Abstract:
A dental abrading tool for use in micro-dentistry that utilizes abrasive dust as the abrasion material, and which provides for effective dust suppression through the use of a water-aerosol spray. The tool consists of a means for the emission of a stream of the abrasive material A spray of water-aerosol is also emitted from the tool in a manner which effectively controls widespread contamination by the emitted abrasive material.

Description:
REFERENCE TO CO-PENDING APPLICATION 
     The subject matter of U.S. provisional application serial No. 60/104,354 filed Oct. 15, 1998 is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to dental abrasion systems and techniques and more particularly to the control of airborne abrasion materials by way of fluid streams, such as for example a water-aerosol spray. 
     BACKGROUND OF THE INVENTION 
     The conventional technique for repairing or otherwise treating teeth in dental procedures such as the removal of caries or in the manufacture/repair of dental prosthetic (eg crowns, dentures) typically involve the use of rotary drills. These drills perform at preset speeds, typically “high or “low”. As a result, these instruments lack fine control and are imprecise. Furthermore, the drilled surfaces are relatively smooth and are generally not ideal adhesive surfaces for the metals, porcelain, acrylics and/or composites routinely used in dental practice. 
     As an alternative, the use of air abrasion in micro-dentistry (AAMD) is attractive Its current but limited use extends to both intra (ie. removal of caries) and extraoral (ie dental prosthetic) applications. A major advantage of AAMD over conventional rotary drills is that it is more precise and affords the user much more control in the aforementioned intra and extraoral applications. Additionally, AAMD typically results in augmented and eroded surface areas which are more amenable to adhesion to metals, porcelain, acrylics and composites. This latter adhesion can be increased by 80% when compared with surfaces resulting from conventional drilling 
     Notwithstanding the apparent advantages of AAMD over conventional rotary drilling, the use of the former has been limited by technical and health-related difficulties. Conventional AAMD devices are not capable of controlling emissions of both the abrasive dust and airborne abraded dental amalgam material, inside the mouth of the patient and outside to the dental operatory. The abrasive material typically includes an aluminum oxide powder of 27.5 to 50.0 microns in particle size and therefore travels easily in ambient air as dust. Its aluminum content makes it a toxicological risk for Alzheimer&#39;s Disease. Meanwhile, the abraded dental amalgam can have toxic constituents such as mercury from old dental fillings. This contamination of dental operatories persists in current applications despite the use of high efficiency particulate air (HEPA) vacuum systems. Furthermore, extensive use of intraoral latex rubber dams are also necessary to aid in the prevention of inhaling the respirable aluminum powder by patients. The use of these latter latex rubber dams is also problematic in light of the possibility of inducing latex-associated asthmatic or respiratory type reactions. As neither prevention technique is particularly efficient or effective, the continuance of exposure to the abrasive dust and abraded dental amalgam and the attendant potential for health complication(s) is of concern to both patients and dental professionals. 
     In light of this prior art, the development of an abrasion system that provides improved dust suppression would be considered revolutionary within the field of micro-dentry As such, overcoming the problem of respirable dust would create better visibility, healthier conditions, make practical extra and intra-oral usage and eliminate the need for costly high efficiency particulate air (HEPA) filter vacuum units. 
     It is therefore an object of the present invention to provide a novel dental abrasion system 
     It is also an object of the present invention to provide novel techniques for dental abrasion. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, there is provided a dental abrasion device comprising first delivery means to deliver pressurized abrasive material to a tooth region and second delivery means to deliver a supply of pressurized fluid near said tooth region under conditions sufficient to suppress airborne emissions of said abrasive material from said tooth region. 
     Preferably, the first delivery means includes a head and a nozzle mounted on the head with a first conduit therein to receive the abrasive material. The second delivery means includes a plurality of second conduits near the first conduit to receive the pressurized fluid The second conduits are arranged so that the fluid leaving them generates, for example, a curtain-like stream toward the tooth region In other words, the individual fluid streams leaving the second conduits converge to a hollow substantially continuous stream to define an inner region Conveniently, the first conduit may be arranged to deliver the abrasive material to the inner region The pressure and content of the fluid stream can thus retard or, in some cases prevent, airborne abrasive material from breaking through the curtain, either causing it to be entrained in the fluid or to be repelled back into the inner region. 
