صورة الأشعة السينية في سجل الأسنان.

It can be understood as a verbless nominal sentence in the present tense:

• صورة الأشعة السينية = the X-ray image
• في سجل الأسنان = in the dental record

So the full sense is The X-ray image is in the dental record.

Depending on context, it could also be just a phrase or label, like a heading in a form or chart.

In Modern Standard Arabic, the verb to be is usually not written or spoken in the present tense.

So:

• الصورة في السجل = the image is in the record

Arabic simply leaves is understood.

If you wanted a past tense, then Arabic would use a verb:

• كانت صورة الأشعة السينية في سجل الأسنان = the X-ray image was in the dental record

Because صورة الأشعة السينية is an iḍāfa construction, often called a genitive/possessive construction.

In an iḍāfa:

• the first noun usually does not take الـ
• the whole phrase becomes definite if the second part is definite

So:

• صورة الأشعة السينية = literally image of the X-rays
• but naturally it means the X-ray image

Even though صورة has no الـ, the whole phrase is definite because الأشعة السينية is definite.

الأشعة السينية is the standard Arabic expression for X-rays.

Breakdown:

• الأشعة = the rays
• السينية = X-ray / relating to X-rays

So the phrase means the X-rays or X-ray radiation, depending on context.

In this sentence, صورة الأشعة السينية means the X-ray image or the X-ray picture.

This is a very common Arabic pattern.

الأشعة is a non-human plural, and in Arabic, non-human plurals usually take feminine singular agreement for adjectives.

So:

• الأشعة = plural
• السينية = feminine singular adjective agreeing with a non-human plural

That is why you get:

• الأشعة السينية not
• الأشعة السينيات or other plural adjective forms

This rule is very common in MSA.

Literally, سجل الأسنان means record of the teeth.

This is another iḍāfa:

• سجل = record
• الأسنان = the teeth

Arabic often uses a noun + noun structure where English prefers an adjective.

So:

• سجل الأسنان = dental record
• literally = record of the teeth

This is very normal Arabic style.

Because the phrase is referring to a specific type of record: the dental record.

In an iḍāfa, if the second noun is definite, the whole phrase becomes definite:

• سجل الأسنان = the dental record
• سجل أسنان or سجلُ أسنانٍ would be more like a dental record

So the definiteness of الأسنان helps make the whole phrase definite.

A helpful pronunciation is:

ṣūratu l-ashiʿati s-sīniyyati fī sijilli l-asnān

A simpler learner-friendly version is:

soo-rat al-ashi‘ah as-seeniyyah fee sijill al-asnaan

A few notes:

• ص is a heavy s
• ع in الأشعة is a consonant English does not have
• السينية begins with س, a sun letter, so the l of الـ is not pronounced clearly; it sounds like as-sīniyya
• سجل is usually pronounced sijill

In fully vocalized formal Arabic, you could read it as:

صُورَةُ الأَشِعَّةِ السِّينِيَّةِ فِي سِجِلِّ الأَسْنَانِ

Why these endings?

• صورةُ: nominative, as the subject/topic of the nominal sentence
• الأشعةِ: genitive, because it is the second part of an iḍāfa
• السينيةِ: genitive too, because it describes الأشعة
• في سجلِّ: في makes سجل genitive
• الأسنانِ: genitive as the second part of the iḍāfa سجل الأسنان

In normal writing, these case endings are usually omitted.

It is best understood as:

• صورة + الأشعة السينية

So the iḍāfa is:

• صورة = first term
• الأشعة السينية = second term

Inside that second part:

• الأشعة is the noun
• السينية is an adjective describing الأشعة

So الأشعة السينية is not another iḍāfa; it is a noun plus adjective.

By contrast, سجل الأسنان really is an iḍāfa.

Yes.

While the core meaning is the same, the most natural English may vary by context:

• The X-ray image is in the dental record
• The X-ray is in the dental record
• X-ray image in the dental record if it is a label or caption

Arabic often allows this kind of flexibility, especially in short medical or administrative phrases.