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Infection control in dentistry

1. INFECTION CONTROL IN DENTISTRY DR. SHRUTI KULKARNI 1 ST YEAR MDS

2. CONTENTS Introduction Infection transmission Categories of tasks, work areas and personnel are classified according to risk of infection Aspects to consider during infection control in dentistry. Patient history – past and present Vaccines for dental health-care workers Personal barrier techniques for infection control Sterilization and disinfection Isolation of the operative field Spaulding's classification: to classify the devices used on patient Office design and ventilation conclusion

3. INTRODUCTION INFECTION: T he invasion and multiplication of microorganisms such as bacteria, viruses , and parasites that are not normally present within the body. INFECTION CONTROL:  It is a practical, evidence-based approach which prevents patients and health workers from being harmed by avoidable infection . Objective of sterilization : Microorganisms are ubiquitous (present everywhere) Since they cause contamination, infection and decay it becomes necessary to remove & destroy them from materials or from areas.

4. Infection transmission Dental patients and dental health care personnel (DHCP) can be exposed to pathogenic microorganisms including cytomegalovirus (CMV), HBV, herpes simplex virus types 1 and 2, HIV, corona virus, Mycobacterium tuberculosis, staphylococci, streptococci, and other viruses and bacteria that colonize or infect the oral cavity and respiratory tract. These organisms can be transmitted in dental settings through direct contact with blood, oral fluids, or other patient materials indirect contact with contaminated objects (e.g.. instruments, equipment, or environmental surfaces) contact of conjunctival, nasal, or oral mucosa with droplets (e.g., spatter) containing microorganisms generated from an infected person and propelled a short distance (e.g., by coughing, sneezing, or talking) inhalation of airborne microorganisms that can remain suspended in the air for long periods

5. Categories of tasks, work areas and personnel are classified according to risk of infection. The American Dental Association (ADA) and Occupational Safety and Health Act(OSHA) guidelines advise that all dental office staff in category I and II and dentists be trained in infection control to protect themselves and their patients . Categories of tasks, work areas and personnel are classified according to risk of infection.

6. Aspects to consider during infection control in dentistry.

7. Patient’s history and screening Generally the history of a patient is taken just before examination. During the present pandemic the urgency of dental treatment should be determined before booking the patient.  A COVID-19 screening questionnaire including symptoms, contacts, family history and travel history should be taken. Apart from the screening questionnaire, temperature and SPO2 should be taken for all the individuals entering the practice using a contact free laser thermometer and oximeter

8. Hand sanitizer containing ≥70% alcohol or other approved substance should be available for the patient and the accompanying person.  Pre -procedural rinse: The use of a therapeutic antimicrobial mouth rinse such as chlorhexidine or betadine prior to the dental treatment can reduce aerosol contamination.

9. VACCINES FOR DENTAL HEALTH-CARE WORKERS The OSHA bloodborne pathogens final rule requires that employers make hepatitis B vaccinations available without cost to their employees who may be exposed to blood or other infectious materials. In addition, centers for disease control(CDC) recommends that all workers, including dental health care workers(DHCWs), who might be exposed to blood or blood-contaminated substances in an occupational setting be vaccinated for HBV. DHCWs also are at risk for exposure to and possible transmission of other vaccine-preventable diseases. Accordingly vaccination against influenza, measles, rubella, and tetanus may be appropriate for DHCWs.

10. PERSONAL BARRIER TECHNIQUES FOR INFECTION CONTROL WASHING AND CARE OF HANDS DHCWS wash their hands before and after treating each patient and after barehanded touching of inanimate objects likely to be contaminated by blood, saliva, or respiratory secretions. Hands should be washed after removal of gloves because gloves may become perforated during use and DHCWs' hands may become contaminated through contact with patient material. Soap and water will remove transient microorganisms acquired directly or indirectly from patient contact; therefore, for many routine dental procedures, such as examinations and nonsurgical techniques, hand washing with plain soap is adequate. For surgical procedures, an antimicrobial surgical hand scrub should be used. When gloves are torn, cut, or punctured, they should be removed as soon as patient safety permits. DHCWS then should wash their hands thoroughly and re-glove to complete the dental procedure .

