 Hello everyone, welcome back to another session in Dentistry and more. Today we have a very important chapter in health sector that is sterilization and disinfection. This is a very fundamental concept. Every health care person, let it be a doctor, dentist, pharmacist or a nurse, whoever it is, they should be very well versed with the concepts of sterilization and disinfection because if any false which is happening from health care people is very detrimental to the patients and to the society. So let us learn about the various procedures in sterilization and disinfection. So by definition sterilization is a process by which an article, surface or medium is freed of all living microorganisms either in vegetative or spore state. So vegetative and spores, the spores are very difficult to be killed or very difficult to be destroyed because it needs to be at a very high temperature, at a very high concentration of the reagent for this spores to be killed. So sterilization is a process where the vegetative forms and spores are killed so it is almost completely germ free. So disinfection, disinfection is a different procedure that is the destruction or removal of all pathogenic organisms or organism capable of giving rise to infection. So disinfection is killing of pathogens but sterilization is killing all the living organisms or most of the living organisms. This is killing only pathogens, pathogens are organism capable of creating an infection. So one more terminology we need to learn that is antisepsis. Antisepsis is nothing but prevention of infection usually by inhibiting the growth of bacteria in wounds or tissues. So various antiseptics, creams, solutions we know so these are preventing infection in wounds. So already there is an injury so we need to apply antiseptic to prevent the infection by inhibiting the growth of bacteria. So sterilization is killing all the microorganism, disinfection killing just the pathogens and antiseptic is inhibiting the growth of bacteria and preventing the infection. So that is about sterilization infection just the introduction, introduction part. So we learned about sterilization and disinfection and about antiseptic solutions. Now we have classification of methods in sterilization and disinfection. So it is broadly classified into physical and chemical methods. In physical there is sunlight, drying, dry heat, moist heat, filtration, radiation, ultrasonic and sonic vibration, chemical methods, alcohols, aldehydes, dyes, halogens, phenols, surface active agents, metallic salts and gases. So let us learn one by one. So in physical agents the sunlight it is active germicidal effect due to the combined effect of UV and heat rays. So there is ultraviolet and heat rays which is commonly clearing the tanks, rivers, lakes. So all these waters are killing the microbes by this method or it is a natural way of disinfection. The microbes will be removed by UV rays and heat rays and drying. Drying is another method where the bacteria cell, the four fifth of bacterial cell is having water. So when there is drying it kills bacteria by removing all the water content from the bacterial body. So that is the importance of drying and sunlight by UV rays and heat rays. And incineration we have heard, incineration procedure it is a method of waste disposal. The single chamber, double chamber incinerator mostly associated with hospital waste management. So it is rapidly destroying materials such as bleeding, animal, waste, pathological material and all these are used in incineration. All these are physical methods. So it is not exactly a method of disinfection it is waste disposal method. So let us learn about dry heat. The principle is protein denaturation. Protein denaturation is a principle of dry heat that is oxidative damage. So there will be oxidative damage happens in dry heat. So in dry heat there will be toxic effects of elevated levels of electrolytes. So the most common one is hot air oven. So hot air oven is working in principle of dry heat, hot air oven which is working in principle of dry heat. It is a very widely used one and it works at a temperature of 160 degree Celsius or 320 Fahrenheit for 1 to 2 hours. So this is dry heat principle working on protein denaturation and oxidative damage. Most commonly it is used in glassways like glass syringes, petri dishes, flasks, pipettes, tubes, surgical instruments like scalpels, scissors, forceps and chemicals such as liquid paraffin, fats, sulfonamide, dusting powder etc. All these can be used in dry heat method. So it is hot air oven 160 degree Celsius for 1 to 2 hours. So what are the precautions we need to take care in hot air oven that is it should not be overloaded. It should be fitted with fans for even distribution of hot air materials to be sterilized should be perfectly dry. Rubber materials will not withstand the temperature so we should take care of rubber material. We should not keep rubber material in hot air oven except silicone rubber which can withstand this high temperature and after the procedure we need to allow it to cool for 2 hours before opening the door. So the advantages are it is very economical, does not rust metals like moist heat, it is easily monitored used for anhydrous oils and powder. But the disadvantage is hot air is bad conductor of heat and it has less penetrating power. Less penetrating power means it might not kill the spores. So that is about moist dry heat and hot air oven. Now we have moist heat principle