STERILIZATION OF ARMAMENTARIUM 5.5 billion/mL of saliva Avg 750 million/mL of saliva Thousands of species of bacteria, fungi and viruses. Myriad oral niches-tongue, gingival, teeth etc Doctors, dentists, patients, diseases Herpes, T.B., Hepatitis, AIDS. AFRAID? We better be-
Let us explore this world of heat, light, chemical, gases etc. under the following subheadings: INTRODUCTION DEFINITIONS HISTORY PRELIMINARIES STERILIZATION DISINFECTION SPECIFIC CONSIDERATIONS INCLUDING HANDPIECES, DENTAL BIOFILMS AND DENTAL ARMAMENTARIUM AND SPECIFIC DISEASE CONCLUSION BIBLIOGRAPHY
1
INTRODUCTION: Today is the age of modern technology and wizardly gedgation. Today is also the age of medical challenges. From the “back with a vengeance� tuberculosis, to the ever prevalent tetanus, typhoid, measles to the modern day pandemics of hepatitis and AIDS, the challenge of microbial infections is omnipresent and ever threatening. Into this scenario comes the dental professional being the center of a health care delivery system, dentists are not only at risk themselves but also pose a pathway of infection to their numerous patients. Thus it becomes the religion of every dentist to implement all those practices and procedures that will result in minimizing the microbial challenge. Let us see how. Firstly the definitions: STERILIZATION: It is defined as freeing the object or substance from all life of any kind. It is defined alternatively as the process by which an article, surface or medium is freed of all microorganisms either in the vegetative or spore state.
2
DISINFECTION: It means the killing, removal of or destruction of organisms capable of causing infection namely pathogens. Disinfectant: Is an agent accomplishing disinfection. It is applicable to inanimate objects. Antiseptic: Closely linked to disinfection, it inhibits or destroys pathogens and is applicable to living tissues. Germicide means killing of germs. Bactericide means killing of bacteria while bacteriostatic mean reversible inhibition of bacteria growth without killing them. Sanitizers are agents, including detergents, used to maintain microbial levels at safe, acceptable levels. Asepsis is the absence of infections microorganisms in bony tissues i.e. absence of sepsis. It is a term applied to any techniques designed to keep all unwanted microorganisms out of any field of work or observation and involves a gamut of aspectic techniques. Gnoto biotics is asepsis at its zenith. Cross infection or cross contamination is the passage of microorganisms from one person to another via any route, direct or indirect.
3
Microbiostasis agents are substances or conditions that do not immediately kill microorganisms but inhibit them, so that after an initial decline, microbes die without significant multiplication.
HISTORY: Zaccharis Jannsen, in 1590 and Robert Hooks in 1660 opened the world of microbes to mankind by their inventions of monocarps. It was Anthony Van Leuwenhock who first described microorganisms (1667). It was Joseph Lister, between 1865-1891 who delineated the principles of wound infection and asepsis. Further process effort of Louis Pasteur added new direction to the field of sterilization. Input by various researchers like John Lyndall, Robert Koch etc. further accelerated the progress, when finally in the 1890’s the advent of stear sterilization, surgical modes, sterile gloves, gowns, drapes and sterile sponges engaged. The modern infection control recommendation and sterilization guidelines were stated by the CDC in 1973 and specific dental infection control guidelines and the ADA is 1878 revised in 1985, and 1988 also defined in 1986
by
CDCC
with
OSHA
(occupational
4
safety
and
health
administration). Comprehensive guidelines for infection control come into effect in Dec. 1991 and continually being ungraded to incorporate the mind numbering advancements in the field. Rationale for sterilization: The basic question among is why should we sterilize: The basic answer lies in the fact that we sterilize to minimize and eliminate the spread of infection and disease. In his classic demonstration in the 1970’s Crawford demonstrated the magnitude of the problem of cross contamination by supporting saliva as a red dye and demonstrating alarming results. Infections microbial agents can spread by direct contact, indirect contact via a contaminated surface or material, spattering of secretions and aerolization. A look here at the small list of microorganisms demonstrates how Herculean the task is and what risk dentists themselves face-as do their patients and auxillaries. Doesn’t look all that small does if. Also mention AIDS, hepatitis, TB, viral, bacterial etc.
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Thus infection control involves: 1. Reduction of pathogen concentration to allow normal host resistance mechanisms to prevent infection. 2. Break the cycle of infection and eliminate cross-infection. 3. treat every patient and instrument as potentially infections and therefore employ universal safety precautions and 4. protect patient and personnel from occupational infection. Utilization of proper sterilization, disinfectants and aseptic procedures helps to achieve the safety or profession demands. The preliminaries: So, beginning the holistic plan of infection control of which sterilization is a key ingredient, firstly comes the patient HEALTH EVALUATION: The beginning is made by performing the patient health evaluation. This is essentially a thorough and exhaustive medical examination and history evaluation, so as to be forewarned and forearmed towards any infectious risks. It helps in: 1. Detecting any unrecognized illness requires medical diagnosis and care.
