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Publication numberUS3882638 A
Publication typeGrant
Publication dateMay 13, 1975
Filing dateOct 4, 1973
Priority dateOct 4, 1973
Publication numberUS 3882638 A, US 3882638A, US-A-3882638, US3882638 A, US3882638A
InventorsRobert B Black
Original AssigneeRobert B Black
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Air-abrasive prophylaxis equipment
US 3882638 A
Air-abrasive equipment is provided for prophylaxis or tooth cleaning purposes. Provision is made for directing not only the air-abrasive stream or jet but also for directing a stream of warmed water, preferably in the form of a curtain surrounding the air-abrasive stream and serving to enhance the cleaning action and also to entrain the abrasive particles so that they may readily be withdrawn or removed through a liquid suction system.
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Description  (OCR text may contain errors)

United States Patent Black May 13, 1975 [54] AIR-ABRASIVE PROPHYLAXIS 2,405,854 8/1946 Ruemelin 5l/l2 X EQUIPMENT 2,696,049 12/1954 Black 51/12 X 2,742,738 4/1956 Hall 51/8 Inventor! Robert Black, 2925 Denrer, 3,769,753 11 1973 Fleischer 51/12 x Corpus Christi, Tex. 78404 [22] Filed: Oct. 4, 1973 Primary ExaminerDona1d G. Kelly 1 pp NO: 403,436 Attorney, Agent, or FirmSynnestvedt & Lechner [52] US. Cl. 51/12 [57] ABSTRACT [51] Int. Cl. B24c 7/00 Air-abrasive equipment is provided for prophylaxis or [58] Field of Search 5 H8 R, 12, l l tooth cleaning purposes. Provision is made for directing not only the air-abrasive stream or jet but also for [56] References Cited directing a stream of warmed water, preferably in the UNITED STATES PATENTS form of a curtain surrounding the air-abrasive stream and serving to enhance the cleaning action and also to 2 entrain the abrasive particles so that they may readily 2:324:250 7/1943 voerge n 5] 1 be withdrawn or removed through a liquid suction sys- 2,325,5l7 7/1943 Howard 51/11 2,376,287 5/1945 Sorrentino... 51/11 r 2,376,616 5/1945 Oechsle 51 /11 6 Clams, 4 Drawmg Figures 5s 55 6| s2 -2s 59 4o 1 41 i 1 25 29 33 L II] 1 E 54 r as 47 L7 27 19 20 21 22 24 4' j} 6 30 35 PAYENTED HAY 1 3l975 SHEET 10$ 2 a aeaeaa PATENTEB HAY I 3l975 SHEET 2 UF 2 AIR-ABRASIVE PROPHYLAXIS EQUIPMENT This invention relates to air-abrasive equipment and is particularly concerned with equipment of this type especially adapted for use in the cleaning of teeth, especially the removal of foreign material from the exposed surfaces of the teeth, such as those materials which are broadly classified as stain and calculus.

As is known, stain may originate from various sources or causes including smoking, tobacco chewing, excessive drinking of tea or from vegetable origin. Calculus is of several different types, especially serumal and salivary, and calculus deposits ordinarily accumulate in pockets between the teeth and the surrounding soft tissues, the serumal calculus originating from blood in this area and the salivary calculus originating from the saiiva. These constituents precipitate and bond themselves to the exposed tooth surfaces.

Various techniques and equipment are already known and used in the cleaning of teeth, including hand instruments, rotary rubber cups carrying an abrasive paste of pumice or silex, all of which techniques may be used effectively in the removal of calculus, but none of which techniques are satisfactory in effecting the removal of various types of stain, especially the removal of stain from broad areas of the teeth.

The equipment and the technique of the present invention are not only usable in the removal of calculus, but are also particularly advantageous in the removal of stain which frequently occurs in relatively broad areas mixed with a thin coating of salivary calculus.

Air-abrasive equipment has been known and extensively used in dental work, but in general such airabrasive equipment has been employed primarily in the cutting of the tooth structure in preparation for the filling of cavities. In contrast, the equipment of the present invention is especially adapted to the cleaning of teeth, particularly to the removal of stain, whether or not mixed with a coating of calculus.