     The pressurized fluid may be provided in a variety of forms including a mixture of water and a gas such as air, or other suitable gases such as nontoxic or inert gases, for example nitrogen or carbon dioxide. In the case of air, the fluid may include 10 to 75 percent water by volume, or more preferably 25 to 65 percent water by volume. The pressurized fluid itself may be dispensed, if desired, at pressures ranging from 5 to 75 psi, for example. 
     In another aspect of the present invention, there is provided a dental abrasion device comprising first delivery means to deliver abrasive material to a tooth region and second delivery means to deliver a supply of pressurized fluid near said tooth region under suitable conditions for retarding the passage of airborne abrasive material there through. 
     Preferably, the pressurized fluid forms a curtain of fluid around the tooth region More preferably, the curtain completely encircles the tooth region 
     In still another aspect of the present invention, there is provided a dental abrasion system operable to deliver an abrasive material stream to a tooth region and a fluid stream near said tooth region under conditions sufficient to suppress airborne abrasive material emissions from said tooth region 
     In still another aspect of the present invention, there is provided a method of abrading a tooth, comprising the steps of delivering first supply of abrasive material to a tooth region in a patient&#39;s oral cavity and delivering a second supply of fluid near said tooth region, wherein said fluid has sufficient volume and pressure to form a barrier to airborne abrasive material between said tooth region and said oral cavity 
     Thus, the invention provides a dental abrading tool that utilizes abrasive dust as the abrasion material, and which provides effective dust suppression by the use of a fluid stream, such as for example a water-aerosol spray. In this example, the tool emits a stream of the abrasive material as well as the water-aerosol spray, the latter under conditions sufficient to minimize the amount of dust leaving the tooth region and thus control widespread contamination by the airborne abrasive material. 
     For example, the dental abrading tool may be hand controlled, by way of “push botton” or “touch sensory” controls. Furthermore, the controls may be such that the fluid and abrasive streams are continuously variable, are regulated in a stepwise manner (ie high-medium-low), or are controlled in a simple on-off manner. The tool may also be used with a foot pedal or other such control mechanisms The invention may also control the composition of the abrasive material stream and the fluid stream, such as pressure, flow rate, temperature and the like. The tool can also be made adaptable to operatory compressors, and water and electrical supply outlets as allowed by available technology. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Several preferred embodiments of the present invention will be provided, by way of example only, with reference to the appended drawings, wherein: 
     FIG. 1 is a side view of a dental abrading tool; 
     FIG. 2 is magnified side view of one portion of the tool of FIG. 1; 
     FIGS. 3 a  to  3   d  are side views of alternatives to the portion shown in FIG. 2; 
     FIGS. 4 and 5 are side views of alternative dental abrading tools; 
     FIG. 6 is a side view of still another dental abrading tool; 
     FIG. 7 is an assembly view of the tool of FIG. 6; 
     FIG. 7 a  is a magnified view of a portion of the tool of FIG. 6; 
     FIG. 7 b  is a schematic view of a dental abrasion system; and 
     FIGS. 8 a  through  8   e  are schematic views of a dental abrading technique. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, an abrading tool is shown at  1  having a head section  2  which is removably attached to a body section  3  by a threaded connection shown at  14   a  and  14   b , it being understood that other attachment modes and means are also feasible. The head section  2  defines a cavity  12  into which a water supply tube  9  opens and across which an abrasive material supply tube  8  extends. A detachable nozzle  10  is affixed to a portion of tube  8  that extends outwards from the head section  2 . 
     Body section  3  is an elongated structure containing a sense of tubes  4 ,  5 ,  6 , and  7  which cross but do not empty internally to body section  3  Tube  7  crosses the entire length of body section  3  and opens externally at either ends of body section  3  at tube openings  7   a  and  7   b  Similarly, tubes  4  and  5  open externally to body section  3  at tube openings  4   a  and  5   a  respectively At a point distal to these tube openings (ie  4   a  and  5   a ) and internal of the body section  3 , tubes  4  and  5  merge into a single tube  6 . This latter tube  6  opens externally to body section  3  at tube opening  6   a . However, it will also be understood that these tubes may be joined at other points both internal and external to the body section For example, an external control portion may be a convenient place to mix the constituents of the pressurized fluid The head section has plate  2   a  which is retained for swivel movement in the threaded section  14   a.    
