Infection control in the dental clinic

Infection control in the dental clinic

By Mohammed Saad

As a matter of fact, the dentist, dental assistant, dental hygienist and dental technician are at risk of exposure to disease agents through contact with blood or other potentially infectious materials. So by studying and by carefully following the infection control and safety guidelines, all the team work can minimize the risks of disease transmission to himself and to the patients in the dental office.All practitioners should incorporate recommended CDC , ADA and OSHA infection control guidelines into their daily practice .

CHAIN OF INFECTION All links must be connected for infection to take place

Pathogen

Source

ModeEntry

Susceptible Host(sufficient virulence & adequate numbers)

(allows pathogen to survive & multiply)

(of transmissionfrom source to host)(portal that the

pathogen can enter the host)

(i.e., one that is not immune)

Definitions:CDC:Center of Disease Control and Prevention .ADA:American Dental Association.ADAA:American Dental Assistants Association.OSHA:Occupational Safety and Health Administration.OSAP:Organization for Safety and Asepsis Procedures.EPA: Environmental Protection Agency.FDA : Food and Drug Administration.NIOSH:National Institute for Occupational Safety and Health.

Why , Who and what Why is infection control necessary in dentistry ?Dental staff and patients may be exposed to a wide variety of pathogenic microorganisms .Who is responsible for infection control in the dental office ?Each member of the dental team must follow the recommended guidelines .What should be done to prevent the transmission of disease in the dental office ?The most effective ways to prevent the transmission of diseases includes : 1) Hand washing2) Gloves3) Face masks4) Protective eye wear5) protective clothing 6) instrument sterilization and disinfection

Diseases Transmission in Dental OfficeThe dental office should have an infection control program to prevent the transmission of disease from the following :Patient to dental teamDental team to patientPatient to patientDental office to community ( include dental team’s family )Community to dental office to patient To prevent such infections, following is a list of all those procedures and precautions that together constitute infection control. These guidelines should be followed each time treatment is performed because we are never certain of the patient's status, either because they themselves do not know or because they have chosen not to inform their healthcare providers of their condition. Following these guidelines for every patient is called "Standard Precautions".

Diseases Transmission in Dental Office

1. IMMUNIZATION2. PATIENT SCREENING3. HAND WASHING4. BARRIER TECHNIQUES -• Personal Protective Equipment (PPE)• Rubber dam, Pre-procedural rinsing6. INSTRUMENT STERILIZATION AND DISINFECTION5. NEEDLE & SHARP INSTRUMENT SAFETY• Occupational Exposure To Blood/Body Fluids7. SURFACE DISINFECTION8. radiographic asepsis9. laboratory asepsis10. infectious dental waste management & disposal

Standard Precautions

Direct contact with blood or body fluids Indirect contact with a contaminated

instrument or surface Contact of mucosa of the eyes, nose, or

mouth with droplets or spatter Inhalation of airborne microorganisms

Modes of Diseases Transmission

• It is the period of protective equipment : An essential pretreatment procedure is the preparation of all personnel involved in patient care. This includes the utilization of personal protective equipment (gown, eyewear, mask and gloves) and hand hygiene.

A) Infection Control during the Pretreatment Period

Infection Control During the Pretreatment PeriodThe process of infection control begins during the period of preparation for clinical treatment. Paying attention to infection control at this time has several payoffs. In addition to reducing the risk of transmission of infectious agents during patient care, thinking ahead will make the treatment session more efficient and will also make the post treatment infection control process easier and more effective.1. Remove unnecessary items from the dental procedure area :

The dental procedure area should be arranged to facilitate a thorough cleaning following each patient.

2. Preplan the materials needed during treatment. Set out all instruments, medications, impression materials,

and other items that are needed for a procedure. Thinking ahead minimizes the need to search for additional items or to enter cabinets and drawers once gloves have become contaminated.

3. Utilize disposable items whenever possible :The use of disposable items saves time during cleanup and decontamination and solves the problem of proper reprocessing.4. Use prearranged tray set-ups for routine or frequently performed procedures.Helps to eliminate the need to go into cabinets once you have started a procedure.5. Use individualized, sterilized bur blocks for each procedure. Using individualized bur blocks containing only the burs required for that procedure helps to eliminate the contamination of other, unneeded burs and to make clean-up easier.

6. If indicated, have the rubber dam setup on the tray.When a rubber dam will be used during a clinical procedure, it also should be included on the tray setup. In addition, include those items needed for high-velocity evacuation.

