S obzirom na karijes, stomatolog će bušiti zub i staviti plombu.

S obzirom na is a fixed expression meaning considering, in view of, or given.

So:

• S obzirom na karijes = Considering the cavity/tooth decay
• more literally: With regard to the tooth decay

It is a very common phrase in Serbian and is often used in both formal and everyday language.

After the fixed phrase s obzirom na, Serbian uses the accusative case.

So the noun after na here is in the accusative:

• karijes = nominative singular
• karijes = accusative singular as well

For this noun, the nominative and accusative forms happen to look the same, so there is no visible change.

That is normal with many masculine inanimate nouns in Serbian.

Karijes means tooth decay, dental caries, or in everyday English often simply a cavity.

A useful nuance:

• karijes can refer to the condition of decay in general
• in practical translation, English often uses cavity

So in this sentence, karijes is the dental problem that makes treatment necessary.

This is the future tense in Serbian, often called Future I.

It is formed with:

• a form of hteti (ću, ćeš, će, ćemo, ćete, će)
• plus the infinitive or a da + present structure

Here:

• će bušiti = will drill
• će ... staviti = will ... put / place

So:

• stomatolog će bušiti zub = the dentist will drill the tooth
• i staviti plombu = and put in a filling

Notice that će does not need to be repeated before the second verb, although it could be understood there.

This is a very natural question, because Serbian verbs often come in aspect pairs.

• bušiti = imperfective
• staviti = perfective

Why this combination?

• bušiti focuses on the process/activity of drilling
• staviti focuses on the completed result of placing the filling

So the sentence presents the treatment as:

1. the dentist will perform the drilling
2. then the dentist will complete the action of putting in the filling

This kind of aspect mix is normal in Serbian.

Yes, in some contexts you might hear izbušiti, which is the perfective partner meaning roughly drill out / finish drilling.

Compare:

• bušiti = to drill, to be drilling, to carry out drilling
• izbušiti = to drill through / drill out completely

In a medical or dental context, bušiti zub sounds natural because it describes the procedure.
If someone said izbušiti zub, it would emphasize the action as completed.

So the version in your sentence is completely normal.

Zub is the direct object of bušiti, so it is in the accusative singular.

• nominative: zub
• accusative: zub

Again, because zub is a masculine inanimate noun, the accusative singular is the same as the nominative singular.

So even though the case changes grammatically, the word looks the same.

Because plombu is the accusative singular form of plomba.

• nominative: plomba
• accusative: plombu

It changes because plomba is a feminine noun, and feminine nouns often show a visible accusative ending in -u.

Here plombu is the direct object of staviti:

• staviti plombu = to put in a filling

Yes, in dental context plomba means filling.

Literally, the basic idea is something like a plug/seal, but in everyday Serbian dentistry it is the normal word for a dental filling.

So:

• staviti plombu = to put in a filling
• imam plombu = I have a filling

Because Serbian has no articles.

English distinguishes:

• a dentist
• the dentist

Serbian does not have separate words like a/an/the.
So stomatolog can mean:

• a dentist
• the dentist

The exact meaning depends on context.

The same is true for:

• zub = a tooth / the tooth
• plomba / plombu = a filling / the filling

Yes. Stomatolog means dentist.

In everyday speech, people may also say things like:

• zubar = dentist

The difference is roughly:

• stomatolog sounds a bit more professional or formal
• zubar is very common in everyday conversation

Both are useful words to know.

Yes. Serbian word order is fairly flexible.

The original sentence:

• S obzirom na karijes, stomatolog će bušiti zub i staviti plombu.

Possible variation:

• Stomatolog će, s obzirom na karijes, bušiti zub i staviti plombu.

The meaning stays basically the same.

The original version puts s obzirom na karijes first, which gives it a slight context-setting or introductory emphasis: given the cavity...

Yes, but the nuance is a little different.

• zbog karijesa = because of the cavity / due to the decay
• s obzirom na karijes = considering the cavity / given the decay

So:

• Zbog karijesa, stomatolog će... sounds more directly causal
• S obzirom na karijes, stomatolog će... sounds slightly more formal or explanatory

Both can work, but s obzirom na has a more considering the circumstances feel.

It is understandable and grammatically fine. A native speaker might also say things like:

• Zbog karijesa, stomatolog će izbušiti zub i staviti plombu.
• Pošto imate karijes, stomatolog će izbušiti zub i staviti plombu.
• Stomatolog će vam izbušiti zub i staviti plombu.

A few notes:

• izbušiti may sound a bit more result-focused
• vam often appears in real-life speech: the dentist will drill your tooth and put in a filling
• speakers often choose wording based on whether they are speaking formally, medically, or conversationally

So your sentence is good for learning, even if everyday speech may vary a bit.