Patent Publication Number: US-2004047761-A1

Title: Methods and arrangements for disinfection of water lines of a dental unit

Description:
[0001] The present invention relates to methods according to claims 1 and 11 and to arrangements according to claims 13 and 21 for disinfection of water lines of a dental treatment apparatus. In particular, the invention relates to solutions in which disinfection is implemented as a separate operation, e.g. at the end of a working day, by supplying a strong disinfectant into the water lines and letting it act in the lines for a longer time, e.g. overnight.  
       [0002] From the perspective of the hygienic requirements concerning dental treatment, one of the most important sub-areas is the microbiological quality of water supplied via dental instruments into the patient&#39;s mouth. Preventing microbial growth in the water lines of the dental unit is particularly difficult because, in typical use of the unit, water may stand in the unit at ambient temperature even for long periods, with the result that biofilm, which provides a propitious breeding ground for harmful microbes, tends to be formed on the walls of the narrow water lines.  
       [0003] Countless solutions have been used to fight the problem of microbes in dental units. As for physical disinfection methods, e.g. UV irradiation involves the problem that it only has a local effect, in other words, its effect is almost exclusively limited to the area exposed to irradiation. By using filters, it is in principle possible to prevent microbes from getting into the water lines and into the patient&#39;s mouth, but then it is necessary to take care of changing/servicing the filters at sufficiently short intervals, and, on the other hand, the filter itself is a potential source of microbial contamination. Obviously laborious solutions are also those in which water is purified elsewhere before being fed into the dental unit from replaceable supply tanks. On the other hand, even the use of purified water does not completely eliminate the need to periodically wash the water lines and/or change used hoses.  
       [0004] Microbial growth in the water systems of a dental unit can also be prevented by chemical means e.g. by mixing water with a suitable disinfectant in concentrations diluted enough to allow such water still to be supplied to dental instruments, and thus further into patient contact. In these solutions, safety considerations naturally have to be given special attention—an accurate and continuous dosing of the chemical is needed, and strong solution should not get into patient&#39;s mouth in any type of malfunction or breakdown. On the other hand, the alternative of using ready-diluted solutions is at least as laborious as is using water purified elsewhere.  
       [0005] The water lines of dental instruments can also be disinfected as a separate operation using strong disinfectants. Some of such substances also have inhibiting effects on the formation of biofilm. When strong solutions are used, it is necessary to make sure that patients will never get into direct contact with the chemical. On the other hand, especially when water to the dental unit is taken from a public tap water network, care should also be taken to ensure that in connection with the disinfection process no chemical may be carried upstream of the main valve of the dental unit and thus eventually further into the public distribution network. Often, authorities and/or water plants have issued technical minimum regulations to exclude such a possibility (e.g. RVV KÄSIKIRJA, RAKENNUSTEN VESIJOHDOT JA VIEMÄRT publication no. 7, Suomen Kunnallistekninen Yhdistys, Helsinki—1979, 6 th  edition, K. J. Gummerus Oy, Jyväskylä 1979).  
       [0006] Additionally, the main valve forms a special problem in dental units as it by itself forms a potential contamination source. The concentration of disinfectant in the water line portion lying upstream of its point of entry is easily left too low and/or its time of action left shorter there than elsewhere, and especially electrically operated valves may be propitious incubation grounds because of, among other things, their operating temperature.  
       [0007] Patent specifications EP 111 249, WO 95/20366 and U.S. 5,526,841 present arrangements for chemical disinfection of the water lines of dental units, but in all of these, careless or thoughtless action may lead to some of the problems dealt with above. Thus, the object of this invention is to enhance the state of the art expressly from the perspective of safety of the processes of disinfection of the water systems of dental units, as to reduce the possibility of strong disinfection chemicals accidentally getting into the patient&#39;s mouth via dental instruments. Further, according to a feature of the invention, its object is to enable better disinfection of the main valve of the water system of the dental unit, yet so that no disinfection solution gets into the dental unit&#39;s supply water line—which may be connected to a public water distribution system.  
       [0008] Generally speaking, the object of the invention is to implement the construction and control system of the disinfection system of a dental unit in a manner that will reduce the chances of the user of the dental unit accidentally doing something that would lead to the realization of the above-described risks relating to the use of strong chemicals. These objects will be achieved especially by the solutions defined in the independent claims presented below.  
       [0009] According to a special feature of the invention, the control system of the dental unit comprises control functions that disable the use of at least instruments using water when there is disinfectant in, or when it is being fed into the water system of the unit, in other words, the possibility of disinfectant getting into the patient&#39;s mouth via instruments is precluded.  
       [0010] On the other hand, according to a special feature of the invention, the supply container of disinfectant can not be connected to the dental unit if the valve connecting the unit to the supply water line is not closed, and likewise the said valve can not be opened if the disinfectant container is connected to the dental unit—especially when the supply water line is in connection with a public water distribution system.  
       [0011] A further object of the invention is to enable as effective disinfection of the main valve of the dental unit as possible, which is realized by arranging the junction for the supply of disinfecting chemical on the upstream side relative to the main valve, in a way that drifting of the disinfectant upstream from this supply point is prevented. 
     