11. HEAD CAP : Hair should be tied and covered with a disposable cover. For males, beard should be removed. Gowns Protective clothing such as reusable or disposable gowns, laboratory coats, or uniforms should be used. Protective clothing should be changed at least daily or as soon as it becomes visibly soiled.

12. Masks and Protective eye wear/face shield Surgical mask and Chin-length plastic face shields or protective eyewear should be worn when splashing or spattering of blood or other body fluids is likely, as is common in dentistry. When a mask is used, it should be changed between patients or during patient treatment if it becomes wet or moist. Face shields or protective eyewear should be washed with an appropriate cleaning agent and when visibly soiled, disinfected between patients. Closed shoes must be worn. Aerosol settles down slowly contaminating surfaces and floor, therefore disposable shoe covers should be used.

13. Gloves For protection of personnel and patients in dental-care settings, medical gloves (latex or vinyl) always must be worn by DHCWS when there is potential for contacting blood, blood-contaminated saliva, or mucous membranes. Nonsterile gloves are appropriate for examinations and other nonsurgical procedures. sterile gloves should be used for surgical procedures. Surgical or examination gloves should not be washed before use; nor should they be washed, disinfected, or sterilized for reuse. Washing of gloves may cause "wicking" (penetration of liquids through undetected holes in the gloves) and is not recommended. Disinfecting agents, oils, certain oil-based lotions, and heat treatments, such as autoclaving, may cause deterioration of gloves . Personal Protective Equipment (including gloves, masks, and face sheild ) should be removed before personnel exit areas of the dental office

14. Donning & Doffing of PPE

15. Studies have shown that aerosol could remains around the dental chair for more than 30min after scaling, therefore the protective barriers should not be removed immediately after the procedure Spray and wipe technique should be used for the disinfection of all the exposed areas including chair, surfaces, light and handles. Dental prostheses, impressions and other prosthodontic materials should be disinfected before receiving and sending them to the dental laboratory. Chlorinated compound such as Sodium dichloroisocyanurate is also beneficial because it is stable and proved to have antiviral effect . Ethyl alcohol (70%) can also be used which is relatively inert and evaporates rapidly leaving surfaces dry.

16. STERILIZATION AND DISINFECTION Sterilization is defined as the process by which an article, surface or medium is freed of all living microorganisms either in the vegetative or spore state. Disinfection is the destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection. Asepsis is the term used to indicate the prevention of infection, usually by inhibiting the growth of bacteria in wounds or tissues.

17. Antiseptics are chemical disinfectants that can be safely applied on the skin or mucous membrane and are used to prevent infection by inhibiting the growth of bacteria. Antisepsis : Antisepsis is a process of removal of germs from the skin. Decontamination and cleaning : Decontamination is the process of removal of pathogenic microorganisms from objects so that they are safe to handle. Cleaning is defined as removal of visible soil (e.g., organic and inorganic materials) from the surfaces and objects. 

18. STERILIZING AGENTS A.PHYSICAL AGENTS Sunlight Drying Dry heat: flaming , incineration, hot air Moist heat: pasteurization, boiling, steam under pressure Filtration: candles, asbestos pads, membranes Radiation Ultrasonic and sonic vibrations B.CHEMICAL AGENTS Alcohol: ethyl, isopropyl, trichlorobutanol Aldehydes: formaldehyde, glutaraldehyde Dyes Halogens Phenols Surface active agents Metallic salts Gases: ethylene oxide, formaldehyde, beta propiolactone

19. DRY HEAT: Principle: Dry heat kills the organisms by denaturation of bacterial protein, oxidative damage and by the toxic effect of elevated levels of electrolytes.. Advantages for dry heat it is nontoxic and does not harm the environment; a dry heat cabinet is easy to install and has relatively low operating costs; it penetrates materials; it is noncorrosive for metal and sharp instruments Disadvantages for dry heat are the slow rate of heat penetration and microbial killing makes this a time-consuming method. In addition,   the high temperatures are not suitable for most materials .