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2. identifying infection or high risk that may be important to a clinical personnel exposed during examination, treatment or cleanup. 3. Assisting in managing and caring for infected patients. 4. reinforcing use of adequate infection control universal procedures bearing in mind that general history taking is not capable of detecting all infections. A complete examination of all organ systems and checklist of possible infections risks coupled with a knowledge of previous diseases all correlate towards a more effective sterilization regimen. Sir William Osler’s statement “Never treat a stranger� finds strong reinforcement in the field of aseptic dentistry. Personal protective equipment and barrier technique: These encompasses all those materials, protectives and techniques that comprise and aid in an aseptic technique.
Personal barrier protection OSHA (Occupational health and safely administration) have suggested basic areas for personal barrier protection. They are : 1. Hand washing. 2. Gloves
7
3. Gowns 4. Masks 5. Protective eye wear 6. Rubber dam 7. Pre procedural mouth rinse. Hand washing : Hands must always be washed at the start of each day before gloving, after removal of gloves and after touching inanimate objects likely to be contaminated by patients saliva or blood . Hand washing with plain soap and water appears to be adequate for routine examination and non surgical procedures. For surgical procedures an antimicrobial surgical hand scrub should be used. Hand washing procedure begins with a thorough initial scrubbing of all surfaces of the nails, fingers, hands and lower arms with an antimicrobial preparation. Drying should be done with a clean paper towel. All gross subnail contaminations should be removed. The scrub begins at the tip of one finger of one hand. The long axis of the finger is then divided into 4 surfaces and 30 scrub strokes are applied to each surface. After this the inter finger webbing is given 30 strokes. The length of the forearm is divided onto thirds and each of the four surfaces is scrubbed toward the elbow. After both arms are scrubbed the rinse should be done with elevated arms so that the H2O will drain from the fingertips down the hands, arms and finally the elbows. Gloves : Gloves are required in dentistry when the dentist has to come in contact with potentially infectious secretions or for contact with oral mucous membrane. Four types of gloves are identified for use in dentistry. i.
Sterile surgical gloves.
ii.
Non sterile latex gloves.
8
iii.
Vinyl examination gloves.
iv.
Utility gloves.
Surgical gloves : Best fitting and generally the most expensive disposable gloves is the sterile surgical glove. Used when maximum protection is indicated. They are made of high quality latex. Latex examination gloves : These are the most commonly used gloves in dentistry. Available in a variety of sizes designated as S,M,L. An occassional hyper sensitivity to latex has been reported. Inadequately drying the hands before gloving has proven to cause dermatitis. Vinyl examination gloves :Sometimes referred to as “Over gloves�. Used when an intra oral procedure is necessarily interrupted for a brief time. Following a washing and drying of the gloved hands, the over gloves can be slipped on over the regular examination gloves and removed when contact with the patient resumes. Heavy utility gloves : These are non disposable gloves. They should be worn when handling contaminated instruments, when using chemical sterilants and during general cleaning of the treatment area. These gloves can be washed, sterilized, disinfected and reused and are puncture resistant.
Protective clothing gowns Gowns, Aprons or lab coats must be worn when the skin or clothing is likely to come in contact with saliva or blood. They should be changed when visibly soiled. These garments should be limited to the dental office and not be worn out side.
9
Masks : Masks protect the face, oral mucosa and nasal mucosa of the dentist from splatter of blood or saliva from the use of high speed hand piece with water coolant. It also protects both the dentist and the patients from aerosol contamination by potential from the respiratory tract. Effective face masks are to have a minimum filtration of 95% of 3.5Âľm particles and the ability to block aerosols as well as larger particles of blood, saliva and oral debris. A good mask should have the following features. -
Fit comfortably.
-
Not leak out air
-
Fit around the entire periphery of the face.
-
Not irritate skin.
-
Provide breathability.
-
Not cause fogging of protective eyewear.
-
Not have an objectionable odour.
-
Not touch lips or nostrils. Face masks should be changed once per hour or between each
patient. The mask should not be touched because wet masks significantly decrease the filtration capacity. They are available in a variety of materials like paper, cloth, foam, fibre glass and other synthetic materials.
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Protective eye wear All dental personnel involved in treatment should wear protective eye wear in the form of glasses to prevent trauma to the eye tissue from flying droplets or aerosols. The eyes due to limited vascularity and lower immense abilities are susceptible to macroscopic and microscopic injury. Protective eye wear should be available to patients as well as dental personnel. The supine position renders the patient particularly vulnerable to falling objects in the head and neck area. Ultrasonics and high speed hand piece spray create potential pathogenic aerosols, droplets and spatters pieces of enamel, amalgam, gold and pumice can be flung and propelled from the oral cavity. All protective eyewear should be cleansed after every appointment. Eyewear be washed with soap first, then rinsed with water and an appropriate surface disinfectant can then be used. Rubber dam : The use of a rubber dam during certain dental procedures is advocated. The role of the dam in barrier technique is emerging as yet another means of controlling airborne contaminants. Rubber dam isolation has been shown to significantly reduce infectious particles in aerosols. Used in combination with a pre-operative rinse of chlorhexidine gluconate the risk of contamination can be further reduced.
