Se ela tivesse mastigado com calma, não teria ficado com dor ao engolir e ao mexer o queixo.

This pattern expresses an unreal past condition: something that did not happen, and a result that did not happen because of it.

• Se ela tivesse mastigado com calma = If she had chewed calmly / more carefully
• não teria ficado com dor = she would not have ended up in pain

This is the Portuguese equivalent of the English third conditional:

• If she had chewed more carefully, she wouldn’t have been in pain.

So the sentence is talking about a hypothetical past situation, not a real event sequence.

Tivesse mastigado is the pluperfect subjunctive.

It is formed with:

• tivesse = imperfect subjunctive of ter
• mastigado = past participle of mastigar

Together, they mean had chewed in a hypothetical or contrary-to-fact situation.

This tense is very common after se in unreal past conditions:

• Se eu tivesse estudado... = If I had studied...
• Se eles tivessem saído... = If they had left...

Teria ficado is the conditional perfect.

It is formed with:

• teria = conditional of ter
• ficado = past participle of ficar

It means would have become / would have ended up / would have been depending on context.

In this sentence:

• não teria ficado com dor = would not have ended up in pain

This structure commonly pairs with se + pluperfect subjunctive:

• Se ela tivesse mastigado com calma, não teria ficado com dor.

Both are possible, but they are not exactly identical in feel.

• ficar com dor = to end up with pain / to become sore / to start having pain
• ter dor = to have pain
• sentir dor = to feel pain

Ficar com dor often suggests a change of state: she wasn’t in pain before, but after doing something, she ended up in pain.

So:

• não teria ficado com dor = she would not have ended up in pain
• não teria tido dor = she would not have had pain

The version with ficado com dor sounds very natural here because it emphasizes the result of chewing badly.

Yes, very common.

Estar com dor or ficar com dor is a very natural way to talk about pain in Brazilian Portuguese.

Examples:

• Estou com dor de cabeça. = I have a headache.
• Ela ficou com dor no joelho. = She ended up with pain in her knee.
• Estou com dor ao engolir. = It hurts when I swallow.

So ficar com dor is a normal everyday expression.

Ao + infinitive is a common Portuguese structure meaning something like:

• when
• while
• upon
• sometimes in the act of

So:

• ao engolir = when swallowing / while swallowing
• ao mexer o queixo = when moving the jaw

In this sentence, it describes the situations in which the pain happened.

Other examples:

• Ao entrar, feche a porta. = When entering, close the door.
• Ela sorriu ao me ver. = She smiled when she saw me.

Yes, the repetition is normal and often preferred for clarity and balance.

• ao engolir e ao mexer o queixo
• literally: when swallowing and when moving the jaw

You may sometimes hear the second ao omitted in casual speech or writing:

• ao engolir e mexer o queixo

But repeating it sounds clearer and more parallel, especially in careful written Portuguese.

Mexer means to move, to stir, to mess with, or to handle, depending on context.

Here, mexer o queixo means to move the jaw.

It does not mean touching the jaw with your hand. It refers to jaw movement itself, such as opening, closing, or shifting it.

So:

• dor ao mexer o queixo = pain when moving the jaw

Both relate to the jaw area, but they are not exactly the same in usage.

• queixo = chin / jaw area, and in everyday speech it can sometimes be used loosely in contexts involving jaw movement
• mandíbula = jawbone / mandible, more anatomical or technical

In everyday Brazilian Portuguese, people often choose the simpler, more familiar word. So mexer o queixo sounds more natural in casual language than mexer a mandíbula, which sounds more medical or technical.

Both are possible, but com calma is usually more natural and conversational in Brazilian Portuguese.

• mastigar com calma = to chew calmly / slowly / carefully
• mastigar calmamente = grammatical, but often a bit more formal or stiff

Portuguese very often prefers a prepositional phrase like com calma where English might use an adverb.

Other examples:

• Fala com calma. = Speak calmly.
• Lê com atenção. = Read carefully.

In Portuguese, as in English, the object can be omitted if it is obvious from context.

So mastigar does not always need an expressed object.

• Ela mastigou muito rápido. = She chewed very fast.
• Você precisa mastigar melhor. = You need to chew better.

Here, the food is understood, so there is no need to say it.

Yes. Portuguese often omits subject pronouns when the verb form already makes the subject clear.

So you could say:

• Se tivesse mastigado com calma, não teria ficado com dor...

However, including ela can help with:

• clarity
• contrast
• emphasis
• avoiding ambiguity in context

So both are possible, but ela may be there because the speaker wants to make the subject explicit.

Yes. In standard Portuguese, não normally comes before the verb phrase.

So:

• não teria ficado = would not have ended up
• não teria sentido = would not have felt
• não teria acontecido = would not have happened

This placement is completely normal.

Yes. Even if the meaning stays the same, English can phrase it in different natural ways. For example:

• If she had chewed more carefully, she wouldn’t have had pain when swallowing and moving her jaw.
• If she had chewed slowly, she wouldn’t have ended up with pain when swallowing or moving her jaw.
• If she had chewed more calmly, it wouldn’t have hurt when she swallowed or moved her jaw.

The Portuguese structure stays the same, but English has several natural ways to express it.