JPWO2019230952A1 - Equipment and methods for sterilizing water in the water supply pipe of the dental unit - Google Patents

Abstract

The device includes a water supply pipe and a heating device attached to the water supply pipe for heating and sterilizing the water in the water supply pipe, and the heating device is water in the water supply pipe downstream from the heating device. It is characterized in that the number of dependent vegetative bacteria in the plant is 2000 CFU / mL or less.

Description

The present invention relates to an apparatus and method for sterilizing water in a water supply pipe of a dental unit.

Nowadays, in a dental unit equipped with dental instruments such as tooth-sharpening equipment (air turbine, micromotor, ultrasonic scaler) and a clinic table (chair) in which a patient sits or lays down to receive medical treatment. Microbial contamination of water that stays inside is drawing attention as a major problem. One of the causes of this microbial contamination is that water tends to stay inside the elongated tube that is often used inside the dental unit, and that the biofilm formed by the aggregation of bacteria easily adheres. It is considered.

As a conventional technique for solving this problem, a neutral electrolyzed water generator (see, for example, Patent Document 1) that automatically corrects the residual chlorine concentration of the dental unit water is used, but it is expensive and the existing amount of bacteria can be reduced. It is unclear whether it is effective in reducing the number of heterotrophic bacteria, which has been attracting attention in recent years as an index to grasp more accurately.

As a means for reducing the number of dependent vegetative bacteria in water used in the medical field, for example, the temperature control of the artificial dialysate production equipment line after hot water disinfection is set to 50 ° C. (Non-Patent Document 1). It has been proposed to treat the inside of the pipe of the hand-washing water place in the operating room and the circulation system with hot water at 65 ° C. (Non-Patent Document 2). Further, in Non-Patent Document 3, unit water collected from a dental unit and in which 3.9 × 10 ⁴ CFU / ml heterotrophic bacteria were detected was heated to 80 ° C. and heat sterilized. It is stated that all bacteria have been sterilized.

JP 2009-118892

Bulletin of Hokkaido University of Science, 41, 185-191 (2016) Medical Examination, 65 (4), 447-452 (2016) Scientific Research Grant Research Results Report Research on in-hospital measures in dental treatment for patients with viral hepatitis and susceptible infections May 8, 2009

By the way, the inventors regarding the number of dependent vegetative bacteria of water staying in the water supply pipe in the general dental unit (that is, the water discharged from the water supply pipe), the water staying place (that is, the discharge point from the water supply pipe). It is reported that the number of (also) tends to increase as the distance from the tap is increased (Health and Labor Science Research Grant Subsidy Regional Medical Infrastructure Development Promotion Research Project 2016 Summary Research Report Dental Unit Water Supply System Pure Water Purification Equipment Research on development). However, Patent Document 1 does not deal with this problem.

In Japan, there is no strict water quality control target setting value for water in the water supply pipes of devices such as dental units, but it is an urgent issue to deal with pollution of water supplied through the inside of dental units. .. If water that meets the strict water quality control target setting values can be supplied even at a location away from the tap in the dental unit, it is possible to provide microbiologically safe water quality to dental care based on scientific grounds. It is beneficial for health and safety management.

An object of the present invention is to provide an apparatus and method for sterilizing water in a water supply pipe capable of easily and inexpensively supplying water having a reduced number of heterotrophic bacteria even at a location away from the tap of the apparatus. be.

The present inventors attach a heater to the water supply pipe of the dental unit, and by using the water supply heated to a moderate temperature of about 55 to 75 ° C. by the heater, the distance from the tap in the dental unit is increased. We have succeeded in suppressing the growth of heterotrophic bacteria that cause microbial contamination of water even at such locations, and have completed the present invention.

That is, the present invention includes the subjects described in the following sections.
Item 1. The water supply pipe is provided with a heating device attached to the water supply pipe for sterilizing the water in the water supply pipe, and the heating device is a dependent nutrient of water in the water supply pipe downstream from the heating device. A device characterized by reducing the number of bacteria to 2000 CFU / mL or less.
Item 2. Item 1 is characterized in that the heating device includes a casing capable of accommodating water in the water supply pipe and a heater provided in the casing, and heats the water in the casing to 50 ° C. or higher. The device described.
Item 3. Item 2. The device according to Item 1, wherein the free residual chlorine concentration of water in the water supply pipe downstream from the heating device is set to 0.1 mg / L or more.
Item 4. The device is a dental unit including an assistant unit and a doctor unit, and the water supply pipe is branched into a water supply pipe leading to the assistant unit and a water supply pipe leading to the doctor unit, and the heating device is the heating device. Item 6. The apparatus according to any one of Items 1 to 3 provided at the branch portion or upstream thereof.
Item 5. Item 4. The apparatus according to Item 4, wherein the doctor unit includes an instrument that fluidly communicates with the water supply pipe, and the number of heterotrophic bacteria in the water discharged from the instrument is 2000 CFU / mL or less. ..
Item 6. Item 5. The device according to any one of Item 5, wherein the temperature of the water discharged from the instrument after 2 minutes of heating at 60 to 70 ° C. for 10 minutes by the heating device is 15 to 35 ° C.
Item 7. It is a method of sterilizing water in the water supply pipe of the device, and uses a heating device attached to the water supply pipe for heating and sterilizing the water in the water supply pipe, and the water supply pipe downstream from the heating device is used. A sterilization method characterized by reducing the number of dependent vegetative bacteria in the water to 2000 CFU / mL or less.

