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STERILIZATION AND INFECTION CONTROL

PRESENTED BY : DR. KELLY NORTON

FIRST YEAR POST GRADUATE STUDENTDEPARTMENT OF PROSTHODONTICS

GUIDED BY :

DR. ARCHANA SHETTY

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CONTENTS Introduction Terminologies Classification of agents Details of individual agents Biological Controls Relevance of sterilization in Prosthodontics Introduction to infection and infection control Occupationally acquired infections Conclusion References Cross references

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DEFINITIONS

STERILIZATION - The process by which an article, surface or medium is freed of all living micro-organisms either in vegetative or spore state.

DISINFECTION- The destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection.

ANTISEPSIS- The prevention of infection, usually by inhibiting the growth of bacteria in wounds or tissues.

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DEFINITIONS

BACTERICIDAL AGENTS: Those which are able to kill bacteria.

BACTERIOSTATIC AGENTS: Only prevents the multiplication of bacteria which may however remain alive.

DECONTAMINATION: The process of rendering an article or area free of danger from contaminants, including microbial, chemical, radioactive and other hazards.

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METHODS OF STERILIZATION AND DISINFECTION

PHYSICAL METHODS

• SUNLIGHT• DRYING• DRY HEAT• MOIST HEAT• FILTRATION• RADIATION• ULTRASONIC AND SONIC

VIBRATIONS

CHEMICAL METHODS

• ALCOHOLS• ALDEHYDES• DYES• HALOGENS• PHENOLS• SURFACE-ACTIVE

AGENTS• METALLIC SALTS• GASES

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Sunlight:- Active germicidal effect due to the combined effect of U.V and heat rays. e.g.:- river, tanks & lakes.

Drying:- 4/5ths of weight of bacterial cell consist of water and hence drying has a deleterious effect on many bacteria.

Flaming:- Inoculating loops or wires, the tip of forceps & needles and spatulas are held in a bunsen flame till they become red hot in order to be sterilized.

Incineration :- Rapidly destroying materials such as soiled dressings, bedding, animal carcasses, pathological materials etc.

PHYSICAL AGENTS

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DRY HEAT

Principle- - Protein denaturation.

- Oxidative damage. - Toxic effects of elevated levels of electrolytes.

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HOT AIR OVEN:-

It’s the most widely used mode of sterilization

Temp.- 160°C ( 320° F ) for 1-2 hr.

Uses :- - Glasswares like glass syringes, petridishes, flasks, pipettes & test

tubes. - Surgical instruments like scalpels, scissors, forceps etc..

- Chemicals such as liquid paraffin, fats, greases, Sulphonamide, dusting powder etc..

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Precautions:-1) Not to be overloaded.2) Must be fitted with fans for even distribution of hot

air.3) Materials to be sterilized should be perfectly dry.4) Rubber materials (except silicone rubber) will not

withstand the temperature. 5) Allowed to cool for 2 hrs before opening the doors.

Advantage: Economical.

Does not rust metals

Easily monitored .

Used for anhydrous oils & powder.

Disadvantage :Hot air is bad conductor of heat hence it has less penetrating power

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Types of Moist Heat:

Temperature below 100°C – Pasteurization Holder method : 63°C for 30 mins.Flash process : 72°C for 20 sec…rapid cooling to 13°C.

Temperature at 100°C - BOILINGTemperatures - 90-1000C, 10 minsSporing bacteria require prolonged periods of boiling – 24hrs.Sterilization may be promoted by..2% Na bicarbonate.