In air-abrasive equipment used for dental purposes, the delivery and dispersal of abrasive particles in air suspension in the mouth in objectionable and in some prior equipment employed for tooth cutting, vacuum means such as an exhaust blower has been employed. This, however, it bulky and cumbersome. In some prior systems it has also been contemplated to wash the teeth with water following the abrasive treatment, but such subsequent washing does not overcome the objectionable initial distribution of the abrasive particles on the soft tissues and other parts of the mouth.

It is an object of the present invention to overcome the various difficulties and disadvantages above referred to and to provide an airbrasive prophylaxis equipment adapted to the convenient and effective removal of stain and or calculus in a manner which is simple and which produces minimum discomfort to the patient.

According to the invention the equipment includes a hand piece having a nozzle with an air-abrasive discharge passage and further having a series of water discharge passages in an array surrounding the airabrasive passage, together with control means by which warmed water is delivered for discharge through the array of water passages and by means of which the control of the air-abrasive and water streams is coordinated in a manner assuring the delivery of water at all times when the air-abrasive stream is being delivered.

In the hand piece provided according to the present invention the water discharge passages are arranged to impinge upon the surface of the tooth being cleaned in an area immediately adjacent to the area of impingement of the air-abrasive stream. Preferably a plurality of water streams are provided arranged in the manner of a curtain surrounding the air-abrasive stream. By positioning the water streams to impinge upon the tooth surface adjacent to but not coincident with the target area of impingement of the air-abrasive stream, the full effectiveness of the air-abrasive stream for its intended prophylaxis purpose is assued, while, at the same time, the water is present in the immediate vicinity of the target area of the abrasive stream, so that the abrasive particles are immediately taken up in suspension in the water and will flow with the ater away from the tooth surface being cleaned for removal from the mouth by the commonly used suction tube.

How the foregoing and other objects and advantages are attained will appear more fully from the following description referring to the accompanying drawings in which:

FIG. 1 is a schematic diagram of equipment according to the present invention includinga hand piece having an air-abrasive discharge passage and also water discharge passages, together with supply and control mechanism for the abrasive and water;

FIG. 2 is an enlarged sectional view of a device for mixing abrasive particles with an air stream to be delivered to the hand piece;

FIG. 3 is a view of the hand piece, with the .parts in section so as to illustrate the interior construction, especially of the head of the hand piece; and

FIG. 4 is a detailed view showing the arrangement of the air-abrasive nozzle and of the surrounding array of water discharge passages.

Referring first to FIGS. 3 and 4, the hand piece comprises a tube 5 by which the instrument is to be held when in use in the mouth. The head of the hand piece is generally indicated by the reference numeral 6, and it will be seen that the head is supported at one end of the tube 5 by means of the block 7 and the connected tubes 8 and 9. Tube 8 connects with the central passage 10 in the head which in turn connects with the abrasive nozzle 11 having a discharge passage extended at right angles to the axis of the handle 5.

Tube 9 connects with the annular chamber 12 surrounding the passage 10 and the air-abrasive nozzle, the chamber 12 serving as a supply chamber for the series of water discharge passages 13.

As will be seen from FIGS. 3 and 4 the water discharge passages 13 are arranged in an array surrounding the air-abrasive nozzle 11 and the water passages are preferably inclined somewhat toward the airabrasive stream, but this inclination is relatively slight and should not be so great as to intersect or join the airabrasive stream at apoint in advance of the impingement of the air-abrasive stream against the tooth surface being cleaned.

It will be seen that the air-abrasive and water nozzle arrangement provides a curtain or envelope of water surrounding but spaced from the air-abrasive stream in the target area of the air-abrasive stream, so that the action of the abrasive particles is not impaired at the target area. At the same time the envelope or curtain of water will merge with the air-abrasive stream at least beyond the normal air-abrasive target distance from the head of the hand piece, and this is of importance because the abrasive particles will be takeninto suspension in the water, without danger of direct impingement upon soft tissues or other parts of the mouth.