According to the sterilization apparatus and method of the present invention, the number of heterotrophic bacteria at a location away from the tap of the apparatus can be easily and inexpensively reduced. According to the sterilization apparatus and method of the present invention, the frequency or amount of the chemical used for sterilizing water in the water supply pipe can be reduced, and the safety is excellent. The present invention can be incorporated into an existing dental unit inexpensively and safely, and is excellent in practicality.

Schematic plan of an example of a dental unit. Schematic cross-sectional view of an example of a heating device. Explanatory drawing showing a water supply pipe in a dental unit and a water sampling point. Photographs showing the results of culturing heterotrophic bacteria and general bacteria in aerobic and anaerobic environments. Graph showing changes in heterotrophic bacteria in a general dental unit due to residual water discharge. Hand: Handpiece water. Gargling: Water for gargle. The graph which shows the change of the free residual chlorine concentration in a general dental unit by the residual water discharge. Hand: Handpiece water. Gargling: Water for gargle. Graph showing the number of heterotrophic bacteria (CFU / mL) at each location of general dental unit piping. (A) Graph from the tap (P1) to the inside of the operator's table (P6). (B) Graph of handpiece (P7). Graph showing free residual chlorine concentration (mg / L) at each part of general dental unit piping. Graph showing the number of heterotrophic bacteria (CFU / mL) in the handpiece drainage of a dental unit with a drug cleaning function. The graph which shows the free residual chlorine concentration (mg / L) in the handpiece discharge water of the dental unit with a drug cleaning function. The graph which shows the influence on the heterotrophic bacteria existing in the handpiece drainage water by heating of the water in the water supply pipe of a general dental unit. At each heating temperature, the bar graph on the left is the data of unit 1, the bar graph in the center is the data of unit 2, and the bar graph on the right is the data of unit 3. The arrows in the graph indicate samples containing bacterial counts below the target value for heterotrophic bacterial counts (2000 CFU / mL). The graph which shows the influence on the temperature of the handpiece drainage water and the heterotrophic bacteria in the drainage water by heating water in a water supply pipe of a general dental unit. # In the graph indicates a sample containing the number of bacteria below the target value of the number of heterotrophic bacteria (2000 CFU / mL). The graph which shows the influence on the temperature of the handpiece discharge water and the free residual chlorine concentration in the discharge water by heating water in a water supply pipe of a general dental unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the present specification, general bacteria are aerobic bacteria, facultative anaerobic bacteria, and aerobic bacteria that form colonies in the medium when cultured in a blood agar medium at 36 ° C. ± 1 ° C. for 7 days. It is a general term for obligate anaerobic bacteria.

Dependent vegetative bacteria refer to all bacteria that form colonies on the medium when cultured at low temperature for a long time using a medium containing low-concentration organic nutrients, specifically, 20 ° C using R2A agar medium. It is a general term for bacteria that form a colony when cultured for 7 days.

FIG. 1 is a schematic plan view of the dental unit 1 according to the embodiment.

The dental unit 1 includes a patient chair 10, dental lighting (not shown), a spitton device 15 connected to one side of the patient chair 10, and an assistant unit 20 connected to the spitton device 15 via an arm 22. , And a doctor unit 30 connected on the other side of the patient chair 10.

A base 2 is arranged below the patient chair 10, and supports the patient chair 10. Various control devices are included in the base 2. Examples of the control device include a hydraulic circuit for raising and lowering the patient chair 10 and tilting and standing up, a hydraulic control means for controlling the hydraulic circuit, and the like. A foot switch (not shown) is provided on the back side of the patient chair 10 on the base 2, and a practitioner such as a dentist or a dental assistant can use the foot switch or the operation panel (not shown) of the doctor unit 30. It is possible to operate and send a command to the hydraulic control means to control the hydraulic circuit to raise and lower the patient chair 10 and to tilt and stand up.

The patient chair 10 includes a headrest 11, a backrest 12, a seat 13, and a leg rest 14.

The spitton device 15 includes a water supply nozzle 16, a bowl-shaped or bowl-shaped spitton 17 for receiving water after the patient has washed and spit out the oral cavity, a pipe (not shown) for supplying water to the water supply nozzle 16, and a spitton. A water supply / drainage box 18 for accommodating a pipe (not shown) for discharging water flowing through the discharge hole 17a on the bottom surface of the 17 is provided.

The assistant unit 20 is connected to an assistant table 21 and an assistant table 21 as a work table, includes an arm 22 capable of rotating the assistant table 21, and a base end portion of the arm 22 is pivotally supported by a spitton device 15.

Various instruments 23 can be placed or suspended on the assistant unit 20, and examples of such instruments 23 include handpieces such as a vacuum, a saliva drainage tube, and a syringe.

The doctor unit 30 includes an operator table 31 and an operation panel 32 as a work table. Various instruments 33 can be suspended on the doctor unit 30, and such instruments 33 are handpieces used by the practitioner during the treatment, such as an air turbine, a micromotor, and an ultrasonic scaler. Syringe Three-way syringe and the like can be mentioned. A part of the instrument 33 is connected to an electric circuit, a water circuit, an air circuit, and the like. The operation panel 32 is provided with a switch (not shown) for operating various instruments 33. For example, a switch for moving the patient chair 10 up and down and tilting it upright, and water for treatment from the instrument 33. Examples include a switch that supplies water and stops water supply. By operating the various switches, the practitioner can appropriately operate the corresponding instruments 33 via a drive circuit and a control circuit (not shown).