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Pre procedural mouth rinse The use of antimicrobial mouth rinse prior to any operative procedure reduces the microorganisms that may escape a patients mouth during dental care through aerosols, spatters or direct contact. Examples of antiseptic mouth rinses are : a. Chlorhexidine, Alexidine from Bis-geranide class. b. Octenidine of Bis-pyridine class. c. Iodine, iodophors from halogen group. d. Peroxide, perborate of oxygenating agents. e. Phenol, Thymol from phenolic compounds. f. Hexitidine from pyrimidines. g. Benzethonium chloride from quaternary ammonium group. Although the antiseptic mouth rinses are effective in reducing the oral micro-organisms, they are bitter in taste and cause staining of teeth. Infection control consideration in the field of restorative dentistry and Endodontics The primary goal of infection control is to reduce the risk of cross contamination between patients and the dental professionals. The same general principles of infection control are applicable in the field of restorative dentistry and endodontics are discussed. The most accepted methods of sterilization can be classified as follows: A) Mechanical or physical; B) Chemical
12
A) Mechanical is further classified into: 1) Sunlight; 2) Drying, 3) Dry heat – this includes flaming, incarnation and hot air; 4) Moist heat includes pasteurization, boiling, steam under normal and high pressure, chemical vapors under pressure, tyndallization, 5) filtration including candles, asbestos pads, membranes; 6) Radiation’ 7) ultrasonic and sonic vibrations. B) Chemicals used in sterilization include alcohols, aldehydes, dyes, halogens, phenols, surface-active agents, metallic salts, and gases though many authors state that: Ethylene oxide is the only chemical considered as a sterilant while others are more often described as disinfectants. Under mechanical: 1. So first is sunlight – It possesses appreciable bactericidal activity and is responsible for spontaneous sterilization under natural conditions. It has limited clinical utility. 2. Drying : Moisture is essential for bacteria, drying therefore has a deleterious effect on most bacteria. Spontaneous drying can often kill bacteria while viruses are more resistant. However, the method
13
is highly unreliable, spores are unaffected by drying and can remain viable for long periods. 3. Next we come to heat: This is the most popular, widely used and reliable source of sterilization which is the technique of universal choice until contraindicated: Heat is the method recommended by OSHA, CDC and ADA it can be utilized in 2 form – moist and dry heat. A) Dry heat means the use of heat without any moisture content. It involves various forms namely: 1) Flaming: Innoculating loops or wires, points of forceps and searing spatulas are held in a Bunsen flame till they become red hot for sterilization. Scalpel, needles, mouth of culture tubes, glass slides, cover stips etc could be flame sterilized. 2) Incineration: This is an excellent method for rapidly destroying materials such as sealed dressings, animal corcases, bedding and pathological materials. Plastic like PVC and polythene can also be incinerated. Incinerated material should be carefully disposed off.
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3) Conventional dry heat hot air ovens: This is the more commonly used form of dry heat. Dry heat kills by proteins denaturation, oxidative damage and the toxic effect of elevated levels of electrolytes. Dry heat sterilization is readily achieved at temperature above 320°F (160°C). Conventional hot air ovens have heated chambers that allow air to circulate by gravity flow i.e. gravity connection. Packs of instrument must be placed at least 1cm apart and a 2 hour holding period at 160°C or/ how at 170°C is used with variations existing. A higher load increases the time factor. Glass were, forceps, scissors, swabs, pharmaceutical products can all be sterilized. The oven is usually heated by electricity with a blower to ensure even air distribution. Oil, glycerol, greases can be sterilized at 150°C for 1 hour while among rubbers only silicon rubbers can withstand high heat. Another innovation are the short cycle, high temperature dry heat ovens. A rapid high temperature process that was a forced draft oven (a mechanical connection oven with a fan or blow for air circulation) reduces sterilization time to 6 minutes for unwrapped and 12 minutes for wrapped instruments. These short cycle oven operate at 370-375°F (190°C). any type used must be properly calibrated and approved. The main precaution
15
is that the sterilization is done after the temperature reaches the required setting. The advantages includes effective and safe sterilization of metal instruments and errors with no corrosion of carbon steel instruments and burs. Rapid cycles can be used at high temperatures and cutting edges are not dulled through disrupted by Cuate and Loyle. Disadvantages include long cycles, poor penetration, damage to heat sensitive items. Heat labile items cant be sterilized by this method. Leverage for error is more due to sensitivity to load cycles, inaccurate calibration, heavy wrapping etc. Dry heat efficiency can be verified by proper strips impregnated with 10 6 nontoxigenic Clostridia tetani spores or Browne’s tube green spot test. Also external temperature gauges i.e. pyrometers and thermocouples can be used. 4) Next technology utilizing high heat are those operating on heat transfer devices. These are of special interest to the endodontist and general dental practitioner as they encompass the glass bead and salt media sterilizers. Glass beads, molten metal and salt are media often used. It essentially
