Abstract:
The supply of water used in dental operations and other applications in a dental office, or other medical facility, wherein non-contaminated water is necessary to avoid transmission of microorganisms, is enriched with oxygen, whether from ambient air or a source of oxygen. The oxygenated water is passed through a silver containing catalyst cartridge. The water borne oxygen is attracted to the silver and forms a weak bond sufficient to permit dissociation to oxidize organic matter, including microorganisms. A small amount of silver dissolves in the water and flows downstream through the attendant conduits to and through dental handpieces and dental implements. A portion of the silver will adhere to the walls of the conduits, handpieces and implements where it is free to react with the oxygen dissolved in the water flowing therepast. The resulting oxidizing of the organic matter will destroy any biofilm present and prevent biofilm buildup. To enhance oxidizing of the organic matter, an ozone generator may be employed to introduce ozone into the water upstream of the silver catalyst cartridge.

Description:
CROSS-REFERENCE RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. application entitled “Dental Unit Water Purifier”, assigned Ser. No. 08/648,204, filed May 14, 1996, now U.S. Pat. No. 5,942,125, issued on Aug. 24, 1999. The present application claims priority to a provisional application entitled “Catalytic Dental Water Apparatus”, assigned Ser. No. 60/089,541, filed Jun. 17, 1998, both of which applications describe inventions by the present inventors. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to purification of dental water lines, to destroying biofilm that may be present and to preventing biofilm buildup and, more particularly, to having oxygen or ozone enriched water react with a silver catalyst and oxidize organic matter, such as microorganisms and biofilm, that may be present in the water, on surfaces of the dental water lines and on the surfaces of any downstream handpieces, implements or nozzles, to provide uncontaminated water at the point of use. 
     2. Description of Related Art 
     Tap water in dental offices is similar to tap water in most homes and offices. While this water is generally considered safe to drink, it is never sterile. Most tap water samples contain fewer than 50 cfu (colony forming units) of bacteria per milliliter (cfu/ml). However, once the water leaves plumbing lines and enters the long plastic tubing that feeds into dental high-speed handpieces and other dental implements, such as air-water syringes and ultrasonic tooth scalers, the environment changes. Here, the flow rate, frequent periods of stagnation and large relative surface area of the small bore plastic lines are ideal for microbial contamination. 
     Water that stagnates in plastic water lines and/or tubing overnight and even during long periods during the day provide bacteria the opportunity to stick to the wall of the lines/tubing. Water, slowly running through the line, provides a constant flow of bacteria that can adhere to the microbes that are already clinging to the wall. A cooperating population of several different species, which depend on each other for survival or are otherwise symbiotically related, continue to multiply and form a matrix that provides nutrients and mutual protection. 
     This bacterial population is known as biofilm, a microbial mass that is bathed in liquids. Dental plaque is another example of biofilm. Biofilm can also be found in air conditioning units, artificial implants and many types of equipment, including dental anti-siphon and check valves. 
     The function of the anti-siphon and check valves is to prevent aspiration of patients&#39; fluids into the dental water lines. Unfortunately, these valves often fail to work properly because of biofilm and other factors. 
     Microbes can become drawn back into the dental water lines as a result of imperfect hygiene sterilization practices, a transient negative pressure when the drill stops rotating and/or mechanical failure of anti-siphon valves or other mechanisms. Once this happens, pathogens originating from patients&#39; mouths can enter the lines and adhere to existing biofilm and multiply within them. 
     These microbes, originating both upstream from municipal water supplies and downstream from patients&#39; blood and saliva, are not very numerous initially. Amplification of the microorganisms is nothing less than astounding. Microbial studies of dental water lines reveal bacterial population explosions averaging over 500,000 cfu/ml and often exceeding 1,000,000 cfu/ml. 
     Thus far, researchers have identified pathogens and opportunists in dental equipment such as Pseudomonas, Legionella, Staphylococci, Streptococci, Nocardia, Serratia, Klebsiella, Moraxella, Bacteroides, Flavobacterium, Escherichia, several species of amoebae known to serve as hosts for  Legionella pneumophila  and even nematodes (worms). 
