oyasirazu wo nuita ato, haguki ga hareta node, yukkuri kamimasu.

Because the two nouns play different roles in the sentence.

• 親知らずを抜いた
  Here, 親知らず is the direct object of 抜いた (pulled out), so it takes を.

• 歯茎が腫れた
  Here, 歯茎 is the thing that became swollen, so it takes が as the subject of 腫れた.

So the structure is basically:

• [wisdom tooth] を [pull out]
• [gums] が [become swollen]

This is very common in Japanese: one clause can use を, and the next clause can use が, depending on the verb.

Because あと means after, and when you say after doing X, Japanese usually uses the plain past form before あと:

• 食べたあと = after eating
• 帰ったあと = after going home
• 抜いたあと = after pulling out

So 親知らずを抜いたあと means after I had my wisdom tooth removed / after pulling out my wisdom tooth.

Using 抜くあと would sound unnatural here.

ので means because / since, and it gives a softer, more explanatory reason than から.

In this sentence:

• 歯茎が腫れたので、ゆっくり噛みます。
• Because my gums got swollen, I chew slowly.

Difference in nuance:

• ので: softer, more neutral, often sounds more polite or explanatory
• から: more direct, sometimes more subjective or assertive

So both could work, but ので sounds very natural in this kind of explanation.

腫れた is the plain past form of 腫れる (to swell).

It shows that the swelling happened after the tooth was removed:

• 歯茎が腫れた = my gums became swollen / got swollen

This past form focuses on the event of becoming swollen.

In real life, the gums may still be swollen now, but this sentence is describing the cause as something that happened:

• I had the tooth removed.
• My gums swelled.
• So I chew slowly.

Yes, and the nuance would change a little.

• 歯茎が腫れたので
  Focuses on the fact that the gums became swollen

• 歯茎が腫れているので
  Focuses on the gums currently being swollen

So:

• 腫れたので = because my gums got swollen
• 腫れているので = because my gums are swollen

Both are natural, but 腫れている emphasizes the present condition more clearly.

Because 噛みます describes the speaker’s current or usual action in response to the situation.

The sentence means something like:

• After my wisdom tooth was removed, my gums swelled, so I chew slowly.

In Japanese, the non-past form can mean:

• present
• future
• habitual action

Here it sounds like a present/current habit: because of the swollen gums, the speaker now chews slowly.

If you wanted to emphasize an ongoing action right now, you might also hear 噛んでいます.

Japanese often leaves out subjects when they are obvious from context.

In this sentence, the person who:

• had the wisdom tooth removed
• has swollen gums
• chews slowly

is naturally understood to be the speaker.

So English needs I, but Japanese does not.

This is one of the most common differences between Japanese and English.

ゆっくり is an adverb meaning slowly.

It modifies 噛みます:

• ゆっくり噛みます = chew slowly

It is very common to place an adverb directly before the verb it modifies.

Examples:

• ゆっくり食べます = eat slowly
• ゆっくり話します = speak slowly
• ゆっくり噛みます = chew slowly

Because the sentence specifically focuses on the act of chewing, not the broader act of eating.

• 食べます = eat
• 噛みます = chew / bite

If your gums are swollen, the painful part is often the chewing itself, so 噛みます is more precise.

Japanese nouns usually do not mark singular vs. plural clearly unless needed.

So 歯茎 could be understood as:

• gum
• gums

In natural English, gums sounds better here, but Japanese does not need to make that distinction explicitly.

It is read おやしらず.

It means wisdom tooth. It is a very common everyday word.

Literally, it is an interesting expression:

• 親 = parent
• 知らず = not knowing

The idea is that it comes in when someone is older, at an age when the parent may not know about it directly. But for learners, the important thing is simply:

• 親知らず = wisdom tooth

Not necessarily.

Japanese often uses a transitive verb like 抜く in a way that can also cover situations where the action was done to you, especially when the context makes it obvious.

So 親知らずを抜いた can often be understood naturally as:

• I had my wisdom tooth pulled
• My wisdom tooth was removed

If you want to make it extra explicit that someone else did it, you could say something like:

• 親知らずを抜いてもらった = I had someone pull my wisdom tooth out for me

But the original sentence is still very natural.

Yes, it is mixed in a very normal way.

• 抜いた
• 腫れた
• ので

These are plain forms used inside the sentence.

• 噛みます

This is polite -ます form at the end.

Japanese often does this:

• plain forms in subordinate clauses
• polite form at the sentence end

So the sentence is polite overall and sounds natural in standard conversation.

Yes.

Both are possible:

• 抜いたあと
• 抜いた後

In everyday writing, あと in hiragana is very common and often easier to read. Japanese often uses hiragana for grammar-like words such as this, even when a kanji exists.