There was actually a 2.3% increase in NHS-registered dentists last year, but it doesn't matter, because of those, they are doing less and less NHS work. Nearly half of the 24,000-odd dentists have cut back on the amount of NHS work they do.
Source
There are also reports that 45% of dentists in the UK are planning on cutting back the amount of NHS work they do. Of course, all of this leaves a complete mess for those who stay, meaning overwork and burnout, leading to more dentists retiring early or leaving the country like yours (especially since someone who would have been able to work without issue in the UK now has to jump through a load of hoops and pay a bunch of money to come - but then this is what Brexit-voters wanted).