My Seminar

VISHNU DENTAL COLLEGE

DEPARTMENT OF PROSTHODONTICS AND IMPLANTOLOGY

SEMINAR ON “STERILIZATION AND DISINFECTION IN PROSTHODONTICS”

PRESENTED BY – GUDURI VINEETH

STERILIZATION AND DISINFECTION IN PROSTHODONTICS

CONTENTS:

• Introduction

• Definitions

• Classification

• Methods of sterilization

• Categories of disinfectants

• Measures of asepsis

• Disposal of waste

• Prosthetic point of view

• Disinfection in prosthodontics

• Laboratory measures

• Standardized guidelines and regulations

• Conclusion

• References

INTRODUCTION:

• Prosthodontists are exposed to a wide variety of microorganisms in the blood and

saliva of the patients whom they treat.

• These microorganisms may cause infectious diseases by means of the impressions,

instruments and other appliances used for the fabrication of a prosthesis.

• The use of proper sterilization and effective disinfection procedures and

recommended precautions in the dental office and the dental laboratory will

prevent cross contamination that could extend to dentists, dental office staff, dental

technicians and patients.

The concept of asepsis and its role in the prevention of infection was put forward

nearly two centuries ago. The general principles for asepsis were laid down by Hungarian

obstetrician, Ignaz Semmelweiss in Europe in early 1850’s and Oliver Holmes in USA.

These principles were accepted after Joseph Lister’s studies on prevention of wound

infection carried out in-between 1865-91. Lister, working on antisepsis, initially used

phenol (dilute carbolic acid) for contaminated wounds, later applied it in all surgical

wounds, also in operating room by nebulization of the solution. Further developments

occurred with the introduction of steam sterilization surgical masks, sterile gloves, sterile

gowns and drapes etc.

In present days certain guidelines and regulations are recommended by accepted

bodies, which have to be followed in dental practice and up graded in every general body

meeting. Guidelines are given by American Dental Association (ADA), Centers for

Disease Control (CDC) and British Dental Association advisory service to name few and

regulations by Environmental Protection Agency (EPA), Occupational Safety and Health

Administration (OSHA) and Health and Safety at Work act 1974

DEFINITIONS:

Sterilization: It is a process by which articles are freed of all

microorganisms both in vegetative or spore state. (or)

The process of completely eliminating microbial viability. (GPT 8)

Disinfection: It is a process, which reduces the number of viable

microorganisms to an acceptable level, but may not in activate some viruses

and bacterial spores.

Asepsis: It is the avoidance of pathogenic organisms from coming in contact

with the wound and other sites and ensuring that only sterile objects and

fluids come into contact.

Sterile Technique: A standard surgical technique in which an aseptic area is

established and maintained, including proper sterilization of instruments,

drapes, gowns, gloves, and the surgical area. With respect to dental implant

placement, the systematic maintenance of asepsis with special emphasis on

non-contamination of instruments and implant elements throughout an

implant placement procedure. (GPT 8)

CDC Dental Guidelines For Sterilization Instruments -As with other medical

and surgical instruments, dental instruments are classified into three categories -

critical, semi critical, or no critical - depending on their risk of transmitting

infection and the need to sterilize them between uses.

CLASSIFICATION:

Each dental practice should classify all instruments as follows: As per May 28,

1993

Critical: Surgical and other instruments used to penetrate soft tissue or bones are

classified as critical and should be sterilized after each use. These devices include

forceps, scalpels, bone chisels, scalers, and burs etc.

Semi critical: Instruments such as mirrors and amalgam condensers that do not

penetrate soft tissues or bone but contact oral tissues are classified as semi critical.

These devices should be sterilized after each use. If, however, sterilization is not

feasible because the instrument will be damaged by heat, the instrument should

receive, at a minimum, high-level disinfection.

Non critical: Instruments or medical devices such as external components of x-ray

heads that come into contact only with intact skin are classified as non critical.

Because these non critical surfaces have a relatively low risk of transmitting

infection, they may be reprocessed between patients with intermediate-level(if

blood is visible on the item) or low-level disinfection (if no blood is visible on the

item) or detergent and water washing, depending on the nature of the surface and

the degree and nature of the contamination .

CLASSIFICATION OF METHODS OF STERILIZATION:

A. PHYSICAL

1. Sun Light

2. Drying

3. Heat

i. Dry

ii. Moist

2. Filtration

3. Gas

4. Irradiation

5. Ultra sonic cleaning

6. Oil

B. CHEMICAL

1. Phenol Derivatives : Phenol, Cresol, resorcinol, chloroxylenol

2. Oxidizing agents : Pot. Permanganate, Hydrogen Peroxide, Benzoyl

Peroxide

3. Halogens : Iodine, chlorine

4. Biguanide : Chlorhexidine

5. Quarternary Ammonium (Cationic) : Cetrimide, Zephiran

6. Soaps : of Sodium & Potassium

7. Alcohols : Ethanol, Isopropanol.

8. Aldehydes : Formaldehyde, Glutaraldehyde

9. Acids : Boric acid, acetic acid

10.Metallic salts: Silver Nitrate, Zinc Sulfate, Zinc Oxide, calamine,

Ammoniated mercury.

11.Dyes : Gentian violet, proflamine, Acriflamine

12.Furan derivatives : Nitro flurazone

PHYSICAL METHODS-

1. Sunlight: Most old & still effective. It possesses appreciable bactericidal

activity. The action is due to ultra violet rays. This is one of the natural

methods of sterilization in case of water in tanks, rivers and lakes.

2. Drying: It has deleterious effect on many bacteria. Spores are unaffected

by drying. Hence it is very unreliable method.

3. Heat: Is the most common and one of the most effective methods of

sterilization. Factors influencing sterilization by heat are : -

i. Nature of heat

a. Dry

b. Moist

ii. Temperature & time

iii. No of organisms present

iv. Whether organism has sparing capacity

v. Type of material from which organism is to be eradicated

A. DRY HEAT

Killing is due to:

1. Protein denaturation

2. Toxic effects of elevated levels of electrolytes

a. Red Heat: It is used to sterilize metallic objects by holding them in flame till

they are red hot. Ex: inoculating wires, needles, forceps etc.

b. Flaming: The article is passed over flame without allowing it to become red

hot. Ex: Glass plates, Cotton wool plays and glass slides.

c. Hot Air Oven: It is used to sterilize items, which do not get damaged by high

temperature such as laboratory glass ware, flasks, scissors, impression trays

(metal), and all stainless steel instruments with sharp cutting edges, (preferred)

B.P. handles, Dapen dishes, mouth mirrors and poles. Hot air is poor conductor of

heat and poor penetrating capacity. So grease, oils, powders plastics, rubber-

containing substances should be sterilized by other methods. High temperature can

damage fabrics or melt them.

Temp. & Time: The sterilization is complete if these two factors are achieved

throughout the load.

Temp. Time (Min.)

160oC 320oF - 120/60

170oC 340oF - 60

150oC 300oF - 150

140oC 280oF - 180

Precautions

1. The heat should be uniformly distributed in side the oven.

2. All the instruments must be clean of dry prior to wrapping.

3. It should not be over loaded.

4. Oven must be allowed to cool for about 2 hours before opening other

wire glass will crack.

Sterilization Control of Hot Air Oven

1. Detectors as spores of non-pathogenous strains of clostridium tetani are used

to test dry heat efficiency.

2. Browne’s tube (green spot) is available for checking sterilization by dry

heat. A green color is produced after 60 min. at 160oC.

3. Thermocouples may be used.

GLASS BEADS STERILIZER:

This method employs a heat transfer device. The media used are glass

beads, molten metal and salt. The temperature achieved is of 220oC. The method

employs submersion of small instruments such as endodontic files and burs, into

the beads; and are sterilized in 10 seconds provided they are clean. A warm-up

time of at least 20 minutes is recommended to ensure uniform temperatures in

these sterilizers.