that is most commonly used one is pasteurization. You must have heard about pasteurization it is principle used in milk preservation. So pasteurization we have two methods that is one is holder method and flash process holder method and flash process. So holder method is 63 degree Celsius for 30 minutes, 63 degree Celsius for 30 minutes whereas a flash process is 72 degree Celsius for 20 seconds not minutes it is 20 seconds then rapid cooling to 13 degree okay then rapidly cooling to 13 degree. So this is holder method this is flash process holder method 63 degree Celsius for 30 minute and flash process 72 degree Celsius for 20 seconds and then rapidly cool to 13 degree Celsius. So that is pasteurization process it is coming under moist heat. Now we have boiling boiling we all of us know what is boiling we use boiled water we remove all the pathogens from drinking water by boiling principle. So temperature we know it is 92 boiling it is coming under moist heat 90 to 100 degree Celsius for 10 minutes. So 10 minutes boiling of water at 100 degree Celsius will kill most of the bacteria and spores. So but some of the spores will not be killed that requires a very prolonged period of boiling and we can accelerate or we can promote the sterilization procedure by adding 2 percentage of sodium bicarbonate okay so if we add sodium bicarbonate to boiling water the procedure will be good compared to normal boiling. So that is boiling okay so in wet sterilization or moist heat sterilization we learnt pasteurization and boiling. Now we have tantalization okay tantalization or intermittent sterilization or intermittent sterilization. So this is used for media containing sugar or gelatin exposure of 100 degrees for 20 minutes 100 degrees for 20 minutes okay this is tantalization 100 degrees for 20 minutes on 3 successive days 3 successive days that is tantalization. So 20 minutes 100 degree Celsius for 3 successive days first exposure will kill all vegetative bacteria then subsequent exposure will kill the spores okay. So vegetative bacteria and spores are there so our aim in sterilization is to kill the spores. So the first day will kill vegetative bacteria they are easily destroyable whereas spores are difficult to be destroyed. So of the successive days will kill the spores so that is moist heat. Now we have the very important sterilization method which is using this moist heat. So very popular very common one is autoclave so all of you must be knowing autoclave you must have seen this in your clinics in your college wherever you are working in a health sector autoclave will be there for sterilization. So autoclave is working under moist heat principle thing is when boiling water is insufficient to kill spores and viruses. So boiling water needs very prolonged period to kill all of the spores and when water boils its vapor pressure equals to that of the surrounding atmosphere. So if you are boiling the same water in a closed vessel what happens the pressure will increase right. So the pressure will increase. So when pressure increases what happens the temperature at which water boils also increases then this saturated steam has more penetrating power. So more penetrating power means more spores will be killed. So the same principle of boiling water but under a closed vessel so there will be more penetrating power of this saturated steam. So when the steam comes in contact with a cooler surface it condense to water and gives up latent heat to that surface. So that is the principle of autoclave that is boiling water in a closed vessel to increase the pressure. So most commonly we know we have three major factors for affecting autoclave that is pressure, pressure, temperature and time. So these three factors we should learn in autoclave. So higher temperature and higher pressure requires shorter time. So we have three, this is pressure, temperature and time. So if the pressure that is atmospheric pressure is 15 the temperature we need 121 degree and if the pressure is 20 psi then the temperature requires is 126 and if the pressure is again 20 136 if we increase the pressure the time reduces that is 15 pressure and 121 temperature requires 15 minutes of working time whereas 20 pressure and 126 degree temperature requires just 10 minutes and 20 pressure and 136 degree requires just 3 minutes. So when pressure increases time decreases. So these are the three things we need to understand in autoclave. So autoclave 15 psi, 20, 20, 121, 126, 136 this is temperature and this is time. So higher pressure less temperature. So what are the considerations what we need to think about autoclaving because there are lots of things to be keep in mind while doing autoclaving because we should ensure complete air removal for temperature to reach 120 degree 120 degree Celsius and ensure loose packing of the chamber and tightly sealed materials may become dangerously pressurized causing injury when removed. It can be used for disposable syringes and glass waste metal instruments it is very commonly used in all the hospitals, dental clinics and every health care facility will be having one or two autoclaves and also can be used for surgical instruments, laboratory, equipment, sculpture, media, pharmaceutical products. The advantage of autoclave is advantages it is very economical, good penetration power, short cycle time easily monitored and no special chemicals or exhaust required. The disadvantage is moisture, moisture retention since it is moisture