16
consist of a metal cup in which table salt or glass beads are kept at a temperature between 425°F(218°C) and 475°F(246°C). A thermometer is used with the unit of temperature indication devices are not incorporated. At this temperature root canal instruments such as broaches, files and reamers may be sterilized in 55 and absorbent points and cotton pellets in 105. It does not affect the temperature of instruments in any way. The hot salt sterilizer has superseded the molten metal and glass bead sterilizer because metal or glass beads could accidentally cling to the instrument and get lodged in root canals, clogging them. Salt eliminates this risk and usual commercial table salt containing about 1% of sodium silica aluminate, magnesium carbonate or sodium carbonate to improve flow and decrease fusion is used. Salt should be changed weekly. Glass beads are often used and their size should be less than 1cm. The hottest part of this apparatus is along the outer rim at the bottom most layer and lowest in the center of the surface layer. Hence a minimum of ¼ inch insertion below the surface in the peripheral area is recommended by Oliet, Sonin, Engel hardt, Walter etc. a warm up time of 20 minutes ensures on firm temperature ranges. This device is indispensable in endodontic armamentarium sterilization. Going further, we now come to the most widely used form of heat sterilization – moist heat:
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The lethal effect is due to denaturation and coagulation of protein and its latent heat liberation. The various modalities are: 1) Temperature below 100°C. a) Pasteurization: Pasteurization of milk is done at 63°C for 30 minutes (hold method) or 72°C for 15-20s (flash process) followed by cooling to 13°C or laser vaccines are heat inactivated in special vaccine bath at 60°C for 1 hour. Serum or body fluids can be sterilized at 56°C for 1 hour for several successive days. Media such as LJ and Loeffler’s can be sterilized 80-85°C for ½ hour on 3 successive days is an inspirator. Many other sensitive instruments can be sterilized at temperatures below 100°C. 2) Temperatures at 100°C: a) Boiling – though highly unreliable as a sterilization technique and more effective for disinfection, it is a very often used. Boiling water in hot water sterilizes reaches 100°C and a time period of 10-30 minutes promotes sterilization. Sterilization may be promoted with addition of 2% sodium bicarbonate. Most vegetable bacteria are killed but sporing bacteria require longer periods. Advantages
18
include
rapidity,
economy,
no
elaborate
equipment,
good
penetration and hardness to wide range of dental materials. Serious disadvantage is that it dulls cutting edges and corrosion. b) Steam at atmospheric pressure (100°C) : An atmosphere of free steam is also used for sterilization. Koch or Arnold steamer or lab autoclaves can be used. Live or free steam containers are of a tinned copper cabinet with walls suitably lagged. The lid is conical, enabling drainage of condensed steam and a perforated tray fitted above the water level ensues material is surrounded by steam. A 90minute exposure is recommended media can be sterilized by this process. Steam is also used for frictional sterilization or tyndallization – John Tyndall devised a process of sterilization by steaming for a few minutes at 100°C on 3-4 successive occasions separated by 24 hour intervals at room temperatures. The principle is that the 1 st exposure kills all vegetative bacteria, spores will germinate and be killed on subsequent occasions. This may fail in case of anaerobes in thermophilas. 3) Temperatures above 100°C: a) Steam under pressure or compressed or saturated steam – saturated steam under pressure is the most effective and practical method of
19
sterilization and has been the standard method for many years. It is performed using the apparatus called Autoclave. In these devices the principle analyzed is that steam under pressure is hotter and the higher the pressure, the higher the temperature. It works basically as a pressure cooker. The autoclave basically has inlet valves for steam, pressure gauges, temperature regulator and indicators, listening down, safety, valves, and exhaust besides the main sterilization chamber. Rapid advances and changing specifications have characterized this device. It utilizes temperatures in the range of 108 to 147°C. The regular cycle is at 250°F(120°C) for 15 minutes at 15 pounds of pressures. Flash sterilization ca be achieved in 3-7 minutes at a temperature of 273°F(134°C) at 30 pounds of pressure. Autoclaves may be manual or automatic and come in various sizes and configuration. A majority of armamentarium can be sterilized by this method. Precaution should be exercised in case of fluid to allow slow subsiding of pressure to prevent boiling are or explosions. All terms for sterilization must be dry and correct instrument load should be used. It is preferable to give a “safe period” time-lag to allow thorough sterilization.