Some hand piece can be sterilized by dry heat. The hand pieces should be

carefully cleaned and lubricated with special heat resistant oils.

B. MOIST HEAT:

It is effective by denaturation and coagulation of proteins.

a. Temperature below 100oC.

i. Pasteurization – milk by Hold Method and Flash Method.

ii. Vaccine bath – for vaccines

iii. Inspissation

b. Temperature at 100oC

i. Tyndallization

ii. Boiling

iii. Steam Baths

c. Temperature above 100oC

AUTOCLAVE

These are three major factors required for effective autoclave; Pressure,

temperature and Time.

i. Pressure: It is expressed in pressure (Pounds) per square inch and it is 15-

PSI pressure.

ii. Temperature: To achieve required pressure, the temperature must be

reached and maintained at 121oC with the increase in temperature and

pressure super heated steam is formed and removed Air from chamber and

this brings about sterilization.

iii. Time: Wrapped loads require a minimum of 20 min. after reaching full

temperature and time cycle, a wide variety of materials can be sterilized by

this method.

Example: Diagnostic and prognostic Instruments, plastic filling Instrument,

impression trays, laboratory equipments, surgical instruments etc. Higher

temperature and greater pressure shorter the time required for sterilization.

Pressure Temperature Time (Min.)

15 psi 121oC 15

20 psi 126oC 10

20 psi 134oC 3

Time required to sterilize for a particular item also varies with the amount of

material for the thickness of the wrap.

WRAPPING INSTRUMENTS FOR AUTOCLAVING

Instruments must be clean, but not necessarily dry. Closed (non-perforated)

containers (closed metal trays, capped glass vials) and aluminium foils cannot be

used, because they prevent the steam from reaching the inner sections of the packs.

Cassettes, drums, trays with opening on all sides may be used.

Packaging used for autoclaving must be porous, to permit steam to penetrate

through; and reach the instruments. The materials used for packaging could be

fabric or sealed biofilm/paper pouches, nylon tubing, sterilization wrap, and paper

wrapped cassettes. The bag or wrap is heat sealed or sealed with tape. The

indicators for testing the completion of the autoclaving are as follows-

- Thermocouple

- Brown’s test

- Autoclave tape

- Spores of a non pathogenic organisms

STORAGE OF STERILE GOODS

The pattern of storage varies from place to place. They are either stored in

drawers, or in containers, in packs or sterilized trays. The maintenance of sterility

during transportation and storage is of utmost importance.

Packs should be stored with the following considerations

i. Instruments are kept wrapped until ready for use.

ii. To reduce the risk of contamination, sterile packs must be handled as

little as possible.

iii. Sterilized packs should be allowed to cool before storage; otherwise

condensation will occur inside the packs.

iv. To prevent contamination from rodents, ants, and cockroaches, the store

must be subjected to adequate pest control.

v. Materials should be stored at least 8” off the floor and 18” from the

ceiling.

vi. Sterile packs must be stored and issued in correct date order. The packs,

preferably, are stored in drums which can be locked. Preset trays and

cassettes, are useful as, the instruments can be organized as per the

procedure.

6. IRRADIATION

Radiation used for sterilization is of two types-

i. Ionizing radiation, e.g., X-rays, gamma rays, and high speed electrons

and

ii. Non-ionizing radiation, e.g. ultraviolet light, and infrared light. These

forms of radiation can be used to kill or inactivate microorganisms.

Ionizing Radiation:

It is effective for heat labile items. Bellamy (1959) reported that it has great

penetrating properties. It is commonly used by the industry to sterilize disposable

materials such as needles, syringes and swabs.

The lethal action of this radiation is believed to be due to its effect on the

DNA of nucleus and on the other vital cell components. There is no appreciable

rise in temperature. High energy gamma rays from cobalt-60 are used to sterilize

such articles.

Non-ionizing radiation:

Two types of non-ionizing radiations are used for sterilization:-

Ultraviolet

It is absorbed by proteins and nucleic acids and kills microorganisms by the

chemical reactions it sets up in the bacterial cell. It has low penetrating capacity

and its main application is purification of air in operating rooms; viz, to reduce the

bacteria in air, water and on the contaminated surfaces. All forms of bacteria and

viruses are vulnerable to ultraviolet rays below 3000 atmospheric pressure.

Excessive exposure of skin can produce serious burns. Care must be taken to

protect the eyes while using U-V radiation for sterilization.

Infrared

It is another form of dry heat sterilization. It is most commonly used to

purify air, such as in the operating room. Infrared is effective, however, it has no

penetrating ability.

7. ULTRASONIC CLEANING

Several studies have shown that, when performed correctly, ultrasonic cleaning

will remove dried serum, whole blood, plaque, zinc phosphate cement, and

polycarboxylate cement from instruments, metal surfaces and dentures. It has been

found to be more effective than manual cleaning.

Ultrasonic cleaning minimizes the handling of contaminated instruments by

the nurse and reduces the chance of injuries from sharp, contaminated instruments.

Instruments are loaded into a metal basket, which is then placed into the

ultrasonic bath. The unit is activated for the time recommended by the

manufacturer (usually about 6 minutes). Instruments, which are contained in

cassettes, are cleaned for 12 minutes.

After the cleaning cycle is complete, the basket is taken to the sink and the

instruments are carefully and thoroughly rinsed under tap water. The instruments

are checked for residual debris, which may be safely removed manually.

Instruments are taken to the packaging area, where they are unloaded from the

baskets onto a thick disposable paper towel. The instruments are thoroughly ‘pat’

dried using strong paper towels. Drying is important.

Small rotary and Endodontic instruments should be held in beakers of

ultrasonic cleaning solution which are suspended in the cleaning bath.

ULTRASONIC CLEANERS AND SOLUTIONS

The Clinical Research Associates (CRA) recommended the following ultrasonic

cleaners:

BIOSONIC – Whaledent

T3C – Health Sonics Group

CLOSTER 3 – Provides ultrasonic clean, rinse and dry, but is noisy

PROCEDURE

Ensure bath is 3/4 full as per manufacturer's instructions.

Ensure lid is well fitting to avoid creating aerosols.

Instruments should always be placed in a basket within the bath to ensure

that they are kept a proper distance from the bottom of the bath. Burs should

be placed in the beakers provided.

Never overload the basket. Overloading the basket with instruments causes

'wave shadows' - inactive zones within the bath.

Choose cycles as per manufacturer's instructions. Currently the counter top

ultrasonic baths in use operate at <400 C. At this temperature a cycle of 15

minutes is recommended. Alkazyme is currently considered an appropriate

solution to use in this manner. (If the throughput is very large and

instruments are heavily contaminated it is currently recommended to change

the solution twice daily after the morning and evening sessions

respectively).

On removal of instruments rinse thoroughly (in basket) under running water,

inspect for any residual cement etc., dry and pack.

Notes

a. Ultrasonic units should be tested on a regular basis. Place a piece of tinfoil

in the solution and run the unit. If the foil shows uniform pitting after 5

minutes this indicates that the submerged items received adequate ultrasonic

cleaning during the cycle. No holes or an uneven pattern may indicate that

the machine is not functioning properly.

b. Every new solution must be 'degassed' by running the ultrasonic bath free of

instruments for 15 minutes.

c. Ultrasonic cleaning is not suitable for hand pieces.

d. Amalgam carriers should not be placed in the ultrasonic bath

8. OIL

Hot oils baths have been used for sterilization of metallic instruments. At a

temperature of 1750C, submersion for 15 minutes is required for sterilization. The

disadvantages of using oil include; poor penetration, poor sporicidal activity,

presents a fire hazard, and is difficult to remove from instruments such as hand

pieces without recontamination. It should not be used for hypodermic syringes or

needles because of the danger of oil embolization.