retention is a big problem which causes corrosion and carbon steels will be damaged, dulling of unprotected cutting edges and destruction of heat sensitive materials all these are the disadvantage of autoclave. But still autoclave is a very commonly used or most commonly used sterilizing equipment in health sector. So we can just compare the dry heat and moist it. So if it is dry heat dry heat it was once if it is 160 degree Celsius we need 45 minutes if it is 170 degree Celsius we need 18 minutes and if it is 180 degree Celsius we need 7.5 minutes whereas in moist heat that is autoclave if it is 121 we need 15 minutes we just need 15 minutes it is very very lesser and 126 we need just 10 minutes and 134 degree we need 3 minutes that is a difference from dry heat and moist heat ok this is moist heat requires very shorter duration 15, 10 or 3 minutes this is almost half an hour or more than half an hour and the temperature also very less you can compare the dry heat and moist heat. So that is advantage of moist heat with respect to dry heat. So the next one we have a glass bead sterilizer glass bead sterilizer we all must have seen in tender clinics and mostly in endodontic departments where the files are cleaned with this particular sterilizer that is a small equipment which has a small glass beads which works at high temperature that is 210 degree and 230 degree for 10 to 30 seconds ok the glass bead sterilizer mainly used to sterilize the files endodontic files and the burst we know the cutting burst so it is most commonly seen in department endodontic department so where this is mostly used cutting burst and files ok so disadvantages we cannot maintain a uniform heat all the areas. So glass bead sterilizer the temperature is to 10 degree to 230 degree and 10 to 30 seconds uses our files and cutting burst and disadvantages maintaining a uniform heat throughout the area is difficult. So that is glass bead sterilizer it is another method of sterilization and next one is filtration so there are many filters such as candle filter candle filter and asbestos filter so many filters are available asbestos filter and sintered glass filter sintered glass filter so all these are also can be used for sterilization of equipments but it is not very commonly used the filters whereas radiation radiation is commonly used we have two types of radiation that is non ionizing radiation and ionizing radiation right two types non ionizing and ionizing ionizing is bad for health non ionizing is not very injurious like UV lights another one which is daily we expose to non ionizing radiation from the sunlight ionizing which is detrimental to health such as which is seen in x-ray protection. So non ionizing radiation which uses longer wavelength and lower energy hence it lose the ability to penetrate substances and can only be used for sterilizing the surfaces like infrared radiation infrared radiation which is used for rapid mass sterilization of prepacked items such as syringes catheters and also UV radiation which is used for disinfecting enclosed areas like operation theaters and operation theater and the laboratories so UV radiation can be used which is high wavelength low energy whereas ionizing radiation ionizing radiation uses shorter wavelength high intensity radiation with high penetrating power to destroy microorganisms this radiation can come in form of gamma rays or x-rays which react with the DNA resulting in damage of the microbes since there is no appreciable increase in temperature it is also known as cold sterilization is very important commonly asked question cold sterilization because there is no increasing in temperature we are using just gamma rays or x-rays so which is known as cold sterilization which is used for sterilizing plastics swabs metal foils etc so that is non ionizing and ionizing this is infrared and UV lights this is the gamma radiation and x-rays okay so ionizing radiation method is also known as cold sterilization now we have the last one which is ultrasonic and sonic vibration ultrasonic cleaning which is a more effective than manual cleaning it removes a dried serum whole blade plaque zinc phosphate and poly carboxylate cements from the instrument or metal surfaces and even from dentures which minimizes the handling contaminated handling of contaminated instruments so during cleaning we need to submerge the instruments in ultrasonic solution for 2 to 20 minutes so these solutions will be available in all the departments so the instruments will be submerged in ultrasonic solution and this solution should be changed at least once a day okay that is about ultrasonic and sonic vibration now we have a few biological controls for different sterilization methods because we need to ensure that our sterilization instruments working properly our method is correct we cannot depend on a instruments efficiency for a very long period we need to monitor it intermittently so for monitoring we have biological control for hot air oven hot air oven the biological control is checking the presence of clostridium tetanus so if clostridium tetanus is present that means the hot air oven is not working properly and autoclave it is basilless group of bacteria and filtration is different pseudo monas diminuta and ionizing radiation also basilless cumulus so all these biological controls we need to use to check the efficiency of all the methods or the instruments or if it is working properly or not now let's move on to the chemical