    
    
     [0012] In the following, the invention and its preferred embodiments will be described in more detail by referring to the attached drawings, wherein  
     [0013]FIG. 1 presents a water line arrangement of a dental unit according to prior art,  
     [0014]FIG. 2 presents a possible water line arrangement of a dental unit according to the invention, and  
     [0015]FIG. 3 presents an arrangement according to the invention for connecting a disinfectant container to the water line of a dental unit. 
    
    
     [0016] In FIG. 1 there is presented a water line arrangement of a dental unit according to prior art, wherein the main valve  102  of the dental unit is placed in the supply water line  101 . Typically, downstream relative to the main valve there is arranged a filtering element  103  and a pressure regulator  104 . Using e.g. a compressed air system not shown in FIG. 1, a disinfectant  105  can be driven from its supply container  106 , which is connected to a fastening device  106 ′ being located in the dental unit, via a disinfectant supply junction  107  into the water lines  108  of the dental unit. Typically, for the duration of the disinfecting process, the dental instruments (not shown in FIG. 1) connected to the end of the water lines  108  are placed in a vessel separate from the dental unit, into which the operating-water having been in the water lines  108 , as well as the disinfectant  105  after the disinfection time has elapsed, are driven.  
     [0017] In FIG. 2 there is presented a possible dental unit water line arrangement according to the invention, wherein the main valve  202  of the dental unit is placed in the supply water line  201  and downstream of it a filtering element  203  and a pressure regulating element  204 . In the solution of the invention, however, the supply junction  207  for disinfectant  205  is so implemented that the container  206  can not be connected to the water line  201 ,  208  unless connection to the supply water line  201  has been cut off. In the solution according to FIG. 2, according to a preferred embodiment of the invention, this has been realized by providing upstream of the main valve  202  an on-off valve  209  being in a functional contact with coupling elements  210  of the disinfectant container  206  so that connecting the container  206  to the dental unit is only possible if valve  209  is closed. Therefore, for example, if the disinfectant  205  supply container  206  is arranged to be pressurized via a compressed air line  212  provided with a pressure regulator  211 , which line may be a branch of the compressed air line of the dental unit, then the disinfectant  205  feed pressure can be arranged to be different, e.g. lower than the operating water pressure in the dental unit, in which case it will be possible to detect, e.g. on the basis of a signal obtained from a pressure gauge (not shown in the figure) placed in the water line  208 , that the disinfectant container  206  is connected, and thus to disable, e.g. by means of the control system of the dental unit, the use of dental instruments—at least of those using water. Naturally, the detection of connection of the chemical container—or of the start of supply of the chemical—can also be realized by many other means known as such, e.g. by using a microswitch. In addition, the connected state of the container can be indicated e.g. by a light or a sound signal.  
     [0018] A modern dental unit contains a large number of electric actuators, and consequently the temperature inside its housing may rise locally considerably above the ambient temperature. The check valve or an equivalent element for cutting off the supply water line is therefore advantageously placed outside the dental unit, substantially in the vicinity of its housing or otherwise at a location as far away as possible from any heat emitting elements of the dental unit, to avoid needlessly providing microbes optimal conditions for growth. Naturally, the choice of materials used in said element is also a factor by which its properties as a breeding ground can be affected.  
     [0019] When the supply water line  201  is closed and use of instruments disabled, disinfectant  205  is fed into the water lines  208  of the dental unit. To make sure that the lines  208  are filled completely, it is possible to use e.g. a visually observable colored solution, or to use a quantity of solution known to be sufficient, or the filling up of the lines can be detected by measuring some certain typical quantity of the solution. In the case of long-duration disinfection process, the dental unit is typically shut down at this point—or its control system may comprise an operation sequence “shutting down the unit after the water lines have been filled with disinfectant”.  
