3.5 year olds teeth

[ellieepayne2001]

does anybody know what this is please? My 3.5 year old brushes her teeth twice a day but I've only just noticed this little black mark on the inside of the top of her tooth and think there may be a little one forming on the opposite tooth on the bottom too?
she had a dentist appointment not long ago and said everything is fine but they weren't looking for it as this is the first I've noticed it.

Obviously, you need to see the dentist again and it is worth discussing sealant to prevent other caries.
Is her brushing supervised? Most kids that age do a very poor job. It is also a matter of diet, especially drinks and other foods kids suck from pouches, breakfast cereals and other sweet/sticky stuff be it cereal bars, puffed snacks and so on.

When you say she brushes her teeth twice a day is she brushing them or are you brushing them and what toothpaste are you using?
It is recommended that you brush your child's teeth until they are 7 as they can do an inadequate job. Also, not all children's toothpastes contain enough fluoride.

I'm not sure what you mean by "they weren't looking for it"?

On the positive side, you can absolutely make changes that protect the teeth. My daughter developed a cavity when she was 3 due to uncontrolled gastric reflux. At the time she didn't have any sweets, juice and dried fruits which are terrible for teeth due to other health issues but would grind refluxed stomach contents into her teeth at night. We got her reflux under control and her dentists started fluoride treatments every 3 months and the cavity didn't get any worse. When she was 5 there was no signs of any active decay in the tooth so the dentist was able to do a no drill filling.

You can’t trust a preschooler to brush their own teeth effectively. I still brush my 8 year olds teeth and will do for as long as they’ll let me. I let them have the odd go to build up the technique but it’s important to make sure you get all teeth for long enough.

Id go back to the dentist for advice, looks like it could be a cavity.