The block 7 at the end of the handle is provided with passages which interconnect the tubes 8 and 9 with tubes 14 and 15 adapted to cooperate with the flexible supply tubes 16 and 17 for the air-abrasive and water, these flexible tubes 16 and 17 desirably being combined in a common sheath indicated at 18. The flexible tubes 16 and 17 are of course extended to the supply and control equipment which is illustrated in FIGS. 1 and 2.

In considering FIGS. 1 and 2 it is first noted that although various gases may be employed as carrier for the abrasive particles, for instance carbon dioxide, air is suitable and for many purposes is preferred. A line 19 from a source of pressurized air, for instance at from 40 to 80 psi is connected through the filter 20 and the normally closed solenoid shut-off valve 21, with the branch lines 22 and 23. Line 22 is provided with a pressure regulated device 24 which delivers the air through connections 25 and 26 to the abrasive mixing device indicated generally at 27. A pressure gauge 28 indicates the pressure following the reduction of the device 24. The connection 25 is provided with a check valve 29 and the connection 26 with a check valve 30.

As best seen in FIG. 2, the device 27 includes an outer casing 31 having a rounded bottom 32, and with a removable closure 33 at the top, the casing 31 serving as a reservoir for abrasive particlesas indicated at 34.

Positioned centrally within the casing 31 is a receptacle or chamber 35 connected with the closure member 33 and projecting downwardly into the casing 31 to provide a central chamber with which the air connection 26 connects. Centrally disposed within the container 35 is a tube 36 which extends through the closure member 33 and is provided with openings with one of which the air connection 25 connects. The lower end of the tube 36 tits in an aperture in the bottom of the container 35 and projects downwardly below the bot- 7 tom of the container 35 where the tube is provided with ports 37 for receiving abrasive. Additional ports 38 in the bottom of the container 35 provide for delivery of air from the container downwardly into the mass of abrasive, thereby effecting introduction of the abrasive particles from the bottom region of the casing 31 into the tube 36. The delivery line for the abrasive-laden air is indicated at 39 and this line is connected with the upper end of the tube 36, preferably in line with the air supply connection 25, the line 39 being extended through a pinch valve 40 from which the connection 16 delivers the air-abrasive stream to the hand piece, as above described in'relation to FIGS. 3 and 4.

The connection 25 is provided with an adjustable needle valve 41 for controlling the amount of air flowing directly to the upper end of the tube 36 of the abrasive mixer. This valve provides for adjustment of the quantity of abrasive picked up by the air stream. When the valve 41 is wide open, a minimum of abrasive will be entrained because the air will readily flow through the line 25 and the connection 39 to the hand piece. As the valve 41 is completely closed, the arrangement then provides for maximum pickup of abrasive, because all of the air reaching the delivery line 39 must pass through the chamber 35 and through the ports 38 and 37, thereby entraining a maximum of the abrasive. If

desired a valve 41 a may also be provided in ,branch .26.

Turning now to the water supply system, as shownin FIG. 1 an appropriate pressurized water supply line is V indicated at 42, this linedelivering water through the filter 43 and through a water pressure regulator 44 to a water heater 45. This water heater is adapted to elevate the temperature of the water, for instance to about F, and thereby provide appropriate temperature for use in the mouth. Desirably the water heater 45 has some storage capacity, so that a supply of the warmed water will always be available for use. The warmed water flows through the line 17 to the hand piece as I shown in FIGS. 3 and 4, a shut-off valve 46 being provided so that the water flow may be started and stopped at will by the operator. While reference has been made maticactuating device of known type indicatedat 47,

this device 47 being supplied with actuating air from the branch 23a of the connection 23 above mentioned.

The device 47 is under the co ntrol of a solenoid operated by the circuit diagrammatically indicated at48,

which circuit is associated with a contact 49 of a switch:

device mentioned just below.

The water shut-off valve 46 is solenoid operated and i the control circuit for that:valve is diagrammatically indicated at 50, being associated with the contact5l of' the main control switch. This main control switch desirably comprises a switch arm 52 connected with'a current source .53, the switch arm having. a contactor" adapted to engage either the contact 51 or both of the contacts 51 and 49. ,Switchesof this type are well known and for dental purposes are commonlyarranged for foot actuation.