CHEMICAL METHODS-

They are used to disinfect the skin of a patient prior to surgery, and to

disinfect the hands of the operator. No available chemical solution will sterilize

instruments immersed in it. Secondly, there is a risk of producing tissue damage if

residual solution is carried over into the wound while it is being used. The

chemicals used are

ALDEHYDE COMPOUNDS

i. Aqueous solution of Formaldehyde (formalin) and

ii. Glutaraldehyde (cidex) is effective disinfectants.

i. Formaldehyde: This is a broad-spectrum antimicrobial agent, which is used

for disinfection. It is a hazardous substance, inflammable and irritant to the eye,

skin and respiratory tract. This is used up to 500C and has limited sporicidal

activity. It is used for large heat-sensitive equipment such as ventilators and

suction pumps excluding rubber and some plastics.

ii. Glutaraldehyde: It is toxic, irritant and allergenic. It is a high level disinfectant.

It is applicable where heat cannot be used. It is active against most vegetative

bacteria (including M. Tuberculosis) and some viruses (including HIV and HBV),

fungi and bacterial spores. It is frequently used for heat sensitive material. A

solution of 2 percent glutaraldehyde (Cidex), requires immersion of 20 minutes for

disinfection; and 6 to 10 hours of immersion for sterilization. Stonehill et al (1963)

reported that glutaraldehyde kills vegetative bacteria, spores, fungi and virus by

alkylation on a 10-hour contact. The Centre for Disease Control includes it in the

list of effective agents against hepatitis viruses. It is also toxic and irritating, and

hence, not used on certain surfaces such as furniture, walls and floors. It can be

safely used on metal instruments (for less than 24 hours), rubber, plastics and

porcelain. It is activated by addition of sodium bicarbonate, but in its activated

form in remains potent only for 14 days

ALCOHOLS

Ethanol and isopropyl alcohols are frequently used as antiseptic. Alcohols

possess some antibacterial activity, against some Gram-positive and negative

bacteria, and especially against M tuberculosis. Alcohols act by denaturing

proteins. They are not effective against spores and viruses.

The alcohol must have a 10 minute contact with the organisms. Solutions of

70 percent alcohol are more effective than higher concentrations, as the presence of

water speeds up the process of protein denaturation as reported by Lawrence and

Block (1968). The alcohols do not function as disinfectants when instruments,

hand pieces, or other equipment are simply wiped with them, since they

evaporate quickly. Alcohols can dissolve cements holding instruments together,

and plastics may harden and swell in their presence.

They are frequently used for skin antisepsis prior to needle puncture. They

are good organic solvents. Their benefit is derived primarily in their cleansing

action. The alcohols must have a prolonged contact with the organisms to have an

antibacterial effect. This contact is prevented due to its rapid evaporation. Alcohol

is sometimes used as a rinse following a surgical scrub. Its effectiveness lies in

the solvent action and not in its antibacterial properties. Ethanol (Ethyl alcohol) is

employed in the concentration of 70 percent as a skin antiseptic. It has poor

activity against bacterial spores, fungi, and viruses. It is used in the concentration

of 60 to 70 percent v/v, for disinfection of skin. The alcohols do not have reliable

sporicidal, virucidal, or fungicidal action; hence, they are not useful for sterilizing

surgical instruments.

PHENOLIC COMPOUNDS

Phenol is itself toxic to skin and bone marrow. The phenolic compounds

were developed to reduce their side effects but are still toxic to living tissues.

These compounds, in high concentration, are protoplasmic poison, and act by

precipitating the proteins and destroy the cell wall.

Lawrence and Block (1968) reported that their spectrum of activity

includes lipophilic viruses, fungi and bacteria but not spores. Hence these are

approved by ADA for use as surface or immersion disinfectant. These compounds

are used for disinfection of in animate objects such as walls, floors and furniture.

They may cause damage to some plastics, and they do not corrode certain metals,

such as brass, aluminium and carbon steel.

AQUEOUS QUARTERNARY AMMONIUM COMPOUNDS

Benzalkonium chloride (Zephiran) is the most commonly used antiseptic.

Its spectrum of activity is primarily Gram-positive bacteria. It is well tolerated by

living tissues. It is not widely used because of its narrow spectrum of activity.

IODOPHOR COMPOUNDS

Many studies have shown, that, iodophor compounds are the most effective

antiseptics,. Iodine is complexed with organic surface-active agents, such as,

polyvinylpyrrolidone (Betadine, Isodine). Their activity is dependent on the

release of iodine from the complex. The surface agent is film forming; this

prevents the solution form staining clothes or skin.

These compounds are effective against most bacteria, spores, viruses, and

fungi. These are the most commonly used surface disinfectants along with

hypochlorite. Concentrated solutions have less free iodine. Iodine is released as

the solution is diluted. An appropriate dilution is 1 : 2 : 3 parts of iodophor and

distilled water, respectively.

Advantages :

1. Low toxicity.

2. Prolonged residual effect

3. Inexpensive and

4. Odorless.

Geraci (1963) reported that these compounds build up on the skin after successive

scrubs, and that this provides long lasting antibacterial activity.

Categories Of Disinfecting / Sterilizing Chemicals

Category Definition Example UseSterilizing chemicals

High level disinfectant

Destroys all microorganisms including high number of bacterial spores.

Destroys vegetative bacteria, mycobacterium, fungi

Alcohols, Aldehydes, HalogensPhenols, Surface active agents, Metallic salts, Gases

Hydrogen peroxide, Gluteraldehyde, Formaldehyde,

Heat sensitive reusable items immersion only.

Heat sensitive reusable items immersion only.

Intermediate level disinfectant

Low level disinfectant

and enveloped (lipid) and non-enveloped (non lipid) viruses, but not necessarily bacterial spores

Kills vegetative bacteria, most viruses and most fungi but not resistant bacterial spores

Kills most vegetative bacteria and some fungi as well as enveloped (lipid) viruses (e.g., hepatitis B, C, hantavirus, and HIV)

Ortho-phthalaldehyde (OPA)and Peracetic acid etc.

Alcohols, Hypochlorites and Iodine and Iodophor disinfectants

Phenolic compounds and Quaternary ammonium compounds

Chemical catnaps non-critical surface with visible blood

Housekeeping surface floors without visible blood contact

ASEPSIS IN DENTISTRY: BARRIER TECHNIQUES -

GLOVES

Gloves must be worn when skin contact with body fluids or mucous

membrane is anticipated or when touching items or surface that may be

contaminated with these fluids. After contact with each patient, gloves must be

removed; hands must be washed and then regloved before treating another patient.

Repeated use of a single pair of gloves to disinfectant or other chemicals

often cause defects in gloves, there by diminishing their values as effective barrier.

Latex or vinyl gloves should be used for patient examination and procedure.

Heavy rubber gloves also called utilizing gloves should preferably be used for

cleaning instruments and environmental surfaces. Dentist show allergic reaction to

latex gloves can use nylon glove liners under latex rubber or plastic gloves.

Polyethylene gloves also known as food handler’s gloves may be worn over

treatment gloves to prevent contamination.

- A surgical glove is fitting and generally the most expensive disposable glove used

in maximum protection is indicated.

- Employers should not wash or disinfect the surgical or examination gloves for

reuse.

- No gloves should be used if they are peeled, cracked or discolored or if they have

puncture, tears or other evidence of distortion.

- Inadequate drying of the hands prior to gloving has proven to be another cause of

dermatitis.

- The utility gloves can be washed, sterilized, disinfected and rinsed and that are

puncture resistant.