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The advantages include excellent penetration, short cycle time, relative ease of use, wide range of materials indicated and economy. The disadvantages are mainly corrosion and dulling of instruments along with contraindication of heat sensitive material or materials impression to moisture. The problem of common can be overcome by using ammonia, dicyclobenzyl ammonium nitrite or yelohezylamiad decylamine. 2% sodium nitrite is also effective. Biological monitoring of moist heat-sterilization is via spores of bacillus stereothermophilus and bacillus subtilis impregnated paper strips. Chemical indications, autoclave layers and thermocouples are also used. b) Next is unsaturated chemical vapor sterilization: This system depends on heat, water and chemical synergism for its efficacy and has the major advantage of greatly reducing corrosion of metal items processed through multiple cycles. The temperature and pressure required is greater than for an autoclave. Sterilization is performed in a chemiclave (chemiclaving). Instead of distilled water, a solution of alcohol, formaldehyde, ketone, acetone and water is used to produce the sterilizing vapor. After preheating, packaged wraps that allow condensation of chemical vapors are used. Chemicals operate at 270째F(131째C) and 20
21
pounds pressure with a cycle lie of 20-40 minutes. Medial instruments used must be dry prior to sterilization. The major advantages include a short cycle time, no rusting or corrosion, dry instruments at the end of the cycle and automatic preset cycle timing. Since it has 8-9% vapor content, much less than the 15% minimum for rusting and dulling, a myriad of items can be routinely sterilized without harm to their structural integrity. Adequate ventilation, however is important and permissible levels of formaldehyde should be monitored. Also the vaposterile solutions use should be inspected. Disadvantages include heat sensitivity of items, necessity of loading dry instruments, chemical odors and constant vigil in use. c) Also under the category come oil baths: Hot oil bath have been used to sterilize metallic instruments. Oil can reach a temperature of 175째C and an immersion time of 15 minutes complete sterilization, however a 1 hour period is recommended. Oil has disadvantages of poor sporicidal activity, being a fine hazard and being difficult to remove. Constant monitoring of all above methods is essential to ensure consistent sterility.
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4) Radiation – Radiation can be ionizing, non-ionizing and lasers: a) Ionizing energy are high energy electromagnetic waves including xrays gama rays, particulate radiations, cosmic rays and are highly lethal with high penetrative power. This is a cold sterilization with so heat involved. The lethal action is on DNA and indirectly through water. Though more used individually, medically they are used for hypodermic syringe sterilization. b) Non-ionizing radiation – this includes infrared and ultraviolet rays. Lethal effect is through generation of heat absorption and DNA damage. Penetration is low but efficacy is high. Infrared is used for rapid runs sterilization of syringes while UV is utilized for disinfections enclosed areas such as entry ways, hospital wards, operation theatres. c) Lasers – These are the latest cutting edge modalities in sterilization. Various types like CO2, Argon, Nd:YAG etc are used. Hoob and colleagues found that exposure of instruments for 35 to a laser beam is sufficient to sterilize. Further research and ongoing advances could bring this technique into popular use in the future. 5) Ultrasonic and sonic vibration- cells of all kinds can be disrupted by
intense
sonic
and
ultrasonic
23
vibrations
generated
by
magnetostrictive oscillation or piezoelectric crystals. Though credited with bactericidal powers, result are variable. The method have limited practical significance for sterilization but valuable in disinfections and instrument cleaning. 6) Freezing: Freezing can both kill- pressure depending on various factors. Super cooling to –106 –15°C freezes water in cells, cases formation of ice crystals and subsequent thawing is also disruptive to cell function. However, this is more often used for preservation of microbes than destruction. 7) Filtration – Filtration has been used since time immemorial in various forms. This is the method of choice for heat labile liquids and solutions. Various materials and media are available for filtration sterilization. They are also used to isolate specific involves for study and culture. The various types of filters are: 1. Candle filters – Manlated in different grades of porosity, they are widely used for water purilization for industrial and drinking purposes. These are of 2 types a) unglazed ceramics e.g. chamberland and doulton filters diatomaceous earth filters e.g. Berkfeld and Mendler filters.
24
2. Asbestos filters: Disposable, single use discs, they have high adsorbing capacity and tend to alkanise filtered liquids. Examples are Seitz, carbon and sterimat filters. 3. Sintered glass filters: Prepared by heat-fusing finely powdered glass particles of graded sizes. Pore sizes are not uniform. The passages larger than bacteria they remove. Their effectiveness depends largely on adsorption of bacteria. 4. Membrane filters : These are made of cellulose acetate or senile substance or esters. They are the most popular filters used in purification and analysis, sterilization and sterility testing and for preparation of solution for potential use. Common pare sizes are 0.22 to 10µ but filters are produced as small as 0.05µ. A 0.45µ size well prevent almost all nonvisual microbes while that 0.005µ can strain out even the smaller viruses. 5. More recent dislodgement is the nucleopore filter, a very thin 10µm poly carbonate film with etched holes and pare sizes of 0.1 to 0.8µ. High flow rates, low toxicity, chemical inertness and resistance to damage are its desirable characteristics.
