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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.
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