Sterilization can be defined as the process by which all the microorganisms are eliminated from a surface of an instrument. Sterilization is a process of yse or no. Nothing can
be half sterilized.
Disinfection, on the other hand, is the process by which most of the pathogenic organisms are eliminated, but not necessary all microorganisms.
Spores microorganisms may survive. Disinfection may be of high, intermediate or low level.
The main methods of sterilization and disinfection in dental clinic are physical methods, as heat and irradiation or chemical methods.
A. Boiling water
This method was commonly used in the dental
clinics in the past, now it is seldom if ever used. Boiling kills most bacteria within short time. However, bacterial spores survive boiling for a very long time and viruses probably survive indefinitely. For this reason boiling is considered a method for
disinfection and not for sterilization.
B. Autoclave (Pressure Steam Sterilizer)
This method of sterilization is the most acceptable method for use in the dental clinics nowadays. It works on the basis of the steam cooker and is an extremely efficient method for sterilization of instruments. The steam is
at pressure of about 15 -30 lb/in. This pressure is enough to destroy all organisms and spores.
Chemiclave is another method for sterilization
where a chemical is used instead of water. However, this method is not common in dental clinics.
C. Hot-Air Sterilizer (Dry Hot Oven)
It is the most common method used in dental clinics. The disadvantages of this method are:
dry condition the organisms are more harder to kill than when they are wet. Also dry heat has very little power of penetration and unless a very high temperatures are used the method is very slow.
- After sterilization the instruments need a considerable time to cool.
- Not suitable for plastic instruments and instruments which have soft
- The heating space is very irregular, the temperature may reach very high degrees in one part and in other part it may not reach the required degree. This is cold
If this method is used in dental clinics a great care must be taken not to open the oven during the sterilization cycle. Such action,
as for adding new instruments, will lower the temperature in the heating space and will mix the dirty and sterile instruments.For proper sterilization the instreuments must remain inside the oven at the required temperature for 120 minutes.
Some small dental instruments may be sterilized by this method,
for example hypodermic needles. However, this method has the disadvantage that the temper of the metal may be spoilt. Irriadioplatinum hypodermic needles can be sterilized by this method. However this is not advisable now as disposable needles are available.
II. Chemical Methods
These methods involve the use of chemical
liquid or gaseous compounds.
liquids are very unreliable for achieving sterilization. Viruses and both vegetative and sporing bacteria may survive liquid chemical sterilization. It is to be used when other methods of sterilization are unsuitable. The most common used liquid chemical in
dental clinics is glutaraldehyde (Cidex). However, this method is used mostly for disinfection as achieving sterilization will take long time (10-12 hours).
The use of effective infection control procedures and universal precautions in dental office and dental laboratory will minimize the risk for cross-infection that could extend to the dentist,
dental clinic staff, dental technicians and patients.
Steam Autoclave use Steam under pressure with/without vacuum the use of vacuum is more efficient. Instruments must be wrapped or packed. Instruments are left inside for 15-20 minutes at 135 oC.