7. Identify those items that will become contaminated during treatment.While preparing the dental procedure area prior to beginning a clinical procedure, consider which items will become contaminated during treatment. Examples of such surfaces include countertops, light handles, X-ray unit heads, tray tables etc. Decide whether to use a barrier, e.g., plastic wrap to prevent contamination of these surfaces and items or to disinfect them when the procedure is complete.8. Review patient records before initiating treatment and place radiographs on the view box.Do not leave the record on the countertop or handle it after beginning treatment. Place the record in a drawer or out of the dental procedure area, so that it doesn’t become contaminated. Entries into the record should be done before and after the procedure.

9. Prepare personnel involved in patient care.An essential pretreatment procedure is the preparation of all personnel involved in patient care. This includes the utilization of personal protective equipment (gown, eyewear, mask and gloves) and hand hygiene.

A .Handwashing and hand care :According to the U.S. Centers for Disease Control (CDC) , hand washing is the single most important procedure for preventing the spread of infection. So , you must wash your hands each time before you put on gloves and immediately after you remove gloves . Handwashing is also required if you touch contaminated instruments or surfaces during working .We should always use liquid soap during handwashing . Bar soap should never be used because it may transmit contamination .

Hands Need to be Cleaned When

Visibly dirty After touching contaminated objects with bare hands

Before and after patient treatment (before glove placement and after glove removal)

Personal protective equipment ( PPE ) OSHA requires the employer to provide employees with appropriate personal protective equipment . Examples of PPE : 1- Protective clothing 2- Surgical masks 3- Face shields 4- Protective eyewear 5- Disposable patient treatment gloves , and 6- Heavy-duty utility gloves .

These PPE must be used whenever you :• Performing tasks that could produce splash or spatter .• Any contact with body fluids• Perform other clinical activities that require handling contaminated items e.g. radiographs , impressions , dentures or contaminated equipment and surfaces .

We will study 4 aspects of each one of these equipments : • The purpose of using .• Types .• Guidelines for the use .• Requirements .

1) Protective clothing : Purpose : to protect the skin and underclothing from the exposure to saliva , blood , aerosol , and other contaminated materials . Types

1) Laboratory coats

2) Gown

3) Surgical scrubs

Guidelines for the use of protective clothing 1) It should not be worn out of the office for any reason .2) Change these work clothes at least daily, or more often if soiled, especially if they become visibly contaminated with blood.3) It must not be worn during eating or in resting rooms .4) It should be washed and laundered separately . Protective clothing requirements :1) Should be made of fluid-resistant material ( cotton , cotton/polyester, or disposable jackets or gowns .2) Clothing should have long sleeves and a high neckline to minimize the amount of uncovered skin .3) Must cover dental personnel at least to the knees when seated

2) Protective masks :Purpose the mask worn over the nose and mouth to protect the person from inhaling infectious organisms spread by the aerosol spray of the handpiece or air-water syringe . Types the two most common types of masks are the dome-shaped and flat types .

The dome-shaped Flat types

Guidelines for the use of protective masks :• Masks should be changed for every patient or more often, particularly if heavy spatter is generated during the treatment or if the mask becomes damp.•Masks should be handled by touching only the side edges to avoid contact with the more heavily contaminated body of the mask.•Masks should conform to the shape of the face .•Masks should not contact the mouth when being worn because the moisture generated will decrease the mask filtration efficiency .Requirements : masks should be at least with 95% filtration efficiency to remove particles 3 – 5 microns in diameter .

3) Protective eyewear :Purpose eyewear is worn to protect the eyes against damage from : • Aerosolized pathogens .• Flying sharp debris such as scrap amalgam and tooth fragments .• Splattered solutions• Caustic chemicalsGuidelines for the use of protective eyewear :1) OSHA requires the use of eyewear with both front and side protection ( solid side shields ) .2) Members who wear correction glasses or contact lenses must wear protective eyewear with a side shields or a face shield .

3) It must be cleaned and decontaminated after each treatment or patient visit according to the manufacture’s instructions .Types :Two types of protective eyewear used during patient care :1) Glasses with protective side shield , and2) Clear face shields .

