No, they're mistaken. Can you try a different dentist?
Yes but I was hoping to use this one because it's the one my husband uses.
You are definitely eligible. You could print this out to show them that, indeed, you are eligible.
newcomer link: http://www.dh.gov.uk/en/Healthcare/Entitlementsandcharges/OverseasVisitors/Browsable/DH_074376 [nonactive]
Thanks, but I don't see it mention dentists anywhere.
Also, regarding this part:
"If you do not have an automatic right to take up permanent residence but have applied to the Home Office for leave to enter/remain on a settled basis, you will be chargeable for any hospital treatment up to the point your application is granted or until you accrue 12 months lawful residence in the UK."
Does this mean I will have to pay for hospital treatment? I entered a few weeks ago on a spouse visa which is valid for 27 months, after which I will apply for permanent residency.