Tyndallisation or intermittent sterilization:-- Used for media containing sugars or gelatin.-Exposure of 100 degrees for 20 minutes on three successive days.- First exposure kills all vegetative bacteria-Subsequent exposure will kill the spores present

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AUTOCLAVING (MOIST HEAT) STERILIZATION Boiling water alone is INSUFFICIENT to kill spores and viruses

water boils when its vapour pressure equals to that of surrounding atmosphere

Hence, when pressure increases inside closed vessel Temperature at which water boils increases

saturated steam has penetrative power

When steam comes in contact with a cooler surface it condenses to water and gives up latent heat to that surface

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AUTOCLAVE Three major factors for effective autoclave:1. Pressure: 15psi.2. Temperature: 121oC3. Time: 15 mins. Higher temperature and pressure require shorter time for

sterilisation.Pressure

(psi)

• 15• 20• 20

Temperature (°C)

• 121• 126• 134

Time (mins)

• 15• 10• 3

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WORKING OF AN AUTOCLAVE

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1. Ensure complete air removal for temperature to reach 121°C.

2. Ensure loose packing in the chamber.

3. Tightly sealed materials may

become dangerously pressurized causing injury when removed.

Considerations during autoclaving

USES:Disposable syringes, Non disposable syringes, Glassware, Metal instruments, surgical dressing, Surgical instruments, Laboratory equipment, Culture media, Pharmaceutical products.

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Advantage:-

Economical.

Good penetration.

Short cycle time.

Easily monitored

No special chemicals or

exhaust required.

Disadvantage:-

Moisture retention

Causes corrosion

Carbon steel gets damaged

Dulling of unprotected cutting

edges.Destruction of heat sensitive

materials.

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Method Temperature Holding time

Autoclave 1210C 15min 126 0C 10 min 134 0C 3 min

Hot air oven 1600C 45min 170 0C 18min 180 0C 7.5min

*Recommendations of the medical research council.

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Glass bead "sterilization" uses small glass beads (1.2-1.5 mm diameter) and high temperature (210 oC -230oC) for 10-30 seconds to inactivate microorganisms. 

Use- endodontic files, burs Disadvantage:- no uniform heat.

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FILTRATIONCandle Filter Asbestos Filter

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Sintered Glass Filters Membrane Filters

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RADIATION

1) Non-ionising radiation: Uses longer wavelength and lower energy. And hence lose the

ability to penetrate substances, and can only be used for sterilizing surfaces

Eg. infrared radiation is used for rapid mass sterilization of prepacked items eg. Syringes, catheters.

UV radiation is used for disinfecting enclosed areas like operation theaters, laboratories.

2) Ionising radiation: Uses short wavelength, high-intensity radiation with high

penetrative power to destroy microorganisms. This radiation can come in the form of gamma or X-rays that

react with DNA resulting in a damaged cell. Since there is no appreciable increase in the temperature, it is

also known as COLD STERILIZATION. Used for sterilizing plastics, swabs, metal foils etc.

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ULTRASONIC CLEANING More effective than manual cleaning. Removes dried serum, whole blood, plaque, zinc phosphate and

polycarboxylate cements from instruments, metal surfaces and dentures.

Minimizes handling of contaminated instruments. During cleaning, totally submerge instruments in the ultrasonic

solution for 2 to 20 minutes . Ultrasonic solution should be changed atleast once a day.

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BIOLOGICAL CONTROLS FOR DIFFERENT STERILIZATION METHODSMETHOD OF STERILIZATION BIOLOGICAL CONTROL

Hot Air Oven Bacillus subtilis subsp. NigerClostridium tetani

Autoclave Bacillus stearothermophilus

Filtration Serratia marcescens, Pseudomonas diminuta

Ionizing Radiation Bacillus pumilis

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• The CDC recommends that flash sterilization not be used routinely in the dental office to sterilize patient instruments—this process should only be used in unavoidable situations.

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CHEMICAL AGENTS

LIQUIDS GASES• Alcohols• Aldehydes• Phenols• Halogens• Heavy Metals• Surface Active Agents• Dyes

• Formaldehyde• Ethylene Oxide• Plasma

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MODE OF ACTION OF CHEMICAL AGENTS Protein coagulation

Disruption of the cell membrane

Removal of the free sulphydryl groups

Substrate competition

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ALCOHOL Mechanism of Action : Denaturation of Proteins Isopropyl alcohol 70% ethyl alcohol

Methyl alcohol is active against the fungal spores and used to treat cabinets and incubator

Suitable for skin preparation before venepuncture

Disadvantage : . Inflammable . Mucous membrane irritant.

