Revisamos el tapón de cerumen antes de que entremos.

Because antes de que is used when a new clause with its own subject follows. Here, the second part has a conjugated verb, entremos, and the subject is understood as we.

• antes de entrar = before entering / before we enter
• antes de que entremos = before we enter

Both can be possible in some contexts, but antes de que + subjunctive is especially common when the speaker wants to present the second action as a separate event.

A useful rule:

• antes de + infinitive → when there is no new finite verb
• antes de que + subjunctive → when there is a new clause

So:

• Antes de entrar, revisamos...
• Revisamos... antes de que entremos.

Both are grammatical, but the structure in your sentence specifically requires que + subjunctive.

Because antes de que normally triggers the subjunctive.

In Spanish, the subjunctive often appears after expressions that refer to something not yet completed, uncertain, expected, or dependent on another action. Entering has not happened yet at the point of checking, so Spanish uses the subjunctive:

• antes de que entremos

This is very similar to other time expressions that trigger the subjunctive when talking about future or pending actions, such as:

• cuando entremos
• hasta que entremos
• en cuanto entremos

So the key point is: antes de que + subjunctive = standard grammar.

Because entremos is the present subjunctive form of entrar, while entramos is the present indicative form.

Here, after antes de que, Spanish needs the subjunctive, so:

• entramos = indicative, not correct here
• entremos = subjunctive, correct here

Conjugation of entrar in the present subjunctive:

• yo entre
• tú entres
• él/ella/usted entre
• nosotros/nosotras entremos
• vosotros/vosotras entréis
• ellos/ellas/ustedes entren

Since the subject is we, the correct form is entremos.

Revisamos comes from revisar, which often means:

• to check
• to inspect
• to examine
• to review

In this sentence, it most likely means we check or we examine.

Depending on context, revisar can be used for:

• checking a document
• inspecting a machine
• examining a patient or body part
• reviewing notes

So here it sounds somewhat medical or practical: we examine/check the earwax blockage before we go in.

Formally, revisamos can be either:

• present indicative: we check
• preterite: we checked

Spanish has some forms that look identical in the present and preterite for nosotros.

Examples:

• Hoy revisamos el tapón de cerumen. = Today we check the earwax blockage.
• Ayer revisamos el tapón de cerumen. = Yesterday we checked the earwax blockage.

In your sentence, the context strongly points to the present reading, because antes de que entremos refers to something still pending.

It is a noun phrase:

• tapón = plug, blockage
• de = of
• cerumen = earwax

So literally it is plug of earwax, which in natural English would usually be earwax plug or earwax blockage.

This noun + de + noun pattern is very common in Spanish:

• taza de café = cup of coffee
• gafas de sol = sunglasses
• dolor de cabeza = headache
• tapón de cerumen = earwax plug

Spanish often uses the definite article more frequently than English.

Here, el tapón de cerumen refers to a specific blockage that both speaker and listener presumably know about, or that is relevant in the situation. So Spanish naturally says the earwax plug/blockage.

Even when English might sound fine with no article or a different structure, Spanish often prefers the article:

• Me duele la cabeza = My head hurts
• Lavé las manos = I washed my hands
• Revisamos el tapón de cerumen = We check the earwax blockage

So el is very normal here.

Not usually in the same register.

• cerumen is the proper medical or anatomical word for earwax
• cera usually means wax in a more general sense

So if you are talking about the substance in the ear, cerumen is the precise word. In everyday speech, some people may use less technical wording, but tapón de cerumen sounds especially medical and standard.

Because Spanish usually drops subject pronouns when the verb ending already shows who the subject is.

• revisamos already means we check
• entremos already means we enter

So there is no need to say nosotros unless the speaker wants emphasis or contrast.

For example:

• Revisamos el tapón de cerumen... = We check the earwax blockage...
• Nosotros revisamos el tapón de cerumen... = We check the earwax blockage... (with extra emphasis, perhaps contrasting with someone else)

This is one of the biggest differences from English.

Yes, it could.

If the subject of both actions is the same, Spanish often uses the infinitive:

• Revisamos el tapón de cerumen antes de entrar.

That means essentially the same thing: We check the earwax blockage before entering / before we go in.

So why use antes de que entremos instead? Because Spanish also allows the fuller clause with subjunctive, and it can sound a bit more explicit or formal.

In other words:

• antes de entrar = shorter, very natural
• antes de que entremos = also correct, with a full subordinate clause

Yes. The sentence is grammatically natural.

Basic structure:

• Revisamos = main verb
• el tapón de cerumen = direct object
• antes de que entremos = time clause

Spanish often places time expressions after the main clause, just as English does:

• We check the earwax blockage before we go in.

You could also move the time clause to the front:

• Antes de que entremos, revisamos el tapón de cerumen.

That is also correct. The difference is mostly one of emphasis or style.

It can mean either to enter or to go in, depending on the context and the tone.

• enter sounds more formal in English
• go in sounds more everyday and natural

So antes de que entremos could be understood as:

• before we enter
• before we go in

The best English choice depends on what the surrounding situation is: a room, an office, an operating area, a consultation room, and so on.

It sounds fairly medical or at least clinical, mainly because of tapón de cerumen.

A more everyday sentence might use less technical wording, depending on the speaker and situation. But this sentence, as written, sounds like something you might hear in:

• a clinic
• a doctor’s office
• a healthcare explanation
• a professional setting

The verb revisar also fits that tone well, since it suggests inspection or examination rather than casual looking.