     Various solutions to prevent exposure of dental patients to contaminated water have been proposed. Such proposals include flushing the dental water lines with distilled water or chemicals but little evidence exists that such flushing eliminates the biofilm. Sterilization of dental instruments between patients has little effect in preventing the microbes in the dental water from entering the next patient&#39;s mouth. Using new disposable sterile water lines between patients does not solve the problem of biofilm upstream of the replaced lines and the costs are significant. Use of containers having sterile or distilled water is effective only if the water conveying lines are replaced after each patient and if the water does not become contaminated prior to disposal of used water lines. Use of check valves to prevent backflow is essentially ineffective one hundred percent (100%) of the time due to contamination of the valve itself. Use of electrical current in combination with antimicrobial agents is impractical due to unavailability of inexpensive ready-to-use equipment. Distilling the water received from a municipal water source only addresses the water and not the contaminants present in the lines conveying the water to the patient. To date, devices using 0.2 micron filters or the like are reasonably effective to prevent transmission therepast of microbes provided that the filters are replaced at least daily and that the process of such replacement does not permit a colony of microbes to be conveyed to a water line downstream of the filter. It is therefore evident that a significant health hazard exists for patients within a dental office and no viable solution is presently commercially available. 
     SUMMARY OF THE INVENTION 
     In the present invention, oxygen, whether from ambient air or a source of oxygen, or ozone from an ozone generator, is introduced to a water source through a sparger or the like to entrain the oxygen or ozone in the water. The water is subsequently conveyed past a silver catalyst cartridge through water lines to each of the various handpieces or water flow dependent implements used by a dentist during the normal course of providing dental services. The oxygen entrained in the water is attracted to the silver in the cartridge and will dissociate from its normal diatomic state to bond with the silver. However, this bond is weak enough that the oxygen will dissociate to oxidize organic matter, including microorganisms in the water. A small amount of the silver will dissolve in the water stream flowing therepast and flow downstream. A portion of this silver will adhere to the surfaces of the water lines, handpieces and implements. The adhered silver is free to react with the oxygen dissolved in the water and any attendant biofilm will be destroyed. Any ozone introduced into the water will destroy any microbial pathogens in the water and help render the water essentially microbe free. Furthermore, the living organisms in any biofilm attendant the walls of the water lines, handpieces and implements will be destroyed upon contact with the ozone. Thus, the water delivered to a patient&#39;s oral cavity during the rendering of dental services will be essentially free of any viable microbial activity. 
     It is therefore a primary object of the present invention to provide apparatus for delivering water from dental water lines free of any living microbes. 
     Another object of the present invention is to provide apparatus for destroying any biofilms formed on the walls of water lines, handpieces and nozzles in a dental operatory. 
     Yet another object of the present invention is to provide apparatus that delivers to a dental patient water free of microbial activity whether such water be from a municipal water system or a water container. 
     Still another object of the present invention is to provide apparatus for destroying any microorganisms present in dental water line or the water itself whether the water is flowing through the line or is stagnant. 
     A further object of the present invention is to provide a silver catalyst to enhance oxidization of microorganisms and biofilm attendant dental handpieces and other dental implements. 
     A yet further object of the present invention is to provide inexpensive apparatus for ensuring that water delivered to a dental patient is free of living microbes. 
     A still further object of the present invention is to provide a method for inexpensively and effectively destroying any biofilm and preventing biofilm buildup attendant dental water lines, dental handpieces and related implements. 
     These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
     FIG. 1 illustrates apparatus for ozonating water delivered to a dental chair; 
     FIG. 2 illustrates details of the ozonating apparatus shown in FIG. 1; 
     FIG. 3 illustrates apparatus for ozonating water within and delivered from a water container to a dental chair; 
     FIG. 4 illustrates apparatus contained within a water container for delivering ozonated water from the container to a dental chair; 
     FIG. 5 illustrates the apparatus shown in FIG. 1 with the addition of a silver catalyst cartridge; 
     FIG. 6 illustrates the apparatus shown in FIG. 3 with the addition of a silver catalyst cartridge; 
     FIG. 7 illustrates the apparatus shown in FIG. 4 with the addition of a silver catalyst cartridge; 
     FIG. 8 illustrates apparatus for entraining air or oxygen in water and passing the mixture through a silver catalyst cartridge; 
     FIG. 9 illustrates a silver catalyst cartridge; 
     FIGS. 10 a,    10   b,  and  10   c  illustrate components of the cartridge shown in FIG. 9; and 
     FIG. 11 illustrates test results obtained with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Ozone entrained in water will destroy microbial life forms in the water itself as well as in any biofilm on the containers for the water or upon the walls of channels or lines through which the ozonated water flows because ozone is a viricide, bactericide, and algicide. Referring to FIG. 1, there is shown apparatus  10  for ozonating water entering a dental office to provide ozonated water to each dental chair. The ozonated water will destroy any microbes or pathogens within the water and reduce or terminate the motility and viability of microbial activity in any biofilm that may be present on the walls of the water lines and attendant dental implements. Furthermore, the ozonated water will terminate the motility and viability of any microbes or pathogens aspirated from a patient and entering any water channels in the dental implements and the water lines extending from the dental implements. 
