My problem is that the study is about students of 2015-2016.Any clue if she was of Russian origin and not Eastern Euro (even though dental work was from there)?
Due to various issues, Russia is known to have an unusually high prevalence of tooth decay and dental issues among its citizens compared to Nordic countries for example.
Dental caries experience and determinants in young adults of the Northern State Medical University, Arkhangelsk, North-West Russia: a cross-sectional study - BMC Oral Health
Background Little information exists about the experience of and risk factors for dental caries in young adults in Russia. We investigated dental caries experience and determinants in medical and dental students in North-West Russia. Methods This cross-sectional study included 442 medical and...bmcoralhealth.biomedcentral.com
We selected our participants from the approximately 3900 students that attended the NSMU in the 2015-2016 academic year.
It is interesting. But the data is unhelpful for JD because our JD was found in 1983 and the study is about students in 2015-2016.
JD was born during the Soviet era, and the study is well post-Soviet era.
So, I am not at ease to say one way or another.
If we had datas of the 1970-1980 during the Soviet era, then, I could have done something about it.
Even studies from the 1950-1960 era would had been helpful.
Also, cavities can be caused by medications. And in those days, meds available in USSR were not the same as in US.
That's why the timing of your study is a hurdle to give you any meaningful opinion.
Could be a US dental work from European dentist or a European dental work from Europe.
So, I can't say one way or another.