Face shields : a chin-length plastic face shield that protects your eyes, nose, and mouth from spatter may be worn and replace the protective eyewear .However , a shield cannot replace the mask because it does not protect against inhalation of contaminated aerosol

Face shield worn in addition to the mask

Patient eyewear :Patients should be provided with protective eyewear because they may subjected to eye damage from : 1) Handpiece spatter 2) Splashed dental materials 3) Airborne bits of acrylic or tooth fragments

4) Gloves : Purpose :Gloves must be worn by the dentist , dental assistant , and dental hygienist during all dental treatment to avoid contact with the patient’s blood , saliva , or mucous membranes or with contaminated items or surfaces .Types :The type of gloves used in dental practice should be determined by the various procedures that are performed in the practice as follow :1) Examination gloves usually are latex or vinyl . These are the gloves most frequently worn by the dental team during patient care .

Examination gloves are inexpensive , available in a range of sizes from extra small to extra large , and are ambidextrous ( used for both right and left hands ) . These gloves are nonsterile and serve only as a protective barrier for the wearer .

Examination gloves

2) Overgloves are made of lightweight , inexpensive , clear plastic . Overgloves may be worn over contaminated treatment gloves ( overgloving ) to prevent contamination of clean objects ( telephone , pen ,opening drawers and cabinets ) that may be handled during treatment . Overgloves are discarded after a single use .

To prevent contamination , an Overgloves is worn while using a pen .

3) Sterile surgical gloves are used during surgical procedures such as oral surgery or periodontal treatment . Sterile surgical gloves are supplied in specific sizes and prepackaged unites to maintain sterility before use .

Sterile surgical gloves

4) Utility gloves are made from a puncture-resistant , heavy material which are not used for direct patient care . Utility gloves may be washed , disinfected , or sterilized and reused and must be discarded when they become old .

Guidelines for the use of gloves :• All gloves used in patient care must be discarded after a single use.• Torn or damaged gloves must be replaced immediately .• Do not wear jewelry under gloves because , it may tear the gloves .• If the procedure is long , change the gloves each hour .• Contaminated gloves should be removed before leaving the chair side during patient car.• Hands must be washed after glove removal and dried well before regloving .

5) Non-latex containing gloves occasionally , the health care providers or patients may experience serious allergic reactions to latex . The person who is sensitive to latex can substitute with gloves made from vinyl , nitrile and other non-latex containing materials .

Hand dermatitis that developed from wearing latex gloves.

B) Infection Control during the treatment Period(Chairside Infection Control ) :

1) Use care when receiving, handling, or passing sharp instruments.

2) Take special precautions with syringes and needles.3) Use a rubber dam whenever possible.

The infection control procedures described in the previous period will help you to reduce the risk of transmission of infectious agents. During treatment there are additional precautions that can be taken to further reduce infection risks.

4) Avoid touching unprotected switches, handles and other equipment once gloves have been contaminated.5) Avoid entering cabinets once gloves have been contaminated.

After patient treatment , dental unite and treatment room surfaces are likely to become contaminated with saliva or by aerosol containing blood . Also a primary source of cross-contamination occurs when a member of the dental team touches surfaces with contaminated gloves .The laboratory studies have proved that microorganisms may survive on environmental surfaces for long time . For example, Mycobacterium tuberculosis may survive for weeks .

c) Infection Control during the Post-Treatment Period

Dental treatment room surfaces :Dental treatment room surfaces are classified as either : • Clinical contact surfaces or• General housekeeping surfaces . Clinical contact surfaces are those that are touched by contaminated hands , instruments or by spatter during treatment . It should be cleaned and disinfected between patients .All the other surfaces , such as the walls and floors , are considered general housekeeping surfaces

Clinical contact surfaces :The clinical surfaces can be classified into three categories :

A) Touch surfaces : are directly touched and contaminated during treatment procedures . Touch surfaces include ;Dental light handles Dental unite controls andChair switches

B) Transfer surfaces : are touched by contaminated instruments such as

instruments trays .

C) Splash , spatter , and droplet surfaces : countertops are a major example .

Touch and transfer surfaces should be either barrier-protected or cleaned and disinfected between patients . In the same time , splash , spatter , and droplet surfaces should be cleaned at least once daily .

Dealing with surface contamination The goal of the two methods to deal with surface contamination are : 1- To prevent the surface from becoming contaminated by the use of a surface barrier . 2- To preclean and disinfect the surfaces between Patients .Each method has advantages and disadvantages , and most dental offices use a combination of surface disinfection and surface barriers .

Surface barriers :Surface barriers are used to prevent contamination on the surface underneath .All the surface barriers should be resistant to fluids in order to prevent microorganisms in saliva , blood , and other liquids from soaking through the barrier and reach the surface underneath .

Chair Drapes

Film Dispenser

Some plastic bags are specially designed to the shapes of the dental chair , air-water syringe , and light handles .