. Promotes rusting.

Used as a skin disinfectant

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Aqueous soultion: Formalin(37% solution) - 10% formalin + 0.5% Na tetraborate used to clean metal instrument e.g. Endoscope, dialysis equipment.

Gaseous form: Fumigation of wards/corridors/ICU’sHave pungent odour & irritating effect on skin & mucous membrane.

ALDEHYDESA)Formaldehyde (formalin)In aqueous solution it acts as a bactericidal and sporicidalActive against Gram -ve bacteria, spores, viruses (HB, HIV) & fungi

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. GLUTARALDEHYDE / CIDEX ( 2% alkaline NaHCO3 ):-

High level disinfectant

Especially active against tubercle bacilli,fungi and viruses

Less toxic than formaldehyde

Can be safely used to treat corrugated rubber anaesthetic tubes, face masks, metal instruments.

Exposure time: > 10hrs.

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PHENOLS: Acts by cell membrane damage thus releasing cell contents and

causing lysis

Eg. Cresol ( LYSOL) ,chlorhexidine ( SAVLON),chloroxylenol (DETTOL) and hexachlorophene

Phenol is commonly found in mouthwashes, scrub soaps and surface disinfectants

Low efficiency disinfectant

Used for decontamination of the hospital environment, including laboratory surfaces, and noncritical medical items.

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HALOGENS :A) Chlorine compounds:

Bleaching powder or hypochlorite solution mostly used disinfectant for HIV infected material.

in concentration of 0.05 or 0.5% used for surface material and instruments disinfection

Should be prepared daily because of instability of sodium hypochlorite solution

Active against bacteria, spores, fungi and viruses (HB, HIV)

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IODOPHORS & IODINE Active against bacteria, spores & some viruses & fungi

Suitable for skin preparation, mouthwash & as a surgical scrub

(7.5% Povidone+iodine= Betadine)

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ETHYLENE OXIDE• Highly inflammable and in concentration more than 3% highly

explosive and hence not used for fumigation of rooms• Mix with carbon dioxide or nitrogen to eliminate its explosive tendency• Alkylation of Amino, carboxyl, hydroxyl and sulphydryl groups in

protein molecules• Effective against all types of micro-organism including viruses and spores.

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PLASMA Any gas which consists of electrons, ions or

neutral particles Used along with chemical disinfectant like

hydrogen peroxide alone or with peracetic acid

Eg. Sterrad 100 S sterilizer and plazlyte sterliser

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Sterrad 100 S sterilizer

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RECOMMENDED CONCENTRATIONSDISINFECTANT CONCENTRATI

ON

Ethyl Alcohol 70%Gluteraldehyde 2%Lysol 2.5%Savlon (chlorhexidine and cetrimide) 2%, 5%Dettol (chloroxylenol) 4%Bleaching powder (Calcium hypochlorite) 14 gm in 1 L

waterSodium hypocholorite 1%, 0.1%Betadine (Iodophore) 2%

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STERILISATION AND DISINFECTION IN PROSTHODONTICS

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CLASSIFICATION OF INSTRUMENTS

Critical instruments

Semi-criticalInstruments

Non-critical Instruments

Penetrate the soft tissue

Contact the bone Enter into or contact

the blood stream They should be

thoroughly cleaned and heat sterilized if they are to be reused.

