Infection control procedures in dentistry

Goal of infection control

To destroy pathogens and prevent their transmission

To reduce or eliminate microorganisms responsible for the contamination of water,food, and other substances

Microbial control methods

Disinfection: The destruction or removal of vegetative pathogens but not bacterial endospores. 

Sterilization: The complete removal or destruction of all viable microorganisms

Antisepsis: Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens

Chemotherapy: Chemicals used internally to kill or inhibit growth of microorganisms with host tissues

Conditions influencing the effectiveness of antimicrobial agents

1. Population size- larger population requires a longer time to die than a smaller one

2. Population composition- Microorganisms differ markedly in susceptibiltiy

3. Concentration or intensity of an antimicrobial agent- the more concentrated a chemical agent or intense a physical agent, the more rapidly microorganisms are destroyed

4. Duration of exposure- the longer, the better

5. Temperature- increase in temperature at which a chemical acts often enhances its activity

6. Local environment- environmental factors that may either offer protection or aid in its description

Disinfection methods

Heat

Physical method

Chemical method

The four most frequently physicsal agents are heat, low temperatures, filtration, and radiation

Physical methods

1. Pasteurization (Louis Pasteur)

Milk is raised to a temperature of either 63-66 degrees Celsius for 30 minutes or 72 degrees Celsius for 15 seconds

Safe from contamination with M.tuberculosis, Campylobacter and other pathogens

Not a sterilization process

2. Boling water

If boiling period is short, bacterial spores can survive

Inadequate for sterilization of dental instruments

3. Ultrasonics

Effective way of disrupting microbial cell membranes

Used for removing debris before autocleaving

4.Filtration

Membranes with pores about 0.2 um in diameter are used to remove most vegetative cells, but not viruses

Used to sterilize pharaceuticals, ophthalmic solutions, culture media, oils, antibiotics, and other heat-sensitive solutions

5. Radiation

Microbiologists take advantage of the effects of ultraviolet and ionizing radiation to sterilize or disinfect objects

Chemical methods- possible stages

External membrane- non-polar molecules may dissolve and enter the lipid phase

specific carrying systems will lead other molecules through the membrane

disturb the organisation of the membrane

Bacterial wall- affinities of the hydrophilic disinfectants

Cytoplasmic membrane- penetrating by passive diffusion or active transport

Energy metabolism- ATP production

Bacterial DNA

Bacterial spores- highly oxidising products destabilise structure

Potency of chemical disinfectants

High-level: Gram+ and - bacteria, spores and M.tuberculosis

Intermediate level: M.tuberculosis, vegetative bacteria, most viruses and fungi, but few spores

Low-level: most bacteria and fungi but not M.tuberculosis

Alcohols and their characteristics

Ethyl alcohol or propyl alcohol (70% in water)

Skin antisepsis

Combined with aldehydes for surface disinfection

Flammability

Limited sporicidal activity

Ready inactivation by organic material

Aldehydes and their characteristics

Glutaraldehyde is the most popular in some regions, whereas it is banned in others

Both skin irritant and a sensitive agent

Both long-term and short-term effects

‘Cold sterilization’ or the high-level disinfection of equipment

High-potency disinfectants

React with free amino groups of proteins in a pH-dependent manner

Cross-linking with proteins such as collagens

Activator has to be added (to a pH of 8)

Shelf-life of up to 14 days

Bisguanides

Chlorhexidine

Antiseptic and a plaque-controlling agent

0.4% in detergent for surgical scrub

0.2% in aqueous solution as antiplaque agent

2% as denture disinfectant

Cell membrane permeability is altered with resulkan leakage of cell contents and precipitation of the cytoplasm leading to cell death

Highly active against both Gram+ and - organisms

Kills Candida

Halogen compounds

Hypochlorites and povidone-iodine

Oxidising agents

Acts by releasing halide ions

Cheap and effective

Corrode metal and are quickly inactivated by organic matter

Chloros, Domestos and Betadine

Phenolics

Clear, soluble or black/white fluids

Do not irritate the skin

They are used for grpss decontamination

Not easily degraded by organic material

Poorly virucidal and sporicidal

Most bacteria are killed by these agents

Widely in hospitals and laboratories

Chemical sterilization

Glutaraldehyde (cold sterilization)

10-12 hours

highly toxic

cleaning after

storage in plastic or stainless steel containers