What is wrong with my DD's teeth?

DD has bad teeth! Ok, I admit that when she first had a cavity we probably didn't brush her teeth as well as we could (though much more often than other people I know)!!! Since then we have made sure to brush her teeth for her (until she turned 7 ish), we got an electric toothbrush and have 6 month check ups on the dot!! Our last check was around 4-5 months ago and she got a clean and fluride treatment and they said her teeth were fine. Well she has just told me she has a hole in her tooth and on inspection sure enough she does! I don't understand what we are doing wrong? Her younger sister has had no cavities as of yet! How can she have had no signs of cavity 4-5 months ago and now all of a sudden she has a visible hole on the edge of her tooth?

Is it a molar? It it between the teeth??
I'm a dental nurse, brush and floss my kids teeth, DD1 had 4 filings a few years ago, I take them 6 monthly too, unfortunately sometimes it just happens!!!

As far as I can see it's on one tooth but on the edge in the middle of where two teeth meet. I'm thinking it's a baby tooth. Will have to see what the dentist says. How quickly do cavities form? I thought if you get checked 6 monthly and have good dental hygiene you 'd be all good!

Do you floss her teeth?? Inter proximal cavities can happen quickly ( I did fir us) the bad news is that it can generally happen on the same tooth in all four quadrants :(
Does that make sense? PM me if you want xx

Dentist said he doesn't tend to push flossing for young children and said its most likely diet. As in constant snacking rather than set meal periods. He found another small cavity too. :-(

If they're interproximal decay then floss floss floss!! My girls use the floss handles,
How old is your DD??

8. What are floss handles?

Some kids just have crap teeth regardless of what you do. DS1 and DD2 have beautiful teeth - never had a single filling or anything, but DD1 and DS2 have terrible teeth, had many, many fillings in their baby teeth, but their adult teeth are fine. Just keep doing what you're doing to minimise it.

Google Reach Flosser.