agents so chemical agents are broadly classified into liquid agents and gases so liquids we have various alcohols aldehydes phenols halogens heavy metals service active agents and dyes in gases formaldehyde ethylene oxide and plasma so what is the basic action of chemical agents it is by protein coagulation disruption of cell membrane removal of the free sulfhydryl groups and substrate computation okay so main is protein coagulation so whereas in we have seen protein denaturation in our dry heat methods this is protein coagulation and cell membrane disruption cell membrane it will disrupt cell membrane and the sulfhydryl groups it removes the sulfhydryl groups that's how these chemical agents are creating a free microbes surface are free of the microbes so alcohols so what is the action of alcohols so it is by the denaturation of proteins most commonly used isopropyl alcohol this is very common nowadays in corona time this is isopropyl alcohol everyone is using it everyone is rubbing it with the hands so they are sanitizing it is used as a sanitizer the common hand rub which is isopropyl alcohol this is 70 percentage ethyl alcohol is another one and methyl alcohol is active agent against the fungal spores and used to treat captains and incubators are cleared by using methyl alcohol okay so isopropyl alcohol and 70 percent ethyl alcohol used as surface or skin disinfectant okay skin disinfectant this is not working on sterilization principle this is working on disinfection okay hope you remember the definition of disinfection it is killing only the pathogenic organism so isopropyl alcohol and 70 percent ethyl alcohol surface or skin disinfectant whereas methyl alcohol is used to is used to clean or disinfect the cabinets and incubators okay so suitable for skin preparation before the vene puncture so before inserting needle into veins we can apply all these so disadvantage is it is inflameable the mucus membrane irritation is a problem and it promotes resting okay when we apply it on the metal there will be resting of the metallic parts so those are the problems of these alcohols they are inflameable metal resting is there and mucus membrane irritant now we have aldehydes aldehydes formaldehyde is a common one formaldehyde which is also known as formalin so in aqua solution it acts as a bactericidal and sporesidle bactericidal means agent which kills bacteria sporesidle means it kills spores bacteriostatic is different bactericidal bacteriostatic it reduces or it suppresses the bacterial action whereas bactericidal bactericidal means it kills the bacteria static is different it suppresses its action okay so bacteriostatic is different bactericidal is different so this is bactericidal and sporesidle that is aldehyde commonly used formalin it is active against gram negative bacteria spores viruses and fungi in aqua solution that is formalin 37 percentage is used in aqua solution and 10 percentage formalin and 0.5 percentage sodium tetra borate used to clean metal instruments like endoscope dialysis equipments all these are used by this formaldehyde that is formalin 10 percentage formalin and 0.5 percentage sodium tetra borate is used for instruments such as endoscope and dialysis equipments this is liquid form whereas in gaseous form it is used for fumigation of wards, corridors, ice use which has very punch and order and irritating effect on skin and mucus membrane so liquid is used here whereas the gaseous mode is used in fumigating operation theaters ice use corridors and other wards okay so that is formaldehyde or formalin in gaseous form okay whereas the glutaraldehyde okay it is another type of aldehyde glutaraldehyde which is also known as cidex you must have heard of it cidex which is 2 percentage alkaline sodium bicarbonate which is high level disinfectant which especially active against tubercle bacilli fungi and viruses which is less toxic than formaldehyde and it can be safely used to treat corrugated rubber anesthetic tubes face mask metal instruments exposure time should be more than 10 hours that is cidex which is glutaraldehyde okay this is less toxic than the formaldehyde one so cidex is glutaraldehyde now we have phenols so phenols is different one different group which acts by cell membrane damage that's releasing cell contents and causing lysis the cresol cresol that is commonly in brand name lysol and chlorhexidine which is savalone chlorhexidine phenol which is savalone and chlorozylinol okay this is the most common chlorzylinol which is detol okay so we have heard of lysol savalone detol all these are phenols which acts by cell membrane damage and releasing cell content and causing lysis which has basically found in mouthwash scrub soaps and surface disinfectants which has very low efficient in disinfection used for decontamination of hospital environment including the laboratory surfaces and non-critical medical items that is about phenols now we have halogens halogens are chlorine compound okay so chlorine compound chlorine compound most common one is you know bleaching powder right bleaching powder or hypochloride solution bleaching powder or hypochloride solution most used disinfectant for HIV infected material the concentration is 0.05 or 0.5 percentage for surface material and instrument disinfection it should be prepared daily because of instability of this sodium hypochloride solution so they are active against bacteria spores fungi and viruses next we have iodophores and iodine okay so