20. Flaming: An inoculating loop or wire, the tip of forceps and searing spatulas are held in a bunsen flame till they become red hot. Inoculation loops carrying infective material may be dipped in a disinfectant before flaming to prevent spattering. Used to sterilize: glass slides scalpel culture tubes

21. Incineration: By this method infective materials are reduced to ash by burning This is an excellent method for safely destroying materials such as contaminated cloth, animal carcasses and pathological materials.

22. This is the most widely used method of sterilization by dry heat. holding period : 180 °C for 30 min 170°C for 1hr 160°C for two hours It is used to sterilize : glassware, forceps, scissors, scalpels, all-glass syringes, swabs, and some pharmaceutical products such as liquid paraffin, dusting powder, fats and grease. Hot air oven

23. The oven is usually heated by electricity, with heating elements in the wall of the chamber. It must be fitted with a fan to ensure even distribution of air and elimination of air pockets . The material should be arranged so as to allow free circulation of air in between the objects. Glassware should be perfectly dry before being placed in the oven. Rubber materials, except silicon rubber, will not withstand the temperature. At 180°C cotton plugs may get charred. The oven must be allowed to cool slowly for about two hours before the door is opened, since the glassware may crack due to sudden or uneven cooling.

24. Sterilisation control: Physical: Temperature monitoring and thermocouples Chemical: A Browne's tube (green spot) is available for dry heat and is convenient for routine use. After proper sterilisation , a green color is produced Biological: The spores of a non-toxigenic strain of Clostridium tetani or Bacillus subtilis subsp. niger are used as a microbiological test of dry heat efficiency. Paper strips impregnated with 10 6 spores are placed in envelopes and inserted into suitable packs. After sterilisation , the strips are removed and inoculated into thioglycolate or cooked meat media and incubated for sterility test under strict anaerobic conditions for five days at 37°C .

25. MOIST HEAT: Principle: Moist heat kills the microorganisms by denaturation and coagulation of proteins a)Temperatures below 100°C : 1) By these processes, all non-sporing pathogens such as mycobacteria, brucellae and salmonellae are destroyed. Coxiella burnetii is relatively heat resistant and may survive the holder method.

26. 2)Inspissation- Some serum or egg media, such as Lowenstein-Jensen's and Loeffler's serum, are rendered sterile by heating at 80 - 85 °C temperature for half an hour daily on three consecutive days. This process of sterilization is called inspissation. The instrument used is called inspissator . 3)Vaccine bath- Bacterial vaccines are sterilised in special vaccine baths at 60 °C for one hour.

27. B) a Temperature at 100°C ( a) Boiling- Boiling for 10 to 30 minutes may kill most of the vegetative forms but many spores withstand boiling for a considerable time. When better methods are not available, boiling may be used for glass syringes and rubber stoppers. It is not recommended for the sterilization of surgical instruments. (b) Tyndallisation - Steam at 100°C for 20 minutes on three successive days is used. This is known as tyndallisation or intermittent sterilization. The principle is that the first exposure kills all the vegetative forms, in the intervals between the heating the remaining spores germinate into vegetative forms which are killed on subsequent heating. It is used for sterilization of egg, serum or sugar containing media which are damaged at higher temperature of autoclave. (c) Steam sterilizer at 100°C for 90 minutes Koch's or Arnold's steam sterilizer is usually used for media which are decomposed at high temperature of autoclave. The articles are kept on a perforated tray through which steam can pass.

