Uzu dentofadenon ĉiutage.

Uzu is the -u form of the verb uzi (to use). The -u ending is used for commands, requests, instructions, and similar meanings.

So:

• uzi = to use
• uzu = use!

In this sentence, the subject vi (you) is understood and left unstated, which is very normal in Esperanto:

• (Vi) uzu dentofadenon ĉiutage.

Also, vi can mean one person or more than one person, so uzu can be addressed to either.

The -n marks the direct object.

Here, uzi is a transitive verb: you use something. The thing being used is dentofadeno, so it takes the accusative ending:

• dentofadeno = dental floss
• dentofadenon = dental floss, as the direct object

So the structure is:

• Uzu = use
• dentofadenon = dental floss
• ĉiutage = daily / every day

Yes, it is one word. Esperanto very often builds vocabulary by combining elements into compounds.

dentofadeno is made from:

• dento = tooth
• fadeno = thread

So it literally suggests something like tooth-thread, which corresponds to dental floss.

The -o- in the middle is a common linking vowel in compounds. This kind of word-building is very typical in Esperanto and often makes meanings easy to guess once you know the parts.

Because the sentence is talking about floss in a general sense, not a specific previously identified floss.

So:

• Uzu dentofadenon ĉiutage. = Use floss daily. / Use dental floss every day.

If you said la dentofadenon, that would mean the floss, referring to some specific floss already known from the context.

Esperanto often leaves out the article when English would also use a general or non-specific noun.

Ĉiutage is an adverb, telling you how often the action happens: daily or every day.

It is built from the idea of:

• ĉiu = every
• tago = day
• -e = adverb ending

So ĉiutage means something like every-day-ly, or more naturally, every day / daily.

It modifies the verb uzu, not the noun.

Yes. That is a very common alternative.

So you can say:

• Uzu dentofadenon ĉiutage.
• Uzu dentofadenon ĉiun tagon.

Both mean essentially the same thing.

The difference is mainly grammatical style:

• ĉiutage is an adverb meaning daily
• ĉiun tagon is literally every day, using the accusative in a time expression

Both are natural Esperanto.

Yes. Esperanto word order is fairly flexible, especially because endings like -n help show what each word is doing.

For example, these are all possible:

• Uzu dentofadenon ĉiutage.
• Ĉiutage uzu dentofadenon.
• Dentofadenon uzu ĉiutage.

The basic meaning stays the same, but the emphasis can shift a little:

• starting with ĉiutage emphasizes how often
• starting with dentofadenon emphasizes what to use

The original version is a very straightforward, neutral way to say it.