Abstract:
This ozone appliance for the professional dental office and other medical applications introduces dissolved ozone into dental and surgical operatory water lines. This dissolved ozone can not only disinfect water and water lines; it can also reduce gum bleeding, gingivitis, bad breath, teeth stains and oral bacteria. Additionally, it can aid in wound disinfection in surgery and attack microbial contamination of water from dental and surgical operatory water lines and attached hand pieces and dispensing devices by automatically killing waterborne germs and destroying biofilms where germs can hide and grow. It can, therefore, be used to disinfect water lines in dental operations and for other medical applications such as providing liquid containing ozone for cleaning and disinfecting skin prior to surgery (and tissue exposed during surgery). Further, a unit connected to operatory water lines can give an audible or other alarm if the water becomes unsafe.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/269,403, filed on Feb. 16, 2001, which provisional application is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Ozone disinfection of operatory water lines, in particular dental operatory unit water lines. 
     BACKGROUND 
     There has been serious concern that microbial contamination of dental office water systems puts dental patients at risk of diseases. The problem of water contamination, especially when due to cross contamination from other patients, is greatest for patients with weak immune systems. Additionally, dental water can become contaminated from the water supply. More commonly, contamination results from growth of microbial biofilms on the inner surface of water lines. Such biofilms can include germs introduced from patients. Germs can slough off from biofilms as water passes through water lines. Thus, it is not uncommon for water coming out of dental hand pieces to have more than one million bacteria per milliliter while the water entering the dental lines has less than 100 bacteria per milliliter. 
     Existing systems do not remove microbial biofilms, do not provide failure warning are inconvenient, are expensive, require excessive dental labor and depend on perfect user compliance with manufacturers&#39; instructions. 
     SUMMARY OF THE INVENTION 
     Our invention makes possible a small, low-cost and user-friendly ozone appliance for the professional dental office and other medical applications. It is based in part on the advantages gained in using dissolved ozone as a disinfectant. Ozone dissolved in water can not only disinfect water and water lines, it can also reduce gum bleeding, gingivitis, bad breath, teeth stains and oral bacteria. Additionally, it can aid in wound disinfection in surgery. Our invention introduces dissolved ozone into dental and surgical operatory water lines. This dissolved ozone attacks microbial contamination of water from dental and surgical operatory water lines and attached hand pieces and dispensing devices. Our system automatically kills waterborne germs and destroys biofilms where germs can hide and grow. It can, therefore, be used to disinfect water lines in dental operations and for other medical applications such as providing liquid containing ozone for cleaning and disinfecting skin prior to surgery (and tissue exposed during surgery). We believe it will also be readily applicable in the context of ophthalmic surgery. Further, a unit connected to operatory water lines can give an audible or other alarm if the water becomes unsafe. 
     Thus, the advantages of our ozone system are numerous. Ozone disinfection via our system is automatic, making it much more convenient for dental personnel. With our system, ozone disinfection automatically adjusts for variable water flow and quality. Further, ozone containing gas is separated from the water before the water is circulated with excess ozone converted to oxygen before venting. Moreover, ozone disinfection using our system does not depend on strict user compliance as our ozone system provides failure warning. In addition, ozone is the only disinfectant that can inactivate all pathogens in a short time. Ozone can destroy endotoxins produced by bacteria and destroy biofilms. (Microorganisms do not develop resistance to ozone). Finally, ozone is user friendly. It does not cause allergic reactions, has no offensive taste, and will not cause problems if accidentally ingested (unlike other disinfectants). It also stops gum bleeding and disinfects wound sites. 
    
    
     
       DRAWINGS 
         FIGS. 1-5  are schematic diagrams of different embodiments of the inventive operatory water disinfection systems having many components in common. 
         FIG. 1  schematically illustrates a first embodiment of our invention. 
         FIG. 2  schematically illustrates a second embodiment of our invention. The system of  FIG. 2  differs from the system of  FIG. 1  primarily in the way the ozone-containing gas is contacted and mixed with the water. 
         FIG. 3  schematically illustrates a third embodiment of our invention. The system of  FIG. 3  differs from the system of  FIG. 1  primarily by economizing the mixing and delivery processes with fewer components. 
         FIG. 4  schematically illustrates a fourth embodiment of our invention. The system of  FIG. 4  differs from the system of  FIG. 1  primarily by economizing the mixing and delivery processes with fewer components. 
         FIG. 5  schematically illustrates a fifth embodiment of our invention. The system of  FIG. 5  differs from the system of FIG.  1  primarily by economizing the mixing and delivery processes with fewer components. 
         FIG. 6  provides a schematic diagram of a preferred external circulation passageway enhancing the operation and effectiveness of the inventive operatory disinfection system. 