     With joint reference to FIGS. 1 and 2, apparatus  10  includes a container  12  for receiving water from a water line  14 . An ozone generator  16  is disposed within container  12  and includes a lamp or tube  18  for emitting ultraviolet light within a watertight steel cylinder  17 . A compressor  20  provides a source of air under pressure through pipe  22  into ozone generator  16 . Outlet  24  of pipe  22  may be at the upper end of the ozone generator, as illustrated. A pipe  26  extends from within the ozone generator and includes an inlet  28  located at the lower end of ozone generator  16 . Thereby, air flowing into the generator through outlet  24  is forced to pass around and along tube  18  to inlet  28  to increase the exposure of the air to the ultraviolet radiation from the tube. It is well known that the oxygen in the air subjected to ultraviolet light will result in conversion of the oxygen molecules into ozone molecules as a function of the intensity of and exposure time to ultraviolet radiation. Thus, ozone enriched air flows into pipe  26  through inlet  28 . A check valve  30  in pipe  26  prevents reverse flow therethrough. Pipe  26  is terminated by a sparger  32 . The sparger emits the ozone enriched air in the form of tiny bubbles which become readily entrained and/or dissolved in the water in and flowing through container  12 . 
     An electronics assembly  34 , connected to a suitable power source, provides the requisite electrical power through conductor  36  to tube  18  to bring about energization of the tube and emission of ultraviolet radiation. To prevent an accumulation of ozone enriched air within container  12 , any such gaseous compound is evacuated through an outlet  40  leading to a gas separator  42  through a pipe  44 . Outflow from the gas separator is through a pipe  46  to an ozone destructor  48 . The remaining air is discharged through a pipe  50  to a drain or the like to accommodate drainage of any moisture that may accumulate downstream of container  12 . 
     As an alternative to air injection, oxygen may be injected into ozone generator  16  to provide a higher concentration of ozone in the gas discharged from sparger  32 . A source of oxygen and an injector for propelling oxygen into the ozone generator is represented by numeral  52  identifying an oxygen injector. The oxygen is injected through pipe  54  into the ozone generator. It is to be understood that injection of air or oxygen is primarily in the alternative although oxygen enriched air could also be injected. 
     The ozonated water produced within container  12  is discharged through outlet  60  into conduit  62 . The conduit serves as a water line to provide ozonated water at each of chairs  64 , 66 , etc. in a dental office. In particular, branch lines  68 , 69  may extend from conduit  62  to a manifold or the like attendant each dental chair and in fluid communication with dental implements and other devices that normally discharge the water received. Waste water generated at chair  64  is conveyed to a drain  70  through drain line  72 . Similarly, waste water generated at chair  66  is conveyed to drain  70  through drain line  74 . Such drain lines would be present for each chair. 
     Ozone entrained in water is somewhat unstable and will revert to the molecular form of oxygen at a higher or lower rate depending upon a number of variables. To ensure a fresh supply of ozonated water within conduit  62  after periods of inactivity or non-flow of ozonated water through one or more of branches  68 , 69 , a flow restrictor  80  may be employed. Such flow restrictor accommodates a low flow rate of ozonated water continuously through conduit  62  into discharge pipe  82  and drain  70 . Alternatively, a return line  90  is in fluid communication with conduit  62  downstream of the last branch leading to a dental chair. Ozonated water from conduit  62  is drawn into the return line by a pump  92 . The pump conveys the ozonated water through return line  94  into water line  14  upstream of inlet  15  in container  12 . Thus, the ozonated water flowing through the return line, which water may have a lowered concentration of entrained ozone, is reintroduced to the ozone generator. Such reintroduction, rather than simply having the ozonated water recirculate through conduit  62  and the return line, ensures that water having at least a minimum level of entrained ozone is always present at each of the branch lines (such as branch lines  68 , 69 ). 