As shown in FIG. 1, the dental unit 1 of the present embodiment includes a heating device 40 for sterilizing water in the water supply pipe of the dental unit 1. The heating device 40 is attached to the water supply pipe of the dental unit 1 and functions to heat sterilize the water in the water supply pipe. The heating device 40 can be accommodated in the water supply / drainage box 18 of the spitton device 15 so that it cannot be visually recognized during the patient's treatment.

FIG. 2 is a diagram showing the structure of the heating device 40 in more detail. The heating device 40 includes a substantially cylindrical (particularly substantially cylindrical) casing 41 capable of accommodating water in the water supply pipe 61, a heater 46 provided in the internal space 42 of the casing 41, and a power source for the heater 46. It is equipped with a thermo switch 47 that switches on / off. The water supply pipe 61 refers to a portion of the water supply pipe 60 (see FIG. 3) from the water tap 4 to the internal branch P3. The casing 41 includes a side member 43, an end member 44 connected to both ends of the side member 43, and a base end member 45. The heater 46 is attached to the end member 44, and the thermoswitch 47 is attached to the base end member 45. The base end member 45 includes holes 45a and 45b for fluid communication with the water supply pipe 61 of the dental unit 1, and one of the holes 45a is water flowing from the water supply pipe 61 into the internal space 42 of the casing 41 (that is, a heating device). It acts as an inflow port for water in the water supply pipe upstream of the water supply pipe, and the other hole 45b is water flowing out from the internal space 42 of the casing 41 to the water supply pipe 61 (that is, water in the water supply pipe downstream from the heating device). ) Acts as an outlet. Since the internal space 42 partitioned by the casing 41 is in fluid communication with the water supply pipe 61, the casing 41 and the internal space 42 also form the water supply pipe of the dental unit 1.

The thermo switch 47 senses the temperature of the surface of the heating device 40, and when the temperature of the surface of the heating device 40 drops due to the decrease of the water temperature in the heating device 40 and reaches a certain constant temperature (first temperature), the thermo switch 47 The switch 47 starts supplying power to the heater 46, and when the temperature of the surface of the heating device 40 rises due to the rise in the water temperature in the heating device 40 and reaches a certain temperature (second temperature), the thermoswitch 47 raises the heater 46. Stop the power supply to. Control by such a thermo switch is a well-known technique.

The target value of Kensui No. 11150002, which was added as a water quality management target setting item in the partial revision of the ministerial ordinance on water quality standards indicated by the Ministry of Health, Labor and Welfare, was "1 ml of water, at 20 ± 1 ° C by R2A agar medium method. The number of colonies formed after culturing for 7 days is 2000 CFU / mL or less.

In order to satisfy the standard that the number of heterotrophic bacteria in water at each location in the water supply pipe 60 downstream of the heating device 40 is 2000 CFU / mL or less, the water in the heating device 40 must be heated to 55 ° C. or higher. It is preferable to heat it to 60 ° C. or higher, and it is more preferable to heat it to 65 ° C. or higher. In particular, even water discharged from an instrument 33 such as a handpiece, which is a long distance from a tap, is preferably heated to 55 ° C. or higher in order to satisfy the above value of the number of heterotrophic bacteria, preferably 60 ° C. It is more preferable to heat it above, and it is further preferable to heat it above 65 ° C. Further, if the temperature of the heated water is too high, it is not suitable for the burden on the parts of the dental unit 1 and the use for the practitioner. Therefore, the temperature is preferably 100 ° C. or lower, preferably 90 ° C. or lower. More preferably, it is more preferably 80 ° C. or lower, and particularly preferably 75 ° C. or lower. It is preferable to heat the water in the heating device 40 to a moderate temperature of 55 ° C. to 75 ° C., and more preferably to 60 ° C. to 70 ° C. Therefore, for example, it is preferable to set the first temperature to about 60 ° C., the second temperature to about 80 ° C., and preferably the second temperature to about 70 ° C.

The heating time of water by the heating device 40 is not particularly limited, but a short time is preferable in terms of speed and cost of the subsequent treatment. The heating time of water by the heating device 40 is preferably 5 seconds or longer, more preferably 30 seconds or longer, still more preferably 1 minute or longer, still more preferably 2 minutes or longer. The upper limit of the heating time is, for example, 60 minutes or less.

Further, the temperature of the water discharged from the instrument 33 including the handpiece after heating by the heating device 40 is preferably 15 to 42 ° C. so that it can be used as it is for the patient's treatment, and is preferably 15 to 42 ° C. It is more preferably 35 ° C., and even more preferably 18 to 35 ° C.

Further, the temperature of the water discharged from the instrument after 2 minutes of heating at 60 to 70 ° C. for 10 minutes by the heating device is preferably 15 to 42 ° C., preferably 15 to 35 ° C. Is more preferable, and 18 to 35 ° C. is even more preferable. In particular, the temperature of the water discharged from the instrument after 2 minutes of heating at 60 to 65 ° C. for 10 minutes by the heating device is preferably 15 to 42 ° C., preferably 15 to 35 ° C. Is preferable, and the temperature is more preferably 18 to 35 ° C.

