Help! Does this tooth require restoration?

[np01]

Hi! So I'm a dental student and we were asked whether the 2nd premolar (distal) in this radiograph requires restoration - it appears to be through the enamel but is it going through dentine? Because it is not so clear to me. We were thought that you restore if there is a radiolucency at least in the outer third of dentine but I'm not sure whether I can see it. Could it potentially be arrested?
And I'm pretty sure the mesial is only in enamel right?
Patient is quite high caries risk.

 

[Dr M]

Mesial is only through the enamel, but distally it is definitely into the dentine and thus requires a filling to be done. If the patient is a high risk patient, one might argue that mesially needs a filling as well, especially if the patient does not regularly attend a dentist for check-ups.

 

[np01]

Mesial is only through the enamel, but distally it is definitely into the dentine and thus requires a filling to be done. If the patient is a high risk patient, one might argue that mesially needs a filling as well, especially if the patient does not regularly attend a dentist for check-ups.

Ok perfect, thank you for your reply!