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After the physical agents, we shall now see the chemical agents used in sterilization and disinfection. A wide range of chemicals exist in use and some of the desirable characteristics include wide spectrum of activity, high penetration and effectiveness, compatibility, noncorrosive, non-toxic, safety and economy. Firstly, 1) Ethylene oxide – this is considered, by many authors and agencies, as the only time chemical sterilant while the others are considered merely as disinfectant. Ethylene oxide is a gas at temperatures above 10.8°C, a highly toxic compound that destroys by alkylation. It is the best method for complex instrument and delicate materials. It is virucidal, sporicidal, does not damage materials and evaporates without residue. Commercial mixtures contain 12% ETO and 88% CFC or ETO and CO2 to reduce flammability. Different materials may require different cycles but 10-16 hours is the norm with variable time periods for degassing to prevent adverse effect with the gas. Items should be clean and dry and specially built autoclaves may be used. Concentration of 500mg of gas/ litre at 58°C and relative humidity of 40% reduce time to 4 hours. Varying these factors can increase the effectiveness manifold.
26
Advantages include high penetration, no damage to heat sensitive and complex devices, evaporation with no residue. Disadvantages are its slowness, toxicity, dry instrument to be used, flammability of material and degassing required. 2) Aldehydes – Glutaraldehyde and Formaldehydes: These are also considered acceptable sterilants. Formaldehyde is a highly irritating gas. It is a strong reducing agent and inactivates enzymes and amino groups of protein. For best results, a relative humidity of about 70% and temperature of 22°C are required. It has low penetrability and high toxicity, being markedly sporicidal bactericidal and virucidal. Used to pressure specimens and sterilize clean metal instruments. The gas is used for sterilizing instrument and heat sensitive catheters as wlel as fumigation. Ammonia vapor is used to counteract the irritant effect of their agent. Glutaraldehyde has a similar action to formaldehyde and are specifically active against tubercle bacilli, fungi and viruses. It is less toxic and irritant then formaldehyde. Commercial preparations are active at different pH and have percentage of 2.0 to 3.2%. They can destroy microbe in a 10 hour impression period. They have a surprising resistance to inactivation by organic matter and do not harm rubber and plastic hence being indicated for impression materials. They may corrode or dicolor metal if mixed. Their shelf life, use and reuse life should be noted. Their main
27
disadvantages are their toxicity and irritation and physical contact with these solutions should be avoided. 3) Beta-Propiolactone (BPL): This is a condensation product of ketone and formaldehyde with a boiling point of 163째C 0.2%. BPL is used for sterilization and is effective against all microbes and viruses. It act by alkylation. A relatively humidify of 70-80% at an temperature of 25째C with a final concentration of 2-4mg/L requires an sterilization time of 2-3 hours. It is more efficient then formaldehyde in fumigation but is carcinogenic too. It is also used to sterilize vaccines, graft tissues and other delicate biological material. Now we shall look at chemicals used exclusively as disinfectants and antiseptics: 1. Alcohols : Ethyl and isopropyl alcohol have been used traditionally. They were used mainly as skin antiseptics and act by denaturation bacterial proteins. They are not effective on spores. A concentration of 60-70% in water is used. Methyl alcohol is effective agent fungal spores is used in cabinets and incubators. Alcohol must have prolonged contact to be effective. Disadvantages include rapid
28
evaporation, dehydration, corrosion and ineffectiveness organic media. 2. Surface active agents: (Detergents) substances which alter energy relationship at interfaces producing a reduction of surface or interfacial tension are referred to as surface active agents. They are used as wetting agents, detergents and emulsifiers and are classified into 4 main groups namely anionic, cationic, nomionic and amphonic. The most important are the cationic surface active agent. They act on phosphate groups and denature proteins. Different groups are: a. Soaps – Active against spirochetes, streptococci, and other microbes. Used most commonly as hard wash agents due to surface tension reducers and detergents. b. Synthetic detergents – synthesized commercially, they are markedly microbicidal and are anions and used for humidies. c. Quaternary ammonium compounds – these are the cationic
surface
29
active
agents.
Benzalkonium
chloride is most commonly used. Primarily active agent gram positive bacteria and is well tolerated by tissues.
Cetyl
trimethyl
ammonium
bromide
(ceteferol) is another one used. However, they cannot penetrate organic debris, not sporicidal or virucidal. They are good cleansing agents and are used as such: d. The amphotonic or ampholytic compound known as Lego are active against a wide range of gram positive and negative organisms and viruses. They however, are not in general use. 3. Hexachlorophene
–
Used
for
surgrical
scrubs
and
preoperative preparation. Particularly effective against gram positive organisms. It has substantitivity action but is used sparingly now. 4. Dyes – 2 groups of dyes – aniline and acidine dyer are used extensively as skin and wound antiseptics. Aniline dyes are brilliant gram, malachite green and crystal violet. More effective against gram positive. They are non-irritant and non
30
toxic. The lethal effect is due to a reaction with acid group in the cell. Acridine dyes are more active against gram positive. Important ones are proflamie, acriflame, euflamie and aminamia. They impair DNA complexes and kill or destroy reproducitivity of the cell. Used in gauge impregnation. 5. Oxidants : Commonly used are hydrogen and metallic peroxidase. Hydrogen peroxide is frequently in treatment of anaerobic infection. Zinc peroxide is another variant. 6. Phenols and its derivatives: The classic antiseptic for surgical procedures was carbolic acid introduced by Joseph Listr in 1850s phenolic compounds have since arrived. They act as cytoplasmic poisons and have high penetration. The various types are: a. Phenol- Bactericidal at 1% and fungicidal at 1.3% it is seldom used now, but is the standard of comparison for other disinfectant. b. Hexyl resorcinol – used widely, specifically as a antihelanthic and in commercial mouth washes.
