Many people dread the sound of the dentist's drill, part of the reason that it has to be used so much is that the dentist has to be absolutely sure that they have got rid of all the bacteria underneath a filling.

DentistResearchers in china are working on an answer, they are developing a plasma needle. Plasmas are gasses where some of the electrons have been ripped off their atoms, or molecules. They are found in stars, fluorescent lights etc. Plasmas have lots of energetic ions and free radials, which are very reactive chemically this means that they will interfere with the workings of a bacterial cell, killing them efficiently. However a plasma is normally extremely hot so you wouldn't want to put one anywhere near your mouth.

A plasma needle on the other hand is much cooler, it consists of a thin tube with a wire running down the middle. you pump gas through the tube and pulse high voltages on the wire. these break some gas molecules apart without heating the gas much. Up till now the largest needles produced have been a few mm long or too hot, but XinPei Lu at Huazhong University of Science and Technology has worked out a way of studying how the electrons are moving in the plasma and so has managed to make a 4cm long needle which is safe to touch.

He is mostly looking at dental hygiene applications reducing the amount of that dreaded drilling, but it could also be used for steralising medical aparatus sensitive to heat.

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