Kawat gigi itu longgar.

In Indonesian, you often do not need a verb like is/are in simple statements.

So:

• Kawat gigi itu longgar = The braces are loose

Here, longgar is an adjective, and it can directly function as the predicate.

This is very normal in Indonesian:

• Rumah itu besar = The house is big
• Anaknya sakit = The child is sick

You may sometimes see adalah, but that is usually not used before adjectives like longgar in ordinary sentences.

In this sentence, itu can feel a lot like the in English, even though its basic meaning is often that.

So kawat gigi itu can mean:

• that set of braces
• or more naturally in context, the braces

Indonesian does not have a true article system like a/an/the, so words like itu are often used to make something sound specific and identifiable.

Compare:

• Kawat gigi longgar = Braces are loose / the braces are loose (less specifically marked)
• Kawat gigi itu longgar = Those/The braces are loose (more specific)

Yes, kawat gigi is a standard and common term for dental braces.

Literally, it breaks down as:

• kawat = wire
• gigi = teeth

But you should learn kawat gigi as a fixed expression meaning braces.

In everyday speech, some people also say behel, which is a very common informal borrowing.

So:

• kawat gigi = standard/common
• behel = very common, more informal/conversational

Because kawat gigi is the established expression in Indonesian for braces.

Not every noun combination can be translated word-for-word from English logic. Even if the literal parts are clear, the accepted phrase is what matters.

A good rule is:

• memorize kawat gigi as one vocabulary item

Trying to reverse it to gigi kawat would sound unnatural or incorrect for braces.

Longgar is an adjective meaning things like:

• loose
• slack
• not tight

In Indonesian, adjectives can act as the main predicate of the sentence without a copula.

So in:

• Kawat gigi itu longgar

longgar is an adjective, but it functions like the English predicate are loose.

It can be used both literally and more broadly.

Literal uses:

• baju ini longgar = these clothes are loose
• sekrupnya longgar = the screw is loose
• kawat gigi itu longgar = the braces are loose

More extended uses:

• aturan itu longgar = the rules are lax/loose
• pengawasannya longgar = the supervision is lax

So yes, longgar is flexible, but in your sentence the meaning is clearly physical.

That is the normal position when the adjective is the predicate.

Structure here:

• kawat gigi itu = subject
• longgar = predicate adjective

So the pattern is:

• [noun phrase] + [adjective]

Examples:

• Mobil itu mahal = The car is expensive
• Pintunya terbuka = The door is open
• Kawat gigi itu longgar = The braces are loose

This is different from an attributive adjective inside a noun phrase, where Indonesian often also places the adjective after the noun:

• rumah besar = a big house

So post-noun adjectives are very common in Indonesian.

Indonesian nouns usually do not change form for singular vs. plural.

So kawat gigi can refer to:

• a braces appliance in general
• the set of braces on someone’s teeth

In English, we usually say braces as a plural form, but Indonesian does not need to match that grammar.

The number is understood from context.

If necessary, Indonesian can mark plurality in other ways, such as:

• reduplication
• numbers
• context words

But here, plain kawat gigi is perfectly normal.

Yes, and that is also very natural.

• Kawat gigi itu longgar = The/those braces are loose
• Kawat giginya longgar = His/her/their braces are loose or the braces are loose, depending on context

The ending -nya can show possession or definiteness, so it is very common in everyday Indonesian.

In many real situations, a speaker might prefer:

• Kawat giginya longgar
• Behelnya longgar

especially if it is already clear whose braces are being discussed.

A practical pronunciation guide is:

• kawat ≈ KAH-waht
• gigi ≈ GEE-gee
• itu ≈ EE-too
• longgar ≈ LONG-gar

A few notes:

• g in Indonesian is always a hard g, like in go
• i is usually like ee in see
• a is usually like the a in father
• Indonesian spelling is fairly phonetic

A rough full pronunciation:

• KAH-waht GEE-gee EE-too LONG-gar

Yes, it sounds completely natural.

It would fit situations like:

• telling a dentist that your braces feel loose
• describing a problem with someone’s braces
• reporting that a bracket or wire is not tight anymore

Depending on context, other natural alternatives include:

• Kawat gigi saya longgar = My braces are loose
• Behel saya longgar = My braces are loose (more conversational)
• Kawat giginya longgar = His/Her braces are loose

So your sentence is grammatically natural and contextually realistic.