A médica olhou o dentinho da bebê e disse que está melhor.

Because médica is the feminine form of médico. The sentence is talking about a female doctor, so both the article and the noun are feminine:

• o médico = the male doctor
• a médica = the female doctor

Portuguese usually marks this kind of gender directly in the noun.

In this sentence, a médica means the doctor, not just doctor. Portuguese uses definite articles very often, sometimes more often than English does.

So:

• A médica olhou... = The doctor looked...

It refers to a specific doctor already known in the situation.

Olhou is the preterite form of olhar. It describes a completed action in the past.

• olhar = to look
• olhou = looked

So A médica olhou o dentinho... means the doctor performed that action and it is finished.

Both are possible, but they are not exactly the same in feel.

• olhou o dentinho often sounds more like looked at / examined the little tooth
• olhou para o dentinho emphasizes the direction of the gaze a bit more: looked toward / looked at the little tooth

In Brazilian Portuguese, using olhar directly with an object is very common, especially when someone is inspecting or examining something.

Dentinho is the diminutive of dente.

• dente = tooth
• dentinho = little tooth

The ending -inho can show:

1. small size
2. affection or tenderness
3. a softer, cuter tone

Since this is about a baby, dentinho sounds very natural. It can suggest either that the tooth is literally small or simply that the speaker is talking in a gentle, affectionate way.

Here da bebê shows possession:

• o dentinho da bebê = the baby's little tooth

Literally, da bebê is like of the baby, but in natural English we usually say the baby's.

So the structure is:

• o dentinho = the little tooth
• da bebê = of the baby / the baby's

Because de + a contracts in Portuguese:

• de + a = da
• de + o = do

So:

• da bebê = de a bebê
• do bebê = de o bebê

These contractions are required in normal Portuguese.

Bebê can be either masculine or feminine depending on the article or other words around it.

• o bebê = the baby boy / the baby
• a bebê = the baby girl / the baby

In this sentence, a bebê tells you the baby is female.

So bebê itself does not change form, but the article shows the gender.

Portuguese often prefers a full noun phrase to avoid ambiguity.

• o dentinho da bebê = the baby's little tooth
• o dentinho dela = her little tooth
• seu dentinho = his/her/your little tooth

The problem is that seu/sua can be ambiguous in Portuguese. It can mean his, her, your, and in some contexts even their. Using da bebê makes the meaning very clear.

This is a very common learner question. Portuguese does not always backshift tenses the way English often does.

• disse que está melhor = she said that it is better
• disse que estava melhor = she said that it was better

Using está suggests that the speaker presents the improvement as still true now, or still relevant at the moment of speaking.

Using estava puts the statement more firmly in the past, as a past situation.

So disse que está melhor is completely natural if the tooth is still better now.

Most naturally, it refers to o dentinho.

So the idea is:

• The doctor looked at the baby’s little tooth
• and said that it is better

Portuguese often omits the subject pronoun when it is understood from context. Here, the most logical understood subject is the tooth.

That said, if the broader context were different, people might briefly wonder whether it means the baby. The sentence relies on context, just as many Portuguese sentences do.

Because Portuguese often leaves out subject pronouns when they are understood from context.

English needs it is better. Portuguese often just says:

• está melhor = is better

The subject is implied rather than spoken. In this sentence, the listener is expected to understand what is better from the previous context.

Because melhor does not change for masculine or feminine in this use.

Whether the thing is masculine or feminine, you still say:

• o dente está melhor
• a boca está melhor

So even though dentinho is masculine, the adjective/comparative form melhor stays the same.

Grammatically, context matters, so a reader could momentarily consider that possibility. But the most natural reading is still that the tooth is better, because the doctor has just looked at the little tooth.

If the speaker wanted to make it clearly about the baby, they might say something like:

• ...e disse que ela está melhor = ...and said that she is better

Adding ela would make the baby the clear subject.