28. AUTOCLAVE Principle of the autoclave is that water boils when its vapour pressure equals to that of the surrounding atmosphere. Hence when pressure inside a closed vessel increases, the temperature at which water boils also increases. Saturated steam has penetrative power. When steam comes into contact with a cooler surface it condenses to water and gives up its latent heat to that surface. The large reduction in volume sucks in more steam to the area and the process continues till the temperature of that surface is raised to that of steam. The condensed water ensures moist conditions for killing the microbes present. Sterilization by steam under pressure is carried out at temperatures between 108°C and 147°C. By using the appropriate temperature and time, a variety of materials such as dressings, instruments, laboratory ware, media and pharmaceutical products can be sterilized. Aqueous solutions are sterilized between 108°C and 126°C. Heat is conducted through the walls of the sealed containers until the temperature of the fluid inside is the same as that of the steam outside. Temperature above 100 °C

29. TYPES OF AUTOCLAVE GRAVITY DISPLACEMENT AUTOCLAVE HIGH VACCUM STERILIZER

30. Principle of the autoclave is that water boils when its vapour pressure equals to that of the surrounding atmosphere. Hence when pressure inside a closed vessel increases, the temperature at which water boils also increases. Saturated steam has penetrative power. When steam comes into contact with a cooler surface it condenses to water and gives up its latent heat to that surface. The large reduction in volume sucks in more steam to the area and the process continues till the temperature of that surface is raised to that of steam. The condensed water ensures moist conditions for killing the microbes present. Sterilization by steam under pressure is carried out at temperatures between 108°C and 147°C. By using the appropriate temperature and time, a variety of materials such as dressings, instruments, laboratory ware, media and pharmaceutical products can be sterilized. Aqueous solutions are sterilized between 108°C and 126°C. Heat is conducted through the walls of the sealed containers until the temperature of the fluid inside is the same as that of the steam outside.

31. Sterilization control : Physical: Temperature and pressure monitoring gauges and thermocouples . Chemical: A Browne's tube (green spot), Chemical pressure indicators or autoclave tapes are available and are convenient for routine use. Bowie Dick tapes are used to test the vacuum obtained in the equipment. Biological: For determining the efficacy of moist heat sterilisation , spores of Bacillus stearothermophilus are used as the test organism. This is a thermophilic organism with an optimum growth temperature of 55-60°C and its spores require an exposure of 12 minutes at 121°C to be killed. Paper strips impregnated with 10 6 spores are dried at room temperature and placed in paper envelopes. These envelopes are inserted in different parts of the load. After sterilisation , the strips are inoculated into a suitable recovering medium and incubated for the sterility test at 55°C for five days

32. FILTRATION Filtration helps remove bacteria from heat labile liquids such as sera and solutions of sugars or antibiotics used for the preparation of culture media. As viruses pass through ordinary filters, filtration can be used to obtain bacteria-free filtrates of clinical samples for virus isolation. Filter discs also help to concentrate bacteria from liquids as, for example, in testing water samples for cholera vibrios or typhoid bacilli. Bacterial toxins can be obtained by passing cultures through filters.

33. Types of filters: Candle filters are manufactured in different grades of porosity and have been used widely for the purification of water for industrial and drinking purposes • Asbestos filters are disposable, single-use discs. They have high adsorbing capacity and tend to alkalinize filtered liquids. The carcinogenic potential of asbestos has discouraged their use. Examples are Seitz and Sterimat

34. Sintered glass filters are prepared by heat-fusing finely powdered glass particles of graded sizes. They have low absorptive property and can be cleaned easily but are brittle and expensive. Membrane filters made of cellulose esters or other polymers have largely replaced other types of filters. They are routinely used in water purification and analysis

35. Radiation

36. Chemical agents Chemical agents act in various ways: By protein coagulation By disruption of the cell membrane resulting in exposure, damage or loss of contents By removal of free sulphydryl groups which are essential for the functioning of the enzymes

37. Alcohols Ethyl alcohol (ethanol) and isopropyl alcohol are the most frequently used. They are used mainly as skin antiseptics and act by denaturing bacterial proteins. They have no action on spores. To be effective, they must be used at a concentration of 60-90 percent in water. Isopropyl alcohol is preferred as it is a better fat solvent, more bactericidal and less volatile. It is used for the disinfection of clinical thermometers. Methyl alcohol is effective against fungal spores and is used for treating cabinets and incubators.