     For reasons set forth above, a number of dental offices have begun to use bottles of distilled or purified water instead of relying upon the municipal water system to satisfy the water needs. Referring to FIG. 3, there is illustrated a variant apparatus  100  for use in conjunction with such bottled water. An ozone generator  102  includes a lamp or tube  104  disposed within a closed steel cylinder  105  and connected to an electronics assembly  106  through a conductor  108 . Upon energizing the electronics assembly, electrical power is provided to tube  104  causing it to emit ultraviolet radiation. The air within cylinder  105  of ozone generator  102  will be irradiated to cause a molecular change of the oxygen into ozone. An inflow of air is provided from outlet  112  of pipe  114  connected to an air source  116  under pressure. A regulator  118  may be disposed in pipe  114  to regulate the pressure of the air flowing into the ozone generator. As suggested by the dashed box identified as an oxygen injector  120 , oxygen may be discharged through outlet  112  into cylinder  105  or a mixture of air and oxygen may be discharged into the cylinder. The ozone enriched air within cylinder  105  flows out through inlet  122  of pipe  124 . As illustrated, outlet  112  and inlet  122  are at opposite ends of tube  104  to maximize exposure of the air to the ultraviolet radiation emitted from tube  104  and thereby enhance the ozone enriched air. 
     Bottle  130  containing distilled or otherwise purified water  132  includes a stopper  134  for sealing the bottle against contact between the ambient air and water  132 . Pipe  124  extends through stopper  134 , illustrated, and is terminated by a sparger  136  located in proximity to the bottom of bottle  130 . The purpose of the sparger is that of discharging the ozone enriched air into the water in the form of tiny bubbles to enhance entrainment within the water. A discharge conduit  138  includes an inlet  140  proximate the bottom of bottle  130 . The ozone enriched water (ozonated water) within bottle  130  is conveyed via discharge conduit  138  through stopper  134  to the various dental handpieces or other water related dental implements. Thereby, these handpieces and implements are supplied with ozonated water which will have the effect of destroying the motility and killing any bacteria, microbes or microorganisms present in either the water or in any biofilm on the wall of the discharge conduit or the walls of channels in the handpieces or dental implements. Under certain circumstances, it may be beneficial to treat chemically the water flowing to the dental handpieces and other implements. This may be accomplished by incorporating a chemical injector  142  in fluid communication via conduit  143  with discharge conduit  138  downstream of bottle  130 . 
     A certain amount of ozone enriched air will separate from water  132  and collect at the top of bottle  130 . This ozone is discharged through discharge line  145  extending through stopper  134  from within the bottle. The impetus for such discharge results from the pressure within the bottle generated by the inflowing ozone enriched air through sparger  136 . The rate of ozone discharge through line  145  is controlled by flow restrictor  146 . To prevent damage to the ambient environment, an ozone destructor  147  eliminates the ozone molecules such that the resulting venting through outlet  148  is a gas essentially ozone free. 
     Referring to FIG. 4, there is illustrated a further variant apparatus  150  similar to variant apparatus  100  shown in FIG. 3 except that ozone generator  152  is disposed within bottle  154 . The ozone generator may be suspended from or otherwise attached to cap  156  in threaded engagement with neck  158  of bottle  154 . A lamp or tube  160  for emitting ultraviolet radiation is disposed within a closed steel cylinder  162  of ozone generator  152 . It is electrically connected to an electronics assembly via a conductor  161 . Air, oxygen, or a mixture of air and oxygen is pumped into the ozone generator through a pipe  163  having an outlet  164  proximate one end of tube  160 . The ozone enriched air produced by radiation from tube  160  is discharged into inlet  166  of pipe  168 . The pipe, which may extend through a wall of cylinder  162 , as illustrated, discharges the ozone enriched air through a sparger  170  located in proximity to the bottom of bottle  154  to enhance entrainment of the ozone enriched air in water  172  as the minute bubbles from the sparger migrate upwardly. The ozone enriched water or ozonated water is discharged from within bottle  154  through inlet  174  of conduit  176 . As indicated, conduit  176  conveys the ozonated water to the dental handpieces and other dental implements using water as part of their function. As noted in the drawing, the air flow from outlet  164  to inlet  166  within cylinder  162  is essentially along the full length of tube  160  to enhance exposure of the air to ultraviolet radiation and thereby promote transformation of the oxygen molecules into ozone molecules. 