Further, the temperature of the water discharged from the instrument during 0 to 2 minutes after heating at 60 to 70 ° C. for 10 minutes by the heating device is preferably 15 to 42 ° C., preferably 15 to 42 ° C. It is more preferably 35 ° C., and even more preferably 18 to 35 ° C. In particular, the temperature of the water discharged from the instrument during 0 to 2 minutes after heating at 60 to 65 ° C. for 10 minutes by the heating device is preferably 15 to 42 ° C., preferably 15 to 42 ° C. The temperature is preferably 35 ° C, more preferably 18 to 35 ° C.

Further, the water in the heating device 40 is heated to a temperature of 55 ° C. to 75 ° C., more preferably 60 ° C. to 70 ° C., further preferably 60 to 65 ° C. for 30 seconds or longer, more preferably 1 minute or longer by the heating device. , Even more preferably, the temperature of the water discharged from the instrument after heating for 2 minutes or more is preferably 15 to 42 ° C, more preferably 15 to 35 ° C, 18 It is more preferably ~ 35 ° C.

Further, by the heating device, the water in the heating device 40 is heated to a temperature of 55 ° C. to 75 ° C., more preferably 60 ° C. to 70 ° C., further preferably 60 to 65 ° C. for 30 seconds or longer, more preferably 1 minute or longer. , Even more preferably, it is heated for 2 minutes or more, and the temperature of the water discharged from the instrument within 0 to 2 minutes after heating is preferably 15 to 42 ° C, preferably 15 to 35 ° C. More preferably, the temperature is 18 to 35 ° C.

According to the tap water quality standards (Article 17, Item 3 of the Waterworks Law Enforcement Regulations) set by the Ministry of Health, Labor and Welfare, the standard value of the free residual chlorine concentration in tap water is set to 0.1 mg / L or more.

The free residual chlorine concentration of water at each location in the water supply pipe 60 is preferably 0.1 mg / L or more, and is particularly discharged from the instrument 33 such as the handpiece, which is a long distance from the tap. In order to satisfy the above values of the free residual chlorine concentration even in water, it is preferable to heat the water in the heating device 40 to 45 ° C. or higher, and the preferable heating temperature and heating time are set to meet the criteria for the number of dependent vegetative bacteria. As described above.

Next, the water supply pipe 60 of the dental unit 1 will be described.

As shown in FIG. 3, the water supply pipe 60 of the dental unit 1 of the present embodiment is connected to the water tap 4, passes through the inside of the water supply / drainage box 18 (see FIG. 1) of the spitton device 15, and branches. In the present embodiment, the water supply pipe 60 includes a water supply pipe 61 which is a part from the water tap 4 to the internal branch P3, a water supply pipe 62 which is a part from the internal branch P3 to the water supply nozzle 16, and an internal branch P3 to the arm 22. It is provided with a water supply pipe 63 leading to the assistant table 21 via the water supply pipe 64 and a water supply pipe 64 leading from the internal branch P3 to the operator table 31 of the doctor unit 30. A practitioner such as a dentist or a dental assistant uses an instrument 23 attached to the water supply pipe 63 of the assistant table 21 and / or an instrument 33 attached to the water supply pipe 64 of the operator table 31 to use the water supply pipe. The treatment is performed using the water discharged from 60 (61, 63, 64) to the instruments 23 and 33.

As will be described later, as the distance from the tap in the water supply pipe 60 increases (the water sampling points P1, P2, P3, P4, P5, P6, P7 are farther in this order), the heterotrophic nutrients of the water staying in the water supply pipe 60 Bacterial counts tend to increase and free residual chlorine concentrations tend to decrease. Therefore, in particular, as the distance from the tap is increased, the water staying in the water supply pipe 60 may not meet the control target value of the number of heterotrophic bacteria of 2000 CFU / mL or less. In addition, it may not meet the tap water standard for free residual chlorine concentration of 0.1 mg / L or more. In particular, the number of heterotrophic bacteria and the concentration of free residual chlorine in the gargling water discharged from the spitton device 15 and the water discharged from the instrument 33 (exemplified as a handpiece in the figure) of the doctor unit 30 farthest from the tap. In some cases, neither the above target value nor the reference value of is satisfied.

According to the dental unit 1 of the present embodiment, the water in the water supply pipe 60 can be heated to a moderate temperature of 55 ° C. to 75 ° C. by the heating device 40 housed in the spitton device 15. Water quality control target value and release of dependent vegetative bacteria in water discharged from dental units such as gargling water discharged through water supply pipe 62 and handpiece discharged water discharged through water supply pipes 63 and 64 It is possible to easily and quickly supply water that meets all the water quality standards for the residual chlorine concentration. In addition, since it is not always necessary to use a chemical for heating water, it is excellent in terms of safety and cost.

The present invention is in the water supply pipe of the heating device 40 for heat sterilizing the water in the water supply pipe, the dental unit 1 provided with the heating device 40, and the dental unit 1 using the heating device 40. It also includes methods for sterilizing water.