     When the head section  2  and the body section  3  are joined or fastened together, tube  9  joins with tube  6  (openings  9   a  and  6   a  form a juncture point) and tube  8  joins with tube  7  (openings  8   a  and  7   a  form a juncture point) Air may be pumped into tube  4  (through tube opening  4   a ) and water into tube  5  (through tube opening  5   a ) or vice versa. The air and water streams are mixed to form a water-aerosol at the point in which tubes  4  and  5  merge, and in tube  6  thereafter. This water-aerosol flows through tube  6 , and then tube  9  to empty into cavity  12  Abrasive material is streamed under pressure into tube  7  via opening  7   b  The abrasive material streams through tube  7  into contiguously joined tube  8  to exit at tube opening  8   b.    
     Referring to FIG. 2, a nozzle  10  is further attached to tube  8  via threaded means  13   a  and  13   b , though it will be understood that other attachment modes and means are feasible. Nozzle  10  opens at some external point ( 10   a ) to head section  2 . This nozzle  10  and its opening  10   a  can be of various sizes and configurations. As previously noted, abrasive material is streamed under pressure through tube  8 , to subsequently exit through opening  10   a  to nozzle  10  The water-aerosol emptying from tube  9  fills cavity  12  of head section  2 . The water-aerosol is channelled through openings  11  of head section  2  to form a water curtain that surrounds nozzle  10  It is the formation of this water curtain that may be configured effectively to control and minimize the widespread contamination of the surroundings by airborne abrasive material emitted through nozzle  10 . 
     FIGS. 3 a  through  3   d  show alternatives to the head section  2  in which the fixed angle that tube  9  crosses cavity  12  varies. It should be noted that other embodiments are envisioned in which a swivel hinge or mechanism is incorporated in a single head section  2  thus allowing for the variable adjustment of this angle. 
     FIG. 4 illustrates an alternative in which the controlling mechanism for regulating the abrasive material stream and the analogous controlling mechanism for regulating the water-aerosol stream are push-button switches ( 15  and  17  respectively). These switches function in a simple on-off format Electrical line  18  supplies electricity to switch  17  and electrical line  16  supplies electricity to switch  15  In the alternative shown in FIG. 5, the controlling mechanism for regulating the abrasive material stream is a touch-control switch  19 , while the touch-control switch  21  regulates the water-aerosol stream. The switches are turned on or activated when depressed. Electrical lines  20  and  22  supply power to switches  19  and  21 , respectively. 
     FIGS. 6,  7  and  7   a  illustrate another dental abrading tool  40 . In this case, the tool  40  has a downstream nozzle portion  42  and an upstream body portion  44 . The body portion has a central section  46  which is joined to two end sections  48  and  50 , each defining downstream and upstream ends  48   a  and  50   a , respectively. The upstream body portion  44  also has a pair of channels  52 ,  54  to receive the fluid stream and the abrasion material stream from external supply lines  56  and  58 , respectively. The supply lines are suitably mounted in a connector  60  which is coupled to the upstream body section by a threaded ring  62 . The channels  52 ,  54  extend between the downstream end  48   a  and the upstream end  50   a  The downstream end is coupled with the nozzle portion  42  by way of threaded collar  64   
     The nozzle portion  42  includes a main portion  70  with a nozzle body  72  threadably coupled therewith. The nozzle body also has a nozzle end piece  74  which is threadably coupled with the nozzle body. 
     The nozzle portion has a cavity which forms, together with the nozzle body, an inner fluids receiving chamber  76  which is open only to the channel  52  and to a number of conduits, in this cases external orifices shown at  78 . Thus, fluids at the entry end of the main body travel through the channel, into the nozzle body, into the chamber and through the orifices to form a curtain which is shown by the short dashed lines at  80   
     The conduits may be provided in a number of configurations including slits or generally circular passages which are oriented to deliver the fluids at an angle β, as shown in FIG. 7 a , which may range from 0 to 45 degrees, for example. 
     The nozzle portion also forms with the nozzle body a single passage for the abrasive material from the channel  54  through to the nozzle, thereby forming a path for the abrasive material through the channel, through the nozzle body and along the path shown by the chain dotted lines at  82 . In this case, the abrasive material path is centrally located relative to the fluid paths leaving the orifices. 
     Referring to FIG. 7 b , the tool  40  may from part of a dental abrasion system  90  which includes an external control portion which includes a first supply channel  92  to supply a pressurized stream of abrasion materials and a second supply channel  94  to supply a stream of pressurized fluid. In this case, the control portion may also include controls  96 ,  98  to adjust the variables for each stream. The first and second channels may include compressors, mixing chambers, heaters and other means for preparing and conditioning the two streams. 
