Dentoplako restas inter la dentoj sen dentofadeno.

Esperanto very often forms new words by combining smaller ones into a single compound.

• dento = tooth
• plako = plaque

So dentoplako literally means tooth-plaque, i.e. dental plaque. This is extremely normal in Esperanto. English sometimes writes similar ideas as one word, two words, or with a hyphen; Esperanto usually just combines them neatly.

Resti means to remain / to stay.
So restas means remains / stays.

That gives a more specific idea than estas (is). The sentence is not just saying that plaque is between the teeth, but that it remains there.

• estas = is
• restas = remains, stays

In Esperanto, all present-tense verbs end in -as.

So:

• resti = to remain
• restas = remains / stay(s)

This ending does not change for different subjects:

• mi restas = I remain
• ĝi restas = it remains
• ili restas = they remain

That is much simpler than English, where remain and remains differ.

Because the subject is already stated: dentoplako.

Esperanto does not need a separate pronoun if the noun itself is present.

So the structure is simply:

• Dentoplako = the subject
• restas = the verb

English might say Plaque remains... and Esperanto does exactly the same kind of thing.

Inter means between / among.

Here it introduces a prepositional phrase:

• inter la dentoj = between the teeth

A useful point: after a preposition like inter, Esperanto usually uses the normal noun form unless there is clear motion toward something. Here there is no motion, just location, so dentoj stays in the ordinary plural form, not accusative.

La is the definite article, meaning the.

So:

• la dentoj = the teeth
• dentoj = teeth

In this sentence, the teeth sounds natural because we are talking about the teeth in a specific, understood situation. Esperanto uses la a lot like English the, though in some places usage can feel a little broader or more general.

The ending -j marks the plural in Esperanto.

• dento = tooth
• dentoj = teeth

Esperanto plural marking is very regular:

• singular noun: -o
• plural noun: -oj

So la dentoj is simply the teeth.

Because it is not the direct object.

The -n ending in Esperanto is usually for:

1. the direct object, or
2. motion toward something

In inter la dentoj, the phrase tells us where the plaque remains. It is a location phrase after a preposition, not a direct object and not motion toward a place. So dentoj is correct.

Sen means without.

So:

• sen dentofadeno = without dental floss

It is a preposition, just like English without. After sen, the following noun normally stays in its basic form unless there is some special reason to mark it otherwise.

Yes. It is another compound.

• dento = tooth
• fadeno = thread

So dentofadeno literally means tooth-thread, that is, dental floss.

This is a very Esperanto-like way to build vocabulary: take familiar roots and combine them logically.

Because the sentence is talking about floss in a general sense, not a specific piece of floss.

• sen dentofadeno = without dental floss
• sen la dentofadeno would suggest without the dental floss, meaning some particular floss already known from context

So the version without la is the natural one here.

Yes, Esperanto word order is fairly flexible, because endings show grammatical roles clearly. But some orders sound more neutral than others.

The given order:

• Dentoplako restas inter la dentoj sen dentofadeno.

is straightforward and natural.

You could also move some phrases for emphasis, for example:

• Sen dentofadeno dentoplako restas inter la dentoj.

That emphasizes without dental floss. The basic meaning stays the same.

Yes, that is the practical meaning in context.

Literally, it just says without dental floss, but in a sentence like this the idea is naturally understood as if one does not use dental floss or in the absence of flossing.

Esperanto often expresses this kind of idea with a simple prepositional phrase rather than a longer clause.

Here it is being treated more like a mass or general substance noun: plaque rather than a plaque.

That is why it appears simply as dentoplako, not dentoplakoj. The sentence is talking about plaque in general, not multiple separate plaques.

In Esperanto compounds, the final element is usually the core word, and the earlier part modifies it.

So:

• dento-plako = a kind of plako
• dento-fadeno = a kind of fadeno

That means:

• dentoplako = plaque related to teeth
• dentofadeno = thread related to teeth

This is very helpful when guessing the meaning of unfamiliar compounds.