The above embodiment has the following effects.
-According to the dental unit 1 of the present embodiment, only by heating the water in the water supply pipe 60 by the heating device 40, the number of dependent vegetative bacteria is located downstream of the heating device 40 and away from the tap. Since it is possible to supply water that meets both the water quality management target value and the water quality standard for the free residual chlorine concentration, it is excellent in convenience and speed.
-In the prior art, there are problems such as the effect on the living body of the residual liquid of the disinfectant solution added to the waterway system of the dental unit and cost effectiveness. However, according to the dental unit of the present embodiment, the water temperature is adjusted. It is a safe, inexpensive and effective approach because it can kill heterotrophic bacteria with a moderate increase. In addition, the possibility of corrosion of the equipment of the dental unit due to the use of the disinfectant solution can be eliminated or reduced.
-No need to frequently purchase and use disinfectant. At least the frequency or amount of disinfectant used can be reduced.
-In the dental unit 1 of the present embodiment, since the heating device 40 is provided at a position upstream of the internal branch P3, the heating device 40 only needs to be provided at one place and branches from the internal branch P3. It is possible to efficiently supply water that satisfies both the water quality control target value of the number of heterotrophic bacteria and the water quality standard of the free residual chlorine concentration to all the locations of the water supply pipe 60.
-In the dental unit 1 of the present embodiment, since the heating device 40 is provided at a position upstream of the internal branch P3, the temperature of the heated water when the practitioner uses the instruments 23 and 33. Is cooled to a temperature that does not irritate the patient and can be used as it is for the treatment.
-In this embodiment, since the heating device 40 can be installed in the water supply pipe of the existing dental unit, it can be inexpensively and safely incorporated into all the dental units currently in use, and is versatile. Excellent in practicality.

The present invention is not limited to the above embodiment, and the following modifications can be made.
The configuration of the heating device 40 is not limited to that shown in FIG. 2, and another heater having a configuration capable of heating the water in the water supply pipe 60, including a known heater, may be used.
-According to the present invention, the number of heterotrophic bacteria may be suppressed to 2000 CFU / mL or less, and the water quality standard of free residual chlorine concentration of 0.1 mg / L or more does not necessarily have to be satisfied.
The mounting position of the heating device 40 is not limited to the position of the pipe 61 between the water tap 4 and the internal branch P3, and as long as the water quality control target value of the number of heterotrophic bacteria is satisfied, the water supply pipe 60 in the dental unit 1 It can be attached to any location. For example, the heating device 40 may be provided between the water tap 4 and the spitton device 15, may be provided in the internal branch P3, or may be provided in the assistant unit 20 or the doctor unit 30 downstream of the internal branch P3. It may be provided. The heating device requires only one installation location, and when the practitioner uses the instruments 23 and 33, the temperature of the heated water is cooled to a temperature that does not irritate the patient. 40 is preferably provided at the internal branch P3 or upstream thereof.
-The present invention is not limited to the dental unit 1, and can be applied to any other device provided with a water supply pipe, such as a water supply pipe of a household water purifier and a water supply pipe of a water storage tank. As a result, the apparatus of the present invention can be used in sites, areas, and overseas where water pollution is a concern.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

1. 1. Collection of water samples from dental units As general dental units, three GC Refinos (serial numbers 00036, 00041 and 00004), which have been in operation since December 2009 in Tohoku University Hospital, have been in operation since September 2012. The target was two GC Iom Regalo (serial numbers 00672 and 00672). In addition, as a dental unit with a drug cleaning function, three Morita Spaceline Spirit V PdW tray systems (serial numbers CH1006, EB1503 and ZC1001) that have been in operation since May 2015 or March 2016 were targeted.

Before using the general dental unit, follow the guidelines in the Nosocomial Infection Control Practice Manual supervised by the Japanese Association for Dental Science, and explain using the symbols in FIGS. 1 and 2, the water supply of the spitton device 15 for use in the spitton device. The rinsing water discharged from the nozzle 16 (P4) (hereinafter referred to as "soothing water") is equivalent to eight paper cups, and the water discharged from the handpiece (P7) for use with the handpiece (P7). (Hereinafter referred to as "handpiece water"), flushing (residual water discharge) was performed by maximum operation for 30 seconds to control the water quality. In addition, in the dental unit with a drug cleaning function, 0.1% hydrogen peroxide solution is retained inside the chair water supply line for about 2 days every weekend, and all routes such as handpieces are placed in a dedicated flushing tank before use every morning. It was connected and tap water was circulated at abundant flow rates for 7 minutes to drain residual water.

For the general dental unit and the dental unit with drug cleaning function, 25 mL each of the patient's rinsing water and handpiece water before and after the residual water was discharged was divided into 10 mL and 15 mL in a sterile polyethylene tube. did. The first 10 mL was used for bacterial testing and the latter 15 mL was used for free residual chlorine concentration measurement.

In addition, the water supply piping parts of the two general dental units GC Refino (serial numbers 00036 and 00041) were removed, and (1) the water tap (water sampling point P1), and (2) immediately after entering the unit piping from the tap ( Water sampling point P2), (3) Internal branch point (water sampling point P3), (4) Water supply nozzle of Spitton device (P4), (5) Inside auxiliary table (water sampling point P5) and (6) Operator Similarly, 25 mL of water was sampled from each point inside the water table (water sampling point P6) into 10 mL and 15 mL in a sterile polyethylene tube (Fig. 3).

2. Method of culturing and observing heterotrophic bacteria and general bacteria 1. Each water sample was diluted 10-fold and 100-fold with milliQ water sterilized with a 0.22 μm filter (Millex-GP SLGP033RS, manufactured by Merck Millipore).