PRACTICAL POINTS ESSENTIAL FOR GLOVE USE

Wash hands before doing gloves

Choose a glove that fits tightly

Replace gloves immediately if torn

Ensure chair side assistants wear gloves

Wash hands immediately after glove removal.

Treat gloves as surgical waste and dispose of them accordingly.

PROTECTIVE CLOTHING

Gowns, apron, lab coats, clinical jackets or similar outer garments either

reusable or disposable must be worn when clothing or skin is likely to be exposed

to body fluid. Protective clothing should be changed when visibly spoiled or

penetrated by fluids. Contaminated articles should be laundered in a normal

laundry cycle in separately. It should be made of or lined with fluid proof or fluid

resistant material and should protect all areas of exposed skin. ADA recommends

long sleeved uniforms. Tuck the bottoms of the sleeves into the gloves. Long

sleeves protect the lower arms from blood splatter, especially if there is skin

damage or wide spread dermatitis on the arms.

OSHA ADVISE THE FOLLOWING CONCERNING GOWNS

1. The clinic attire should be worn only in the dental environment and should be

changed at the end of the treatment schedule. 2. The day should begin with freshly

laundered garments and the garments should be changed immediately it soaked or

spattered with blood or other contaminants.3. Clinic attire should be handled

separately from family laundry.

MASKS

Masks were initially used to protect the patient from potential pathogenic

from the respiratory tracts of the caregiver. Today we realize that just as important

is protection for the caregiver from the patient. The ultrasonic scaler and air

turbine hand piece with air coolant procedure the same amount of aerosol as

cough. The dental personnel face is from 8 to 12 inches from the oral cavity

during any given procedure, masking is clearly indicated. Effective face masks are

to have a mini-filtration of 95% of 3.5 um particles and ability to block aerosols as

well as larger particles of blood, saliva and oral debris. The mash should be

changed once per hours or between each patients contact. Paper cloth or foam has

proven much less effective in filtering aerosols than having glass or synthetic

fibers. Mash should be properly disposed of after each use and not left handing

around the neck. Make sure before starting work that it is well adapt to the face.

Do not reuse masks or pull them down on the neck.

PROPER MASK SHOULD BE

Fit comfortably

Not look air out the sides

Fit around the entire periphery of the face

Not touch lips or nostrils

Not irritate skin

Provide breath ability

Not cause jogging or protective eyewear.

Not have an object able odor.

PROTECTIVE EYE WEAR

Protective eyewear in combination with a mask must be worn to protect the

eye when spatter and splash of body fluids is anticipated and a fan shield is not

used. All dental personal involved in treatment should wear protective eye wear in

the form of glasses and or a face shield to prevent trauma to the eye tissue from

flying droplets or aerosols. It is recommended that disposable eyewear or eye wear

than can be disinfected can be use. All protective eyewear should be cleaned after

every appointment. Eyewear should be washed with soap first, and then rinsed

with water and an appropriate surface disinfectant can be used.

HANDS

Hands must always be washed at the start of each day before gloving, after

removal of gloves and after touching intimate objects likely to be contaminated by

body fluids from patient. For many routine dental procedures, such as examination

and non-surgical procedures hand washing with plain soap appears to be adequate.

Since soap and water will remove transient microorganisms acquired directly or

indirectly from patient contact. For surgical procedures are antimicrobial surgical

hand scrub should be used. Hand washing should be designed to avoid cross

contamination at the scrub sink from water valve handles and soap dispenses.

HAND MICROBIAL AND WASH

It is a specific art of washing or otherwise treating hands with a chemical

soap or lotion with resulting reduction in the number of hand microbes. One

should not attempt to interchange the use of disinfectants, sterilants, antimicrobial

and antiseptics. If the products are not designed for such usage unfortunately,

misuse of products is common and led to numerous tissue toxic reactions.

ANTISEPTICS USED IN HAND WASHING

Chlorhexidine: i.e. 2-4% Chlorhexidine gluconate with 4% isopropyl alcohol

in a detergent solution with a pH of 5.0 to 6.5.

Povidone iodine: 7.5 to 10% Povidone iodine (3 minutes duration)

Phenolic compound: Hexachlorophene (it is toxic if the blood concentration

rises with repeated exr.) Parachlorometexylenol (is bactericidal and

fungicidal at 2% concentration).

Alcohols: Ethyl alcohol and isopropyl alcohol used in 70% concentration

WASHING

- Scrupulous hand washing procedures are essential for patient clinician and family

protection.

- The area under the nail can harbor residual blood and bacteria for up to 5 days

when gloves not routinely worn.

- The hand washing procedure begins with a thorough initial

scrubbing of all surfaces of the nail, fingers hands and lower arm with

antimicrobial preparations.

- Care should be taken to avoid the over use of a stiff bristle

brush, which will cause abrasion and laceration to the skin and nail area.

- The initial scrubbing should be accomplished with a soft

sterile brush or a disposable storage in three lathering. Each followed by a 2 to 3

minutes with cool to Luke warm water.

- Rinse water should flow from the fingertips to the elbow and

should not run back toward the area previously rinsed.

- Using a separate paper towel, drying should begin at the

fingers, moving to the hands and other to the surface of the arm.

- Hand must be washed between patient contact, before

gloving, after each patient contact when gloves are removed and prior to regloving.

PRECAUTIONS NECESSARY TO AVOID HAND SKIN DAMAGE

- Change to a different product if any disinfectants, hand

washing solutions, or soaps cause skin irritation.

- Remove all rings and jewellery before washing, as irritants

may accumulate under these.

- Rinse hands with cool water. Hot water opens the skin pores.

Cool water prevents debris from penetrating the skin pores, and minimizes the

shedding of resident micro organisms from the sub surface layers of the skin.

- Dry hands thoroughly after washing.

- Change protective gloves regularly to avoid a build up of

sweat.

- Use of good quality moisturizing cream regularly after each

clinical session.

- Minimize skin contact with potentially sensitizing chemicals

or medicaments. Some may penetrate rubber, eg: acrylic monomers or nickel.

- Wear heavy work gloves when undertaking work outside the

surgery, which is likely to damage the hands.

- Keep fingernails short and well manicured, and avoid wearing

nail varnish or false fingernails at work.

- Protect cuts or abrasions on the hands or forearms, with a

waterproof dressing, before undertaking dental procedures.

- Dental personnel who have widespread exudative or weeping

dermatitis, which cannot be protected, should refrain from all direct patient care,

and from handling contaminated equipment.

FOOTWEAR

A pair of smooth, ship on shoes should be kept exclusively for use in the

surgery. These should be cleaned at the end of each clinical session.

HEAD COVERS

Head covers provide an effective barrier. They are recommended during

invasive dental procedures, which are likely to involve extensive blood splatter.

ADDITIONAL PRECAUTION

All the above mention will protect dental health care work from

contaminated dental aerosols and splatter. There are other precautions which

maybe taken to reduce this risk.

1. Pre-treatment tooth brushing

2. High volume aspiration

3. Correct use of rubber dam

4. Efficient air filtration and ventilation

5. Oral antiseptic agents

ANTISEPTIC ENVIRONMENT

The principle is to minimize bacterial contamination, especially, in the vicinity of

operating table; the concept of zones in useful, and must be employed.

Outer, or general access zone – e.g. patient reception area and general office.

Clean, or limited access zone – e.g. the area between reception and general

office, dispersal area, and corridors and staff room.

Restricted access zone – e.g. for those properly clothed personnel engaged in

operating theatre activities, anesthetic room etc.

Aseptic or operating zone – e.g. the operating theatre.

Airflow: The air may be filtered, or allowed to flow past an ultra violet

radiation device to reduce bacterial counts.

