Re: there are more mobile phone owners than toothbrush owners
'In the UK, do they have dentists and subsidized bi-annual dental exams available for everyone?'
Never have done. Dentistry wasn't folded into the NHS so the only NHS provision is via contracts with private dentists. The contracts are shit so few dentists will take up the offer which leads to a massive shortage of patient capacity. Even then, it's only subsided and not free for a lot of procedures. Only kids and the spectacularly poor are eligible for NHS dentistry, anyway.
The contracts work by allowing the dentist to claim for the cost of any procedures they do on patients but there's a fixed price list. This leads to occasional outright fraud wherein dentists claim for procedures that never happened. The other side effect is dentists stalling treatment on teenagers with unprofitable problems so that they turn 18 and get kicked off NHS dentistry and are forced to pay the full private dentistry price. Obviously, there's an inherent gamble that the teens don't move to another dentist when they go private but there's also the shortage of capacity in private dentistry to limit their choice.