Before starting the series of experiments, heterotrophic bacteria and general bacteria in the residual water sample collected from the handpiece part were cultured in an aerobic and anaerobic environment as a preliminary experiment for examining the culture conditions. The aerobic culture was carried out in the same manner as the heterotrophic and general bacterium detection methods described below. _{The anaerobic culture was performed in a highly anaerobic environment (80% N 2} , 10% CO ₂ , 10% H ₂ ) using a Teher-type Anaero box (ANB-18-2E, manufactured by Hirasawa).

For culturing dependent bacterium, 100 μL of undiluted solution and diluted sample were inoculated on R2A agar medium (251258, Japan BD), and 20 ° C, 7 using a cool incubator (CN-25C-1, manufactured by Mitsubishi Electric Engineering Co., Ltd.). After culturing for one day, the number of colonies on each agar medium was visually counted, and the number of bacteria (CFU / mL) in each sample was calculated.

In the culture for detecting general bacteria, 100 μL of the undiluted sample was seeded on CDC sheep blood agar medium (251733, BD Japan), and after culturing at 37 ° C for 7 days using an incubator (CI-410, manufactured by Advantech). , Similarly, the number of bacteria (CFU / mL) was calculated.

For dependent vegetative bacteria, it was added as a water quality management target setting item in the partial revision of the ministry ordinance on water quality standards, and was set as the immediate target value in Kensui No. 1115002. The pass / fail judgment was made based on "2000 CFU / mL or less as the number of colonies formed after culturing at 20 ° C for 7 days."

3. 3. Measurement of free residual chlorine concentration Measurement of free residual chlorine concentration is performed by diethyl paraphenylenediamine reagent (reagent for measuring free residual chlorine DPD Plus, Oyalux Co., Ltd., Cat. # OYWT-11-03) and a residual chlorine measuring device by the absorptiometry. (Photometer CL, Oyalux Co., Ltd., Cat. # OYWT-31) was used and the procedure was performed according to the attached instruction manual. 10 mL of the 15 mL water sample was dispensed into the sample cell, zero calibration was performed, and then one packet of the powder reagent was dissolved. It was set in the cell insertion part of the measuring instrument and allowed to stand for about 30 seconds before measurement. Zero calibration and cleaning of the sample cell with ultrapure water were performed for each sample. Pass / fail was judged based on the standard value (0.1 mg / L or more) of the tap water quality standard (Article 17-3 of the Waterworks Law Enforcement Regulations) indicated by the Ministry of Health, Labor and Welfare.

4. Handpiece Verification method of heating effect on heterotrophic bacteria in residual water (in vitro)
In vitro, a handpiece water sample that had remained in the handpiece from the previous day, collected from three general dental units GC Refino (serial numbers 00036, 00041 and 0402) without flushing (residual water discharge). In order to verify the bactericidal effect on heterotrophic bacteria in the sample when heated, the sample was treated as follows.

5 ml of the residual water sample was dispensed into each 15 ml sterile conical tube. In a small dry incubator (BSR-M002, manufactured by Bio Medical Science) equipped with an aluminum block, the above 1. After setting the conical tube containing the water sample of No. 1 and the same conical tube containing the same amount of tap water, heating was started. A mercury thermometer is set in the conical tube containing tap water, and when the temperature of this thermometer reaches 30, 35, 40, 45, 50, 55, 60 ° C, from the conical tube containing each sample. A 300 μL water sample was immediately collected with a sterilized fin pipette, transferred to a sterilized tube (assist tube 72.693.100S, Zalstat Co., Ltd.), and stored in ice-cooled until seeding.

5. How to verify the moderate heating effect on the water supply pipe of the general dental unit General dental unit GC company Iom Regalo 2 units (serial numbers 00672 and 00672) in the water supply / drainage box (18) of the spitton device (15) of the water supply pipe. Immediately before the internal branch P3 (the position indicated by the arrow in FIG. 3) (see FIG. 3), a moderate heating device having the structure shown in FIG. 2 was installed. This heating device can heat the temperature inside the heating device 40 of the dental unit from 23 ° C. to 65 ° C. in 9 minutes. The capacity of the casing of the heating device was 180 ml, the voltage of the heating device was AC24V, the power was 52.8W, the power density was 2.5W / cm ² , and the maximum temperature (maximum water temperature at the heater outlet) was about 65 ° C.

Before the operation of the heating device, 25 mL of handpiece water remaining in the handpiece from the previous day without flushing (residual water discharge) was collected in 10 mL and 15 mL in a sterile polyethylene tube. Then, the heating device was operated and heated for 10 minutes. After that, the operation at the maximum output of the handpiece was started, and 25 mL of water was sampled in the same manner 30 seconds after the operation of the handpiece, 1 minute after the operation, and 2 minutes after the operation. At each water sampling, the temperature was measured using a digital thermometer (CT-05SD, manufactured by CUSTOM). The warmer continued to operate until the end of the experiment.

6. result
(1) Examination of culture conditions: Culture results of heterotrophic bacteria and general bacteria in aerobic and anaerobic environments As shown in Fig. 4, residual water collected from a handpiece as a preliminary experiment before the start of a series of experiments. When the heterotrophic bacteria and general bacteria in the sample were cultured in an aerobic and anaerobic environment, colonies of the heterotrophic bacteria were observed only in the aerobic environment, and were not detected in the anaerobic environment. In addition, general bacteria were not detected under either condition. Therefore, in subsequent experiments, the number of heterotrophic bacteria detected in aerobic culture was the subject of research.