Eg: Surgical instruments,Scalers, ScissorsSurgical dental

bursScalpel blades

Forceps

Contact the mucous membrane but will not penetrate the soft tissue

Eg : Mouth mirror, impression trays, handpieces, probe, tweezers

STERILIZATION OR HIGH LEVEL DISINFECTION must be done

Come into contact with intact skin

Eg : X-Ray tubes, Light handles, Counter tops

LOW LEVEL DISINFECTION

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IMPRESSION TRAYS

Metallic : Autoclave Plastic : Ethylene Oxide Custom tray made of

acrylic resin : Discard

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DISINFECTING IMPRESSIONS Methods

Spraying

Immersion Iodophors, sodium hypochlorite (1:10 concentration), chlorine

dioxide, phenols,formaldehyde,glutaraldehyde

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DISINFECTION OF ALGINATE IMPRESSIONS

0.5% sodium hypochlorite iodophors

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Immersion disinfection for prolonged periods will cause distortion due to imbibition

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AGAR- REVERSIBLE HYDROCOLLOID

Found to be stable when immersed in 1:10 dilution sodium hypochlorite

or 1:213 iodophor. Recommended immersion time is 10 minutes.

ZINC OXIDE EUGENOL Immersion in 2% glutaraldehyde Iodophors or Chlorine compounds. Adverse effect have been reported on ZOE immersed for 16 hours

in diluted hypochloriteIMPRESSION COMPOUND Immersion in 1:10 dilution sodium hypochlorite or iodophor for

specified time period.

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ELASTOMERIC IMPRESSION MATERIALS

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Polysulphide and Addition Silicone: Glutaraldehyde, Iodophor, 0.5% sodium hypochlorite should be

used

Polyether: Spray and wipe in iodophor, 0.5% Sodium hypochlorite should be used.

Prolonged immersion causes some distortion. Polyether shows dimensional changes on immersion in 2%

glutaraldehyde.

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An in vitro study to evaluate the effect on dimensional changes of elastomers during cold sterilization

24 specimens: Polyether, polyvinyl siloxane (PVS) (heavy body), PVS (regular body) and Hydrophilic addition reaction silicone (medium body) 2 disinfectants :2% glutaraldehyde and 0.525% sodium hypochlorite Result: PVS (heavy body) was most stable, and polyether was least stable of

all the impression materials.

Khinnavar PK, Dhanya Kumar B H, Nandeeshwar D B. An in vitro study to evaluate the effect on dimensional changes of elastomers during cold sterilization. J Indian Prosthodont Soc 2015;15:131-7

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OCCLUSAL RIMS AND WAX BITES

Wax rims and wax bites are disinfected using an iodophor, chlorine dioxide, or sodium hypochlorite spray and a "spray-wipe-spray" technique. Following the second spray, the wax bites can be enclosed in a sealed plastic bag for the proper contact time.

Immersion disinfection may cause distortion to some items

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DENTAL CASTS Spraying until wet or Immersing

in a 1:10 dilution of sodium hypochlorite or an iodophor then rinse

Casts to be disinfected should be fully set (i.e. stored for at least 24 hours)

Microwave irradiation of the casts for 5 minutes at 900 W gives high level disinfection of the gypsum casts .

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ADA recommends use of : Chlorine compounds Iodophors Combination of synthetic

phenols Glutaraldehyde.

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To evaluate the effectiveness of disinfecting solutions incorporated into dental stone casts against a standard and representative group of microorganisms and to note changes in the physical properties of the casts.

Irreversible hydrocolloid impressions were contaminated individually with Escherichia coli, Staphylococcus aureus, Candida albicans etc..

4 disinfecting solutions: glutaraldehyde, povidone-iodine, chlorhexidine and sodium hypochlorite were added to the die stone mix used to pour up the impressions.

The physical properties assessed were setting time, setting expansion, compressive strength, detail reproduction and delayed expansion of the stone.

RESULTS: 2% glutaraldehyde was the most effective disinfectant with the least adverse effects on the physical properties of the set cast

Povidone-iodine caused a decrease in the compressive strength of the set cast, but can be considered as an alternative.

Disinfection of dental stone casts: antimicrobial effects andphysical property alterations.