     
    
    
     DETAILED DESCRIPTION 
     The preferred embodiments of the drawings have comparable advantages in features such as convenience, reliability, safety, cost and size. Different embodiments, using different combinations of such features, may be preferred for different users with different requirements. In addition, some of the different features that are illustrated in the drawings can be interchanged among the various embodiments, and the drawings are arranged to illustrate the different features that can be combined and not to delimit one combination of features from another. 
     Our description will assume that the apparatus is installed in a dental operatory. The invention will first be explained relative to the embodiment illustrated in  FIG. 1  and the detail illustrated in  FIG. 6 . The order of presentation will follow the flow passageways of the ozone-containing gas, the liquid and ozone-containing gas mixing system and the ozonated liquid delivery system. This will reveal aspects of the invention in an order that is understandable but differs from the order of importance of the features involved. 
     First, the device generates an ozone containing gas using corona discharge, preferably using the corona discharge generator  11  disclosed in Burris&#39; U.S. Pat. No. 5,529,760. The corona discharge method is preferred over the ultraviolet (UV) method, because it can produce the much higher gas ozone concentration needed to achieve an ozone concentration in the liquid adequate for disinfection. The device dissolves the ozone in the liquid by mixing continuously during operation. (See mixing methods disclosed in Burris&#39; U.S. Pat. Nos. 4,555,335; 5,207,993 and 5,213,773.) Our preferred mixing method uses a positive pressure pump  12  (such as a piston, rotary vane, diaphragm, or, preferably, a gear pump) in a liquid bypass. In the bypass mixing method, a liquid line  13  from the treatment chamber  14  and the line  9  from the ozone generator  11  come together at the pump  12  inlet. The mixing pump  12  mixes the ozone-containing gas and liquid and pumps both through the bypass line  15 , which preferably includes a static mixer  16  back to the treatment chamber  14 . 
     The air used to generate ozone is preferably first dried to a low dewpoint to improve the efficiency of ozone generation. This may be accomplished by use of replaceable desiccant cartridges  42  or an air drying system. Replaceable desiccant cartridges  42  can be protected from loss of drying capacity by entry of moist air when the system is not operating through the use of spring-loaded check valves  43  at the entrance and exit passageways to the cartridge. It would be advantageous to make use of the operatory supply of dry air  41  through regulator  40  to provide reduced dew point air for use in generating ozone in the device. This would also extend the life of the desiccant. More expensive sources for generator supply gas are oxygen generators or replaceable oxygen tanks. The use of oxygen instead of air greatly increases the ozone generator  11  efficiency and ozone output. 
     With a constant flow of ozone containing gas in excess of what can be dissolved according to Henry&#39;s law, the ozone concentration in the liquid is maintained at the desired level during the operation of the device. One of the great advantages of ozone is that according to Henry&#39;s law, the dissolved ozone concentration is determined by the partial pressure of ozone in the gas rather than the amount of ozone so long as there is an excess of ozone. 
     The ozone containing gas is separated from the liquid after mixing, preferably by gravity in the treatment chamber  14 . The alternative methods of using a porous hydrophobic material  54  or a float valve  51  will be discussed in more detail relative to  FIG. 5 . The separated gas is passed through an ozone reducing material  20  before the gas is released to the atmosphere. Thus, no ozone gas is released from the device to the atmosphere, and bubbles are eliminated from the liquid output line where they might cause problems. The gas/liquid separation is preferably conducted at minimal pressure to reduce the solubility of the gas and the tendency of bubble formation after the liquid is outputted to atmospheric pressure. Liquid is prevented from entering the ozone generator  11  preferably by use of a porous hydrophobic material  18  or a check valve  19 . Liquid is preferably prevented from entering the ozone reducing material  20  by use of a porous hydrophobic material  18  or  50 . The use of porous hydrophobic materials, such as polytetrafluoroethylene, eliminates moving parts and thus improves reliability. 
     The liquid supply can be either a pressurized water line  21  or a reservoir  22 , which can be refilled or changed when the liquid supply runs low. The liquid from a pressurized water line  21  should be connected according to locally accepted practices through back flow preventers  23  and pressure regulators  24  as required, all of which are well known in the industry. The liquid from a pressurized water line  21  can be admitted to the operatory disinfecting system by a valve  25 , responsive to a float or liquid level sensor  26 , as needed to replace outputted liquid. Admission of replacement liquid from a reservoir  22  can be controlled by a valve  25  as with a pressurized water line  21  or in the case where gravity will not be adequate, a pump  31  responsive to a float switch or liquid level sensor  26 . 