(2) Changes in the number of heterotrophic bacteria in general dental unit water due to residual water discharge As shown in Fig. 5, the number of heterotrophic bacteria in handpiece water and rinsing water after residual water discharge is compared with that before discharge. However, it decreased significantly by about 94% in handpiece water and 98% in gargle-containing water. (P <0.01, paired t-test). In the rinsing water, the number of bacteria after the residual water was discharged was below the target value of 2000 CFU / mL, but in the handpiece water, the number of bacteria was detected to be close to 5 times the target value even after the residual water was discharged.

(3) Changes in free residual chlorine concentration in general dental unit water due to residual water discharge As shown in Fig. 6, the free residual chlorine concentration in rinsing water is the standard value of the Waterworks Law (0.1 mg /) before residual water discharge. Although it was lower than L), it was 0.2 mg / L or more after the residual water was discharged, which greatly exceeded the standard value (P <0.01, paired t-test). On the other hand, the free residual chlorine concentration of the handpiece water was about 0.5 mg / L regardless of the presence or absence of residual water discharge, and did not exceed the standard value.

(4) Number of heterotrophic bacteria in each part of the water supply pipe of the dental unit As shown in Fig. 7, water samples were taken from each point in the unit and the numbers of each heterotrophic bacteria were compared. And, while heterotrophic bacteria were hardly detected in the sample immediately after entering the unit pipe from the tap (P2), the internal branch (P3), the water supply nozzle of the spitton device (P4), and the assistant In the sample collected from the pipe in the table (P5), although it was within the target value of 2000 CFU / mL, the number of detections gradually increased. Furthermore, in the operator's table (P6), the number of detections was around 2000 CFU / mL, and in the sample (P7) from the tip of the handpiece connected by a thinner pipe, the number of detections reached 150,000 CFU / mL at once. Increased. These results show that the number of heterotrophic bacteria tends to increase according to the distance from the main plug, and the heterotrophic bacteria contained in the water stay in the piping in the unit far from the main plug, and the bacteria such as biofilm are supplied. It was suggested that it may form a source.

(5) Free residual chlorine concentration of each part of the water supply pipe of the dental unit As shown in FIG. 8, the free residual chlorine concentration of the tap (P1) and immediately after entering the unit pipe from the tap (P2) is 0.3 mg / It was L or more, which greatly exceeded the standard value (0.1 mg / L) of the Waterworks Law. The concentration of free residual chlorine decreased as it proceeded to the inside of the general dental unit, but it was still above the standard value at the internal branch (P3) and the inside of the assisting table (P5). However, the water supply nozzle (P4) of the spitton device, the inside of the operator's table (P6), and the sample from the tip of the handpiece (P7) were below the reference value. The farther away from the tap, the lower the concentration of free residual chlorine tended to be.

(6) Handpiece of dental unit with drug cleaning function Number of heterotrophic bacteria in water As shown in Fig. 9, as a reference example, in the water sample collected from the handpiece of the dental unit with drug cleaning function, before residual water is discharged. However, the number of heterotrophic bacteria was very small, and the target value was cleared. The number decreased further after the residual water was discharged. It was suggested that the heterotrophic bacteria in the channel were sterilized by the daily circulation of the hydrogen peroxide solution in the channel.

(7) Free Residual Chlorine Concentration in Water of Handpiece of Dental Unit with Drug Cleaning Function As shown in Fig. 10, as a reference example, in the water sample collected from the handpiece of the dental unit with drug cleaning function before the residual water is discharged. The free residual chlorine concentration in was less than the standard value of the Waterworks Law. The concentration of free residual chlorine tended to increase due to the discharge of residual water, but it did not necessarily exceed the standard value. In this way, there was concern that the concentration of free residual chlorine would not necessarily comply with the Waterworks Law, and that hydrogen peroxide would cause successive corrosion of pipes.

(8) Effect of heating on heterotrophic bacteria (in vitro)
The effect of each water sample collected from the handpiece on heterotrophic bacteria in the sample when heated to each temperature in vitro was examined.

As shown in Fig. 11, in the samples collected from the three general dental units targeted this time, the number of heterotrophic bacteria detected was almost flat from room temperature to 45 degrees, but it was 50 degrees or more. The detection amount decreased sharply at 55 ° C or higher, and the detection amount was below the target value of 2000 CFU / mL. It has been shown that moderate heating at about 50-60 ° C can significantly reduce the number of heterotrophic bacteria in the handpiece water.

(9) Handpiece by moderate heating of the water supply pipe of the general dental unit Handpiece when heated to a maximum of 65 ° C by the heating device in the water supply pipe of the unit, the bactericidal effect on the heterotrophic bacteria in the water The change over time in the temperature immediately after collection and the number of heterotrophic bacteria in the piece water sample was examined.

As shown in FIG. 12, the temperature of the water sample collected from the tip of the handpiece after moderate heating was about 33 ° C at the maximum. It was considered that this was because there was a distance in the piping inside the unit from the heating device to the tip of the handpiece, so it was cooled in the flow path.

The number of heterotrophic bacteria in the sample collected 30 seconds after continuing to drain water from the tip of the handpiece is significantly reduced compared to the sample before heating, and both units clear the target value of 2000 CFU / mL. I got the result. After that, the decreased state was maintained until 1 minute and 2 minutes later.

It has been shown that this heating device kills heterotrophic bacteria in the unit and maintains its effect during drainage.

