Lecture 1- Sterilization and Disinfection (Preclinic Theory)

Antiseptic

a substance that prevents and arrests the growth or action of microorganisms either by inhibiting their activity or destroying them; term used especially for preparation applied topically to living tissue.

Asepsis

free from contamination with microorganisms; includes sterile conditions in tissues and on materials, as obtained by exclusion, removing, or killing organisms.

Bioburden

the number and types of microorganisms like bacteria, fungi, and viruses present on instruments, materials, or in dental unit water systems before they are sterilized or disinfected.

Biocidal

the ability of the chemical disinfectant to destroy or inactivate living organisms.

Biologic Indicator

a spore test used to confirm that a dental sterilizer (autoclave) is functioning correctly and has killed highly resistant microorganisms.

Biostatic

inhibiting the growth or multiplication of an organism but does not kill it directly.

Chemical indicator

a color change stripe or other mark, often on autoclave tape or bag, used to monitor the process of sterilization; color change indicates that the package has been brought to a specific temperature, but color change is not an indicator of sterilization.

Contaminated waste

items that have contacted blood or other body secretions.

Contamination

introduction of microorganisms, blood, or other potentially infectious material or agent onto a surface or into tissue.

Disinfection

Process in which most pathogenic agents or disease producing microorganisms (not spores) are destroyed

Hazardous waste

poses a risk to humans or the environment.

Infectious waste

capable of causing an infectious disease; contaminated with blood, saliva, or other substances; potentially or actually infected with pathogenic material; officially called "regulated" waste.

Regulated waste

liquid blood or saliva, sharps contaminated with blood or saliva, and nonsharp solid waste saturated with or caked with liquid or semisolid blood or saliva or tissue including teeth.

Toxic waste

materials generated during procedures that are hazardous to public health or the environment due to the presence of toxic, corrosive, reactive, or ignitable substances.

Sanitation

Process by which the number of organisms on inanimate objects is reduced to a safe level. It does not imply freedom from microorganisms, and generally refers to a cleaning process. THIS ALWAYS PRECEDES DISINFECTION AND STERILIZATION.

Sterilization

The process by which all forms of life, including bacterial spores and viruses are destroyed. Highest level of disease control.

What is the action of moist heat/steam under pressure?

-inactivates essential cellular proteins and enzymes

-causes the proteins to coagulate resulting in cell death

What is the pressure, temp, and time of moist heat?

Temp- 121°C (250°F)

Pressure- 15psi

Time- 15min

What is the flash treatment of moist heat?

Temp- 132°-135°C (250°F)

Pressure- 30psi

Time- 7min

What do you use to wrap moist heat items?

1. Nyclave bags

2. Peel-vue bags

3. Paper bags

4. Paper

5. Cloth wraps (muslin)

6. No wrapping (flash sterilization for immediate use)

What is the procedure for moist heat?

1. Instruments are place in cassette

2. Run cassette through ultrasonic according to manufacturer's recommendations (2-12 min)

3. Remove from solution/rinse and let dry

4. Package

5. Load autoclave (loosely)

6. Set timer once pressure and temperature are achieved

7. Vent autoclave

8. Dry and cool instruments

What is the advantage of moist heat?

-Microorganisms, spores, and viruses are destroyed.

-Material friendly

What is the disadvantage of moist heat?

corrosion to carbon steel instruments

What is the action of dry heat?

destroys bacteria by oxidation

What is the time and temperature of dry heat?

Temp- 160°C (320°F)

Time- 2 hours at 160°C or 1 hour at 170°C (340°F)

What are the advantages of dry heat?

-Materials that can't withstand steam under pressure

-Excellent for sharp instruments

-No corrosion

What are the disadvantages of dry heat?

-Long exposure time

-Slow and uneven penetration

-Temperatures over 160°C- sharp edges are destroyed

-Temperatures over 170°C- paper and cotton begin to scorch

What is the action of chemical vapor sterilizer?

microbial and viral destruction occurs by permeation of heated formaldehyde and alcohol

What are the chemicals used in the Chemclave?

-Alcohols

-Formaldehyde (embalming solution)

-Ketone

-Acetone (fingernail polish)

-Water

What is the temperature, pressure, and time of the chemical vapor sterilizer?

Temp- 127°-132°C (260-270°F)

Pressure- 20-40psi

Time- 20 or more minutes

What are the advantages of the chemical vapor sterilizer?

-Corrosion and rust free for carbon steel

-Short cycle

-Ease of operation and care of equipment

What are the disadvantages of the chemical vapor sterilizer?

-Adequate ventilation required

-Unpleasant odor

What is the action of Ethylene Oxide?

Alkylation of DNA

What is the time and temperature of ethylene oxide?

Time- 10-16 hours (depends on temp and concentration of solution)

Temp- 61°C (110°F)

What are the advantages of ethylene oxide?

-Many types of materials can be sterilized with minimal or no damage

-Low temp

What are the disadvantages of ethylene oxide?

-High cost of equipment

-Exhaust

-Length of sterilization cycle

-Gas absorption requires airing

Biological Indicator Spore Test

-Tests for sterility only

-Bacillus stubtilis: used on dry heat and ethylene oxide

-Stearothermophilus: used on steam and chemical vapor

Chemical Indicator Tape/Strip

-Work by a color change

-Color change indicates instruments have been processed not sterity

High level disinfectants

inactivate spores and all forms of bacteria, fungi, and viruses - same as sterilization. (10 hours) Mycobacterium tuberculosis is the benchmark organism for high level disinfection. (Sporox)

Intermediate level disinfectants

inactivates all forms of microorganisms but does not destroy spores. (Cavi Wipes).

Low level disinfectants

inactivates vegetative bacteria and certain lipid-like viruses, not spores, tubercle bacilli, or non-lipid viruses. (Iodine)

What are the properties of an ideal disinfectant?

1. Broad spectrum (widest antimicrobial spectrum)

2. Fast acting

3. Stable and active - not affected by physical factors

4. Non-toxic

5. Surface compatibility

6. Residual effect on treated surfaces

7. Easy to use

8. Odorless

9. Economical

What is the criteria for selection of a chemical agent?

1. EPA Approval

2. Tuberculocidal, bacteriocidal, virucidal, and fungicidal

The label must state:

1. Shelf life

2. Use life

3. Re-use life

4. Directions for activation

5. Directions for use

6. Instructions for disposal of used solution

7. Warnings

What are the recommended chemical disinfectants?

1. Glutaraldehydes 2%

2. Chlorine compounds (chlorine dioxide, sodium hypochlorite)

3. Iodophors (Biocide)

4. Phenolics (synthetics) (Vital defense)

5. Quaternary Ammonia Compounds (Cavi Wipe)

6. Silver Ion- Steriplex/Sterisil (now Solmetex)

What is the procedure for chemical sterilants (Immersion using Glutaraldehyde)?

1. Scrub thoroughly or use ultrasonic cleaner to remove organic matter

2. Rinse thoroughly to remove soap

3. Dry

4. Immerse instruments completely

5. Room temperature

6. Time: 30 minutes to 10 hours

7. Do not add other instruments without starting timing over

8. Drain instruments and dry with sterile towel

Comparison of the 4 Approved Sterilization Methods