Possible to reuse personal statement on ucas for a different subject?

If you’re reapplying to the same universities then they’ll have access to both PSs.
It’s not going to do you any favours if they see that large parts of your PS have the same content with the degree subject substituted. And to be frank if you could substitute the degree subject then you probably should rewrite it anyway as you don’t seem to understand your chosen subject well or demonstrate any real enthusiasm for it.

The only reason they were similar were due to my work experience in volunteering in a various range of medical environments, due to having talked about the technical and medical aspects of it alongside communication which I had thought last year was also relevant to biomedicine. I am a bit confused, I thought the people checking my personal statements if I were to apply to dentistry would be those working in the oral health department surely? Rather than those working in the biomed/medical department. I messaged UCAS and they said it was fine but now I'm concerned because if what you are saying is correct, does that mean they had seen I had applied last year to biomed, and would they assume I don't have real enthusiasm for dentistry (despite the fact I was only applying to biomed at the time because I wanted to study dentistry afterwards).