Si a vostè li fan mal les dents, pot anar al dentista avui amb la seva filla.

Yes, in a way they both point to you, but they do different jobs.

• a vostè is the stressed, explicit form: to you
• li is the indirect object pronoun that normally appears with verbs like this

Catalan often uses this kind of doubling, especially with indirect objects. So a vostè li fan mal les dents is completely natural.

You can think of it as something like:

• As for you, your teeth hurt
• or more literally, To you, the teeth do pain

Also, vostè is the formal singular word for you, like Spanish usted.

Because vostè is the formal way to say you in Catalan.

So:

• tu = informal singular you
• vostè = formal singular you
• vosaltres = informal plural you
• vostès = formal plural you

That affects the verb too. Here we get:

• pot = you can for vostè
• not pots, which would go with tu

An informal version would be:

• Si et fan mal les dents, pots anar al dentista avui amb la teva filla.

Because fer mal is the normal Catalan expression for to hurt / to cause pain.

So:

• Em fa mal el cap = My head hurts
• Li fan mal les dents = Their teeth hurt / The teeth hurt them

Literally, fer mal means to do harm / to cause pain.

In this structure:

• the thing that hurts is the grammatical subject
• the person who feels the pain is expressed with an indirect object pronoun

So in li fan mal les dents:

• les dents = subject
• li = to him / her / you-formally

This is a very common Catalan pattern.

Because the subject is les dents, which is plural.

So the verb agrees with les dents:

• la dent fa mal = the tooth hurts
• les dents fan mal = the teeth hurt

Even though English often uses you have toothache, Catalan here is structured more like:

• the teeth hurt

So the verb must be plural.

Catalan often uses the definite article with body parts where English might not.

So Catalan prefers:

• em fa mal el cap = literally the head hurts me
• li fan mal les dents = literally the teeth hurt them

This is very normal. English often says:

• my head hurts
• your teeth hurt

But Catalan commonly uses:

• article + body part
• plus a pronoun showing whose body part it is

So li fan mal les dents already implies your teeth because li tells us who is affected.

Yes. Si here means if.

The first part is a conditional clause:

• Si a vostè li fan mal les dents = If your teeth hurt

Then the main clause follows:

• pot anar al dentista avui amb la seva filla = you can go to the dentist today with your daughter

So the whole sentence has the structure:

• If X, you can do Y

This is a very straightforward real-condition pattern in Catalan.

Both can be possible depending on context, but pot anar al dentista is perfectly normal because the destination is already stated explicitly: al dentista.

• anar al dentista = to go to the dentist
• anar-hi = to go there

You would use hi when replacing a place already mentioned:

• Al dentista? Sí, hi pot anar avui.
• To the dentist? Yes, you can go there today.

Since the sentence already says al dentista, hi is not needed.

In normal usage, anar al dentista means to go to the dentist, just like in English.

Grammatically:

• a + el = al
• so al dentista = to the dentist

Like English, this can refer either to:

• the professional person
• or the appointment/place associated with that person

It is the standard idiomatic way to say it.

In this sentence, it most naturally means your daughter, referring to vostè.

But grammatically, seu / seva / seus / seves can sometimes be ambiguous, because they can mean:

• his
• her
• your formal
• its
• sometimes even their in certain contexts, depending on structure

Here, because the sentence is addressing vostè, learners will usually understand la seva filla as your daughter.

If someone wanted to make it extra explicit, Catalan can use a different structure, for example:

• amb la filla de vostè

But that sounds less natural in ordinary language. La seva filla is the normal phrasing.

In theory, prepositional phrases can sometimes create ambiguity, but in this sentence the natural reading is:

• you can go to the dentist today with your daughter

So amb la seva filla attaches to anar and describes who accompanies you.

A native speaker would normally understand it that way, not as describing the dentist.

Yes, avui can move around somewhat.

This sentence has:

• pot anar al dentista avui amb la seva filla

That is natural, but Catalan also allows:

• pot anar avui al dentista amb la seva filla
• avui pot anar al dentista amb la seva filla

The exact position can change the rhythm or emphasis a little, but all of these are possible.

The original sentence sounds neutral and natural.

An informal singular version would be:

• Si et fan mal les dents, pots anar al dentista avui amb la teva filla.

Changes:

• a vostè / li becomes et
• pot becomes pots
• la seva filla becomes la teva filla

So the original is formal, while this version is for someone you address as tu.

Both are possible.

• Si li fan mal les dents... is shorter and still perfectly grammatical.
• Si a vostè li fan mal les dents... is more explicit and can sound more formal, careful, or emphatic.

Including a vostè can help make the sentence feel more directly addressed to the listener, especially in polite or professional speech.