Operating theatres have two types of air flow :

1. Conventional and

2. Unidirectional.

The normal turbulent airflow through theatre is necessary to maintain

humidity, temperature, and air circulation. Besides, an increased rate of air change

is necessary to reduce the number of contaminated particles over the patient. Air is

pumped into the room through filter and passed out of vents in the periphery of

operating room and does not return to operating room.

DRAPING THE PATIENT

The purpose of draping a patient is to isolate the field of surgery from other

parts of body that have not been prepared for surgery, and also from non-sterile

equipment and equipment.

DISPOSAL OF WASTE MATERIALS:

Disposable materials such as gloves, masks, wipes, paper drapes and surface

covers that are contaminated with body fluids should be carefully handled with

gloves and discarded in sturdy, impervious plastic bags to minimize human

contact. Blood, disinfectants and sterilants may be carefully poured into a drain

connected to a sanitary sewer system. Care should be taken to ensure compliance

with applicable local regulations. It is recommended that drains be flushed or

purged each night to reduce bacteria accumulation and growth. Sharp items, such

as needles and scalpel blades, should be placed in puncture-resistant containers

marked with the biohazard label. Human tissue may be handled in the same

manner as sharp items, but should not be placed in the same container. Regulated

medical waste (sharps and tissues, for example) should be disposed of according to

the requirements established by local or state environmental regulatory agencies.

FROM PROSTHETIC POINT OF VIEW:

RISKS

There is limited evidence of transmission of infection technician through

direct contact with impressions and prostheses. Dental prostheses and impressions

may prove a hazard to the dentist and dental assistant who handle them after

removal from the teeth.

A study has found that 67% of materials sent from dental offices to

laboratories were contaminated with bacteria of varying degrees of pathogenicity.

With care this risk can be substantially reduced.

Good cross infection control is essential both in the dental office and in the

dental laboratory.

CROSS INFECTION CONTROL IN THE DENTAL OFFICE

Practitioners should implement cross infection control described in

American Dental Association (ADA) and Centers for Disease Control (CDC)

guidelines. Follow described with regard to critical, semi-critical instruments

whenever possible.

Many items and instruments used in prosthetics cannot be heat sterilized nor

subjected to prolonged high-level disinfection without damage. The majorities do

not have direct contact with blood and oral fluid and may be considered non-

critical. Some have direct contact with blood and are classed as semi-critical.

SEMI-CRITICAL INSTRUMENTS AND ITEMS

The following instruments and items should be subjected to heat

sterilization or high-level disinfection compromise medium-level disinfection

with a tuberculocidal hospital infect ant is recommended.

Impressions: medium-level disinfection.

Prostheses which have been worn are either adjusted in the surgery, or

repaired or adjusted in the laboratory; medium-level disinfection

The face bow fork; heat sterilization

Wax knife, if used for adjustments at the chair side: heat sterilization

Prostheses, at try-in stage: medium-level disinfection

Metal dispensing syringes for impressions should be cleaned and heat

sterilized.

Bite blocks: medium-level disinfection

Polishing stones and rag wheels: heat-sterilization if possible.

Impression trays returned from the laboratory: aluminium or chrome plated -

heat sterilization, plastic-discard.

The handles of disposable trays can be detached and autoclaved but

corrosion and rusting may occur after a few cycles. Sterilization using a

chemiclave may be preferred.

NON-CRITICAL INSTRUMENTS

These non-critical items should be disinfected with a medium-level

tuberculocidal hospital disinfectant using the spray-wipe-spray technique.

Articulators and face bows (without the face and bow fork)

Mixing bowls and spatulas. (Some stainless-steel mixing bowls and

autoclavable spatulas are available. These may be heat sterilized if preferred.)

Shade and mold guides-if the shade guides are disinfected using an

iodophor, wipe immediately with alcohol or water to avoid discoloration.

Prosthetic rulers.

Wax rims should be discarded.

UNIT-DOSE CONCEPT

This means dispensing, prior to patient contact, a sufficient amount of a

material needed to accomplish a procedure. Any excess is discarded on

completion. The unit-dose concept minimizes the chances of cross infection

during prosthetic procedures. To minimize contamination of packaged items

stored in drawers or cupboards, unit doses of impression materials, wax, etc.

should be dispensed before beginning the procedure.

BITE BLOCKS AND PROSTHESES AT THE TRY-IN STAGE

These should be disinfected by immersion in a medium-level tuberculocidal

hospital disinfectant for the recommended time.

Disinfect bite blocks and 'try-ins’, which have been returned from the

laboratory, before fitting.

Disinfect bite blocks and 'try-ins' after fitting, before they are returned to the

laboratory.

Procedure:

Immersion in sodium hypo chlorite: bleach (5.25% sodium hypo chlorite)

is diluted 1:10, i.e. 1 part bleach to 9 parts water. Immersion time is 10 minutes

Decontamination should be carried out in the dental surgery, not in the

dental laboratory or in both.

A package sticker or instructions on the worksheet should inform the

dental technician that these items have been disinfected.

IMPRESSIONS DISINFECTION

Impressions have been shown to be contaminated on arrival at

laboratories and casts poured in non-disinfected impressions have been shown

to contain microorganisms. ADA guidelines state the impressions should be

rinsed to remove saliva, blood, and debris and then disinfected before being

sent to the laboratory.

Stability of impression materials following disinfection of materials is a

major concern, and it has been established that distortion of impressions may

occur following some disinfection routines.

DISINFECTION OF IMPRESSIONS

Immersion disinfection has been preferred to spraying. This is based on the

assumption that immersion is more likely to assure exposure of all surfaces of

the impression to the disinfectant for the recommended time.

Spraying disinfectants onto the surface of the impression reduces the chance

of distortion, especially in the case of alginate, hydrocolloid, and polyether

materials, but may not adequately cover areas of undercut. Two studies have

indicated that there is no difference in accuracy of casts obtained by spraying

with or immersion in recommended disinfectants.

Thorough rinsing of the impression is necessary before and after

disinfection. Rinsing before removes the bio-burden present, which may

exposure of the surface to the disinfectant. Rinsing after disinfection removes

residual disinfectant, which may affect the stone surface after casting.

ADA recommended disinfectants must be used.

o Chlorine compounds

o Iodophors

o Combination synthetic phenolics

o Glutaraldehydes

Distortion of impressions following disinfection is determined by the brand

of impression material and the disinfectant used.

When an alginate is disinfected the choice of product is very important.

POLYSULPHIDES AND ADDITION-CURED SILICONES

Addition-cured silicones and polysulphide impressions have been shown

to be generally stable when immersed in ADA recommended tuberculocidal

hospital disinfectants.

Note: Addition-cured silicone materials appear to be able to withstand damage

by disinfectants, exception of neutral glutaraldehyde.

Alternative disinfectant: iodophors

ALGINATE

Alginate is a complete carbohydrate that imbibes water. Immersion

disinfection for long periods will cause a distortion of alginate impressions due

to the intake of water and the action of the disinfectant. Avoid prolonged

immersion.

Investigations to evaluate the stability of alginate impressions following

disinfection, have produced varying results, depending on the techniques and

materials evaluated.

Recommended procedure:

Rinse the impression thoroughly under running tap water, shake the

impression to remove excess water.

Dip the impression in a 1:10 solution of sodium hypochlorite for several

seconds to ensure maxi- mum contact of undercut with the disinfectant Wrap

the impression in gauze soaked in 1:10 sodium hypochlorite, place in a plastic

bag and seal for 10 minutes

Remove the impression and rinse thoroughly under running tap water

Recent research has indicated that inactivation of viruses may be highly

unpredictable when a disinfectant is sprayed onto impressions. Simple spray

disinfection and an immediate rinse should not in general be considered an

appropriate method.