38. Aldehydes Formaldehyde is active against the amino group in the protein molecule. In aqueous solutions, it is markedly bactericidal and sporicidal and also has a lethal effect on viruses. It is used to preserve anatomical specimens, and for destroying anthrax spores in hair and wool; 10% formalin containing 0.5% sodium tetraborate is used to sterilise clean metal instruments. Formaldehyde gas is used for sterilising instruments and heat-sensitive catheters and for fumigating operation theatres, wards, sick rooms and laboratories. Under properly controlled conditions, clothing, bedding, furniture and books can be satisfactorily disinfected. The gas is an irritant and toxic when inhaled. Surfaces which have been disinfected by this agent may give off an irritant vapour for some time after disinfection. This can be nullified by exposure to ammonia vapour after disinfection has been completed . Glutaraldehyde is specially effective against the tubercle bacilli, fungi and viruses. It is less toxic and irritant to the eyes and skin than formaldehyde. It has no deleterious effect on the cement or lenses of instruments such as cystoscopes and bronchoscopes. It can be safely used to treat corrugated rubber anesthetic tubes and face masks, plastic endotracheal tubes, metal instruments and polythene tubing.

39. Halogens Iodine in an aqueous and alcoholic solution has been widely used as a skin disinfectant. It is actively bactericidal, with moderate action against spores. It is active against the tubercle bacteria and viruses. Chlorine and its compounds have been used as disinfectants for many years. Water supplies, swimming pools, and food and dairy industries use chlorine for disinfection. Chlorine is used commonly as hypochlorites . Chlorine and hypochlorites are markedly bactericidal. They have a wide spectrum of action against viruses. The organic chloramines are used as antiseptics for dressing wounds.

40. Phenols (carbolic acid) Lister, the father of antiseptic surgery, first introduced them in surgery (1865). Since then a wide range of phenolic compounds has been developed as disinfectants. The lethal effect of phenols is due to their capacity to cause cell membrane damage, releasing cell contents and causing lysis. Low concentrations of phenol precipitate proteins. Membrane-bound oxidases and dehydrogenases are inactivated by concentrations of phenol that are rapidly bactericidal for microbes. Used to disinfect the skin. Lysol and cresol are active against wide range of organisms.

41. Gases: Ethylene oxide Its use as a disinfectant presents potential toxicity to human beings, including mutagenicity and carcinogenicity. It is effective against all types of microorganisms including viruses and spores. Formaldehyde gas: This is widely employed for fumigation of operation theatres and other rooms. When formaldehyde vapour is generated, the doors should be sealed and left unopened for 48 hours. This method is no longer preferred. Betapropiolactone (BPL): It was earlier used for fumigation but is no longer used as it has carcinogenic activity. Hydrogen peroxide fogging : This is a better method replacing fumigation. It is done by a fogging machine using hydrogen peroxide as disinfectant. It has the advantage of short cycle time and is non-toxic.

42. Metallic salts The salts of silver, copper and mercury are used as disinfectants. They are protein coagulants and have the capacity to combine with free sulphydryl groups of cell enzymes, when used in appropriate concentrations. Mercuric chloride is highly toxic. The organic compounds thiomersal, phenyl mercury nitrate and mercurochrome are less toxic and are used as mild antiseptics and have marked bacteriostatic but weak bactericidal and limited fungicidal action Copper salts are used as fungicides.

43. Plasma sterilization: New methods of sterilization of heat-sensitive articles Plasma is known as the fourth state of matter. It consists of ions, electrons or neutral particles. For sterilization, radio frequency energy is applied to create an electromagnetic field. Into this, hydrogen peroxide vapours are introduced which generates a state of plasma containing free radicals of hydrogen and oxygen. This state has a sterilizing action on the articles and is used for arthroscopes, urethroscopes , etc.