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ACRYLIC DENTURES

Sodium hypochlorite is recommended. Iodophors can also be used

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REMOVABLE CAST PARTIAL DENTURES

ADA recommendation : immersion in iodophor or chlorine compounds.

Damage of heat cured denture base resin has been shown to occur after only 10 minutes of immersion in glutaraldehyde.

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FIXED PROSTHESES

Immersion in glutaraldehyde OR dilute hypochlorite

A completely metallic prostheses can be sterilized with ethylene oxide or even by autoclaving

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ROTARY INSTRUMENTS - BURS Diamond and carbide burs: After use they are placed in 0.2% gluteraldehyde

and sodium phenate (Eg. Sporicidin) for at least 10 minutes, cleaned with a bur brush or in an ultrasonic bath. Sterilize in an autoclave or dry heat sterilize after cleaning.

Steel burs: May get damaged by autoclaving. Can be sterilized by using a chemical vapor sterilizer or glass bead sterilizer at 2300C for 20-30 seconds.

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INFLUENCE OF MICROWAVE STERILIZATION ON THE CUTTING CAPACITY OF CARBIDE BURS This study compares the cutting capacity of carbide burs sterilized with microwaves and

traditional sterilization methods. Sixty burs were divided into 5 groups according to the sterilization methods: dry heat (G1),

autoclave (G2), microwave irradiation (G3), glutaraldehyde (G4) or control – no sterilization (G5).

Conclusion: Sterilization by dry heat was the method that least affected the cutting capacity of the carbide burs and microwave sterilization was not better than traditional sterilization methods

Burs sterilized by chemical solution showed the lowest cutting capacity

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Handpiece All dental hand pieces should be heat/pressure

sterilizable and must be sterilized in between patient sessions.

Unit should be thoroughly scrubbed with soap and water to remove external contamination, all traces of water are removed prior to lubrication and sterilization.

Can be sterilized using autoclave, chemical vapour or uv radiations.

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Dental water unit line

Municipal Supply OR

WellsDental Unit

Multi – channel

Control Box

Hoses feeding various

attachments

Water entering the Dental Unit contains 0 -100 Colony Forming Units (CFU) per ml

Water leaving the handpiece may contain up to 100,000 CFU/ ml

ADA Guidelines : Not more than 200 CFU/ml

Flushing for 2 minutes in the morning and for 20–30 seconds between

patients should be considered the norm for dental surgery procedures to remove bacterial growth that may have accumulated

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IMPLANTS Pre sterilized with Gamma radiation In case the implants needs to be re-sterilized conventional

sterilization techniques are not satisfactory Steam sterilization should not be used as it results in

contamination of surfaces with organic substances Dry heat sterilization also leaves organic and inorganic surface

residue Radio frequency glow discharge technique (RFGDT) or Plasma

cleaning is used. In this, material to be cleaned is bombarded by high energetic

ions formed in gas plasma in a vacuum chamber. Removes both organic and inorganic contaminants.

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Waste Management Categories of bio-medical waste in india

Options Waste category

Category 1 Human anatomical waste(tissues ,organs,body parts)

Category 2 Animal wasteCategory 3 Microbiology and

biotechnology wasteCategory 4 Waste sharps

(needles,syringe,scalpels…)

Category 5 Discarded medicine and cytotoxic drugs

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Waste ManagementCategory 6 Solid waste(items contaminated with

blood and fluid including cotton dressing….)

Category 7 Solid waste (waste generated from disposable items )

Category 8 Liquid waste(waste generated from laboratory and washing cleaning …)

Category 9 Incineration ashCategory 10 Chemicals used in production of

biological, chemical used in disinfection

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COLOUR CODING AND WASTE DISPOSAL

COLOUR CONTAINER WASTE CATEGORY

TREATMENT OPTIONS

YELLOW Plastic bag 1, 2, 3, 6 Incineration OR deep burial

RED Plastic Bag 3,6,7 Autoclaving OR microwaving OR chemical treatment

BLUE / WHITE Puncture Proof container

4, 7 Autoclaving OR microwaving OR chemical treatment OR shredding

BLACK Plastic bag 5 ,9, 10 Disposal in secure landfill

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INFECTION AND INFECTION CONTROL