     [0020] After the disinfectant  205  has acted for a desired length of time and/or for a length of time defined in the control system, it is driven out from the water lines  208  via the instruments e.g. using compressed air obtainable from the compressed air line  212 . This can be done e.g. when the utilization of the dental unit is being started again or automatically after a predetermined time of action. However, as implied above, the use of instruments for dental treatment as well as the connection of water lines  208  to the supply water line  201  are still disabled as long as the disinfectant container  206  remains connected to the water line  208 . The detachment of the chemical container  206  can be realized so that the control system of the dental unit controls automatically, or via a compulsory operation sequence, flushing of the water lines  208  after the container  206  has been detached. Thus, the dental unit will only be usable for dental work after the disinfectant  205  has been removed from the water lines  208 , the disinfectant container  206  detached, the check valve  209  opened and the water lines  208  flushed. The arrangement preferably also comprises appropriate means for detecting the execution of the flushing operation, so that the user can not accidentally omit the flushing of the lines, either.  
     [0021] The flushing of the water line can also be arranged to be realized by supplying e.g. flushing water purified elsewhere into the line  208  via the same junction  207  through which the disinfectant was supplied. Different alternatives for implementing this solution in practice are obvious to a man skilled in the art—e.g. by using a separate replaceable purified water container attachable to the coupling elements  210  or by providing a possibility to connect two containers to this coupling arrangement, yet taking account of the requirements of operational safety according to the invention. This manner of implementation would naturally involve the loss of some of the convenience and ease of use provided by other embodiments of the invention.  
     [0022] In FIG. 3 there is presented an arrangement according to the invention for connecting the disinfectant container to a water line of a dental unit. Placed in the supply water line  301  at a location upstream of the main valve (not shown in the figure) and the disinfectant supply junction  307  is an on-off valve  309 , which is always open when the dental unit is being used for dental work, permitting flow of water toward the water lines  308  of the dental unit. The coupling element  310  of the disinfectant container  306  is so implemented that the container  306  can not be coupled to corresponding elements  310 ′ ( 309 ) in the dental unit unless the check valve  309  is closed. The container  306  connected to the dental unit can be pressurized e.g. in a manner corresponding to that presented in FIG. 2 by using compressed air obtained via a compressed air line  312  and its supply junction  313 , and the disinfection chemical can be fed into the water lines  308  of the dental unit via its supply junction  307 . As long as the disinfectant container  306  remains connected to the dental unit, the on-off valve  309  can not be opened.  
     [0023] Naturally, functional connection of the on-off valve  309  to the coupling elements  310 ,  310 ′ of the disinfectant container  306 /dental unit can be realized in many different ways, e.g. by using such a quick-coupling that, when engaging or disengaging, it at the same time closes/opens the on-off valve  309  or an equivalent element.  
     [0024] According to a preferred embodiment of the invention, the connecting pipe of the disinfectant supply junction  307  is made longer than the corresponding pipe of the compressed air supply junction  313  to ensure that, when the chemical container  306  is being detached, a possible pressure difference between, it and the environment will be equalized before the chemical supply junctions  307 ,  3071  are released from the coupling. In this way, the splashing of any chemical residues from the disinfectant container in connection with its release can be largely prevented.  
     [0025] In the foregoing, the invention has largely been described by only referring to embodiments as illustrated in the attached FIGS. 2 and 3, in which, however, many details may be varied within the framework of the invention within the scope defined in the following claims. Let it be stated, for example, that although in the above description reference has mainly been made to the instrument water lines of the dental unit, the invention can naturally be advantageously applied to the entire water system of the dental unit. On the other hand, although in the invention it is naturally possible to use any suitable disinfection chemical, it is preferable to use a substance that, besides disinfection, also contributes towards removing a possible biofilm layer from the walls of the water lines. Moreover, as already stated in places above, many steps in the disinfection process can, if so desired, be partially or completely automated and/or realized in compulsory phases.