Question

@meisen Lines 44-50 say that high fiber and grit can wear down teeth making caries less likely but then turns around and says that too much fiber and grit can wear down teeth to the point that caries form in the tooth's pulp.

I don't see where it says it can make them less likely?

@alymathieu, The key part of the text to look at is the second half of the second paragraph of Passage B. In lines 42 through 44, we're told that increased caries frequency can occur from alterations in tooth wear. We're then told in lines 44 through 47 that the wearing down of the tooth crown reduces caries formation by removing fissures that can trap food particles. In lines 47 and 48, the author states, "A reduction of fiber or grit in a diet may diminish tooth wear, thus increasing caries frequency." The key thing about this quote is that it also means that the fiber or grit in a diet is keeping caries frequency down because when fiber or grit is reduced, caries frequency increases. This also means that when fiber or grit is increased, caries frequency decreases. This is the part of the text that shows us that fiber and grit can either limit or promote caries formation, depending on their prevalence in the diet. Also note, however, that we have a bit of a 'Goldilocks' situation going on with the fiber and grit as well because at the end of the second paragraph of Passage B, we're told that "severe wear that exposes a tooth's pulp cavity may also result in caries." This means that adding fiber or grit UP TO A CERTAIN POINT can reduce caries frequency, but if so much fiber and grit is consumed that dental wear is severe, then caries frequency can increase. Nonetheless, we know that fiber or grit—when added in a reasonable amount so that it doesn't cause severe tooth wear—can reduce the frequency of dental caries. And we know that very, very little fiber or grit doesn't dimish tooth wear enough (increasing caries frequency) and A TON of fiber or grit might wear teeth down too much, also increasing caries frequency, but a moderate amount that causes reasonable tooth wear can lower the frequency of caries. Does this make sense? Let us know if you have any more questions!