I'm thinking of doing dentistry because of good hours, good pay very quickly after uni and the sheer easiness of the day but I could see myself getting bored due to the repetitiveness of it and the lack of mental challenges.
But when I think of engineering, what aspect can compare to dentistry with pay etc?
I think you need to go and spend a week or two shadowing a dentist, or in a dental hospital to work out if it is something you would seriously want to do.
Yes - it is extremely well paid - but "sheer easiness of the day"? It's not as easy as it looks, especially if you take any pride in your work!
Don't forget that your "work" is performed on real people, you can have a dramatic effect on their life - so unless you can see yourself taking pride and pleasure in the skills of the job I'd think very carefully before committing. Having a bad day can even be life threatening for your patient
I started studying dentistry at university but after a year switched to and completed an engineering degree. I'm actually now an accountant!
What I would say is that it's hard studying something your heart isn't into, and it's equally hard working a job you don't enjoy regardless of the financial rewards. Bear that in mind when making your choices.
You will almost certainly earn a LOT more as a Dentist .. only the very top paid engineering jobs will come close, and they often require moving to where the work is (abroad?) or working extremely hard to get to that position.
It's very hard to know what you want to do with the rest of your life at 16/17 (I didn't have a clue until i was nearer 30) but you can give yourself the best chance of working it out by going out and seeing what it is like to work in these jobs. Try and shadow a dentist and engineer for a few days/weeks over the school holidays and see what you think.
If you decide to do engineering, I'd say that although not essential, maths and perhaps physics A levels will help when you get to uni. Particularly the mathematics as those without A level maths seemed to struggle more on my course since it was a big jump from GCSE standard.
If you decide to do dentisty - Biology and perhaps Chemistry will be useful. As you probably know it's extremely competetive to get a place though, so you'll need not only very high grades in good subjects, but they'll also want to make sure you are genuinely interested and committed to becoming a dentist. Straight As alone doesn't guarantee you a place at all - they'll see straight through you in the interview if you are only doing it for the money (or at least aren't very good at disguising the fact you are only doing it for the money!)
Have you considered any other careers?