     It is common for dental offices to have a master water valve that is shut off when there are no patients being treated in the office. In the event of the contents of the reservoir  22  being consumed or the water system  21  turned off (by a master control valve in the facility) a pressure switch  32  or sensor can communicate with the control system  33  to signal a shortage of liquid supply and or shut down the operatory disinfection system. If the pressure switch  32  is to be relied upon to shut down the operatory disinfecting system, we prefer that a bleeder valve or orifice  34  be installed in the supply line  21  upstream of valve  25 . This arrangement eliminates the possibility of the system remaining on after the water supply  21  is turned off. This situation can occur if no liquid is required by the operatory disinfecting system to run down the pressure of the supply line  21 . Alternatively, a sensor, such as liquid level sensor  26 , can communicate with a controller  33  to determine that the system has not put out any liquid for a predetermined period of time and can shut down the operatory disinfecting system, it is preferred that a warning is given prior to actually shutting the system down. 
     Second, the liquid containing dissolved ozone is outputted from the dissolving system at a controlled constant rate and pressure to points as close as possible to the outlets to atmospheric pressure. The pressure and flow rate in the circulating liquid line is regulated by appropriately sizing the liquid passageways and the circulating pump  30  (if used) or by use of devices such as pressure regulators  27 , pressure relief valves  28  and flow controllers  29 . The liquid not demanded by dental hand pieces  61 , syringes  62  and rinse cups  67  could be either recirculated to the mixing system at liquid return  38  or discarded as waste as shown in  FIG. 6 . A preferred and beneficial point of discharge as waste, via alternative line  71 , is the cuspidor  63 , this provides an air gap to the waste line  68  and allows ozonated liquid to flush and rinse the cuspidor  63 . With the flow of liquid containing dissolved ozone the objective is to prevent significant delays between ozonating and final use to avoid ozone concentration reduction caused by ozone reversion to oxygen. Ozone dissolved in water has a half-life of approximately 15 minutes before the ozone reverts to normal oxygen. Recirculating and reozonating the liquid has the advantage of requiring a smaller ozone generating and mixing system and providing more holding time to increase germ killing in the liquid. Discharging the ozonated liquid to waste has the advantage of possibly eliminating the circulation pump  30 . In either design, the concept is that when the device is turned on to make available ozonated liquid, the system operates continuously to produce more freshly ozonated liquid than the maximum that might be required. If desired, due to water quality considerations, a filter  37  can be added to the water inlet line and/or to the pressurized liquid circulating passageway. 
     The dental office disinfection system preferably should be installed in each operatory at the point where water is connected to the chair or treatment apparatus. Preferably, as detailed in  FIG. 6 , the flexible tubing  65  connecting the treated water supply to the hand pieces  61  and syringes  62  should have an extra lumen  66  so that ozonated water can be circulated continuously through the tubing. This would bring freshly ozonated water as close as possible to the point of use. In situations were the control valves are remotely located from the hand pieces  61 , it would be beneficial to have the liquid valve  64  located at the hand piece  61 . One way to accomplish this is to make use of the commonly used foot operated control valve  69 , which controls the air supplied to the turbine of the hand piece  61 . In this arrangement, a relay valve  64  is actuated according to the air pressure received to determine the flow of liquid to the hand piece  61 . For example, as more air pressure is applied (faster turbine speed, more heat is generated) more liquid is dispensed (for greater cooling). 
     Ideally, an ozone sensor  45  would be in the treated liquid passageway. The ozone sensor circuit would provide assurance that the system is operating properly or warn if it is not. For example, the sensor circuit could activate an alarm such as a beeper  46  and or a lamp  47  if the ozone concentration falls too low. In practice, this alarm could activate briefly each morning after the system was turned on, and then activate only if there were a problem with the system. Another possibility is that after a time delay to get the system started, the sensor in communication with the controller  33  could prevent liquid outputting if the ozone concentration fell below an established minimum level. An alternate or additional ozone sensor  72  would be as close as possible to the point of use (possibly made as part of the hand piece  61  or syringe  62 ) and further it could be powered by battery or the sensor current to indicate to the user that ozone is present in the liquid or not. One possible way for the sensor  72  to communicate with the user is through a two-color light emitting diode where red indicates insufficient dissolved ozone and green indicates sufficient dissolved ozone. The ozone sensor could use an ORP (Oxidation Reduction Potential) electrode, which is well known to those skilled in the art, or preferably, two dissimilar (with different positions in the electromotive series) metals in the liquid stream connected to generate a galvanic potential proportional to the ozone concentration. While use of an ozone sensor  45  to warn of system problems should be adequate, additional sensor circuits to warn of low liquid pressure or flow rate could be added for additional safety. 