44. Isolation of the operative field GOAL: To minimize the formation of droplets, spatter and aerosols during patient treatment Gingival bleeding is an unavoidable consequence of subgingival instrumentation. Blood and debris can be removed from the operative field with suction and by wiping or blotting with gauze squares. The operative field should also be flushed occasionally with water or saline.

45. Methods of isolation

46. Spaulding's classification: To classify the devices used on patient Device/Item Definition Risk of Infection Example Reprocessing Procedure Critical Medical device that is intended to enter a normally sterile environment, sterile tissue, or the vasculature High Surgical instrument, cardiac catheter, implants, needle, forceps, scalpel, scalers, burs, bone chisel Sterilization by steam, plasma, or ethylene oxide Semicritical Devices that are intended to come in contact with the mucous membrane or nonintact skin High/intermediate Mirrors, condensers, Flexible endoscope, respiratory therapy equipment, laryngoscope Sterilization desirable, high-level disinfectants Noncritical Devices come in contact with intact skin Low Blood pressure cuff, stethoscope, external component of Xray heads Intermediate or low-level disinfectant

47. High-level disinfectant: A chemical that kills all microbial pathogens except large numbers of spores. They may have some activity against a smaller number of spores if the contact time is increased. For example, gluteraldehyde and hydrogen peroxide. Intermediate-level disinfectant: A chemical that kills all microbial pathogens including mycobacteria and non-enveloped viruses except spores. For example, alcohol, phenolic compounds and iodophors. Low-level disinfectant: A chemical that kills only vegetative bacteria, fungi and lipid enveloped viruses. For example, quaternary ammonium compound.

48. Office design and ventilation High efficiency particulate air (HEPA) filters and UV chambers in the ventilation system can reduce the aerosol related contamination UV chamber with HEPA filters is ideal because regular decontamination of filters is not necessary. If possible these filters should be installed directly above the dental chair with an air flow as such that the contaminated air can be filtered . Or portable HEPA filters should be used placing as close as possible to the patient during treatment Bathroom air extractors must be kept running continuously during consulting time. Generally no carpets are allowed in dental practices. Floor material and upholstery of the dental chair should have minimum stitching. The floor must be disinfected twice a day. The dental chair can be covered with plastic which can also be disinfected before and after patient treatment and at the beginning and at the end of the day. Medical waste can be disposed according to the local regulations.

49. Biomedical waste management

50. CONCLUSION Infection prevention and control is an important dimension of safe care and integral aspect of day-to-day care Infection control strategies should aim to reduce the risk of transmission of infectious disease. Because all infected patients cannot be identified by medical history, physical examination or lab test. The aim of infection control is to control iatrogenic, nosocomial infections among patients, and potential occupational exposure of care providers to disease causing microbes during provision of care. Therefore, the dental health care provider must be knowledgeable about the diseases commonly encountered in the dental operatory and must follow high standards of infection control for the safety of the patients and the dental health care workers.

51. References Ananthanarayan and Paniker’s Textbook of microbiology, 9 th edition C.P. BAWEJA Textbook of microbiology, 5 th edition Soben Peter Essentials of public health dentistry, sixth edition Infection control in dentistry during COVID – 19 pandemic: what has changed ? Heliyon volume 6 issue 10, October 2020, e045402 Mrudula Patel *Department of Clinical Microbiology and Infectious Diseases, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, and Infection Control Services, National Health Laboratory Services, Johannesburg, South Africa CDC Guidelines for infection control in dental health care settings 2003 Sterilization and Disinfection S. Mohapatra Department of Neuroanaesthesiology and Critical Care, All India Institute of Medical Sciences, New Delhi, India 2017 Safety protocols for dental practice in the covid 19 era 2020 Regulations of biomedical waste feb 8, 2020