     Referring to FIG. 5 there is shown an apparatus  200  similar to a great extent with apparatus  10  shown in FIG.  1 . For identification purposes, the same reference numerals for common elements will be used. By operation of ozone generator  16 , a combination of air and ozone is introduced into water  202  within container  12  by sparger  32 . Accordingly, the water outflowing from container  12  through conduit  62  will have a mixture of entrained and/or dissolved oxygen and ozone. Prior to flow of this mixture into branch lines  68 , 69  etc. It is passed through a silver catalyst cartridge  204 . Within the cartridge, the oxygen entrained/dissolved in the water makes contact with the silver and will dissociate from its normal diatomic state to bond with the silver. However, this bond is weak enough that the oxygen will dissociate to oxidize organic matter (such as microorganisms) in contact therewith. Through such oxidation, the microorganisms, which are the major dangerous constituents of biofilm and present potential health hazards, will be destroyed. Thereby colonization of such microorganisms will not and cannot occur. Additionally, a small amount of silver dissolves into the water flowing therepast and conveyed downstream through branch lines  68 , 69 , etc. to the various handpieces and dental implements attendant each of chairs  64 , 66  etc. A portion of the silver dissolved into the water will adhere to the interior surfaces of the branch lines, the handpieces and the implements. Upon such adherence, the silver is free to react with the oxygen conveyed therepast by the flowing water. Typically, the concentration of silver is only order of about three parts per million (3 mg/L). 
     The apparatus shown in FIG. 5 provides numerous beneficial features for a dental operatory or other medical facility using water from a municipal water source. The introduction of ozone into the water has the beneficial effect of sterilizing the water received. By using a sparger, to introduce the ozone and attendant air from the ozone generator establishes elevated levels of oxygen and ozone in the water. The solubility of the ozone in the water is essentially proportional to the pressure. The ozone assists in biofilm reduction by dissociating to form oxygen containing radicals which will react (oxidize) organic matter and microorganisms. Additionally, the presence of ozone within the silver catalyst cartridge increases the activity of the silver catalyst and thereby increases the reaction rate between the silver and oxygen. It is believed that an interaction between the silver and the ozone may cause some reaction with the water itself to convert a small amount of the water to hydrogen peroxide; it is well known that hydrogen peroxide is a strong oxidizer and functions as a disinfecting agent. Accordingly, the presence of hydrogen peroxide may have a further beneficial effect in destroying existing biofilm and preventing the formation of biofilm. As the ozone is carried downstream, it will spontaneously decompose to oxygen and its effectiveness for biofilm destruction will be reduced. However, the silver present in the water and adhered to the walls of the conduits, pipes, handpieces and implements will react with the dissolved oxygen decomposed from the ozone and provide further destruction of organic matter and the microorganisms. As a result of the combination of ozone and oxygen entrainment in the water and the silver catalyst, the water flowing into the dental handpieces and dental implements will be sterile and a residual disinfecting agent will exist throughout the plumbing network of a dental operatory. 
     For the above and below described configurations employing ozone, it may be prudent from time to time to purge the water conduits and related water conveying equipment with ozone. Such purging, after evacuation of all water, would expose and tend to destroy any residual biofilm that may be present on the exposed surfaces. 
     The use of ozonated water, with or without purging with ozone, will help keep the water conduits and associated equipment clean. Thus, the maintenance (cleaning) is reduced and the performance and life of dental drills, irrigation faucets and all water using dental tools will be enhanced. 
     Referring to FIG. 6 there is shown an apparatus  210 , which apparatus is similar to that shown in FIG.  3 . With respect to common elements, the same reference numerals will be applied. The major difference between the apparatus  100  (FIG. 3) and apparatus  210  is the introduction of a silver catalyst cartridge  212  in series with discharge conduit  138 . As set forth in further detail with reference to FIG. 3, sparger  136  introduces ozone and oxygen to water  122  with container  130 . The ozone and oxygen is entrained and to some extent dissolved in the water overflow through discharge conduit  138  and enters silver catalyst cartridge  212 . The beneficial effects of the water outflowing from the cartridge through discharge conduit  138  will be essentially the same as discussed above with respect to FIG.  5 . 