Sticky tape as a plastic barrier is frequently used to protect smooth surfaces , such as electrical switches on chairs and x- ray unite

1. Continue to wear personal protective equipment during clean-up: After patient care is completed, begin the cleaning and disinfection process by removing contaminated gloves used during treatment, wash your hands and use the utility gloves before beginning the clean up. Continue to wear protective eyewear, mask, and gown.

2. Remove all disposable barriers : All of the barriers placed before treatment, including light handle covers and countertop barriers, should be removed.

3. Clean and disinfect all items not protected by barriers.

Infection Control During the Post-Treatment Period

Cleaning and disinfection of the dental treatment room surfaces are important components in an effective infection control program . Precleaning Precleaning means that all contaminated surfaces must be precleaned before they can be disinfected . Precleaning reduces the number of microbes and remove blood , saliva , and other body fluids .Precleaning techniques are most effective when used on contaminated surfaces that are smooth and easily accessible for cleaning .

Materials used for precleaning regular soap and water always used for precleaning . However , a disinfectants that can cleans as well as disinfect are present today .DisinfectionDisinfection is directed to kill disease-causing microorganisms that remain on the surface after precleaning .

N.B always do not confuse disinfection with sterilization . Sterilization is the process in which all forms of life organisms are destroyed .The term disinfectant is used for chemicals that are applied for cleaning surfaces , such as countertops and dental equipment .

Disinfectants Disinfectants are chemicals that destroy or inactivate most species of pathogenic ( disease-causing ) micro-organisms . In dentistry , only those products that registered with the U.S Environmental protection Agency ( EPA ) with tuberculocidal action should be used to disinfect dental treatment areas .

Ideal surface disinfectant The ideal surface disinfectant must be rabidly kills a broad spectrum of bacteria , has residual activity , minimal toxicity , odorless , inexpensive and does not damage surfaces to be treated .

Disinfectant such as :Iodophors :• Iodophors are EPA-registered hospital disinfectants with tuberculocidal action . • It is recommended for disinfecting surfaces after dental treatment .• Iodophors are usually effective within 5 to 10 minutes .• Non-irritant and non-toxic .• Unstable solution → must be changed regularly .• Because they contain iodine , iodophors may corrode or discolor certain metals and temporarily may cause red or yellow stains on clothing and other surfaces .

Synthetic phenol compounds :• Are EPA-registered intermediate-level hospital disinfectants with broad-spectrum activity ( can kill a wide rang of microbes ) that used for surface disinfection .• Phenol can be used on metal , glass , rubber , or plastic .• They also may be used as a holding solution for instruments , however , phenols leave a residual film on treated surfaces . • Synthetic phenol compounds must be prepared daily .• Non irritant , non-toxic and non-corrosive .

Sodium hypochlorite :Sodium hypochlorite is a fast-acting , economic and broad-spectrum intermediate-level disinfectant .Disinfectant effect observed after 10 minutes .The Centers for Disease Control and prevention ( CDC ) currently recommended the use of up to 1 – 100 dilution of sodium hypochlorite for surface decontamination .The disadvantages → • Unstable solution need daily preparation .• It has a strong and unpleasant odor .• Irritant for skin and eyes .• Corrosive for some metals . hypochlorite is destructive to fabrics and may eventually cause plastic chair covers to crack .

Alcohol : Ethyl alcohol and isopropyl alcohol have been used over the years as skin antiseptics and surface disinfectants . However , alcohol are not effective in the presence of blood and saliva droplets because of the rapid rate of evaporation will limits the antimicrobial activity of alcohol . In addition , alcohols are damaging to certain materials , such as plastics and vinyl . The American Dental Association ( ADA ) , CDC , and OSAP do not recommend alcohol as an environmental surface disinfectant .

Chlorine dioxide :Chlorine dioxide can be used as an effective , rapid-acting , environmental surface disinfectant ( 3 minutes ) or as a chemical sterilant ( 6 hours ) . The disadvantages → (1) it must be prepared fresh daily . (2) it is corrosive to aluminum containers

Classification of instruments and equipment :

According to the Centers for Disease Control and Prevention, dental instruments are classified into three categories depending on the risk of transmitting infection.

1) Critical instruments are those used to penetrate soft tissue or bone and should be sterilized after each use. Sterilization is achieved by steam under pressure (autoclaving), dry heat, or heat/chemical vapor . Critical instruments include forceps, scalpels, bone chisels, scalars, and burs .

