in preparation for implementation of a central water processing system at a dental department , we analyzed the costs of conventional decentralized disinfection of dental units through daily continuous decontamination , purging and regular intensive decontamination against a central water treatment concept based on electrochemical disinfection . this was studied at six departments running dental clinics in germany with a total of 44 dental units and approximately 35,000 patient contacts per year . the necessity for preventive microbiological maintenance of dental units water line is given because of the ambient water temperature in the water lines , the synthetic material of water lines supporting biofilm formation together with curves and kicking leading to stagnation , , , because of dead spaces , and because of water stagnation during non - operational times , . the combination of the above conditions is an ideal prerequisite for biofilm formation in case of bacterial contamination of the indwelling water , which is always the case . biofilms , harboring non - pathogenic and pathogenic micro - organisms , are a source for continuous contamination of the cooling water in dental units , , , , . aside of the total bacterial count , which also includes non - pathogenic microorganisms , also facultative and obligate pathogenic bacteria such as pseudomonas aeruginosa , , , legionella pheumophilia , , , mycobacteria and amoeba ,   may be present in contaminated cooling water . if a microbial contamination with high colony counts of pathogenic bacteria is present , patients may be exposed to the risk of infection , particularly because of aerosol generation during treatment .   because of this , the cooling water in modern dental units is continuously processed with hydrogen peroxide during patient treatment . this , however , will not eliminate already existing biofilms , but may only be feasible to prevent initial biofilm formation , if continuously applied , , . therefore , continuous purging and intensive purging is required and recommended by the manufacturers of dental units . alternatively , instead of a decentralized , in the dental unit based purging system , a centralized decontamination concept may be applied , whereby the indwelling water is continuously treated before entering the dental unit s water line . which of the both methods , however , is more cost effective , was not systematically investigated so far . for calculation of the costs of the conventional decentralized water treatment concept , the intervals of the treatment and the volume of water usage during the decontaminating process were determined . water costs are based on the price of 1 m water , during the time of the investigation at  1.96/m of water . the unit price of decontamination chemicals was  23.34 respectively  13.34 per 1,000 ml of disinfectant . the added concentration of hydrogen peroxide during the routine operation and the costs of the individual water usage for a dental unit could not be calculated because of technical restrictions . the concentration of hydrogen peroxide was monitored continuously during patient treatment . for this , 1 ml of a sample was added to 100 ml using deionized water and mixed . the hydrogen peroxide concentration was measured by titration against potassium permanganate until the color changed to pink over 30 seconds . the hydrogen peroxide concentration was calculated using following formula : h2o2 + 2 kmno4 + 3 h2so4  2 mnso4 + 3 o2 + 4 h2o   1 ml kmno4 = 1.701 mg h2o2 for calculation of the costs of the blue safety technology concept , the costs of the required resources for generating hypochlorous acid , fundamentally nacl and water were calculated . the system delivers a maximum of 10 liter hypochlorous acid per hour at a ph of 7.0 . the 44 investigated dental units consisted of two different models from different manufacturers each . hence , the water line processing programs varied among the models , but also between the 6 encompassed dental departments ( table 1 ( tab two hydrogen peroxide based products of two different manufactures were used . for sirona units , a product with 1.41% hydrogen peroxide ( recommended dilution of hydrogen peroxide : 0.0141% ) , and for kavo - units with 6% hydrogen peroxide ( recommended dilution of hydrogen peroxide : 0.02% ) was used . for maintenance , the sirona - unit has a purge rinsing function . the concentration of the decontamination product corresponds to a dosage of 1:100 hydrogen peroxide during the normal operation of the unit . this program is also available as auto - purge which consists of two single rinse procedures . the typical flow rates range between 150 ml / min and for motor , turbine and ultrasound 60 ml / min , each . during intensive additionally , one rinse is run before and after intensive purge with a total water volume of 500 ml . the concentration of the decontaminating agent during the rinsing operations corresponding to the normal operation for the kavo - unit 12 litres of water and 60 ml of the 6% decontamination product ware used for intensive purge . the concentration of the decontamination product ranges at 0.25% during intensive purge ( 1.5 litres decontamination product / water mixture ) . the kavo - unit does not possess a comparable purge function like the sirona - unit . in total annual costs of  4,448.37 were determined for the 6 investigated departments for routine maintenance of the dental units water lines ( table 2 ( tab . the hydrogen peroxide concentration ranged above the 1:100 dilution recommended by the manufacturer for 8 sirona - units at 36.5% 23% above the target concentration . for 4 kavo - units , the target concentration for hydrogen peroxide at 0.02% as recommended by the manufacturer was not reached . in total , the mean hydrogen peroxide dosage for constant dosage ranged at 2.5% 16.5% above the target concentration . the blue safety technology device generates hypochlorous acid through membrane electrolysis of a 0.2%0.3% nacl solution . according to the manufacturer , the anolyte at a concentration of 200 mg / l contains ~158 mg / l hypochlorous acid , ~2 mg / l hypo chlorite ions , < 1 mg / l ozone , < 2.5 mg / l chlorine dioxide , < 1.5 mg / l chlorous acid , and <3 mg / l chlorine acid at a ph of 7.0 and a half life time of up to 48 hours . the redox potential of the anolyte solution is + 914 mv ( 1 mv ) . the anolyte solution is stored in a storage tank and a concentration of 0.6 mg / l hypochlorous acid is injected directly into the water - works network centrally . therefore , issues with manufacturer s warranty of dental units do not arise , since the active compound in injected into the water work of the indwelling water before it enters the dental unit itself . based on the calculated annual water consumption of approximately 1,012 m water ( table 2 ( tab . 