With the arrangement just described, the operator in I using the equipment will operate the switch arm 52 and this will initially engage the contact 51, thereby openf ing the water supply valve 46. By further movement of the arm 52 the contact 49 is engaged, and by opening the valve 40 in order to deliver the air-abrasive stream to the hand piece. It is advantageous that the switcharm 52 may be operated to substantiallyconcurrently initiate flow of both the water and the air-abrasive' stream, but it is preferred to employ an arrangement such as shown, so that water alone may be delivered and also so that whenever abrasive is delivered thereis' assurance that water will also be delivered. I

The upper portion of the casing 31 of the abrasive mixer (see FIGS. 1 and 2) is'provided with an exhaust:

port 54 which is connected to atmosphere by the line 55 through a bleed valve 56 and through an abrasive powder trap 57. This valve 56 is normally open and may be of the pinch valve type such as described above with reference to valve 40, the valve 56 being supplied with actuating air pressure through the branch 23b of the line 23, and being under the control of a circuit in-.

dicated at 58 which is connected with the contact 59 of a master on-off switch 60. This switch 60 is associ-.

ated with a power source diagrammatically indicated at 61 and serves not only to operatethe valve 56 but furto the use of a spray; of water, it is to be understood that certain other liquids.

ther to operate the valve 21 by virtue of the connection 62.

When the equipment is to be used, the switch 60 is closed, thereby opening the normally closed solenoid valve 21 and thereby also closing the normally open valve 56. The flow of the air-abrasive and of the water is then manually controlled by the foot switch 52 in the manner described above. When the equipment is no longer needed for operation, the master shut-off switch 60 may then be opened and the normally closed solenoid valve shuts off the air supply, and in addition the valve 56 opens and provides for bleed-off of the pressure in the system including the abrasive mixing device, discharge of abrasive particles being prevented by the powder trap 57. This automatic bleed-off of pressure is important particularly for the purpose of providing for refilling the abrasive casing 31. If the pressure has been exhausted from the system, the removable closure 33 may be separated in order to permit introduction of a new charge of abrasive.

A valve 63 may be provided in order to adjust the pressure of the air supplied through the connection 23 to the pinch valves 40 and 56.

For prophylaxis purposes it is preferred to employ abrasive particles of very small particle size and of uniformity of particle size, for instance particles of the order of -70 microns. It is preferred according to the invention to provide such particles formed of pure lceland spar. As an alternative, fine microbeads of glass may be used, either one of these abrasives being capable of removing stain from the teeth without, however, any appreciable etching effect on the tooth enamel, and thus without any of the possibly detrimental effects which could flow from certain other abrasives, such as free silicates or dolomite.

In addition to various of the advantages mentioned above, the equipment of the present invention is also advantageous in that it eliminates the necessity for drying the teeth prior to cleaning. Bulky suction or vacuum equipment is not needed and since the abrasive is readily removed by means of the customary saliva ejector, separate disposal of the abrasive is not required.

I claim:

1. A system for handling and feeding abrasive particles comprising means for mixing abrasive particles with a gaseous stream, first nozzle means for delivering the abrasive laden stream to a point of use, controllable supply means for starting and stopping the abrasive laden stream, second nozzle means in predetermined relation to the first nozzle means for delivering a stream of liquid adjacent said point of use, controllable supply means for starting and stopping the stream of liquid and control means for the supply means including means providing for substantially concurrently starting and stopping of the discharge of the gaseous and liquid streams from the nozzle means.

2. A system as defined in claim 1 in which the first and second nozzle means are integrated in a common handpiece.

3. A system for handling and feeding abrasive particles comprising means for mixing abrasive particles with a gaseous stream, first nozzle means for delivering the abrasive laden stream to a point of use, a first shutoff valve between the mixing means and the first nozzle means, a water feed line, a water heater in said line, second nozzle means for receiving heated water from the water heater and for delivering a stream of heated water substantially to said point of use, a second shutoff valve between the water heater and the second nozzle means, and control means including means interrelating the opening of both of the shut-off valves, and means providing for opening of the second shut-off valve without opening the first shut-off valve.

