We went private and our UK dentist is just as good if not better than anything I have had in the USA. Exceptionally clean and very careful about everything. Friendly too.
I have not always had dental insurance in the USA and have found that even with the horrible exchange rate that my check up and cleanings (IDH and I needed a scaling as we waited too long) were cheaper than in the USA. Oh and 100% better than my one HMO nasty ,dirty office experience in hole in the wall GA.
You can purchase insurance from
http://www.denplan.co.uk/ if you are worried about cost for long term care.
You do need to be aware that if you need a deeper cleaning you will need two appointments. The first is with a Dentist that will do a check of your teeth and an assessment. They also will do quick cleans.
If you need scaling you will then need to make an appointment for the hygenist.
I think that some people think that since they used to get free or near free care that they are entitled to it, and therefore refuse to pay for it.
Some obviously can't afford to pay.