2) Semicritical instruments are those that do not penetrate soft tissues or bone but contact oral tissues, such as amalgam condensers, air/water syringe , tips mirrors, intraoral radiography accessories, digital radiography sensors, and other dental high-technology instruments . These devices should also be sterilized after each use. In some cases, however, high-level disinfection is appropriate. A high-level disinfectant is registered with the U.S. Environmental Protection Agency (EPA) as a "sterilant/disinfectant" and must be labeled as such.

3) Noncritical instruments are those that come into contact only with intact skin

such as external components of X-ray heads. Such devices have a relatively low risk of transmitting infection and, therefore, may be reprocessed between patients by intermediate-level or low-level disinfection.

Managing contaminated sharps :Contaminated needles and other disposable sharps , such as scalpel blades , orthodontic wires , and broken glass must be placed into a sharps container .OSHA , CDC and the EPA classify sharps as infectious waste . According to OSHA regulations , disposable sharps must be placed in a puncture resistant , closable , and color-coded or labeled with the biohazard symbol container immediately after use .

Biohazard symbol

Proper processing of contaminated dental instruments in a six-steps process as :1) Transport : transport contaminated instruments to the processing area .2) Cleaning : clean instruments with a hand-free , mechanical process such as an ultrasonic cleaner or instrument washer.3) Packing : warp/package instruments in appropriate materials containing an external process indicator . 4) Sterilization : place the packages in a single layers or in racks to increase circulation of the sterilizing agentaround the instruments . Operate the sterilizer according to the manufacture’s instructions . Allow packages to cool before removing them from the sterilizer .

5) Storage: Store instruments in a clean , dry environment in a manner that maintains the integrity of the package . Rotate packages so that those with the oldest sterilization date will be used first .6) Delivery : deliver packages to point of use in a manner that maintains sterility of the instruments until they are used . Inspect each package for damage .

Holding solution : If the instruments can't be cleaned immediately after procedures, they should be placed in a holding solution to prevent drying of blood and debris on the instruments . A holding solution is a liquid disinfectant/sterilizing solution used to soak contaminated instruments before they are cleaned and sterilized. It has the purpose to:• Decrease infectious microbes on instruments .• Loosen and minimize debris before scrubbing or ultrasonic cleaning .• Minimize the physical handling of the instruments .

The holding solution must be:Non-corrosive liquid, Of low cost,Non-staining andReadily available.

The holding solution should be changed at least twice daily It is important to use a covered container with a separate instrument basket to ensure complete immersion.Remember , a holding solution is necessary only when contaminated instruments cannot be processed immediately .

The holding solution

Precleaning and packaging instrumentsPrecleaning is done in three ways:- Hand scrubbing- Ultrasonic cleaning-Instrument washing machine

Hand scrubbing This method is unfavorable because it requires direct hand contact with the contaminated instrument and accidental injury from these contaminated items may happen.During hand scrubbing we must follow the following precautions 1- Wear eye wear and puncture-resistant gloves (P.P.E ) .1- Clean only one by one .2- Use only a long-handled brush .3- Do not immerse items in soapy water or deep basin so you can see the sharp edges.

Ultra-sonic cleaning• Ultrasonic cleaning is recommended in place of hand-scrubbing in order to reduce direct staff contact with contaminated instruments. • The ultrasonic cleaner works by producing sound waves which causes formation of bubbles in liquid . The bubbles are too small to be seen .• The mechanical cleaning action of the bubbles combined with the chemical action of the ultrasonic solution removes the debris from the instruments . • Instruments should be processed in the ultrasonic cleaner until they are visibly clean . The time may vary from 5 to 15 minutes .

Automated washerIt looks similar to a household dishwasher. It uses a combination of very hot water together with a detergent to remove the organic material. It is considered as disinfector because it subjects the instruments to a level of heat that kills most vegetative microorganisms.

Packaging instrumentsBefore sterilization the instruments must be packaged to protect them from becoming contaminated after sterilization .They can be contaminated by aerosols in the air , dust , or contact with nonsterile surfaces .An additional advantage to packaging instruments is that

they can be grouped into special setups.

Sterilization monitoring Sterilization monitoring Because sterilization failure can occur at any time, it is critical to determine that dental instruments are properly sterilized or not because microorganisms can not be seen by naked eye.

