Hello, you've come to the right place

First of all yes there's no guarantee that after a gap year you would be given offers to study dentistry, so if you are on track for the entry requirement grades then there's every reason to apply.
Second, what grades are you expecting to be on your UCAS application as teacher predictions?
About 5 years ago I (with some helpers) compiled a list of dentistry entry requirements, which can be found here:
https://www.thestudentroom.co.uk/university/courses/dentistry/dentistry-entry-requirementsSome of these will have changed, but it's a starting point.
Always do your own research.
Based on your 5 in maths, there are some courses that are closed to you, the physics is less of a barrier as few universities specify physics as a stipulation.
Even with exceptional circumstances explained in your reference, it's possible (personally I think it's likely) that some university courses will reject you outright. These are competitive courses and the admissions teams need ways to narrow down applicants.
There are some gateway courses you can apply to which are essentially dentistry + foundation year at the start. Some of these courses are targeted towards non-A Level entry. Entry requirements here:
https://www.thestudentroom.co.uk/university/courses/dentistry/entry-requirements-for-pre-dental-coursesHave you considered resitting GCSE Maths when you take your A Level exams? Your school may not be willing to pay the entry fee but it could be 1 way of broadening how many dental schools you would be able to access
Let me know what you're thinking