(10) Effect of moderate heating of the water supply pipe of the general dental unit on the temperature of the handpiece discharged water and the free residual chlorine concentration As shown in Fig. 13, the temperature of the handpiece water of the general dental unit is before and after heating. The residual water in the water was at room temperature of about 20 ° C, and increased as the residual water was discharged after heating, but reached a plateau at around 30 ° C.

The free residual chlorine concentration in the handpiece residual water sometimes fell below the standard value (0.1 mg / L) of the Waterworks Law before heating, but the free residual chlorine concentration in the handpiece residual water increased significantly after moderate heating. In unit 1, it was 0.3 mg / L or more, which greatly exceeded the standard value of the Waterworks Law. During the 2-minute residual water discharge, the free residual chlorine concentration did not fall below the standard value of the Waterworks Law, and all units were always 0.2 mg / L or more.

Based on the above results, the method of following the guidelines in the existing Nosocomial Infection Control Practice Manual and the sterilization using hydrogen peroxide solution in a dental unit with a drug cleaning function in terms of both the number of heterotrophic bacteria and the concentration of free residual chlorine. , It was shown that water quality management is difficult according to the standards based on the Waterworks Law. On the other hand, in this embodiment, by attaching a moderate heating device to the branch of the water supply pipe inside the dental unit, the water quality of the handpiece water of the dental unit is highly safe and reliable, and heterotrophic nutrition. It was shown that both the number of bacteria and the concentration of free residual chlorine can be controlled at a level compliant with the Waterworks Law.

40 ... heating device, 60 ... water supply piping.

0016.
[0059]
Before the operation of the heating device, 25 mL of handpiece water remaining in the handpiece from the previous day without flushing (residual water discharge) was collected in 10 mL and 15 mL in a sterilized polyethylene tube. Then, the heating device was operated and heated for 10 minutes. Then, the operation at the maximum output of the handpiece was started, and 25 mL of water was sampled in the same manner 30 seconds after the operation of the handpiece, 1 minute after the operation, and 2 minutes after the operation. At each water sampling, the temperature was measured using a digital thermometer (CT-O5SD, manufactured by CUSTOM). The warmer continued to operate until the end of the experiment.
[0060]
6. result
(1) Examination of culture conditions: Culture results of heterotrophic bacteria and general bacteria in aerobic and anaerobic environments As shown in FIG. 4, residual water collected from a handpiece as a preliminary experiment before the start of a series of experiments. When the heterotrophic bacteria and general bacteria in the sample were cultured in an aerobic and anaerobic environment, colonies of the heterotrophic bacteria were observed only in the aerobic environment, and were not detected in the anaerobic environment. In addition, general bacteria were not detected under either condition. Therefore, in subsequent experiments, the number of heterotrophic bacteria detected in aerobic culture was the subject of research.
[0061]
(2) Changes in the number of heterotrophic bacteria in general dental unit water due to residual water discharge As shown in FIG. 5, the number of heterotrophic bacteria in handpiece water and rinsing water after residual water discharge is compared with that before discharge. However, it decreased significantly by about 94% in handpiece water and 98% in gargle-containing water. (P <0.01, paired t-test). In the irrigation water, the number of bacteria after the residual water was discharged was lower than the target value of 2000 CFU / mL, but in the handpiece water, the number of bacteria was detected to be close to 5 times the target value even after the residual water was discharged.
[0062]
(3) Changes in Free Residual Chlorine Concentration in General Dental Unit Water Due to Residual Water Discharge As shown in Fig. 6, the free residual chlorine concentration in rinsing water is the standard value (0.1 mg) of the Waterworks Law before the residual water is discharged. Although it was lower than / L), it was 0.2 mg / L or more after the residual water was discharged, which greatly exceeded the standard value (P <0.01, paired t-test). On the other hand, the free residual chlorine concentration of handpiece water is about 0.05 mg / L regardless of the presence or absence of residual water discharge.

Claims (7)

Water supply piping and
It is equipped with a heating device attached to the water supply pipe for sterilizing the water in the water supply pipe.
The heating device is a device characterized in that the number of heterotrophic bacteria in water in a water supply pipe downstream of the heating device is 2000 CFU / mL or less. The heating device includes a casing capable of accommodating water in the water supply pipe and a heater provided in the casing, and heats the water in the casing to 50 ° C. or higher. The device described in. The device according to claim 1, wherein the free residual chlorine concentration of water in the water supply pipe downstream from the heating device is set to 0.1 mg / L or more. The device is a dental unit including an assistant unit and a doctor unit, and the water supply pipe is branched into a water supply pipe leading to the assistant unit and a water supply pipe leading to the doctor unit, and the heating device is the heating device. The device according to any one of claims 1 to 3 provided at the branch portion or upstream thereof. The fourth aspect of claim 4, wherein the doctor unit includes an instrument that fluidly communicates with the water supply pipe, and the number of heterotrophic bacteria in the water discharged from the instrument is 2000 CFU / mL or less. Device. The device according to any one of claims 5, wherein the temperature of the water discharged from the instrument after 2 minutes of heating at 60 to 70 ° C. for 10 minutes by the heating device is 15 to 35 ° C. It is a method of sterilizing water in the water supply pipe of the device, and uses a heating device attached to the water supply pipe for heating and sterilizing the water in the water supply pipe, and the water supply pipe downstream from the heating device is used. A sterilization method characterized by reducing the number of dependent vegetative bacteria in the water to 2000 CFU / mL or less.

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