they are also halogen family that is iodine and iodophores iodine and iodophores they are active against bacteria spores and virus and fungi suitable for skin preparation mouthwash and surgical scrub most common one is betadine okay this is used in post surgical disinfection it is 7.5 percentage povidone and iodine okay povidone and iodine is known as betadine okay so betadine is very important one which is 7.5 percentage povidone and iodine now we have gaseous one that is ethylene oxide ethylene oxide is highly inflammable and in concentration more than 3 percentage is highly explosive and it is not used for fumigation of rooms mixed with carbon dioxide or nitrogen to eliminate its explosive tendency so this ethylene oxide will be mixed with carbon dioxide and nitrogen to eliminate its explosive tendency so this ethylene oxide it will be mixed with carbon dioxide and nitrogen gas to remove its explosive capacity and how does it work this principle is basic alkylation of amino carboxyl hydroxyl and sulfhydryl groups in protein molecules it is very effective against all types of microorganisms includes virus and spores but thing is it should be mixed with carbon dioxide and nitrogen and now we have the plasma plasma is any gas which consists of electrons ions electrons ions or neutral particles it's used along with chemical disinfectant like hydrogen perox so what are the basic concentration of these liquids such as ethyl alcohol glutaraldehyde lysol so the percentage is for ethyl alcohol we learned it is 70 percentage glutaraldehyde it is 2 percentage savalon it is 2.5 percentage and lysol also sorry savalon is 2 percentage 2 or 5 percentage lysol is 2.5 percentage detal is 4 percentage and glitching powder we commonly use 15 grams in 1 liter of water sodium hypochlorate it's 0.1 percentage or 1 percentage and beta adenis 2 percentage now we have learned all the methods of sterilization on disinfection in detail now we need to learn about the instruments okay so instruments are basically categorized as critical instruments semi-critical and non-critical instruments critical instruments they are penetrating the soft tissues contacting the bond or enter into or contact the blood stream and they should be thoroughly cleaned and heat sterilized if they are to be reused such as surgical instrument okay surgical instrument which are coming in with blood, bone and tissues scalars we used for scaling in periodontics and scissors which cutting for tissues and scalpel blades scalpel blades and dental bus used in endodontics and forceps various forceps used in extraction all considered critical items okay so this should be sterilized this should be heat sterilized if it needs to be reused it is very very important because it will be containing pathogens okay so heat sterilization or sterilization autoclave methods is very important for critical whereas a semi-critical items which contact the mucous membrane but will not penetrate the soft tissue such as a mouth mirror is a semi-critical item then impression trays we use to take impression and prostatonic and hand pieces various hand pieces micromotor aerotor and probe and tweezers all are diagnostic instruments so these are semi-critical items which can be go for a high level disinfection or sterilization okay high level disinfection or sterilization this is sterilization compulsory sterilization okay this is high level disinfection or sterilization whereas a non-critical items comes into contact with intact skin like x-ray tubes x-ray tubes light handles light handles such things are non-critical items just lower level disinfection is required okay so these are the basic instruments critical semi-critical and non-critical based on the type of category we need sterilization high level disinfection and lower level disinfection okay it is very important the types of instruments so that's all about sterilization and disinfection we are covered in detail about various methods why it is very important in health care people because we the dental health care providers so we need to follow very high standards of infection control not just for the safety of patient but also for the safety of dental health care workers it is easily transmissible to the health care providers also so it is very important to keep a very high standards of sterilization and disinfection and we should always give emphasis on the monitoring of the efficiency of all the instruments and cross contamination is also very much vital nowadays that's why the disposable instruments are into practice but still the waste management also is a big concern proper waste management is another issue so waste management we are already covered solid waste management and hospital waste management so that's all about sterilization and disinfection it's very important chapter you can expect a lot of questions maybe as a essay question short essay question or a short note but more than the exam purpose it is very much vital for your practice in when you're going for a practice it is very much important you need to follow all the principles of sterilization and high standard keeping a high standard not just to prevent the spread of disease to your patients and also to the people who are working inside the clinic or hospital so it is a mutual benefit so if you keeping a very good sterilization and disinfection protocol it is beneficial to the health care workers and the patients so i'll come up with a new topic in microbiology thank you