like shape and has one lateral side of the slot cut back shorter than the other side for projecting said abrasive ma.- terial in a flattened stream of greater width than thickness and in a direction extending laterally from the shortened lateral side of the slot.

10. A dental hand tool as specified in claim 1 in which the pressure conductor is mounted on said body for longitudinal sliding movement to advance and retract the nozzle thereof and is provided With resiliently yieldable means for slidably moving said conductor and advancing said nozzle.

11. A dental hand tool as specified in claim l in which the suction conductor is mounted on said body for longitudinal sliding movement to advance and retract the nozzle thereof and is provided with resiliently yieldable means for slidably moving said conductor and advancing said nozzle.

12. A dental hand tool as speciiied in claim 1 in which the pressure and suction conductors are both mounted on said body for longitudinal sliding movement to advance and retract the nozzles thereof and are provided with resiliently yieldable means for slidably moving said conductors and advancing said nozzles.

13. A dental hand tool as specified in claim 1 in which means are provided for detachably mounting said suction conductor on said body for detaching and replacing said conductor and its nozzle.

14. A dental hand tool as specified in claim 1 in which the nozzle of the suction conductor has its extremity formed of yieldable material for sealing the space between the nozzle and the tooth around the work area.

15. A dental hand tool as speciiied in claim 1 in which the conductors are concentrically arranged and the other suction conductor is formed with an observation opening for observing the operation of the inner pressure nozzle and the work j pressure for withdrawing said uid and material through said other conductor and the nozzle thereof by suction after abrading contact with said tooth surface and means for mounting said conductors on said body for longitudinal sliding movement provided with resilient means for yieldably advancing said conductors and the nozzles thereof.

18. A unitary dental hand tool comprising a body provided with inner and outer tubular conductors terminating in juxtaposed nozzles in concentrically spaced relation, means connected With the inner conductor and adapted for connection with a source of fluid under pressure containing abrasive material for projecting the same through said conductor and the nozzle thereof against a tooth surface, means connected with the other of said conductors and adapted for connection with a source of sub-atmospheric pressure for withdrawing said fluid and material through said other conductor and the nozzle thereof by suction after abrading contact with said tooth surface, and means for detachably mounting said nozzles for ,detaohing and replacing the same.

19. A unitary dental hand tool comprising a body provided with inner and outer tubular conductors terminating in juxtaposed nozzles in concentrically spaced relation with each other, means connected with the inner conductor and adapted for connection with a source of fluid under pressure containing abrasive material for projecting the same through said conductor and the nozzle thereof against a tooth surface, and means connected with the other of said conductors and adapted for connection with a source of subatmospheric pressure for withdrawing said fluid and material from said other conductor and the nozzle thereof by suction after abrading contact with said tooth surface, said outer conductor being formed with an observation window for observing the pressure nozzle of the inner conductor and the Work area.

20. A unitary dental hand tool comprising a body provided with inner and outer tubular conductors terminating in juxtaposed nozzles in concentrically spaced relation with each other, means connected with the inner conductor and adapted for connection with a source of fluid under pressure containing abrasive material for projecting the same through said conductor and the nozzle thereof against a tooth surface, and means connected with the other of said conductors and adapted for connection with a source of sub-atmospheric pressure for withdrawing said iiuid and material through said other conductor and the nozzle thereof by suction after abrading contact with said tooth surface, the nozzle of said other suction conductor having its extremity formed of yieldable material for sealing the space between the nozzle and the tooth around the work area.

JAKOB MAURER. ROBERT MAURER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date Y 1,730,348 Anstiss Oct. 8, 1929 2,455,514 Mead Dec. 7, 1948 2,483,176 Bishop et al Sept. 27, 1949

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