Infection Control PDF

Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 Infection Control: Definitions: Cleaning: It is the process of effectively removing the debris witho...

Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 Infection Control: Definitions: Cleaning: It is the process of effectively removing the debris without putting oneself at the risk of exposure to puncture from the contaminated instrument or from spatter of the debris (blood or saliva) on the instruments; for example, scrubbing with a brush and ultrasonic cleaning. Sterilisation: It is defined as a process by which an article, a surface or a medium is freed of all microbes, in either a vegetative or spore state. Disinfection: It is a process which reduces the number of viable microbes to an acceptable level, but may not inactivate some viruses and bacterial spores. Disinfectant: These are substances that are applied onto the non-living objects to destroy microorgan- isms that are living on the objects.  Disinfection does not necessarily kill all micro-organisms, especially resistant bacterial spores; it is less effective than sterilisation, which is an extreme physical and/or chemical process that kills all types of life. Sanitisers: These are substances that clean and disinfect simultaneously. Asepsis: It is the term used to describe methods that prevent contamination of wounds and other sites by ensuring that only sterile objects and fluids come into contact with them and that the risk of air-borne contamination is minimised. Classification of Methods Used for Sterilisation and Disinfection: The method of sterilisation employed depends on the purpose for which sterilisation is carried out and the nature of microbes that are to be destroyed. 1. Physical Methods: (a)Heat:  Dry: Flaming, Incineration Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9  Moist: Boiling, Steam under normal pressure, Steam under pressure (b) Filtration, for example, membranes (c) Radiation (d) Ultrasonic and sonic vibrations 2. Chemical Methods: (a) Alcohols: Ethyl, isopropyl (b) Aldehydes: Formaldehyde, glutaraldehyde (c) Halogens (d) Phenols (e) Surface-active agents (f) Metallic salts (g) Gases: Ethylene oxide, formaldehyde Cleaning of Instruments and Equipment: 1. Manual cleaning: This can be done by using scrubs or different kinds of brushes. Soap solutions can be used along with the scrubs. 2. Ultrasonic cleaning: Certain chemicals are also provided that can be mixed in water in the ultrasonic cleaner. there is no risk of injury from the sharp instruments to the operator as well. 3. Chemical cleaning agents: (a) Soaps: These are salts of fatty acids and are effective at pH 9 or higher; also, they are effective in a weakly acidic environment. (b) Detergents: These are synthetic compounds compatible with Ca++ and Mg++, effective in a neutral or slightly acidic environment. Chemicals for Disinfection and Sterilisation:  Alcohols: The alcohols routinely used for sterilisation in dentistry are ethyl alcohol and isopropyl alcohol. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9  Mechanism of Action: Alcohols cause denaturation of bacterial proteins. Isopropyl alcohol is better than ethyl alcohol since it is a better fat solvent, more bactericidal and less volatile.  Aldehydes: Formaldehyde is bactericidal and sporicidal and also lethal to some viruses. Glutaraldehyde is also used for sterilisation purposes. Advantages: 1.It can sterilise heat-sensitive equipment. 2.It is non-corrosive and non-toxic. Disadvantages: 1. Long time required for sterilisation 2. Objectionable odour 3. Non-verifiable sterilisation 4. Irritating to eyes and mucous membrane  Halogens: Iodides and chlorides are considered as effective disinfectants. It is biocidal against vegetative bacteria, viruses and some spores. But it is corrosive to metals and irritating to eyes and skin.  Phenols: hey cause cell membrane damage and precipitation of proteins and irreversibly inactivate membrane-bound oxidases and dehydrogenases. Dry Heat (Hot Air Oven):  The basic action of dry heat sterilisation is by dehydration and oxidation of microbes.  Hot air oven is the most widely used method of sterilisation by dry heat. A holding period of 160°C for 1 hour is used (although 2 hours is considered safer).  The oven must be allowed to cool slowly for about 2 hours before the door is opened, since the glass-ware may crack by sudden or uneven cooling. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 Uses To sterilise glassware, forceps, scissors, scalpels, glass syringes, etc. Advantages 1. No rusting if dry instruments are placed in it 2. Sharp instruments can be sterilised without the loss of their sharpness 3. Large load is accommodated at a time 4. Verifiable sterilization Drawbacks 1. Time consuming. 2. Dry heat has less penetration than moist heat. 3. The instrument needs calibration and monitoring. 4. The instrument gets damaged if temperature is too high. Moist Heat:  The basic action of moist heat sterilisation is dena- turation and coagulation of the proteins. 1. Boiling at 100°C vegetative bacteria are killed almost immediately at 90°C–100°C, but sporing bacteria require a considerable period of boiling. Hard water should not be used. Sterilisation can be promoted by adding 2% NaHCO3 to the water. The material should be immersed in the water and boiled for a period of 10–30 minutes. The lid of the steriliser should not be opened during this period. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 2. Steam under pressure (autoclaving) can be used. Advantages 1. The moist heat acts by denaturation and coagu- lation of enzymes and proteins, whereas dry heat acts by destructive oxidation of cell contents. 2. Moist heat kills more rapidly and at much lower temperature than dry heat. 3. Sterilisation is verifiable. Drawbacks 1. Corrosion of carbon steel instruments may occur. 