Direction (Q. No. 26 to 30) : Read the following passage carefully and choose the best answer to each question out of four alternatives.

Infections in the roots of teeth are hell to treat. The tooth needs to be drilled into, right down to the bottom of the nerve-carrying canal that runs through the root. The infected material must then be cleaned out completely and the drilled section filled in. Although, the procedure is routine, it is common for some of the bacteria to survive it and therefore for infections to re-emerge shortly after treatment.

The surviving bacteria are often gathered in the form of what is known as a biofilm. Bacteria in such a film are embedded in a polymer matrix, which makes them harder to kill than isolated individuals. High temperatures can destroy biofilms, as can some chemicals, but neither approach is safe to use inside the delicate interior of a human tooth. However, Chunqgi Jiang, a physicist at the University of Southern California, Los Angeles, and her colleagues have come up with a possible alternative: a dental plasma torch.

Plasmas are gases in which the molecules have been stripped of some or all of their electrons, to create positive ions. One way to do this is to heat the gas up.

Conventional plasma torches employ such hot plasma to cut metal. But cold plasmas can be made using high electrical voltages. Bacteria in biofilms are also more resistant to antibiotics than their isolated confreres, so the new device could have other medical applications. Wound infections, for example, often form biofilms. If they cannot be treated successfully, the result may be gangrene. And if Dr. Jiang’s version of St. Elmo’s fire can deal with that problem, the saint may become patron of a lot more people than just sailors.

Question-27 : Why does the writer say’ Infections in the roots of teeth are hell to treat?

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