Nowadays, three forms for sterilization monitoring are used:

 PHYSICAL CHEMICAL BIOLOGICAL

Physical monitoring:Physical monitoring of the sterilization process involves looking at the gauges and readings on the sterilizer and recording the temperatures, pressure, and exposure time. Remember that the temperature recorded is for the chamber, not the inside of the pack. Therefore, problems with overloading or improper packaging would not be detected from the reading on the gauges.

Chemical monitoring:Chemical monitoring involves the use of heat-sensitive chemicals that change color when exposed to certain

conditions .The two types of chemical indicators are process

indicators and process integrators.

Process indicatorsThis is used externally outside the instruments packages like autoclave tape and color change marking. Its aim is to determine if the package is processed or not. They simply identify instrument packs that have been exposed to a certain temperature.

They do not measure the duration or the pressure. They are useful only in distinguishing between packages that were processed and those that were not processed. This can prevent accidental use of unprocessed instruments.

Process integratorsProcess integrators are placed inside instrument packages. They respond to a combination of pressure, temperature, and time. All sterilization factors are integrated. Examples of pro cess integrators include strips, tabs, or tubes of colored liquid.

Biologic monitoringThis is the best way to determine if sterilization has

occurred .Biologic monitoring , or spore testing, is the only way to determine if sterilization has occurred. The CDC, American Dental Association recommend at least weekly biologic

monitoring of sterilization equipment. Biologic indicators (BIs), also known as spore tests, are vials or strips of paper that contain harmless bacterial

spores (spores are highly resistant to heat). Method:

Three BIs are used in testing. Two BIs are placed inside instrument packs, and the sterilizer is operated under

normal conditions .

The third strip is set aside as a control. After the load has been sterilized, all BIs are cultured. If the spores survive the sterilization cycle (a positive culture), a sterilization failure has occurred. If the spores are killed (a negative culture), the sterilization cycle was successful.

Sterilization in the dental office :

The three most common forms of heat sterilization in the dental office are :

Steam sterilization, Chemical vapor sterilization, and Dry heat sterilization.

1) Steam sterilization : involves heating water to generate steam, producing a moist heat that rapidly kills microorganisms. As the steam completely fills the sterilizing chamber, the cooler air is pushed out of an escape valve, which then closes and allows the pressure to increase which increase the temperature reaches up to 120 C which is higher than boiling water . It is the heat, not the pressure that actually kills the microorganisms.

A disadvantage of steam sterilization is that the moisture may cause corrosion on some high-carbon steel instruments. Distilled water should be used in autoclaves instead of tap water, which often contains minerals and impurities. Distilled water can minimize corrosion and pitting. 0peration cycles :Dental office steam sterilizers usually operate through four cycles :1) heat-up cycle 2) sterilizing cycle 3) depressurization cycle 4) drying cycle

Flash Sterilization involves sterilizing unpackaged instruments using short exposure times. The instruments are placed in the chamber unwrapped. The sterility of the instruments is defeated immediately when the instruments are removed from the sterilizer. Flash sterilization should be used only for instruments that are to be used promptly on removal from the sterilizer.

Dry-heat Sterilizers Dry-heat sterilizers operate by heating air and transferring that heat from the air to the instruments. This form of sterilization requires higher temperatures than steam or chemical vapor sterilization . temperature ranges between (160 C to 190 C) .The total cycle time : placing instruments in oven, heating to 170 C, timing for 1 hour, and then cooling it from 2–2.5 hours . The advantage of dry heat is that the instruments will not rust if they are thoroughly dry before they are placed in the sterilizer. The disadvantage of dry heat is the risk of damaging plastic and rubber instruments and also it need long time .

Chemical liquid sterilization Used for some types of plastics items that can damaged by heat such as some rubber dam frames , shade guides , and x-ray film-holding devices .A liquid sterilizer such as 2% to 3.4% Glutaraldehyde must be used for sterilizing these items .Sterilizing in Glutaraldehyde requires a 10 hours contact time, but if it is less than 10 hours, it is only disinfection, not sterilization .Glutaraldehyde must be used full strength ( not diluted ( This material is highly toxic .

STERILIZATION FAILURE 

Several factors can cause the sterilization process to fail. Examples of common mistakes include :• overloading of sterilizer chamber . • lack of separation between packs or trays in the chamber .• wrong packaging material for method of sterilization . • more than two layers of wrap, inhibiting penetration . • sterilizer timer malfunction . • improper cleaning of items to be sterilized.

Sterilization of hand pieces is recommended whenever possible : Hand pieces that are designed for steam sterilization between uses are preferred. When a hand piece cannot be heat or steam sterilized, chemical disinfection can be used as an alternative.

The End