31
c. Cresols – Alkyl derivatives of phenol composed of ortho,
meta
and
para
cresol.
Here
greater
tuberculocidal activity and used for disinfection of floors and walls. d. Halogenated phenols – they are active germicides. Camphorated p-chlorphenol used as a root canal antiseptic. PCMX (Parachlorometaxylenol) is a halogen substituted phenol employed in hand wash antiseptics. It is bactericidal and fungicidal.. e. Bisphenols – Hexachlorophere and chlorhexidine have high bacteriostatic properties. Used as skin antiseptics, they demonstrate substantivitiy. They are not effective against tubercle birth. f. Complex synthesis phenols: These are constraints of 2 or 3 phenols acting synergistically to produce asepsis. g. Orthophenylphenol similar to hexachlorphores, used as irrigation solutions in surgical wounds.
32
7. Heavy metal compounds: All metal ions inhibit microbes in sufficient concentrations but a few are useful as antiseptics and disinfectants. Metals inhibit nonsporulating bacterias by oligodynamic actions. They have a high affinity for proteins especially the sulphydryl groups and gel readily absorbed. Asrenic compounds were the first areas used other include: a. Mercury
compounds: Mercury
bichloride
and
chloride are used as skin antiseptics mebromin is used as an antiseptic and various ointments. Mercury poisoning has discouraged their use. b. Silver compounds – simple silver salts like silver nitrate, silver lactate and pirate are used as antiseptics 1 to 2% solutions are used. c. Copper sulphate and zinc compounds like zinc sulphate are also used especially the latter in skin asepsis. 8. Chlorine and its compounds: The halogen chlorine precisely acts against microbial forms by oxidation, as hypochlorous acid. Elemental chlorine kills most bacteria in 15-30s at 0.1 to 0.25ppm. It has been used since 1774. commonly used
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compounds are hypochloride solution and chlorine dioxide preparations. Diluted sodium hypodiute (1:10) in water is very useful for disinfection especially for hepatitis virus, CDC has recommended 500-5000ppm. Being unstable, fresh solution should be prepared daily through same newer formulae have tried to offset this. Other dead stages include corrosion and irritative nature. 9. Iodine and iodophors: It is one of the oldest skin and wand halogen antiseptics. Its high reactivity gives it potent germicidal effects. It acts by iodination of proteins. Being insoluble in water, it is used as a tincture i.e. dissolved in alcohol. Drawbacks are irritation, allergenicity, corrosion and staining as well as hypersensitivity. Iodophors are preparations in which iodine is held in dissociable complexes and have a broad antimicrobial spectrum but are less irritating, non staining and have stained activity, common carries used are polyvinyl pyrolidine (PVP) and ethylated polyoxamers. These release iodine slowly as well as are surface acting agents improving penetrability. They are also used as skin antiseptics and hospital disinfectants in concentration of 200ppm. Solutions are unstable and should be diluted with distilled water. Common preparations are iodide and betadine.
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Monitoring of sterilization and disinfectants: An integral part of the sterilization process is its efficient monitoring. A periodic verification (at least weekly) should be integrated into the sterilization progress. Monitoring can be chemical and biological: Chemically treated tapes and other heat sensitive indications that change color generally inform the practitioner that sterilization conditions have been reached. However, these are not perfectly reliable as they change color much earlier too with autoclave tapes being notoriously unreliable. Heat sensitive indications consist of paper strips, labels and steam patterns cards impregnated with chemicals designed to change color on heat and / or chemical exposure. Chemical formulations may be sensitive to myriad factors like time, temperature and saturated steam simultaneously. Indications can detect gram process malfunctions quickly. Biological monitoring in the form of calibrated biological indicators remain the main guarantee of sterilization. These preparations contain bacterial spores more resistant to heat thus viruses and vegetative bacteria with color indicators. Bacillus stereothermophilus and subtilis are organisms often used. These provide must reliable sterilization monitors.
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Thus a combination of the 2 should be used for clinical needs. Evaluation of disinfectants – Disinfectants are usually strong, mild or weak and are evaluated by the phenol coefficient determination where phenol is the control, use dilution test, inactivation tests and specific filter testing for gaseous disinfectants are should follow guidelines and be regularly monitored. Now we come to the specific considerations and applied aspects in dentistry: Firstly, The dental chair and delivery system. The chair should be smooth and seamless. The greatest potential for cross contamination is from chair mounted controls. Disposable covers should be used as for as possible and should be lipid with any of the acceptable above described disinfectants between patients. The delivery system has a myriad panel susceptible to infection retention and spread. Control should be seamlessly integrated or can be remote controlled. Cart tops should be smooth and preferably separate. The entire unit should be covered with disposable covers where possible and disinfected and wiped between patients on exposed surfaces.
