Sterilization and disinfection:
Sterilization: it indicate a procedure which will completely kill all living organisms including bacteria, vegetative bacteria and viruses in any given set of condition . sterilization should be done to prevent the cross infection between patients there are very dangerous diseases like viral hepatitis and AIDS transmitted by dental instruments.Disinfection: it indicate aprocedure affording a valuable measure of control of infection, but definitely inferior to sterilization, in particular bacterial spores and many vegetative organism and viruses may not be killed.
Methods of sterilization:
1-Physical methods 2-chemical methods 3- combination between bothPhysical methods:
Physical methods:Physical methods:
Physical methods:3- Pressure steam sterilization “autoclaving”:In this method moist heat in form of super heated under pressure is one of the most effective in destroying microorganisms including viruses, fungi and spores in relatively short time, to ensure sterilization; instruction related to time, temperature, and pressure must be followed carefully. (For light load of instrument the use of 20 pounds/inch3 the time should be 20minutes the temperature 170C0 is enough to kill all M.O)Disadvantage is rusting of the instrument to minimize this instrument must be put in 1% sodium nitrate solution before autoclaving for 2minutes.
Physical methods:
Physical methods:
5- Ultrasonic vibration method: We use it especially for reamers, files and burs. The advantages of this method are: *16 times more efficient than hand scraping ** reduce erosion of the instruments *** reduce puncturing woundsPhysical methods:
6- Radical sterilization: its efficient method but expensive we use ultra violet light , gamma, beta rays. we use this method to sterilize disposable needles and drugs.Physical methods:
7- Gas methods: Ethylene oxide is used which is highly bactericidal, Ethylene oxide sterilization is the best method for sterilizingcomplex instruments and delicate materials. hand pieces are sterilized by this method.Chemical methods:
All chemical disinfectants are poor alternative to proper physical sterilizing procedure. Disinfectant antiseptics do not kill all spores , the ways that these disinfectant acts are: 1-react with the cell protein of the bacteria 2-react with the enzyme system of the bacteria 3- cause disruption of the cell wall of the bacteriaChemical methods:
properties of ideal antiseptic:they must destroy the M.O.it should penetrate deeply through bacterial cell.Rapid in actionDoesn’t damage material or living tissue when coming in contact.Return its potencySoluble in water Non corrosion and doesn’t stain the instrumentChemical methods:
Some points should be taken in consideration concentration: we should follow the instruction of each agent before using as a general rule temperature : higher temperature more efficient sterilization P.H.: each agent act perfectly at certain P.HChemical methods:
Examples of chemicals used widely in dentistry: eugenol : eugenol is pal yellow solution and goes darker with time. Eugenol is protoplasmic poison (antiseptic) Alcohol: methylated spirit its protoplasmic poison , its most effective at concentration of 70%.