يعقم أخصائي صحة الأسنان مرآة الأسنان.

A natural breakdown is:

• يعقّم = the verb, sterilizes / disinfects
• أخصائي صحة الأسنان = the subject, the dental hygienist or literally specialist of dental health
• مرآة الأسنان = the direct object, the dental mirror

So the structure is:

• verb
  • subject
    • object

That is a very common word order in Modern Standard Arabic.

Because Arabic often uses verb–subject–object order, especially in formal written style.

So:

• يعقّم أخصائي صحة الأسنان مرآة الأسنان = Sterilizes the dental hygienist the dental mirror in literal order

In natural English, of course, you translate it as The dental hygienist sterilizes the dental mirror.

Arabic can also put the subject first:

• أخصائي صحة الأسنان يعقّم مرآة الأسنان

That also means The dental hygienist sterilizes the dental mirror, but it has a slightly different discourse feel, with more focus on the subject.

يعقّم means he sterilizes, he disinfects, or he sanitizes, depending on context.

It comes from the root ع ق م, which is connected with sterilization/disinfection. In a medical or dental context, sterilizes is often the best translation.

Grammatically, يعقّم is:

• present/imperfect tense
• 3rd person
• masculine singular

So by itself it means he sterilizes.

Because the subject أخصائي is masculine singular.

In the present tense:

• يـ often marks 3rd person masculine singular
• تـ can mark 3rd person feminine singular or certain 2nd person forms

So:

• يعقّم أخصائي... = A male specialist sterilizes...
• تعقّم أخصائية... = A female specialist sterilizes...

If the sentence had أخصائية صحة الأسنان instead, the verb would normally be تعقّم.

Because Arabic often uses the iḍāfa construction, usually called the construct phrase.

In an iḍāfa, Arabic puts two nouns next to each other instead of using a separate word like of.

So:

• صحة الأسنان = literally health of the teeth
• مرآة الأسنان = literally mirror of the teeth
• أخصائي صحة الأسنان = literally specialist of dental health

In natural English, these are usually rendered more idiomatically as:

• dental health
• dental mirror
• dental hygienist

So this sentence contains two iḍāfa phrases, and one of them is nested inside another.

Because أخصائي is the first noun in an iḍāfa, and the first noun in an iḍāfa normally does not take الـ.

That does not mean the whole phrase is indefinite.

Here is what happens:

• الأسنان is definite because it has الـ
• therefore صحة الأسنان is definite
• therefore أخصائي صحة الأسنان is also definite

So even without الـ on أخصائي, the whole phrase can still mean the dental hygienist.

This is a very common point of confusion for English speakers.

If you read the sentence with case endings, it would be:

يُعَقِّمُ أخصائيُّ صحةِ الأسنانِ مرآةَ الأسنانِ.

The endings show the grammar:

• أخصائيُّ = subject, so it is nominative
• صحةِ = genitive, because it is part of an iḍāfa after أخصائي
• الأسنانِ = genitive, as the second noun of the iḍāfa
• مرآةَ = direct object, so it is accusative
• الأسنانِ = genitive, because it is the second noun of another iḍāfa

In everyday reading, these short final vowels are often not written and often not pronounced fully, but they are still part of the grammar.

Because both words end in ة (taaʾ marbuuṭa), and that ة is pronounced as t when the word is in an iḍāfa or when full endings are pronounced.

So:

• صحة الأسنان is pronounced like ṣiḥḥat al-asnān
• مرآة الأسنان is pronounced like mirʾat al-asnān

But when a word ending in ة is said by itself in pause, it is usually pronounced more like -a or -ah, not -t.

That is why learners often hear both patterns.

There are two main clues:

1. Word order
   In this sentence, after the verb يعقّم, the next noun phrase is the subject:

   • أخصائي صحة الأسنان

   Then comes the object:

   • مرآة الأسنان

2. Case endings, if pronounced

   • أخصائيُّ has nominative -u, marking the subject
   • مرآةَ has accusative -a, marking the direct object

So even though English relies heavily on word order, Arabic can also show these roles through case.

Yes. That is also correct.

Compare:

• يعقّم أخصائي صحة الأسنان مرآة الأسنان
• أخصائي صحة الأسنان يعقّم مرآة الأسنان

Both mean the same thing overall: The dental hygienist sterilizes the dental mirror.

The first is a common verbal sentence pattern in MSA.
The second puts the subject first, which can sound more topic-focused: As for the dental hygienist, he sterilizes the dental mirror.

So both are grammatical; the difference is mostly in style and emphasis.

Because Arabic often uses a noun phrase where English prefers an adjective.

Literally:

• صحة الأسنان = health of the teeth
• مرآة الأسنان = mirror of the teeth

But natural English usually says:

• dental health
• dental mirror

So you should not expect a one-to-one match between Arabic nouns and English adjectives. Very often, Arabic says X of Y, while English turns that into an adjective like dental, medical, school, governmental, and so on.

Yes, three especially:

• ع in يعقّم
  This is ʿayn, a sound English does not have. It is produced deep in the throat.

• قّ in يعقّم
  The ق is a strong q sound, and the shadda means it is doubled: -qq-

• ء in مرآة and أخصائي
  This is hamza, a glottal stop, like a catch in the throat.

So a learner often needs extra practice with:

• يعقّم
• مرآة
• أخصائي

These are all normal words, but they contain sounds and spelling patterns that are less familiar to English speakers.