2. Cutting edges of sharp instruments may get dulled. To avoid or minimise corrosion, use of ammonia or 20% sodium nitrate has been recommended. Gas Sterilisation:  Ethylene oxide is a highly penetrative noncorrosive agent with a cidal action against bacteria, spores and viruses. It destroys microbes by alkylation and causes denaturation of nucleic acids.  It is a strong irritant, highly inflammable and a toxic agent and therefore should not be used if other means of sterilisation are feasible. Gas sterilisation is used for pre-sterilising single-use medical devices. The gas is used at room temperature and at 30% humidity for periods as long as 24 hours. Advantages 1.Good penetration ability 2.Can be used for sterilising heat and moisture-sensitive equipment Disadvantages 1. Cost of equipment is high. 2. Gas is toxic. 3. Long period of aeration is required. 4. Concentration exceeding 3% could be explosive. Therefore, it is necessary that the room is properly vented. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 Chemiclaving (Chemical Vapour Sterilisation):  The method uses a vapour created by heating a deodorised alcohol–formalde- hyde solution in a pre-heated tank chamber called a chemiclave or Harvey chemiclave. H2O content is below 15%, the level where rusting occurs.  The vapour is collected at a temperature of 132°C and brought up to a pressure of 20–40 psi. The superheated vapour condenses upon the instru- ments in chamber and the cycle is maintained for 20–25 minutes.  It takes longer time than an autoclave and shorter time than a hot air oven. It is also called low-tem- perature-steam-formaldehyde (LTSF) Advantages 1. Short 25-minute cycle of sterilisation 2. No rusting of instruments 3. Availability of dry, immediately usable instruments with no delay for aeration Disadvantages 1. Cost is high. 2. It requires provision of adequate ventilation to expel chemical vapours released from the chamber at the end of the cycle. 3. Vapour odour may be offensive. 4. Vapours may not penetrate the intricate internal workings of the handpiece. Radiations: Ionising Radiations: Ionising radiations such as gamma rays have great penetrating properties and are commonly used at the industrial level for sterilisation of disposable items such as syringes and gloves. Non-Ionising Radiations: 1. UV rays: Main application is for purification of air in the operating rooms or for surface sterilisation, as for handpieces. Care must be taken to protect skin and eyes while using UV for sterilisation. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 2. Infrared radiations (IR): These too are used for air purification in operatories and for sterilising a large number of syringes contained in a metal container. Glass Bead Steriliser/Hot Salt Steriliser: This compact apparatus is considered indispensable for the procedure of root canal treatment. It consists of a metal cup in which glass beads or table salt is kept at a temperature between 425°F and 475°F. At this temperature, broaches, files and reamers may be sterilised in 5 seconds and absorbent points in 10 seconds. The Concept of Asepsis: The asepsis protocol involves the utilisation of infection control procedure and use of personal protection equipment (PPE). Personal Protection Equipment: Gloves It is mandatory to wear gloves during treatment procedures and these must be changed after treating every patient. Protective Eyewear, Masks, Head Caps 1. Protective eyewear must be worn to protect the eyes from splatter. 2. Clear glasses should be worn with protective side shields. 3. Alternatively, face shields can be used which cover the entire face. Both the eyewear and the face shield should be disinfected. 4. The face mask has to be changed after every patient or at times during the procedure if it becomes wet. 5. Touching the face mask during the procedure should be avoided. 6. The mask must not be kept hanging around the neck. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 7. Head caps should be used to cover the hair. If uncovered, contamination of hair occurs, which can be hazardous. Concept of Zones: Zones in the Vicinity or Area of Operation:  The operatory can be categorised into four zones: 1.Outer/general access zone, for example, patient reception area 2.Clean/limited access zone, for example, area between reception and general office, corridors and staff room 3. Restricted access zone, for example, for properly clothed personnel engaged in operating theatre activities and anaesthetic room. 4. Aseptic or operating zone, for example, operation theatre. Classification of Items Used in Dental Operatory: 1. Critical items: Instruments that contact cut tissues or penetrate the tissues are considered to be critical items. These require thorough cleaning and sterilisation for reuse, as described earlier. 2. Semi-critical items: These include items attached to the dental unit that are used intra- orally or are handled and touched interchange- ably with mucosa by gloved hands coated with blood and saliva, for example, suction tips and handpieces. Semi-critical items should not be disinfected. They should be covered or cleaned and sterilised or discarded. 3. Non-critical items: These include chairs, tables, etc. These, if contaminated, will need cleaning and disinfection. Needle-Stick Injuries: Despite utilising all preventive measures, in case a sharp’s injury/contamination incident occurs, the following procedure is recommended: 1. The wound should be pressed to express blood from the site. 2. The wound should be washed with soap and warm running water. 3. A dressing can be placed over the wound. Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9 4. In case of a splash, the eyes and face should be washed with plenty of water. 5. The incident should be reported to the immediate supervisor. 6. The details of the patient should be seen to evaluate the need of post-exposure prophylaxis (PEP). Preclinical conservative dentistry 1 Dr. Maryam F. Ibrahim lec: 9