2 ) ) , which is added additionally 0.6 mg / l of allowed free chlorine , the system must generate 3,036 liters of a 200 mg / l concentrated anolyte solution . a 25 kg bag of nacl costs approximately  6 . calculated on an annual consumption , since the water consumption of 4 m will incur anyway , the water costs are not to be included further into this calculation . the cost of the consumables for the blue safety technology accounts for 0.05% of the costs for the decentralized , in - built disinfection procedure . this , however , is only based on the required consumables and disinfection products during maintenace , since for both methods the additional costs of electricity could not be calculated because of missing information not provided by the manufacturers . also , the costs for investment could not be calculated , since the disinfection program in the dental - units are part of the device , making it difficult to assess the sole price of this feature without the price for the dental unit alone . because the blue safety technology was newly developed at the time of this study , the manufacturer was not able to provide commercial prices for purchasing the technology , installation , and validation . however , because the blue safety technology fundamentally uses salt as medium to generate antimicrobially active hypochlorous acid as chief active agent , it can be concluded that the one - time only investment costs of possibly  10,000 to 15,000 will quickly amortize during routine usage . if the avoided costs for sanitizing heavily contaminated water lines , loss of income due to closure of a unit during sanitation etc . are added , then the breakeven will occur even faster . finally , because of no requirement for purchasing , storage , manual preparation and maintenance of decontamination products , an additional saving of staff time , and hence money , may be assumed . after installation of the blue safety technology , a continuous dosage of hydrogen peroxide is dispensable and can be omitted as cost factor . a comparable procedure to the blue safety technology is the electrochemical generation of ecasol. the efficacy of this was demonstrated during a 2-years clinical study . the authors concluded that no higher concentrations than 12 mg / l free chlorine were required . the necessary constant water conditions were achieved by a cascade of lavishly processing steps , starting with particle filtration , water softening , an active charcoal module , and kdf ( kinetic degradation fluxion ) 80 medium , and finally a kdf-55 filter . by means of gas chromatographic mass spectrometry the processed water was regularly checked for unwanted side products such as chloroform , bromodichloromethane , dibromochloromethane , bromoform , trichloroethane , tetrachloroethane , and 1,2-dichloroethane . for all , the levels ranged below < 0.01 mg / l , the level of 1,2-dichloroethane was below 0.001 mg / l . at these concentrations , however , a comparison of the corrosivity related to the hydrogen peroxide - based decontamination has not been made so far . although the concentrations of hydrogen peroxide partly surpassed the manufacturer s recommendations , the mean concentration of 0.021% 0.007% was not exceeded . because of the high d - value particularly of candida spp . even at planktonic state , such a hydrogen peroxide concentration may not be able to inhibit biofilm formation , particularly in segments with stagnation or dead spaces , if used only during patient treatment . this is further supported , if the unit s routine preventive maintenance using purge and intensive purge is not regularly performed .
background : in preparation for implementation of a central water processing system at a dental department , we analyzed the costs of conventional decentralized disinfection of dental units against a central water treatment concept based on electrochemical disinfection.methods : the cost evaluation included only the costs of annually required antimicrobial consumables and additional water usage of a decentralize conventional maintenance system for dental water lines build in the respective dental units and the central electrochemical water disinfection system , blue safety technologies.results : in total , analysis of costs of 6 dental departments reviled additional annual costs for hygienic preventive measures of  4,448.37 . 
 for the blue safety technology , the additional annual total agent consumption costs were  2.18 , accounting for approximately 0.05% of the annual total agent consumption costs of the conventional maintenance system . 
 for both water processing concepts , the additional costs for energy could not be calculated , since the required data was not obtainable from the manufacturers.discussion : for both concepts , the investment and maintenance costs were not calculated due to lack of manufacturer 's data . 
 therefore , the results indicate the difference of costs for the required consumables only . 
 aside of the significantly lower annual costs for required consumables and disinfectants ; a second advantage for the blue safety technology is its constant and automatic operation , which does not require additional staff resources . 
 this not only safety human resources , but add additionally to cost saving.conclusion : since the antimicrobial disinfection capacity of the blue safety was demonstrated previously and is well known , this technology , which is comparable or even superior in its non - corrosive effect , may be regarded as method of choice for continuous disinfection and prevention of biofilm formation in dental units water lines .