Karies gigi itu berbahaya.

In Malay, demonstratives such as ini and itu usually come after the noun phrase they describe.

So:

• karies gigi itu = that tooth decay / the tooth decay in question

The whole noun phrase is karies gigi, and itu goes after the entire phrase, not in the middle.

Compare:

• buku itu = that book
• rumah besar itu = that big house
• karies gigi itu = that dental caries / that tooth decay

It can do both, depending on context.

In many Malay sentences, itu can literally mean that, but it is also often used to mark something as specific or already known, which can feel closer to English the.

So karies gigi itu berbahaya could be understood as:

• That tooth decay is dangerous
• The tooth decay is dangerous
• That case of dental caries is dangerous

The exact nuance depends on the situation.

Malay often leaves out the verb to be in simple sentences like this.

So instead of saying something like X is dangerous with a separate word for is, Malay simply says:

• X berbahaya = X is dangerous

That means:

• Karies gigi itu berbahaya literally follows the pattern
  [subject] + [predicate]

This is very normal in Malay.

Because berbahaya is the predicate of the sentence.

In Karies gigi itu berbahaya:

• karies gigi itu = the subject
• berbahaya = what is being said about the subject

So the structure is:

• [subject] [predicate]

This is similar to English The tooth decay is dangerous, except Malay usually omits is.

Yes. Karies gigi is a noun phrase made of two nouns:

• karies = caries / decay
• gigi = tooth / teeth

Malay often puts nouns together directly, without a word like of.

So karies gigi means something like:

• tooth decay
• dental caries
• literally, caries tooth/teeth

This kind of noun + noun structure is very common in Malay.

It can cover either idea, depending on context.

Malay nouns usually do not change form for singular and plural the way English nouns do. So gigi can refer to:

• tooth
• teeth
• teeth in a general sense, as in dental

In karies gigi, it is best understood as part of the set phrase dental caries / tooth decay, not as one separately counted tooth.

In this word, ber- helps form berbahaya, which means dangerous or harmful.

The base word is:

• bahaya = danger

And:

• berbahaya = dangerous / hazardous

For a learner, it is best to treat berbahaya as a vocabulary item you learn as a whole. Even though ber- is a common prefix in Malay, here the most useful thing is simply:

• bahaya = danger
• berbahaya = dangerous

You might see forms with adalah in formal writing, but in everyday Malay, Karies gigi itu berbahaya is the natural and normal version.

Malay usually does not need adalah in simple adjective sentences.

So for learners, the safest and most natural choice is:

• Karies gigi itu berbahaya.

It is correct, and it is especially common in medical, educational, or formal contexts.

In everyday conversation, speakers may also use more familiar expressions such as:

• gigi berlubang = cavities / a tooth with a hole
• kerosakan gigi = tooth damage / tooth decay

So karies gigi sounds a bit more technical than some everyday alternatives.

Yes. Berbahaya is a general word for dangerous, hazardous, or harmful.

It can be used for:

• health risks
• dangerous objects
• risky situations
• harmful substances

So in this sentence, it means the tooth decay is something harmful or dangerous to health.

A simple approximation is:

• KA-ries GI-gi EE-too ber-ba-HA-ya

A few notes:

• g in gigi is always a hard g, like in go
• r is usually tapped or lightly rolled
• caries/karies has clear vowels; do not reduce them too much
• bahaya is pronounced roughly ba-HA-ya

Malay pronunciation is usually more regular than English spelling, so each vowel is usually pronounced clearly.

Yes, at least slightly.

• Karies gigi berbahaya = Tooth decay is dangerous / Dental caries is dangerous
  This sounds more general.
• Karies gigi itu berbahaya = That/The tooth decay is dangerous
  This points to something specific or already identified.

So itu makes the noun phrase more definite or more context-specific.