🔻It is the most widely used method of sterilisation by dry heat.

🔻 The oven is electrically heated and is fitted with a fan to ensure adequate and even distribution of hot air in the chamber

🔻It is also fitted with a thermostat that maintains the chamber air at a chosen temperature.

Temperature and time

160°C for two hours (holding time) is required for sterilisation.

Uses

It is used for sterilisation of

(i) Glassware like glass syringes, petri dishes, flasks, pipettes and test tubes.

(ii) Surgical instruments like scalpels, scissors, forceps etc.

(iii) Chemicals such as liquid paraffin, fats, sulphonamide powders etc.

Precautions-

(i) It should not be overloaded.

(ii) The material should be arranged in a manner which allows free circulation of air.

(iii) Material to be sterilised should be perfectly dry.

(iv) Test tubes, flasks etc. should be fitted with cotton plugs.

(v) Petri Dishes and pipettes should be wrapped in craft paper.

(vi) Rubber materials (except silicone rubber) or any inflammable material should not be kept inside the oven.

(vii) The oven must be allowed to cool for two hours before opening the doors, since the glasswares may crack by sudden cooling.

Sterilisation control

(i) The spores of nontoxigenic strain of Clostridium tetani are kept inside the oven. These spores be destroyed if the sterilisation is proper

(ii) Thermocouples may also be used.

(iii) Browne’s tube with green spot is available .

After proper sterilisation a green colour is produced (after two hour at 160°C).

Source – textbook of microbiology for dental students c p baveja