     FIG. 7 illustrates apparatus  220 , which is essentially the same as apparatus  150  shown in FIG.  4 . Accordingly, common elements have been given the same reference numerals. Apparatus  220  includes a silver catalyst cartridge  222  disposed in series in conduit  176  conveying water to the various handpieces and implements, as discussed above. The ozone and oxygen discharged by sparger  170  into water  172  contained in container  154  is transmitted to and through silver catalyst cartridge  222 . The reactions within the cartridge and beneficial effects of the water flowing therefrom discussed above with respect to FIGS. 5 and 6 will also be true for the water flowing from cartridge  222  of apparatus  220 . 
     FIG. 8 illustrates an apparatus  230  similar in many respects to the apparatus shown in each of FIGS. 5,  6  and  7  except that an ozone generator is not formed a part thereof. The deletion of the ozone generator constitutes a significant cost reduction and avoids maintenance efforts and expenses associated therewith. Apparatus  230  includes a container  232 , which may be referred to a saturation chamber (a term which could also be applied to the containers associated with each of apparatus  200 ,  210  and  220 ). A source  234  of air, which could be air from a dental operatory supply, is conveyed through a conduit  236  into container  232 . A regulator  238  may be disposed in conduit  236  to maintain the pressure therein at a predetermined pressure, such as 45 psig. To prevent overflow from container  232  through conduit  236  a check valve  230  may be employed in the conduit. A sparger  242  is disposed at the terminal end of conduit  236  to introduce fine bubbles of air into water  244  to entrain/dissolve these bubbles in the water. To prevent a buildup of an air space  246  within container  232 , a vent conduit  248  may be employed. Such conduit would include a flow restrictor  250  to prevent discharge of water therethrough. The air (gas) flow past the restrictor may be vented to the atmosphere through an outlet  252 . 
     To increase the amount of oxygen to be entrained in water  244 , a source  254  of oxygen may be employed, as depicted in dashed lines. The oxygen is conveyed through conduit  256  from the source of oxygen into conduit  236 . A valve  258  may be used to select inflow from either source  234  of air or source  254  of oxygen; alternatively, a valve capable of metering a flow from each of the sources of air and oxygen may be used. 
     Because each of the source of air and the source of oxygen must be under pressure to cause gas to flow therefrom into conduit  236 , water  244  in container  232  becomes pressurized. Such pressure environment also assists in expelling gas through vent conduit  248  to prevent existence of a significant air space  246 . The pressure environment present within container  232  causes the water to be discharged into inlet  260  of discharge conduit  262 . The discharge conduit conveys the water with entrained air/oxygen to silver catalyst cartridge  264 . The chemical reactions resulting within the cartridge are the same as those described above with respect to FIGS. 5,  6  and  7 . The outflow from the cartridge is conveyed via conduit  266  to the branch lines associated with each dental chair and the related handpieces and implements, as described above. To further assist in destroying microorganisms within the water discharged from container  232 , a UV source  268  may be used in conjunction with discharge conduit  262  to irradiate the water flowing therepast and thereby kill irradiated microorganisms. As UV source  268  is an alternate embodiment, it is shown in dashed lines. 
     Referring jointly to FIGS. 9,  10   a,    10   b  and  10   c,  a representative silver catalyst cartridge will be described in detail. A cartridge of this type may be used as each of the silver catalyst cartridges discussed above. The cartridge is formed of a tube or sleeve  282  having an interior diameter of 0.0875 inches and of a 2 inch length. A plug  284  is disposed at each end. The plug includes a cylinder  286  for insertion into an end of sleeve  282  and an annular protrusion  288  to limit insertion of the plug. A centrally located threaded aperture  290  is formed in the plug to threadedly receive a fitting  292  having a barbed nipple  294  extending therefrom for penetrable engagement with an attached conduit. A downstream fitting engaging downstream plug  284  may be similar to fitting  292 ; alternatively, it may be a fitting  296  threaded engaging plug  284  and configured to receive and engage the end of tubing or a conduit extending therefrom. A twenty micron (20 μ) filter  298  may be attached to the downstream plug, which filter prevents outflow of particulate material larger than twenty microns. Silver catalyst  298  comprises beads of silver packed between the end plugs within sleeve  282 . These beads comprise silver deposited on a mineral substrate (alumina) and are available from Fountainhead Technologies, Inc. of Providence, R.I. They are described in further detail in an article entitled “Fountainhead Technologies talks about their unique approach to catalytical water purification” published in the November, 1994 issue of the Catalyst Review Newsletter, which article is incorporated herein by reference. As set forth in a Material Safety Data Sheet prepared by Fountainhead Technologies, Inc. and incorporated herein by reference, the ratio of alumina (Al 2 O 3 ) to silver (Ag) is in the range of about 97.9% to about 98.3% and in the range of about 2.1% to about 1.7%, respectively. 