4. A system for entraining abrasive particles in a gas stream comprising a receptacle having walls defining a reservoir for abrasive particles, a wall structure within the reservoir defining a chamber separate from the abrasive reservoir and having a gas inlet, an abrasive pick up tube extended through said chamber and having its inlet end projecting from said chamber downwardly into the abrasive supply in a lower region of the abrasive reservoir, a port through the chamber wall for delivering gas from the chamber into the supply of abrasive in the region of the inlet end of said tube, a delivery connection extended from the pick up tube at a point remote from the inlet end of the tube, and a gas supply line connected with said tube near the delivery connection.

5. A system as defined in claim 4 and further including an adjustable valve in said gas supply line.

6. A system as defined in claim Sand further including a controllable shut-off valve in said delivery connection.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US794122 *Nov 29, 1904Jul 4, 1905Leo RosengartenSand-blast device.
US2071472 *Oct 26, 1936Feb 23, 1937Clarence PletcherWater-sand blast gun
US2324250 *Dec 26, 1941Jul 13, 1943Voerge John NicholasSand blasting
US2325517 *Feb 7, 1942Jul 27, 1943Robert O HowardSandblast nozzle
US2376287 *Mar 28, 1944May 15, 1945Oceanic Ship Scaling Co IncSandblasting nozzle
US2376616 *Jan 18, 1944May 22, 1945Metalweld IncSandblasting apparatus
US2405854 *Sep 7, 1944Aug 13, 1946Richard RuemelinGun for blasting and spraying
US2696049 *Feb 24, 1949Dec 7, 1954Black Robert BMethod of and apparatus for cutting tooth structure by means of an abrasive-laden stream of gas
US2742738 *Feb 24, 1953Apr 24, 1956George L HallWet abrasive dispenser
US3769753 *Mar 16, 1972Nov 6, 1973H FleischerAutomatic car sand blaster
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4174571 *Jul 28, 1978Nov 20, 1979Dentron, Inc.Method for cleaning teeth
US4209952 *Sep 8, 1978Jul 1, 1980F. A. Hughes And Company LimitedUnderwater jet blasting apparatus
US4487582 *Feb 18, 1983Dec 11, 1984Cooper Lasersonics, Inc.Dental cleaning system
US4492575 *Apr 27, 1983Jan 8, 1985Electro Medical Systems, S.A.Dental prophylactic apparatus
US4494932 *Feb 18, 1983Jan 22, 1985Cooper Lasersonics, Inc.Dental cleaning apparatus and method
US4540365 *Nov 23, 1983Sep 10, 1985Advanced Design CorporationDental cleansing system
US4975054 *Apr 18, 1989Dec 4, 1990Esrock Bernard SDental tool
US4984984 *Jul 18, 1988Jan 15, 1991Esrock Bernard SDental tool and nozzle therefor
US5123206 *Mar 13, 1991Jun 23, 1992Whitemetal, Inc.Wet abrasive blasting method
US5158455 *Feb 9, 1990Oct 27, 1992Young Dental Manufacturing CompanyControl unit for a scaler and a polisher
US5186625 *Nov 28, 1990Feb 16, 1993Young Dental Manufacturing CompanyControl for dental air-polisher
US5312251 *Jun 18, 1993May 17, 1994Jackson Paul CDental implement
US5393228 *Nov 18, 1993Feb 28, 1995Policicchio; Piero A.Dental prophylaxis and water conservation device
US5395240 *Sep 14, 1993Mar 7, 1995Dentsply Research & Development Corp.Sterilizable dental medical handpiece containing electric coil
US5525058 *Jul 19, 1994Jun 11, 1996American Dental Technologies, Inc.Dental treatment system
US5718581 *May 9, 1995Feb 17, 1998Danville Manufacturing, Inc.Air abrasive particle apparatus
US5746596 *Jun 10, 1996May 5, 1998American Dental Technologies, Inc.Dental treatment method
US5775901 *Mar 7, 1996Jul 7, 1998Hu-Friedy Mfg. Co., Ltd.Insert for ultrasonic scaler