Immersion of alginate

Immersion of alginates in disinfectants is very much dependant on the

product used.

Algioplast and New Kromopan may be immersed in sodium

hypochlorite solution (1:10) for 10 minutes without distortion.

Jeltrate Plus may be immersed in iodophor (wesco- dyne) for 10-15

minutes, or for 10 minutes in sodium hypo chlorite, without distortion.

It is strongly recommended that alginate impressions are cast as soon as

possible after disinfection. This is possible if the dental office has its own

laboratory, but difficult if commercial laboratories are employed.

ALGINATE IMPREGNATED WITH DISINFECTANT

Disinfectants such as didecyl-dimethyl ammonium chloride have been

impregnated into alginate. One such product is commercially available

(Blueprint Asept).

A recent study recommended Blueprint Asept as an effective means of

reducing the number of viable microorganisms surviving on the actual

impression, but the problem of microbial contamination of the impression tray

itself remains.

POLYETHER IMPRESSIONS

Research results with polyether impressions have also varied. Care must

be taken, as some distortion is possible after prolonged immersion, Sodium

hypochlorite 1:10 should be used.

Rinse the impression thoroughly, shake off excess water.

Dip the impression in sodium hypochlorite solution for several seconds and

remove.

Wrap the impression in gauze soaked with sodium hypochlorite and place

the impression in a sealed bag for 10 minutes.

Remove the impression from the bag and rinse.

Note: Polyether impressions (Impregnurn) have been found to stand immersion

for 10 minutes in a disinfectant (Gigasept, Sterling Medicare UK) without

distortion. Short immersion times are recommended. A further study indicates

that immersion of polyether impressions for short periods may be acceptable.

AGAR- REVERSIBLE HYDROCOLLOIDS

Reversible hydrocolloids have been shown to be stable when immersed

in 1:10 sodium hypochlorite or 1:213 iodophor.

Recommendation

Immerse in sodium hypochlorite solution (1:10) for 10 minutes using the

procedure described for addition- cured silicone materials.

Alternative disinfectant- iodophor

It has been found that immersion in iodophor solution I (Wescodyne) is a safe

and effective method for disinfecting agar materials.

ZINC OXIDE EUGENOL (ZOE) AND COMPOUND IMPRESSIONS

Only limited data are available on the disinfection of zinc oxide eugenol and

compound impressions.

ZINC OXIDE EUGENOL

Immersion in 2% glutaraldehyde or a 1:213 iodophore solution for 10 minutes.

Materials disinfected with glutaraldehyde should be thoroughly rinsed to

remove residual traces of the disinfectant, Glutaraldehyde is a strong irritant to

the skin and mucous membranes.

COMPOUND

Immersion in sodium hypochlorite (bleach, diluted 1:10)

IMPRESSION TRAYS

If plastic disposable trays are used, the handle is removed and heat

sterilized.

If aluminum or chrome-plated trays are used, routine examination of the

trays is essential to monitor corrosion if sodium hypochlorite is used. If

corrosion occurs, use an alternative disinfectant.

DISINFECTING IN PROSTHODONTICS:

Disinfect prostheses and appliances before returning them to a dental

laboratory, following insertion into the mouth.

Disinfect prostheses and appliances returned from a dental laboratory,

before insertion into the mouth.

CHOICE OF DISINFECTANT

METAL DENTURES

Some concern has been expressed over the use dilute sodium

hypochlorite on metal dentures. Recent research indicates that the use of

sodium hypochlorite for 10 minutes will not damage denture base metals. One

study recommends 2% hypochlorite 1: 5 for 5 minutes, as 1% does not remove

all micro-organisms.

Other studies conclude that sodium hypochlorite should not be used and that

iodophors are the first choice disinfectants.

Iodophor or 1:10 diluted sodium hypochlorite be used for single or

infrequent disinfection cy However, both disinfectants should be used :;are as

either can be corrosive with repeated or prolonged exposure.

ACRYLIC DENTURES

Sodium hypochlorite is recommended for disinfection of complete acrylic

dentures. Glutaraldehyde with phenolic buffer (Sporacidin) should not be used.

“In-office” adjustments

Care must be taken with in-office adjustments. Use sterilized rag wheels and

unit doses of pumice and polishing compounds. These will prevent cross

contamination of prostheses and the need for multiple disinfections when repeat

try-ins are necessary

CORRECT LUBRICATION PROCEDURE FOR HANDPIECES

1. Remove bur from head

2. Remove hand piece from tubing

3. Remove head from shank, and shank from motor

4. Shake oil can to ensure contents are well mixed

5. Place can on a horizontal surface in a supported vertical position

6. Bring individual item to can and locate in correct nozzle

7. Wrap tissue around item to absorb excess spray

8. Fully depress spray button

9. Release spray button but keep holding hand piece on nozzle until all residual

can pressure has been dissipated.

10.Unwrap tissue and check for debris

11.Continue cleaning/lubricating until tissue shows clean uncontaminated oil

12.Wipe excess external oil and place hand piece on either a hand piece stand

or in a glass to drain excess internal oil

13.When sterilizing item in an autoclave, oil before each and every cycle. Do

not re-lubricate after sterilization

For high-speed hand piece, check that O-rings on multiflex coupling are clean

and in good condition

BURS Steel Burs: Single use. Dispose of these in Sharps bin

Diamond Burs

a. Clean with bur brush. b. Place in ultrasonic bath.

c. Dry, bag and autoclave.

CHANGING DISINFECTANT SOLUTIONS

Disinfectant solutions recommended should be changes daily.

Manufacturer’s recommendations

Refer to the manufacturer’s recommendations before undertaking any of the

procedures described.

Note: A recent study indicated that some impression manufacturers do not have

appropriate complete disinfection protocols.

OTHER PRECAUTIONS

Technicians should be vaccinated against infectious diseases, e.g.hepatitis-B

Frequent hand washing is essential.

Work gowns should be changed frequently.

Work benches, sinks, and equipment in the production area should be

cleaned and disinfected daily.

Do not eat in the laboratory

Sterilize burs and stones

Instruments, attachments; and materials used with new prostheses and other

appliances should be separate from those used on prostheses and appliances

which have previously been inserted in the mouth

Disinfect bristle brushes and rinse with water

Discard impression material from the tray and the bite registration wax

Outgoing cases should be disinfected before they are returned to the dental

office unless the dental office staff undertakes disinfection procedures.

TABLE 1: DISINFECTION OF IMPRESSIONS AND STONE CASTS

POLYSULPHIDES Use immersion in disinfectants of proven effectiveness*

SILICONES Use immersion in disinfectants of proven effectiveness*

POLY ETHERS Use immersion in disinfectants of proven effectiveness*

ALGINATE Use immersion in disinfectants of proven effectiveness* or spray with adequate coverage with disinfectants

AGARUse immersion in hypochlorite, iodophor or glutaraldehyde with phenolic buffer

STONE CASTUse immersion in hypochlorite, iodophors, alternately use spray disinfectants

ZINCOXIDE EUGENOL

Use immersion in glutaraldehyde or iodophor.

TABLE 2: DISINFECTION OF PROSTHESES, CASTS, WAX RIMS AND JAW RELATION RECORDS

Material Method Stone Casts Spray or immerse in hypochlorite or

iodophorFixed (Metal/Porcelain)

Immerse in glutaraldehyde

Removable Dentures

Immerse in iodophors or chlorine compounds (Acrylic/Porcelain)

Removable Partials  Immerse in iodophors or chlorine compounds (Metal/Acrylic)

Wax Rims/Bites Spray, wipe, spray with iodophors 

TABLE 3: DISINFECTANTS AND CONDITIONS FOR USE

CHEMICAL TIME TEMPERATURE

CHLORINE COMPOUNDS

3 minutes 200C

COMBINATION PHENOLICS    

10 minutes 200C

GLUTARALDEMYDES 10-90 minutes    

200-250C

HYPOCHLORITE 10 minutes 200C

IODOPHORS 10-25 minutes

250C

LABORATORY MEASURES:

COMMUNICATION WITH DENTAL LABORATORY STAFF

Responsibility for disinfection of items sent to the dental laboratory lies with

the dental office. All items disinfected in the dental office should be labeled,

indicating that such items have been decontaminated using an accepted

disinfection routine. This will avoid duplicating disinfection procedures, which

may damage materials.

