Dental hygiene aficionados have surely noticed a new format battling for a share of the oral hygiene market. Toothpaste tablets are dry, pressed-powder pills about the size of an aspirin or a pea.

We don’t always have the answers, but we have some people on speed dial who do — which is why we present our FYI series, where we have experts explain if lip balm is actually bad, how often you should ...