     The operation of the tool is illustrated in the FIGS. 8 a  to  8   e  In FIG. 8 a,  three teeth are shown schematically by the rectangles ‘T’ The abrasive path is shown as the ‘bullseye’ of a target shown at  82  while the fluid path is shown as a relatively wider circle near the periphery of the tooth T by the dashed lines at  80 . While not intending to be bound by theory, it is believed that individual abrasive materials collide with the tooth in the tooth region and assume random trajectories illustrated for example by the four compass like arrows in FIG. 8 b , thereby toward the fluid curtain at the circle  80   
     If desired, the curtain  80  may be larger than the periphery of the tooth as shown by FIG. 8 c  may take on an ellipsoid like pattern relative to the tooth, as for example might occur if the dental tool is positioned at a smaller angle relative to the tooth In this latter case, the trajectories of the abrasive materials is shown generally in the right hand direction 
     The curtain is in fact a convergence of fluid flows from the individual orifices  78 , in this particular example. The fluid will have a momentum which will be dependent on the proportion of the fluid which is a relatively dense material such as water. The greater the proportion of water in the fluid stream, the greater the chance that the approaching abrasion material particle with collide with or become entrained with an individual droplet in the fluid This may cause the particle to be repelled back toward the tooth region and thus remain airborne or otherwise be entrained in the fluid. 
     While the technique may not in some cases have the capability to inhibit each and every abrasion particle from actually penetrating the curtain, passing through it and remaining airborne on outside the curtain, it is believed that the technique can be adjusted to provide very high recapture rate 
     In those cases where the abrasive particles do successfully pass through the curtain, such liberated particles should have lost a significant portion of its energy, thereby reducing its capacity to damage or otherwise penetrate tissues near the tooth region and outside the curtain The abrasive material thus becomes entrained in the fluids or the saliva of the patient or both which can subsequently be removed by conventional suction techniques. 
     While not intending to be bound by theory, there are believed to be several variables that are interdependent and changes to them may have positive, for that matter negative, effects on the ability for the system to suppress airborne abrasion materials. For example, increasing the liquid content of the fluid supply, such as water for example, may improve the dust suppression ability of the fluid, as will an increase in the fluid pressure. An increase in the beam intensity (that is the pressure at which the abrasion material is delivered to the nozzle) may reduce the effectiveness of the fluid curtain, simply because the airborne abrasion materials may penetrate the curtain with a greater speed, for example. An increasing content of liquid in the fluid may increasingly impair or obstruct the dental health professional&#39;s view of the target region. Therefore, it may be desirable in some cases to permit the professional to adjust these variables at his discretion, to allow the system to suppress the airborne abrasive material to a degree deemed satisfactory by the professional while at the same time allowing the dentist sufficient viewing of the target region with a suitable beam intensity. 
     It will understood by those skilled in the art that the device should be prepared in a manner suitable for its intended used This may include, for example, fabricating the device from autoclavable materials or those which are capable to be sterilized by other techniques It may also be appropriate in some cases to provide the tool as a disposable article. 
     While the above system makes use of a tool which supplies both an abrasive material stream and a fluid stream capable of establishing a barrier for suppressing airborne abrasive material, the system may alternatively be arranged wherein the abrasive material is supplied by one tool and the barrier-forming fluid stream supplied by another implement. 
     The terms ‘suppress’ and ‘barrier’ are intended not to limit the invention necessarily to only those cases where the suppression and barriers are absolute Rather, these terms are intended to include cases where the suppression and barriers may only function to prevent a portion of the airborne abrasive material from leaving the tooth region For example, there may be significant benefit to be gained by preventing, for example, 90 percent of the airborne abrasion materials from leaving the tooth region. 
     The device is also convenient because the curtain can be arranged to provide improved suppression without significantly blocking the dental professional&#39;s view of the tooth region. 
     While the curtain shown above completely encircles the tooth region, there may be cases where the fluid need not form a complete circumferential barrier. For example, there maybe some cases where the fluid barrier cooperates with a physical barrier, the latter being, for example behind the tooth region and there is in a position not to impair the professional&#39;s view of the tooth region, for example 
     The foregoing description of some embodiments of the invention should be considered as merely illustrative of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. Accordingly, all suitable modifications and equivalents may be resorted to, and are considered as falling within the scope of the invention.