Materials returned to the dentist from a laboratory should be disinfected in the

dental office prior to fitting.

Mutual communication of infection control routines in the office and the

laboratory is essential to prevent duplication of such routines.

'IN-HOUSE' DENTAL LABORATORIES

Infection control routines are easily delegated between the dental office and the

laboratory.

COMMERCIAL DENTAL LABORATORIES

Many items received from dental offices are contaminated. This leads to the

assumption that items arriving at the dental laboratory have not disinfected.

The majority of the routines described below are unnecessary if good

cross infection control is practiced by the dental office and communicated to the

dental laboratory. However, unless laboratories are certain that this is the case.

Cross infection control procedures should e undertaken at the laboratory to

protect staff.

CROSS INFECTION CONTROL ROUTINES

RECEIVING AREA-

All items received from dental offices "are placed in this area. A member of the

laboratory staff wearing heavy rubber utility gloves, a mask, and protective

eyewear unpacks the items. The packaging is disposed of as contaminated

medical waste.

If the dental laboratory staffs have not been notified that incoming work

is decontaminated, all incoming items must be disinfected using routines

described in this section. Boxes for work should be disinfected after unloading.

Receiving area benches are thoroughly disinfected after dealing with

each case, using a recommended hard-surface disinfectant.

INCOMING CASES-

Unless the laboratory employee knows that the case has been disinfected by the

dental office, all cases should be disinfected as they are received. Containers

should be sterilized or disinfected after each use. Packing materials should be

discarded to avoid cross contamination.

DISPOSAL OF WASTE MATERIALS-

Solid waste that is soaked or saturated with body fluids should be placed in sealed,

sturdy impervious bags. The bag should be disposed of following regulations

established by local or state environmental agencies

PRODUCTION AREA-

Persons working in the production area should wear a clean uniform or

laboratory coat, a face mask, protective eyewear and disposable gloves. Work

surfaces and equipment should be kept free of debris and disinfected daily. Any

instruments, attachments and materials to be used with new prostheses or

appliances should be maintained separately from those to be used with prostheses

or appliances that have already been inserted in the mouth. Rag wheels can be

washed and autoclaved after each case. Brushes and other equipment should be

disinfected at least daily. A small amount of pumice should be dispensed in small

disposable containers for individual use on each case. The excess should be

discarded. A liquid disinfectant (1:20 sodium hypochlorite solution) can serve as a

mixing medium for pumice. Adding three parts green soap to the disinfectant

solution will keep the pumice suspended.

CASTING IMPRESSIONS

If impressions are carefully disinfected, precautions to prevent

contamination of stone models are unnecessary.

As an alternative to disinfecting impressions, techniques have been suggested:

Stone models may be sprayed with an iodophor or with sodium hypochlorite

prior to handling or the dental cast may be soaked for on 5.25% sodium

hypochlorite saturated with dental stone (calcium sulphate dihydrate).

Disinfectant may be added to the gauging liquid. A recent study suggests

that sterilization poured against a contaminated impression is possible by

adding 25% by volume of commercial bleach to the gauging liquid without

affecting cast accuracy, hardness, or surface character.

The set of a cast can be accelerated to be compatible with hydrocolloid

impression materials by adding 50% slurry when making up the gauging liquid.

Mix 25% water, 25% sodium hypochlorite, and 50% slurry as a gauging liquid.

A biologically safe cast can be produced from contaminated impressions.

Microwaves are unacceptable for sterilizing dental casts.

POLISHING PROSTHESES

Studies have described contamination of pumice and polishing lathes,

contaminated aerosol following polishing and transmission of infection to a

technician.

Add 3 parts of green soap to the disinfectant solution (5 parts sodium

hypochlorite to 100 parts distilled water) before mixing the pumice. This helps

to keep the pumice suspended. The pumice should be changed daily and the

lathe disinfected. Unit doses of pumice may be used in each case and then

discarded. The technician should wear protective eyewear and a mask when

polishing. Polishing lathes are available with integral dust-chip evacuators. Use

a new sterile rag wheel when polishing a prosthetic appliance.

Special precautions when handling used prostheses Acrylic prostheses that

have been worn for some time are porous; grinding of the surface may expose

micro-organisms that have not been subjected to disinfection procedures. It has

been suggested that gloves should be worn when grinding 'old' acrylic, despite

the danger of gloves becoming caught up in polishing instruments. The US

National Association of Dental Laboratories does not suggest the use of gloves

for grinding disinfected prostheses, it suggests having a disinfectant at the lathe

side for immediate disinfection following exposure by grinding of previously

worn prostheses.

REVIEW OF LITERATURE:

Chiaji Shen did a study on the effect of gluteraldehyde base disinfectants

on denture base resins he concluded that the disinfectant with phenolic buffer

caused surface pitting of the material after 16 mts. of immersion and softening

and swelling of the surface after 2 hours of immersion (JPD 1989 ; 61-5; 583).

J.A. Bell conducted a study on the effectiveness of two disinfectants on

denture base acrylic resin with an organic load of staphylococcus aureus. Consida

albicas and E. Coil he concluded that chlorine dioxide achieved complete

disinfection of all three organisms with 2 minutes. Sodium hypochlorite achieved

complete disinfection of all organism within 4 minutes (JPD 1989; 61-5; 580).

David G. Drennon in his a study on the accuracy and efficiency of

disinfection by spray automization on elastomeric impression in concluded that all

four disinfectants chlorophenol 0.25% acid glutaraldehyde, Iodophor, Phenyl

phenol, were effective in disinfecting the surface and most accurate stone cast was

produced by addition silicone impression materials after disinfecting. (JPD 1989;

62-4; 468).

Robert W. Schutt in his study on bactericidal effect of a disinfectant dental

stone on irreversible hydrocolloid impression and stone casts he concluded that

impression poured with 0.25% choramine-T inhibited the growth of bacteria in the

cast impression compare with the non-disinfectant stone cast (JPD 1989; 62-5;

605).

Shogo Minagi did a study on prevention of AIDS and Hepatitis B

disinfection of hydrophilic silicone rubber impression material he concluded that

glutaraldehyde solution is effective as disinfectant for virus. It shows slight

expansion less than 0.03% of the impression (JPD 1990; 64-4; 463).

J. Matyas conducted a study on the effects of disinfectant on dimensional

accuracy of impression materials he concluded that no difference in the accuracy

of the cast obtained either by spraying with or immersion in any of the disinfectant

tested (JPD 1990; 64-1-2).

E.M. Langer Walter concluded in his study that there is no linear

dimension variation after disinfection of elastic impression material with iodophor,

Sodium hypochlorite, glutaraldehyde (JPD 190 ; 63-3; 270).

D.H. Pratten conducted a study on effect of disinfectant solution on the

wettability of elastomeric impression materials. The wettability of impression

material affects the number of volume of air bubbles generated during pouring of

gypsum casts. He concluded that addition silicone was the material most resistant

to change in contact angle. Chloride dioxide had the greatest beneficial effect on

wettability (JPD 1990; 63-2; 223).