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Also included are the task seating surfaces and foot controls. The dental operators chair or stool should be of breakable materials or high quality sheepskin or vinyl plastics. They can be covered with disposable materials and disinfected between uses. Foot control too should be routinely disinfected with the may available agents described. Next come the X-ray unit – an integral part of all practices it is subject to heavy contamination. Single disposable plastic wraps minimize infection spread. Also disinfectants can be used on the surfaces. Film holders, bite blocks and the processing unit which are all subject to high contamination should be routinely disinfected and sanitized. Also, cabinets and work surfaces should be kept to a minimum and should be simple in design. Sinks should be stainless steel or porcelain with foot or electronic controls. Materials should be orderly assayed and all cabinets should be routinely wraped down to limit infection. Tubings and hoses including suction and delivery hose can harbor infection. All surfaces should be smooth and without crevices. Ideally they should be removed and sterilized. Suction systems should be routinely closed with water and disinfectant while hand piece and air water syringe tubings should be in enclosed retractions devices. Outer surfaces with the
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connector assembly should be washed with detergents and disinfected by immersion. After this we shall have a look at handpiece sterilization and asepsis. The handpiece is a delicate and highly specialized equipment that is literally an extension of the dentist’s personality and professional expertise proper speed, need size, chuck, hose and connector and handpiece lighting should be considered. Disposable handpieces are the ultimate in high teeth sterilization. Hand piece contamination is natural and multifaceted. It occurs by contamination of external surfaces, turbine chamber contamination, water and oral fluid retraction, water line contamination and spatter and aerosol generation. Hence handpieces should be thoroughly sterilized. External surfaces should be cleansed and after proper lubrication methods of sterilization like autoclaving or chemiclaving can be used for modern sterilizable handpieces while ethylene oxide and chemical sterilize are recommended for contraangles and non-heat sterilizable systems. Careful manufacturer institution
should
be
adhered
to
avoidable
chemicals
include
glutaraldehyde as they may dense the assembly and be subsequently toxic to tissues. Hand pieces should be storaged between patients and hence a
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through knowledge of them mechanics should go into their purchase. Common brands like KaVo, Midwest, Star etc use specified lubricants and can withstand autoclaving sterilization. Next come the water system asepsis – water line asepsis should be a factor considered in the clinic firstly water and oral fluid fraction should be avoided using antiretraction valves, repositioning of internal ‘O’ rings or upgrading versions. Periodic checks should be made secondly water lines should be cleansed for a minimum of 20-30s between patients and running disinfectants regularly through them microbial biofilm contamination of dental waterlines is a reality and can be limited by use of regular cleansing and disinfectants like iodophore or diluted sodium type chloride. Biocide solutions, filters, and dedicated water systems for infection control are recommended. Now lets see infection control for impression and related registration – different impression materials will withstand various disinfection procedures. Impression and related materials should be properly closed and treated with an appropriate disinfectant as shown. Prosthesis and appliances should also be disinfected and rinsed as should casts. Some properties (like increased hardness with glutaraldehyde) are actually improved. Dental laboratories whether in clinic or outside should also
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follow decontamination procedures hardly materials as biohazardous and using aseptic precautions in their processing. Lastly, a small look at recommended and available procedures for sterilizing and disinfecting specific dental armamentarium. Burs for e.g. can be autoclaved, dry heated, chemiclaved or chemically sterilized. Endodontic instruments sterilize well with salt / glass bead sterilizers. Plies, cements spatulas etc can be flamed. Metal instruments ca be autoclaved or dry heated or chemically sterilized. Glass slabs and dappen dishes may be chemically sterilized with thimerosal (merthiolate) while gutta percha can be sterilized with sodium hypochlorite impression can be disinfected with glutaraldehyde or other chemicals while claps and stones can be heat sterilized. Various other items are shown in the table. Also note, numerous items are recommended for disposable use in a single use and throw fashion. Disposable equipment should be used where practical and feasible. Also barrier methods and plastic or other disposable covers should be used for complex devices or straight surfaces like light are units to optimize infection control procedures. Remember when anything can be sterilized, do it. Another specific consideration is the universal precaution to be employed in treating known infection patients. Along with straight personal barrier protection, use of disposables and of artificially sterilized units should be
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mandatory. Special considerations should be made in use of HIV and hepatitis infected patients. Vaccination for hepatitis should be compulsory. Barrier techniques the double gloving etc should be used. Sharps should be ultra cautiously handled and disposable kits and armamentarium should be performed. Stringent sterile precautions are called for while dealing with known infectious cases so as to maintain absolute asepsis in the operatory and ensure protection to personnel and patients. CONCLUSION: “Prevention is better than cure�. A proverb so well suited to sterilization and asepsis. A thorough understanding and application of the intricacies of sterilization will help ensure safety from the invisible but deadly world of microbial pathosis and assist the practitioner in delivering holistic care with maximal efficiency ensuing happy and healthy patients, personnel and physicians themselves.
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