US5984677 *May 9, 1996Nov 16, 1999Danville EngineeringAir abrasive particle apparatus
US6030212 *Sep 27, 1996Feb 29, 2000Dentsply Research & Development Corp.Stacking reservoir and scaler system
US6293793Sep 29, 1999Sep 25, 2001Dentsply Research & Development Corp.Stackable reservoir and scaler system
US6416321Jan 26, 2001Jul 9, 2002Kaltenbach & Voight Gmbh & Co.Medicinal or dental hand instrument
US6719561May 17, 2002Apr 13, 2004Kaltenbach & Voight, Gmbh & Co.Medicinal or dental hand instrument
US7083411Mar 15, 2001Aug 1, 20063M Espe AgTooth cleaning powders and methods of use thereof
US20040091429 *Mar 15, 2001May 13, 2004Thomas FlemmigSupragingival powder spraying
US20040166474 *Feb 23, 2004Aug 26, 2004Bernd GugelMedicinal or dental hand instrument
US20040202980 *Apr 14, 2003Oct 14, 2004Policicchio Piero A.Dental prophylaxis and air appliance
US20050089816 *Oct 21, 2004Apr 28, 2005Krisch Stefan S.Dental hand piece
US20100297576 *Mar 11, 2010Nov 25, 2010Marcel DonnetPowder for powder blasting, powder mixture and method of use for the treatment of tooth surfaces
DE2930836A1 *Jul 30, 1979Feb 14, 1980Gallant Ben JosephSchleifverfahren und -geraet
DE2930836C3 *Jul 30, 1979Jan 21, 1999Dentsply Res & DevVerfahren und Vorrichtung zum Reinigen von Zähnen
DE4122979A1 *Jul 11, 1991Jan 14, 1993Kaltenbach & VoigtBearbeitungsgeraet zum bearbeiten von feinwerktechnischen, insbesondere dentaltechnischen werkstuecken in einem von einem gehaeuse umgebenen bearbeitungsraum
DE4122980A1 *Jul 11, 1991Jan 21, 1993Kaltenbach & VoigtAbrasive blasting cabinet for fine dental finishing work - has compressed air passage leading to interior chamber and stand pipe within chamber being fed by supply inlet
DE10014416B4 *Mar 24, 2000Feb 19, 20093M Espe AgVerwendung feinkörniger Pulver bzw. Pulvergemische zur Herstellung eines Mittels für supragingivales Pulverstrahlen
EP0119021A1 *Feb 14, 1984Sep 19, 1984Dentsply Research and Development CorporationImproved dental cleaning system
EP0119735A1 *Feb 14, 1984Sep 26, 1984Dentsply Research and Development CorporationDental cleaning apparatus and method
EP0201145A1 *May 6, 1986Nov 12, 1986Rijndelta Coating Technieken B.V.Grit blasting apparatus
EP2228175A1Mar 12, 2009Sep 15, 2010Ferton Holding SAPowder for powder streams, powder mixture and use for processing in particular dental surfaces
WO1985002107A1 *Nov 12, 1984May 23, 1985Sven Karl Lennart GoofTooth cleaning instrument
WO1996035390A1May 9, 1996Nov 14, 1996Danville Engineering, Inc.Air abrasive particle apparatus
WO2002038071A1Nov 5, 2001May 16, 2002Dentsply International Inc.Dental/medical prophylaxis device with sterilizable components
WO2003011164A1 *Aug 1, 2002Feb 13, 2003Medivance Instruments LimitedDental sandblast tool
WO2005041805A2 *Oct 25, 2004May 12, 2005American Medical Technologies, Inc.Dental hand piece
WO2005041805A3 *Oct 25, 2004Feb 16, 2006American Medical TechnologiesDental hand piece
U.S. Classification451/91, 451/102, 451/101
International ClassificationB24C7/00, B24C5/02, A61C17/02, A61C19/00, A61C3/025
Cooperative ClassificationB24C7/0046, A61C3/025, B24C5/02, B24C7/0084
European ClassificationB24C7/00E, A61C3/025, B24C5/02, B24C7/00C
Legal Events
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Owner name: V-CUSA, INC.
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Aug 7, 1986ASAssignment
Effective date: 19860730
Aug 7, 1986AS02Assignment of assignor's interest
Owner name: BLACK, ROBERT B.
Effective date: 19860730