"Potato starch is hardly likely to hurt your teeth,"

It ain't the potato per se, it is the bacteria that feed on it that was postulated as the concern. Crisps, being rather, er, what word should I use, er crisp - they can find there way into crevices where them pesky bacteriums live.

For once I did actually accept the above fact from QI as being moderately appropriate. They once came up with the old chestnut about the level of caffeine in tea and coffee and failed to point-out that instant coffee has about 1/2 the caffeine. Which tells me what kind of coffee them Lundun QI elves drink all day long (innit?).