Pringle gets a dental every 6-8weeks. He goes under GA and gets his trimmed down, his normally ranges between £60-90 depends how bad his are. Pringle can be so good at hiding it though, he will still eat, poo fine etc, i just seem to sense it at near his 8weeks i get him checked.
Pringle got neutered when he was in getting his teeth done and they gave me a discount as it was only one GA they mainly charged for the neuter but added a little on for the teeth, my vets are very good with me though.
I would reccomend getting them done asap as like others have said they will only get worse then Bella will need a longer GA and it will be more risky for her and cost more.
I would try save as much as you can, or ask your mum/ dad to help you out or even give you so much a week £5 or that to go towards vets. Not trying to scare you but it does only get worse. I think most of my wages go on the vets. and some bills have been a few hundred pound. And Pringle and Patch are currently on long-term medication which is costing me a few pound every week, Patch is currently in for check-ups every tuesday and has been for past couple of months. Its all the small things too that add up
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Just to make you aware. Hope Bella is ok, and i advise on the spaying too, as she may get problems from not being spayed which will cost more money than a dental xx
EDIT- For the part im saying about your mum and dad giving you money, of course you would do dishes, or car washing or that
. Or you could get yourself a wee job, delivering catelogues (betterware, avon for example) you have to be 16 but i done it when i was younger and my mum signed up for it, i just done the job, got money, delivered catelogues etc. Maybe worth looking into