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BASIC CONCEPT OF INFECTION CONTROL

Prevent spread of infection from the Clinician to the patient

Prevent the spread of infection from the Patient to the Clinician

Prevent the spread of infection from one patient to another

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Patient

OperatorOther

personnel

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RECOMMENDATIONS FOR GLOVING

Wear gloves when contact with blood, saliva, and mucous membranes is possible

Remove gloves after patient care Wear a new pair of gloves for each patient Remove gloves that are torn, cut or

punctured Do not wash, disinfect or sterilize gloves

for reuse

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Hegde et al in their study stated that the bar soap

under the "in use" condition is a reservoir of microorganisms and washing hands with such a soap may lead to spread of infection. (Microbial contamination of "in use" bar soaps in dental clinics. Indian J Dent Res 2006;17:70-3)

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FACE MASKS Protects face and eyes from contaminated

splatter and inhalation of contaminated aerosols It is essential when choosing a face mask to note

that; It has a bacterial filtration efficiency of 95% or

more. Does not contact nostrils or lips. It has both high filtration of small particles and

tolerable breathability. Close fit around entire periphery. Does not cause fogging of eye glasses.Facemasks should be changed once every

hour or between each patient contact, whichever occurs first.

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OCCUPATIONALLY ACQUIRED INFECTIONS

HIV : 0.3%

Hepatitis C : 1.8%

Hepatitis B (HBeAg +ve) : 30%

Occupational exposures that may result in HIV, HBV, or HCV transmission include needlestick and other sharps injuries; direct inoculation of virus into cutaneous scratches, skin lesions, abrasions, or burns; and inoculation of virus onto mucosal surfaces of the eyes, nose, or mouth through accidental splashes

All health care professionals should be immunized against Hepatitis A, Hepatitis B, Varicella, MMR, DPT, Rubeola, Meningitis, Polio, Influenza, Tetanus, Diptheria, Rubella.

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Post exposure prophylaxis-HIV Wound care: Clean wounds with soap and water Flush mucous membrane with water. No evidence of benefit for: – application of antiseptics or

disinfectants – squeezing puncture sites

Chemoprophylaxis Initiating occupational 4 week regimen of PEP as soon as

possible, ideally within 2 hours of exposure. HIV- antibody testing should be performed for atleast 6 months

post exposure

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CONCLUSION A steady increase in the serious transmissible diseases over

the last few decades have created a global concern and impacted the treatment mode of all health care practitioners.

Emphasis has now expanded to assuring and demonstrating to patients that they are well protected from risks of infectious disease.

The dental health care provider has to follow high standards of infection control for the safety of the patients and the dental health care workers

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References

Textbook of Microbiology, 7th edition – Ananthanarayan and Paniker Textbook of Microbiology – C.P. Baveja Infection Control in Dental Practice – S. Anil, L.P. Samaranayake, Georges

Krygier Essentials of Preventive and Community dentistry, 4th Edition - Soben

Peter

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Cross References Infection control in prosthodontics rachuri narendra kumar , karthik K S ,

sudhakara V maller JIADS VOL -1 issue 2 april - june,2010 |22 An in vitro study to evaluate the effect on dimensional changes of elastomers

during cold sterilization.Khinnavar pk, dhanya kumar b h, nandeeshwar d b. J indian prosthodont soc 2015;15:131-7

Efficacy of various disinfectants on dental impression materials the internet journal of dental science 2009, volume 9 number 1, sukhija et al

Guidelines for infection control in dental health-care settings – 2003 Risk and management of blood-borne infections in health care worker Clin

microbiol rev. 2000 jul; 13(3): 385–407 Influence of microwave sterilization on the cutting capacity of carbide burs J

appl oral sci. 2009;17(6):584-9

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