     The embodiment of  FIG. 2  is substantially similar to the embodiment of  FIG. 1 , but differs in the way ozone-containing gas is introduced and mixed with the liquid. Specifically the mixing pump  12  along with static mixer  16 , bypass passageway  15  and inlet passageway  13  has been replaced with an ozone-containing gas pump  55 , an ozone-containing gas passageway  56  and a gas diffuser  57 . The diffuser  57  is preferably the fine bubble diffuser disclosed in Burris&#39; U.S. Pat. Nos. 5,422,043 and 5,858,283. One advantage of this embodiment is possibly quieter operation. To further quiet and economize the operation, the ozone-containing gas pump  55  can be replaced with a solenoid valve  58  that makes use of the pressure supplied by the operatory air system  41 . The air treatment and ozone generator would then be configured for a pressurized application including a pressure relief valve  60  to prevent over pressurizing the gas system. The gas liquid separation, the control system and liquid delivery system remains the same as described with regard to  FIG. 1 . 
     The embodiment of  FIG. 3  is similar to the embodiment of  FIG. 1 , but differs in that the functions of the delivery and dissolving systems have been combined to be achieved with one pump. In this arrangement, the mixing pump  12  is configured to mix the ozone-containing gas and liquid, the gas and liquid mixture then preferably enters a static mixer  16  as in the preferred embodiment of  FIG. 1 . At this point, the gas and liquid mixture are directed to an inline gravity liquid separator  39 . All of the gas and some of the liquid exit the upper region of the separator  39  and are directed to the treatment chamber  14 . Liquid exits the lower region of the liquid separator  39  and is directed to the exterior circulation passageway  6  as described in reference to  FIG. 6 . The pump  12  and the passageways are sized to provide the proper flow and backpressure to cause the treated liquid to flow through circulation passageway  6 . Alternatively, pressure controls  35  and liquid flow control  36  and gas flow control  8  can be used to direct the gas and liquid on the proper course at the proper pressure and at the proper flow rate. 
     The embodiment of  FIG. 4  further economizes the embodiment of  FIG. 3 . In this configuration the treatment chamber  14  is eliminated and the apparatus for contacting the ozone-containing gas with the liquid is similar the difference is in the separation of the gas from the liquid. The gas/liquid separator  48 , using a float valve or preferably a porous hydrophobic material, separates the gas from the liquid and directs the gas to a passageway leading to an ozone reducing material  20  prior to releasing the gas to the atmosphere. The float valve type of gas/liquid separator  51 , as shown in  FIG. 5 , makes use of a float  52  riding on the liquid in a chamber allowing gas to pass through a valve port  53 , when the liquid level drops and blocks the exit of liquid through the valve port  53  when the liquid level rises. A porous hydrophobic gas/liquid separator  54 , as shown in  FIG. 5 , contains no moving parts; instead, it makes use of a porous hydrophobic material  50  resisting the flow of liquid through its porosity due to the low surface energy of the hydrophobic material  50 . The liquid only, exiting the gas/liquid separator  48  is directed to an external circulation passageway  6  and is preferably returned to the operatory water disinfecting device through water return  38 . Once the circulated liquid is returned to the device, it preferably travels through an ozone sensor  45  and then on to a pressure relief valve  28 , which can maintain the backpressure as required for dispensing the ozonated liquid along its circulation passageway  6 . At this point, the liquid is joined with the incoming liquid  44  in a region  49  upstream of where the ozone-containing gas and liquid are joined and mixed. This provides for recirculation of the liquid and also results in a higher concentration of dissolved ozone. The supply liquid is provided through a demand regulator  59 , this arrangement will also provide a draw from reservoir  22  if so equipped. In this embodiment the flows of the gas and the liquid can be controlled by flow controllers  29 , pressure relief valves  28  and orifices  36  but we prefer to use spring loaded check valves  43  and passageways sized according to the requirements for controlling the desired flows. 
     The embodiment of  FIG. 5  further economizes the embodiment of  FIG. 4 . The two primary differences being: one; the circulated liquid is discharged to waste  68  such as in the cuspidor  63  and two; the mixing pump  12  can be replaced with a venturi injector  70  to add and mix the ozone-containing gas with the liquid. Since the effectiveness of the venturi injector is dependant upon liquid flow, it is preferable to include a pressure sensor  32  to warn of low incoming liquid pressure. It is also possible to make use of the pressure in the oxygen-containing gas supply  41  to aid in mixing the ozone-containing gas with the liquid. 
     The embodiment of  FIG. 6  illustrates in detail the preferred arrangement of the circulation passageway  6  of the inventive device. The treated liquid may also be dispensed to fill the rinse cup  67  and to rinse the cuspidor  63  through valves  77  and  73  respectively. As previously disclosed it is most desirous to place the output valves  62 ,  64 ,  73  and  77  and circulate the treated liquid as close to the point of treated liquid discharge as possible. In the non-recirculated version, the liquid can flow through an ozone sensor  45  prior to discharge through alternate passageway  71  as shown in  FIG. 5 . This way the treated liquid is checked for ozone content at the completion of its intended purpose. The alternate flow passageway  71  can be used when the circulation destination is to waste  68  through the cuspidor  63 .