     As described above, the silver catalyst cartridge works essentially in the following manner. Dissolved oxygen in the water flowing through the cartridge contacts the beads of silver. The bond of diatomic oxygen molecule is ruptured upon contact to create individual oxygen atoms which then become loosely bound to the silver surface. The unique ability of silver to enter into oxidative reactions is due to the very weak bond it forms with oxygen (approximately 7 to 8 kcal/mol; most other transition metals bond with oxygen at strengths of more than 100 kcal/mol). These weak bonds allow silver to readily transfer the loosely held oxygen atoms to any oxidizable substrate, such as organic matter and microorganisms. When other organic matter and microorganisms make contact with the loosely bound oxygen atoms, oxidation occurs and the bonds in the organic matter and microorganisms are ruptured. The oxidized fragments will depart from the surface of the silver beads to expose the beads and the process is repeated. Silver ions are slowly released into the water by a combination of erosion and galvanic action. The silver ions so produced provide a residual oxidation activity downstream to affect any organic matter or microorganisms coming in to contact therewith. 
     To test the efficacy of the present invention, a number of experiments were conducted in different dental office locations. The results of these experiments are tabulated in FIG.  11 . During these tests, the number of colony forming units (cfu) per millimeter at each noted sampling cite were recorded. In office No.  1  prior to use of the present invention, the water at handpiece A had 220,000 cfus and a water irrigation implement had 450 cfus. During the succeeding three weeks, the number of cfus dropped to 1,3 and 0 and 1,4, and 0, respectively. In office No.  2 , a handpiece A and a water irrigation implement prior to installation of the invention had 34,000 cfus and 355,000 cfus, respectively. After one week, the sample at handpiece A contained less than 100 cfus and there were none in the irrigation implement. For the following three weeks, there were no cfus measured at either the handpiece A or the irrigation implement. In the office No.  3 , prior to use of the invention, handpiece A had 9,400 cfus and water irrigation implement had 12,150 cfus. After installation of the invention, the cfus at handpiece A dropped to 80 and the cfus at the irrigation implement dropped to 13. After a week, the cfus at handpiece A dropped to 5 and cfus at the irrigation implement increased to 23 (the reason for the increase is unknown and may have been poor data or due to an intervening activity). In office No.  4 , the number of cfus at handpiece A was 40,000 and at water irrigation implement was 41,000 prior to installation of the invention. Thereafter, the cfus dropped to zero after installation and for the ensuing four weeks. In office No.  5 , the number of cfus prior to installation were 212 at the handpiece A and 89,500 at the water irrigation implement. Thereafter and for the next five weeks, the number of cfus at each of the handpiece and the water irrigation implement was essentially zero. In office No.  6 , handpiece A contained 4,100 cfus and the water irrigation implement contained 350 cfus prior to the installation of the present invention. After installation and one week thereafter, the cfus at both locations dropped to zero. 
     Accordingly, one must come to the inescapable conclusion that the present invention is highly effective in destroying microorganisms in the environment of a dental operatory. Furthermore, it will destroy any existing biofilm and will prevent the buildup of biofilm in the attendant water conduits and water conveying and pieces and implements used in the dental practice. 
     While the invention has been described with reference to several particular embodiments thereof, those skilled in the art will be able to make the various modifications to the described embodiments of the invention without departing from the true spirit and scope of the invention. It is intended that all combinations of elements and steps which perform substantially the same function in substantially the same way to achieve the same result are within the scope of the invention.