David G. Drennor conducted study on the effect of immersion disinfection

of elastomeric impression on the surface detail reproduction of improved gypsum

casts he concluded addition silicone and polyether impression materials combined

with the acid glutaraldehyde provided the model system closest to be mean surface

roughness of the reference standard (JPD 1990; 63-2; 233).

John O. Look conducted a study on preliminary results from disinfection of

irreversible hydrocolloid impression he concluded that 0.5% sodium hypochlorite

spray inactivate and the virus when the spray was allowed to remain on the

impression 3 to 10 minutes. Iodophor requires a 3 to 10 mts. immersion for total

inactivation. 2% glutarldehyde achieved total viral inactivation in less than 1

minutes (JPD 1990; 63-701-11).

Stanley J. McNeme conducted a study on effect of laboratory disinfecting

agents on color stability of denture acrylic resins he concluded no observable color

change of any acrylic resin was seen before 2 hours. Both 1% sodium

hypochlorite and 2% cidex produced the least discoloration of the acrylic resin

compare to Wescodyne-D disinfectants (JPD 1991; 66-1; 132).

Lakshman P. Samaranayake did a study on carriage of oral flora on

irreversible hydrocolloid and elastomeric impression material he concluded about 2

fold to five fold retention of bacteria on the irreversible hydrocolloids compared

with the elastomeric impression surfaces. It is concluded that the total bacterial

load on impression surface is relatively low and decreases rapidly after impression

materials. The survival of organisms on impression materials increases in order ;

S. mutans, S. aureus, E. coli and E. albicas (JPD 1991; 65-2; 244).

Mitchell A. Stern did an evaluation of dental stones after repeated exposure

to spray disinfectants to abrasion and compressive strength he concluded greater

resistance to abrasion with increasing number of water or disinfectant spray

application. Acid glytaraldehyde spray decreased the compressive strength of type

III stone by 26%, phenol increase the compound strength of type IV stone by 18%,

Iodophor had no significant effect on either type (JPD 1991; 65-5; 713).

Themina Asad did a study on the effect of disinfection procedures on

flexural properties of denture base acrylic resin he concluded that alcohol based

disinfectants are not suitable for use with denture base materials of non-cross

linked acrylic resin (JPD 1992; 68-1; 191).

Richard A. Boss did a study on the effect of surface disinfectant on a dental

cast he concluded that a saturated calcium sulfate (clear slurry) solution with

0.525% sodium hypochlorite was an effective disinfectant and acted without

damaged to the dental cast (JPD 1992; 67-5; 723).

Frederick A. Rueggeberg did a study on sodium hypochlorite (NaClo) of

irreversible hydrocolloid impression materials he concluded both spray and

immersion treatment have antimicrobial effect, spray disinfectant did not cause

dimensional change, immersion created dimensional distortion. Both treatment

equally decreased the surface detail reproducibility (JPD 1992; 67-5; 628).

CONCLUSION:

Prevention is better than cure. The main way of control is by discarding all

the contaminated instruments and materials and try to use as much as disposable

items. The dentist and assistant should take proper vaccination in proper time. It

should be done any treatment with minimal instruments using.

The material, which is sent to the laboratory, should be disinfected before

the technician contact it should be kept in a separate room for disinfection, for all

the patients’ work, which is sent. For each patient the material used should be

separate or it should be discarded after each patient work or disinfect it before use

of it.

The dentist should not think only their health, they should consider the

environment also when the dispose of the used materials. They should be

discarded in sturdy, impervious plastic bags to minimize human contact. Blood

and disinfectants be carefully poured into a drain connected to a sanitary sewer

system. Sharp instruments should be paced in puncture resistant containers

marked with the bio hazard label.

REFERENCES

BOOKS:

1. Harsh mohan

2. Cross infection control in dentistry-P.R.Wood

INTERNET

1. CDC guidelines

2. OSHA regulations

3. ADA guidelines

ARTICLES:

1. Chiaji Shen did a study on the effects of glutarldehyde base disinfectants

on denture base resins JPD 1989; 61-5;583

2. J.A. Bell conducted a study on the effectiveness of two disinfectants on

denture base acrylic resin with an organic load of staphylococcus aureus. JPD

1989; 61-5; 580.

3. David G. Drennon in his a study on the accuracy and efficiency of

disinfection by spray automization on elastomeric impression. JPD 1989; 62-4;

468.

4. Robert W. Schutt in his study on bactericidal effect of a disinfectant

dental stone on irreversible hydrocolloid impression and stone casts. JPD 1989;

62-5; 605.

5. Shogo Minagi did a study on prevention of AIDS and Hepatitis B

disinfection of hydrophilic silicone rubber impression material. JPD 1990; 64-4;

463.

6. J. Matyas conducted a study on the effects of disinfectant on dimensional

accuracy of impression materials. JPD 1990; 64-1-25.

7. E.M. Langer Walter concluded in his study that there is no linear

dimension variation after disinfection of elastic impression material with

iodophor, Sodium hypchlorite, glutaraldehyde JPD 1990 ; 63-3; 270.

8. D.H. Pratten conducted a study on effect of disinfectant solution on the

wettability of elastomeric impression materials. JPD 1990; 63-2; 223.

9. David G. Drennor conducted study on the effect of immersion

disinfection of elastomeric impression on the surface detail reproduction of

improved gypsum casts. JPD 1990; 63-2; 233.

10. John O. Look conducted a study on preliminary results from disinfection

of irreversible hydrocolloid impression. JPD 1990; 63-701-7.

11. Stanley J. McNeme conducted a study on effect of laboratory disinfecting

agents on color stability of denture acrylic resins. JPD 1991; 66-1; 132.

12. Lakshman P. Samaranayake did a study on carriage of oral flora on

irreversible hydrocolloid and elastomeric impression material he concluded about

2 fold to five fold retention of bacteria on the irreversible hydrocolloids

compared with the elastomeric impression surfaces. JPD 1991; 65-2; 244.

13. Mitchell A. Stern did an evaluation of dental stones after repeated

exposure to spray disinfectants to abrasion and compressive strength. JPD 1991;

65-5; 713.

14. Themina Asad did a study on the effect of disinfection procedures on

flexural properties of denture base acrylic resin. JPD 1992; 68-1; 191.

15. Richard A. Boss did a study on the effect of surface disinfectant on a

dental cast. JPD 1992; 67-5; 723.

16. Frederick A. Rueggeberg did a study on sodium hypochlorite (NaClo) of

irreversible hydrocolloid impression material. JPD 1992; 67-5; 628.

17. McGowan, M. J., Shimoda, L. M., Woolsey, G.D. Effects of sodium

hypochlorite on dental base metals during immersion for short term sterilization.

J. Prosthet. Dent., 1988; 60:212-18.

18. Rudd, R. W., Senia, E.S., McCleskey, F.K., Adams, E. D. Sterilization of

complete dentures with sodium hypochlorite. J. Prosthetic Dent. 1984;51:318-

21.

19. Shen, C., Javid, N. S., Collaizzi, F. A. The effect of glutaraldehyde on

dental base resins. J. Prosthet. Dent., 1989; 61:583-9.

20. Kahn, R. C., Lancaster, M. V., Kate, W. The microbiological cross

contamination of dental casts. Quint. Int., 1989-20:583-5.

21. Gerard Kugel , Ronald. D.P., Marco, Paul, A – Disinfection and

Communication Practices; A Survey.JADA, Vol.131, June 2000, Pg. 787-92.

22. John A.M.: Dental Infection Control at the year 2000 JADA, Vol. 130,

Sep. 199. Pg. 12, 91-98.

23. Daniel L.L. – Performance of high speed Dental Hand pieces subjected to

simulated clinical use & sterilization. JADA, Vol. 130, Sept. 1999. Pg. 1301-11.

24. A Guide to Selection and Use of Disinfectants; CDC; 2003; Pg 3-16.

******